for Journals by Title or ISSN
for Articles by Keywords
  Subjects -> CHEMISTRY (Total: 841 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (593 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (44 journals)
    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (593 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 233)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 55)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 68)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 219)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 212)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 2)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 293)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 119)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 96)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 13)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 71)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 174)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 142)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 257)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 12)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 58)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 17)

        1 2 3 | Last

Journal Cover Angewandte Chemie International Edition
  [SJR: 6.229]   [H-I: 397]   [212 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1433-7851 - ISSN (Online) 1521-3773
   Published by John Wiley and Sons Homepage  [1577 journals]
  • Rapid Assembly of Diversely Functionalized Spiroindenes by a
           Three-Component Palladium-Catalyzed C-H Amination/Phenol Dearomatization
           Domino Reaction
    • Authors: Liangxin Fan; Jingjing Liu, Lu Bai, Yaoyu Wang, Xinjun Luan
      Abstract: A novel palladium-catalyzed three-component reaction of phenol-derived biaryls with N-benzoyloxyamines and norbornadiene (NBD) has been developed for the assembly of highly functionalized spiroindenes. This domino process was realized through NBD-assisted C-H amination and phenol dearomatization by forming one C-N bond and two C-C bonds in a single step. Preliminary studies indicated that asymmetric control of this transformation was feasible with chiral ligands. Moreover, the potential synthetic utility of this methodology was highlighted by a series of further transformations.
      PubDate: 2017-09-20T04:20:28.63497-05:0
      DOI: 10.1002/anie.201708310
  • High-Temperature Formed Protective Film at Cathode/Electrolyte Interface:
           A Functional Layer in Lithium-Sulfur Batteries
    • Authors: Shuang-Yan Lang; Yang Shi, Yu-Guo Guo, Rui Wen, Li-Jun Wan
      Abstract: Lithium-sulfur (Li-S) batteries have been attracting wide attention due to their promising high specific capacity. Deep understanding of Li-S interfacial mechanism including the temperature (T) effect is increasingly required to meet the burgeoning demands for battery modification and systematic researches. Herein, interfacial behavior during discharge/charge is investigated at high temperature (HT) of 60 ̊C in electrolyte based on lithium bis(fluorosulfonyl) imide (LiFSI). By in situ atomic force microscopy (AFM), dynamic evolution of insoluble Li2S2 and Li2S is studied at the nanoscale. An in situ formed protective film can be directly monitored at 60 ̊C after Li2S nucleation, retarding side reactions and facilitating interfacial redox. The deep insight into the interfacial processes at HT discovers a direct evidence of the existence of the protective film and reveals its dynamic behaviors, providing a new avenue for electrolyte design and performance enhancement with a long span.
      PubDate: 2017-09-20T03:15:25.082223-05:
      DOI: 10.1002/anie.201706979
  • Morphology Dependent Cell Imaging by a Self-assembled Diacetylene Peptide
    • Authors: Carsten Schmuck; Hao Jiang, Xiao-Yu Hu, Stefanie Schlesiger, Mao Li, Elio Zellermann, Shirley Knauer
      Abstract: Herein, a novel cationic peptide gemini amphiphile containing diacetylene motifs (DA2P) is presented which self-assembles into novel tadpole- and bola-shaped nanostructures at low concentration and nanofibers at higher concentration, respectively. Interestingly, the DA2P assemblies can be polymerized to a fluorescent red phase but only during incubation with HeLa cells, most likely owing to the reorganization of the diacetylene chains of DA2P upon interaction with the cell membrane. The red-fluorescent polymerized DA2P assemblies can serve as a novel cell imaging probe. However, only vesicles, tadpole- and bola-shaped DA2P assemblies can be translocated into HeLa cells, while the nanofiber-like DA2P assemblies are trapped by the cell membranes and do not enter the cells. Hence, morphology dependent cell imaging is observed.
      PubDate: 2017-09-20T02:21:02.395234-05:
      DOI: 10.1002/anie.201708168
  • Stable Oxindolyl-based Chichibabin's Hydrocarbon and Müller's
           Hydrocarbon Analogues
    • Authors: Jishan Wu; Jian Wang, Xingdong Xu, Hoa Phan, Tun Seng Herng, Tullimilli Y. Gopalakrishna, Guangwu Li, Jun Ding
      Abstract: Chichibabin's hydrocarbon and Müller's hydrocarbon are classical open-shell singlet diradicaloids but they are highly reactive. Herein we report the successful synthesis of their respective stable analogues, OxR-2 and OxR-3, based on the newly developed oxindolyl radical. X-ray crystallographic analysis on OxR-2 reveals a planar quinoidal backbone similar to Chichibabin's hydrocarbon, in accordance with its small diradical character (y0 = 11.1%) and large singlet-triplet gap (ΔES-T = -10.8 kcal/mol). Variable-temperature NMR studies on OxR-2 disclose a slow cis-/trans- isomerization process in solution through a diradical transition state, with a moderate energy barrier (ΔGǂ298K = 15~16 kcal/mol). OxR-3 exhibits a much larger diradical character (y0 = 80.6%) and a smaller singlet-triple gap (ΔES-T = -3.5 kcal/mol), and thus can be easily populated to paramagnetic triplet diradical. Our studies provide a new type of stable carbon-centered monoradical and diradicaloid.
      PubDate: 2017-09-20T02:20:43.283179-05:
      DOI: 10.1002/anie.201708612
  • Frontispiece: Facile One-Pot Synthesis of Functional Giant Polymeric
           Vesicles Controlled by Oscillatory Chemistry
    • Authors: Bishnu Prasad Bastakoti; Juan Perez-Mercader
      Abstract: Polymeric VesiclesB. P. Bastakoti and J. Perez-Mercader show in their Communication on page 12086 ff., how the oscillatory Belousov–Zhabotinsky reaction can be used to synthesize self-assembling giant polymeric vesicles in one pot.
      PubDate: 2017-09-20T02:00:16.366745-05:
      DOI: 10.1002/anie.201784061
  • High thermoelectric performance of new rhombohedral phase of GeSe
           stabilized via alloying with AgSbSe2
    • Authors: Zhiwei Huang; Samuel Miller, Binghui Ge, Mingtao Yan, Shashwat Anand, Tianmin Wu, Pengfei Nan, Yuanhu Zhu, Wei Zhuang, Jeffrey Snyder, Peng Jiang, Xinhe Bao
      Abstract: GeSe is a IV-VI semiconductor, like the excellent thermoelectric materials PbTe and SnSe. Orthorhombic GeSe has been predicted theoretically to have good thermoelectric performance but is difficult to dope experimentally. Like PbTe, rhombohedral GeTe has a multivalley band structure, which is ideal for thermoelectrics and also promotes the formation of Ge vacancies to provide enough carriers for electrical transport. Herein, we investigate the thermoelectric properties of GeSe alloyed with AgSbSe2, which stabilizes a new rhombohedral structure with higher symmetry that leads to a multivalley Fermi surface and a dramatic increase in carrier concentration. The zT of GeAg0.2Sb0.2Se1.4 reaches 0.86 at 710 K, which is 18 times higher than that of pristine GeSe and over four times higher than doped orthorhombic GeSe. Our results open a new avenue towards developing novel thermoelectric materials via crystal phase engineering using a strategy of entropy stabilization of high symmetry alloys.
      PubDate: 2017-09-20T01:16:03.728942-05:
      DOI: 10.1002/anie.201708134
  • Total Synthesis of (+)-Gracilamine Based on Oxidative Phenolic Coupling
           Reaction and Determination of its Absolute Configuration
    • Authors: Kazuo Nagasawa; Minami Odagi, Yoshiharu Yamamoto
      Abstract: The Amaryllidaceae alkaloid (+)-gracilamine (1), isolated from Galanthus gracilis, contains a characteristic pentacyclic ring system with seven consecutive stereogenic centers, including an all-carbon quaternary stereocenter. Herein, we report the first enantioselective total synthesis of (+)-gracilamine (1), featuring a diastereoselective phenolic coupling reaction followed by a regioselective intramolecular aza-Michael reaction to construct the ABCE ring system. The stereochemistry at C3a in 1 is controlled by the stereocenter at C9a, which was selectively generated (91% ee) by utilizing an organocatalytic enantioselective aza-Friedel-Crafts reaction developed by our group. This synthesis reveals that the absolute configuration of (+)-gracilamine (1) is (3aR, 4S, 5S, 6R, 7aS, 8R, 9aS).
      PubDate: 2017-09-19T20:50:59.861607-05:
      DOI: 10.1002/anie.201708575
  • One-pot, Three-Component Sulfonimidamide Synthesis exploiting the
           Sulfinylamine Reagent N-Sulfinyltritylamine, TrNSO
    • Authors: Thomas Q Davies; Adrian Hall, Michael C. Willis
      Abstract: Sulfonimidamides are increasingly important molecules in medicinal chemistry and agrochemistry, but their preparation requires lengthy synthetic sequences, which has likely limited their use. We describe a one-pot de novo synthesis of sulfonimidamides from widely available organometallic reagents and amines. This convenient and efficient process uses a stable sulfinylamine reagent, N-sulfinyltritylamine (TrNSO), available in one step on 10 gram scale, as a linchpin. In contrast to classical approaches starting from thiols or their derivatives, our TrNSO-based approach facilitates the rapid assembly of the three reaction components into a variety of differentially substituted sulfonimidamides containing medicinally relevant moieties, including pyridines and indoles. Analogues of the sulfonamide-containing COX-2 inhibitor Celecoxib were prepared and evaluated.
      PubDate: 2017-09-19T20:50:39.353823-05:
      DOI: 10.1002/anie.201708590
  • (4+3)-Cycloaddition Reactions of N-Alkyl Oxidopyridinium Ions
    • Authors: Chencheng Fu; Nestor Lora, Patrick L. Kirchhoefer, Dong Reyoul Lee, Erich Altenhoefer, Natasha L. Hungerford, Elizabeth H. Krenske, Michael Harmata
      Abstract: N-Methylation of methyl 5-hydroxynicotinate followed by reaction with a diene in the presence of triethylamine afforded (4+3)-cycloadducts in good to excellent yields. High regioselectivity was exhibited with 1-substituted and 1,2-disubstituted butadienes. Density functional theory calculations indicate that the cycloaddition involves concerted addition of the diene onto the oxidopyridinium ion. The process provides rapid access to bicyclic nitrogenous structures resembling natural alkaloids.
      PubDate: 2017-09-19T20:46:25.516822-05:
      DOI: 10.1002/anie.201708320
  • Olefin-Supported Rhenium(III) Terminal Oxo Complexes Generated by
           Nucleophilic Addition to a Cyclopentadienyl Ligand
    • Authors: Trevor Lohrey; Robert Bergman, John Arnold
      Abstract: The reactivity of the oxo Re(V) β-diketiminate, OReCl2(BDI), with various cyclopentadienide (Cp) sources has been investigated. As a result, we have developed a route to a new class of terminal oxo complexes of Re(III) supported by olefin moieties of substituted cyclopentadienes. The success of this pathway is due to the electrophilic nature of the Cp ligand in the cation, [ORe(η5-Cp)(BDI)]+ (3+), which allows for nucleophilic attack by a variety of reagents under mild conditions. In contrast, tBuNC was found to attack at the oxo moiety to produce isocyanate by oxygen atom transfer.
      PubDate: 2017-09-19T20:46:13.509844-05:
      DOI: 10.1002/anie.201707957
  • Synthesis and Utilization of Nitroalkyne Equivalents in Batch and
           Continuous Flow
    • Authors: Peter D Morse; Timothy F Jamison
      Abstract: We report a method for overcoming the low stability of nitroalkynes through the development of nitrated vinyl silyltriflate equivalents. Because of their instability, nitroalkynes have only rarely been utilized in synthesis. The reactivity of these silyltriflates, which are prepared in situ, is exemplified by dipolar cycloaddition reactions with nitrones to give highly substituted 4-nitro-4-isoxazolines in high yields. This approach has proven general for several different alkyl and aryl substituted alkynes. In order to minimize the accumulation of potentially hazardous reaction intermediates, we have also developed a continuous flow variant of this method that is capable of carrying out the entire reaction sequence in a good yield and a short residence time.
      PubDate: 2017-09-19T20:46:04.422419-05:
      DOI: 10.1002/anie.201706157
  • Alkynylation of sp2 C(O)−H Bonds Enabled by Photoredox-Mediated
           Hydrogen Atom Transfer
    • Authors: Satobhisha Mukherjee; Aleyda Garza-Sanchez, Adrian Tlahuext Aca, Frank Glorius
      Abstract: The development of new Hydrogen Atom Transfer (HAT) strategies within the framework of photoredox catalysis is highly appealing for its power to activate a desired C−H bond in the substrate leading to its selective functionalization. Reported here, is the first photoredox mediated Hydrogen Atom Transfer protocol for the efficient synthesis of ynones, ynamides and ynoates with high regio- and chemoselectivity by direct functionalization of sp2 C(O)-H bonds. The broad synthetic application of this method has been demonstrated by the selective functionalization of C(O)-H bonds within complex molecular scaffolds.
      PubDate: 2017-09-19T20:45:33.48316-05:0
      DOI: 10.1002/anie.201708037
  • Covalent Triazine Frameworks via a Low Temperature Polycondensation
    • Authors: kewei Wang; Liming Yang, Xi wang, Liping Guo, Guang Cheng, Chun Zhang, Shangbin Jin, Bien Tan, Andrew Cooper
      Abstract: Covalent triazine frameworks (CTFs) are normally synthesized by ionothermal methods. The harsh synthetic conditions and associated limited structural diversity do not benefit for further development and practical large-scale synthesis of CTFs. Herein we report a new strategy to construct CTFs (CTF-HUSTs) via a polycondensation approach, which allows the synthesis of CTFs under mild conditions from a wide array of building blocks. Interestingly, these CTFs display a layered structure. The CTFs synthesized were also readily scaled up to gram quantities. The CTFs are potential candidates for separations, photocatalysis and for energy storage applications. In particular, CTF-HUSTs are found to be promising photocatalysts for sacrificial photocatalytic hydrogen evolution with a maximum rate of 2647 µmol h-1 g-1 under visible light. We also applied a pyrolyzed form of CTF-HUST-4 as an anode material in a sodium-ion battery achieving an excellent discharge capacity of 467 mAh g-1.
      PubDate: 2017-09-19T11:41:11.487346-05:
      DOI: 10.1002/anie.201708548
  • Hydrogen Transfer-Mediated a-Functionalization of 1,8-Naphthyridines by a
           Strategy Overcoming the Over-Hydrogenation Barrier
    • Authors: Xiuwen Chen; He Zhao, Chunlian Chen, Huanfeng Jiang, Min Zhang
      Abstract: By a hydrogen transfer-mediated activation mode for non-activated pyridyl nucleus, a general catalytic hydrogen transfer-mediated -functionalization of 1,8-naphthyridines is reported for the first time. Its -site selectively couples with the C8-site of various tetrahydroquinolines (THQs) to afford novel -functionalized tetrahydro 1,8-naphthyridines, a class of synthetically useful building blocks and potential candidates for the discovery of therapeutic and bio-active products. The utilization of THQs as inactive hydrogen donors (HDs) appears to be a key strategy to overcome the over-hydrogenation barrier and address the chemo-selectivity issue. The developed chemistry features operational simplicity, readily available catalyst and good functional tolerance, and offers a significant basis for further development of new protocols to directly transform or functionalize inert N-heterocycles.
      PubDate: 2017-09-19T10:46:42.97732-05:0
      DOI: 10.1002/anie.201707702
  • Cobalt versus osmium: control of both trans and cis selectivity in
           construction of the EFG rings of pectenotoxin 4
    • Authors: Ahria Roushanbakhti; Yifan Liu, Paul Winship, Michael Tucker, Wasim Akhtar, Daryl Walter, Gail Wrigley, Timothy James Donohoe
      Abstract: Catalytic oxidative cyclisation reactions have been employed for the synthesis of the E and F rings of the complex natural product target pectenotoxin 4. The choice of metal catalyst (cobalt or osmium based) allowed for the formation of THF rings with either trans or cis stereoselectivity. Fragment union using a modified Julia reaction then enabled the synthesis of an advanced synthetic intermediate containing the EF and G rings of the target.
      PubDate: 2017-09-19T10:46:14.554356-05:
      DOI: 10.1002/anie.201708278
  • Asymmetric Total Syntheses of Communesin F and a Putative Member of the
           Communesin Family
    • Authors: David Yu-Kai Chen
      Abstract: Here we report asymmetric total syntheses of communesin F and a putative member of the communesin family of bis-aminal alkaloid natural products. The successful strategy featured the invention of an asymmetric organocatalytic reaction to unify two oxindole subunits, a Ti(OiPr)4-mediated dehydrative skeletal rearrangement, and a late-stage Pd(OAc)2-catalyzed directed CH-alkenylation reaction. Collectively, the synthetic technologies disclosed herein enabled the preparation of a late-stage polycyclic intermediate catered for the synthesis of both naturally occurring and designed communesins. More importantly, speculated and yet to be discovered member(s) of the communesin family can now be accessed to facilitate a better understanding of the communesin biosynthetic network.
      PubDate: 2017-09-19T10:45:45.444969-05:
      DOI: 10.1002/anie.201707806
  • Synthesis of a Metallo-Iminosilane via a Silanone-Metal π-Complex
    • Authors: Matthias Driess; Terrance J Hadlington, Tibor Szilvási
      Abstract: Facile oxygenation of the acyclic amido chlorosilylene-bis(N-heterocyclic carbene) Ni0 complex 1, [{N(Dipp)(SiMe3)ClSi:Ni(NHC)2] (Dipp = 2,6-Pri2C6H4; N-heterocyclic carbene = C[(Pri)NC(Me)]2) with N2O furnishes the first Si-metallo-iminosilane complex, [DippN=Si(OSiMe3)Ni(Cl)(NHC)2] 3, in a cascade of rearrangement reactions. Markedly, the formation of 3 ensues via a silanone (Si=O)-Ni pi-complex 2 as the initial product, which has been predicted by DFT calculations and could be observed spectroscopically. Both the Si=O and Si=N moieties in 2 and 3, respectively, undergo hydroboration, a reaction which typically requires a catalyst for the C=O and C=N analogues.
      PubDate: 2017-09-19T10:45:22.818522-05:
      DOI: 10.1002/anie.201708923
  • Intramolecular π–π Interactions in Flexibly Linked Partially
           Fluorinated Bisarenes in the Gas Phase
    • Authors: Sebastian Blomeyer; Marvin Linnemannstöns, Jan Hendrick Nissen, Jannik Paulus, Beate Neumann, Hans-Georg Stammler, Norbert W. Mitzel
      Abstract: Three compounds with phenyl and pentafluorophenyl rings bridged by (CH2)3 and (CH2)2SiMe2 units were synthesized by hydrosilylation and C−C coupling reactions. Their solid-state structures are dominated by intermolecular π stacking interactions, primarily leading to dimeric or chain-type aggregates. Analysis of free molecules in the gas phase by electron diffraction revealed the most abundant conformer to be significantly stabilized by intramolecular π–π interactions. For the silicon compounds, structures characterized by σ–π interactions between methyl and pentafluorophenyl groups are second lowest in energy and cannot be excluded completely by the gas electron diffraction experiments. C6H5(CH2)3C6F5, in contrast, is present as a single conformer. The gas-phase structures served as a reference for the evaluation of a series of (dispersion-corrected) quantum-chemical calculations.Undistorted structures of compounds with C6H6 and C6F6 groups linked by (CH2)3 and (CH2)2SiMe2 moieties show folding by intramolecular dispersion forces in the gas phase whereas in the solid state, extended conformers are adopted that interact intermolecularly. The experimental data served as a reference for the quality of quantum-chemical calculations.
      PubDate: 2017-09-19T08:10:41.731836-05:
      DOI: 10.1002/anie.201707716
  • One-Step Reforming of CO2 and CH4 into High-Value Liquid Chemicals and
           Fuels at Room Temperature by Plasma-Driven Catalysis
    • Authors: Li Wang; Yanhui Yi, Chunfei Wu, Hongchen Guo, Xin Tu
      Abstract: The conversion of CO2 with CH4 into liquid fuels and chemicals in a single-step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one-step process from CO2 and CH4 at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH4 and CO2 is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.Liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one-step process from CO2 and CH4 at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid as the major component.
      PubDate: 2017-09-19T08:10:27.381621-05:
      DOI: 10.1002/anie.201707131
  • Alkynyl Thioethers in Gold-Catalyzed Annulations to form Oxazoles
    • Authors: Raju Jannapu Reddy; Matthew P. Ball-Jones, Paul W. Davies
      Abstract: Non-oxidative, regioselective, and convergent access to densely functionalized oxazoles is realized in a functional-group tolerant manner using alkynyl thioethers. Sulfur-terminated alkynes provide access to reactivity previously requiring strong donor-substituted alkynes such as ynamides. Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides.Taking a different path: The first gold-catalyzed annulations with alkynyl thioethers are reported. This transformation provides ready and convergent access into densely-functionalized 1,3-oxazole motifs. The sulfur substituent is integral to accessing the desired reactivity and provides a useful synthetic handle for later elaboration. In contrast with recent reports, the reaction does not follow a ketenethionium pathway.
      PubDate: 2017-09-19T08:06:27.186749-05:
      DOI: 10.1002/anie.201706850
  • Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium
           Hydride and 1,4-Dioxane
    • Authors: Tobias Hokamp; Abhishek Dewanji, Maximilian Lübbesmeyer, Christian Mück-Lichtenfeld, Ernst-Ulrich Würthwein, Armido Studer
      Abstract: A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.It is the combo! NaH in combination with 1,4-dioxane serves as the reagent for the radical chain reduction of various aryl halides. Hydrodehalogenation is initiated by 1,10-phenanthroline (phen) at elevated temperature and can be combined with a typical radical cyclization reaction. the reactions proceed via electron catalysis.
      PubDate: 2017-09-19T08:06:15.890358-05:
      DOI: 10.1002/anie.201706534
  • Iron-Catalyzed anti-Selective Carbosilylation of Internal Alkynes
    • Authors: Takahiro Iwamoto; Tatsushi Nishikori, Naohisa Nakagawa, Hikaru Takaya, Masaharu Nakamura
      Abstract: Reported is the anti-selective carbosilylation of internal alkynes with silylborane and alkyl halides using a FeBr2/DPPE catalyst system. The iron catalyst allows simultaneous introduction of a carbon electrophile and a silicon nucleophile to simple internal alkynes, including diaryl-, dialkyl-, and aryl/alkyl-substituted alkynes, in a highly stereoselective manner. Alkyl halides are applicable as the electrophiles, thereby enabling the synthesis of a variety of tetrasubstituted alkenylsilanes. In addition, syn-selective carbosilylation was achieved through stereoswitching, by using a silylborane having oxygen functionality on the silyl group. This novel iron-catalyzed carbosilylation is a useful tool for expedient synthesis of stereodefined multisubstituted olefins, a fundamental structural motif in organic chemistry.Pin on: anti-Selective carbosilylation of internal alkynes with PhMe2SiBpin and alkyl halides was achieved using a FeBr2/dppe catalyst system. The reaction exhibits high anti selectivity irrespective of the structure of the alkyne and electrophile. Additionally, syn-selective carbosilylation was achieved using Ph2(MeO)SiBpin. The oxygen functional group plays a key role in the syn selectivity.
      PubDate: 2017-09-19T08:06:03.184969-05:
      DOI: 10.1002/anie.201706333
  • Preorganization and Cooperation for Highly Efficient and Reversible
           Capture of Low-Concentration CO2 by Ionic Liquids
    • Authors: Yanjie Huang; Guokai Cui, Yuling Zhao, Huiyong Wang, Zhiyong Li, Sheng Dai, Jianji Wang
      Abstract: A novel strategy based on the concept of preorganization and cooperation has been designed for a superior capacity to capture low-concentration CO2 by imide-based ionic liquids. By using this strategy, for the first time, an extremely high gravimetric CO2 capacity of up to 22 wt % (1.65 mol mol−1) and excellent reversibility (16 cycles) have been achieved from 10 vol. % of CO2 in N2 when using an ionic liquid having a preorganized anion. Through a combination of quantum-chemical calculations and spectroscopic investigations, it is suggested that cooperative interactions between CO2 and multiple active sites in the preorganized anion are the driving force for the superior CO2 capacity and excellent reversibility.Two for one: A novel preorganization and cooperation strategy has been designed for a superior capacity (22 wt %, 1.65 mol mol−1) to capture low-concentration CO2 (10 vol. % CO2 in N2) by imide-based ionic liquids with excellent reversibility (16 cycles). Multiple-site cooperative interactions between CO2 and active sites in the preorganized anion are operative.
      PubDate: 2017-09-19T07:46:29.300997-05:
      DOI: 10.1002/anie.201706280
  • Protonation of Ferrocene: A Low-Temperature X-ray Diffraction Study of
           [Cp2FeH](PF6) Reveals an Iron-Bound Hydrido Ligand
    • Authors: Moritz Malischewski; Konrad Seppelt, Jörg Sutter, Frank W. Heinemann, Birger Dittrich, Karsten Meyer
      Abstract: Ferrocene, Cp2Fe, is quantitatively protonated in a mixture of liquid HF/PF5 to yield [Cp2FeH](PF6), which was characterized by 1H/13C NMR and 57Fe Mössbauer spectroscopy as well as single-crystal X-ray diffraction analysis. X-ray diffraction analysis at 100 K revealed a disordered, iron-coordinated hydrido ligand, which was unambiguously located by aspherical atom refinement at 100 K, and by analyzing the non-disordered crystal structure at 30 K, revealing a non-agostic structure.After more than 50 years, the mechanism of electrophilic substitutions on ferrocene was reinvestigated for the simplest electrophile, H+, and the potential intermediate [Cp2FeH]+ was isolated. Single crystals of [Cp2FeH](PF6) were obtained from an anhydrous HF/PF5 system. X-ray diffraction analysis revealed a non-agostic structure with an iron-bound hydrido ligand.
      PubDate: 2017-09-19T07:46:23.749197-05:
      DOI: 10.1002/anie.201704854
  • Meta-Selective C−H Borylation of Benzylamine, Phenethylamine and
           Phenylpropylamine-Derived Amides Enabled by a Single Anionic Ligand
    • Authors: Holly J. Davis; Georgi R. Genov, Robert J. Phipps
      Abstract: Selective functionalization at the meta position of arenes remains a significant challenge. In this work, we demonstrate that a single anionic bipyridine ligand bearing a remote sulfonate group enables selective iridium-catalyzed borylation of a range of common amine-containing aromatic molecules at the arene meta position. We propose that this selectivity is the result of a key hydrogen bonding interaction between the substrate and catalyst. The scope of this meta-selective borylation is demonstrated on amides derived from benzylamines, phenethylamines and phenylpropylamines; amine-containing building blocks of great utility in many applications.Clever positioning: A bipyridine ligand incorporating a remote anionic sulfonate group directs iridium-catalyzed borylation to the meta-position on a range of amide-containing arenes. It is proposed that this selectivity is a result of a hydrogen bonding interaction to correctly position the iridium metal centre in the crucial C−H activation.
      PubDate: 2017-09-19T07:40:40.295402-05:
      DOI: 10.1002/anie.201708967
  • Solution Structure of AlMe2F and its Reactivity with Metallocenes:
           Mimicking Cation-Anion Interactions in Metallocenium-MAO Inner-Sphere Ion
    • Authors: Leone Oliva; Patrizia Oliva, Nunzia Galdi, Claudio Pellecchia, Leonardo Sian, Alceo Macchioni, Cristiano Zuccaccia
      Abstract: The solution structure of AlMe2F and its reactivity with a prototypical ansa-metallocene have been investigated by advanced NMR techniques, in an attempt to indirectly shed some light on the "structure and working principles" of methylalumoxane (MAO) mixtures in olefin polymerization. In solution, AlMe2F leads to a complex equilibrium of oligomeric species, including a heterocubane [(Me2Al)4F4] tetramer, resembling the behavior of MAO. Such a complex mixture reacts with the prototypical ansa-zirconocene (ETH)ZrMe2 affording [(ETH)ZrMeδ+(μ-F)(AlMe2F)nAlMe3δ-] inner-sphere ion pairs through the successive insertions/deinsertion of AlMe2F units into the Zr…(μ-F) bond.
      PubDate: 2017-09-19T06:45:30.131046-05:
      DOI: 10.1002/anie.201707194
  • Highly 2,3-Selective Polymerization of Phenylallene and Derivatives with
           Rare-Earth Metal Catalyst: from Amorphous to Crystalline Products
    • Authors: Fei Lin; Zhaohe Liu, Tiantian Wang, Dongmei Cui
      Abstract: Rare-earth metal complexes (Flu-CH2-Py)Ln(CH2SiMe3)2(THF)n (Ln = Sc(1), Lu(2), Tm(3), Y(4) and Gd(5)), upon the activation of [Ph3C][B(C6F5)4] and AliBu3, were firstly employed to catalyze the polymerization of allene derivatives under mild conditions. The Gd, Y, Tm, Lu metal based precursors exhibited distinguished 2,3-selectivity (>99.9%) for phenylallene (PA) polymerization, whereas the smallest Sc metal based precursor showed a moderate 2,3-selectivity. The activity increased with the central metal size following the trend of Gd(5)>Tm(4)>Y(3)>Lu(2)>Sc(1). Moreover, Gd(5) also realized unprecedentedly the purely 2,3-selective polymerizations of polar or nonpolar allene derivatives, para-methylphenylallene, para-flourophenylallene and para-methoxyphenylallene, regardless of the electron donating or withdrawing substituents. Owing to the highly regular backbones, these polymers except PPA were crystalline, which represent the first crystalline allene derivatives based polymers.
      PubDate: 2017-09-19T04:40:53.517103-05:
      DOI: 10.1002/anie.201707601
  • Stereospecific Reaction of Donor-Acceptor Cyclopropanes with Thioketones:
           A Novel Access to Highly Substituted Tetrahydrothiophenes
    • Authors: Daniel B. Werz; André Augustin, Peter G. Jones, Maximilian Sensse
      Abstract: Lewis-acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with thioketones are described. Highly substituted tetrahydrothiophenes with two adjacent quaternary carbon atoms were obtained in a stereospecific manner under mild conditions and in high yield using AlCl3 as Lewis acid. Moreover, an intramolecular approach was successfully implemented to gain access to sulfur-bridged [n.2.1] bicyclic ring systems. Conversion of selenoketones, the heavier analogs, under similar conditions resulted in the formation of various tetrahydroselenophenes.
      PubDate: 2017-09-19T04:40:43.086596-05:
      DOI: 10.1002/anie.201708346
  • Organocatalytic Enantioselective Protonation for Photoreduction of
           Activated Ketones and Ketimines Induced by Visible Light
    • Authors: Lu Lin; Xiangbin Bai, Xinyi Ye, Xiaowei Zhao, Choon-Hong Tan, Zhiyong Jiang
      Abstract: The first catalytic asymmetric photoreduction of 1,2-diketones and α-keto ketimines under visible light irradiation is reported. A transition-metal-free synergistic catalysis platform harnessing dicyanopyrazine-derived chromophore (DPZ) as the photoredox catalyst and a non-covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Brønsted acid or base in H+ transfer interchange to control the elusive enantioselective protonation, a variety of chiral α-hydroxy ketones and α-amino ketones were obtained with high yields and enantioselectivities.
      PubDate: 2017-09-19T03:41:10.839606-05:
      DOI: 10.1002/anie.201707899
  • A Simple and Broadly Applicable C-N Bond Forming Dearomatization Protocol
           Enabled by Bifunctional Amino-Reagents
    • Authors: Xiaofeng Ma; Joshua Farndon, Tom Young, Natalie Fey, John Bower
      Abstract: A C-N bond forming dearomatization protocol with broad scope is outlined. Specifically, bifunctional amino-reagents are used for sequential nucleophilic and electrophilic C-N bond formations, with the latter effecting the key dearomatization step. Using this approach, γ-arylated alcohols are converted to a wide range of differentially protected spirocyclic pyrrolidines in just two or three steps.
      PubDate: 2017-09-19T02:41:05.220619-05:
      DOI: 10.1002/anie.201708176
  • Fluorine Pseudocontact Shifts Used for Characterizing the Protein–Ligand
           Interaction Mode in the Limit of NMR Intermediate Exchange
    • Authors: Jia Gao; E Liang, Rongsheng Ma, Fudong Li, Yixiang Liu, Jiuyang Liu, Ling Jiang, Conggang Li, Haiming Dai, Jihui Wu, Xuncheng Su, Wei He, Ke Ruan
      Abstract: The characterization of protein–ligand interaction modes becomes recalcitrant in the NMR intermediate exchange regime as the interface resonances are broadened beyond detection. Here, we determined the 19F low-populated bound-state pseudocontact shifts (PCSs) of mono- and di-fluorinated inhibitors of the BRM bromodomain using a highly skewed protein/ligand ratio. The bound-state 19F PCSs were retrieved from 19F chemical exchange saturation transfer (CEST) in the presence of the lanthanide-labeled protein, which was termed the 19F PCS-CEST approach. These PCSs enriched in spatial information enabled the identification of best-fitting poses, which agree well with the crystal structure of a more soluble analog in complex with the BRM bromodomain. This approach fills the gap of the NMR structural characterization of lead-like inhibitors with moderate affinities to target proteins, which are essential for structure-guided hit-to-lead evolution.The severe line broadening in the intermediate exchange limits the applicability of NMR spectroscopy for interrogating the interaction modes of lead-like inhibitors with moderate affinities to target proteins. A 19F chemical exchange saturation transfer approach is used to retrieve the low-populated bound-state 19F pseudocontact shifts, which enable the identification of the best binding pose of the BRM bromodomain inhibitor.
      PubDate: 2017-09-19T00:35:52.936425-05:
      DOI: 10.1002/anie.201707114
  • Constructing a Strongly Absorbing Low-Bandgap Polymer Acceptor for
           High-Performance All-Polymer Solar Cells
    • Authors: Zhi-Guo Zhang; Yankang Yang, Jia Yao, Lingwei Xue, Shanshan Chen, Xiaojun Li, William Morrison, Changduk Yang, Yongfang Li
      Abstract: All-polymer solar cells (all-PSCs) offer unique morphology stability for the application as flexible devices, but the lack of high-performance polymer acceptors limits their power conversion efficiency (PCE) to a value lower than those of the PSCs based on fullerene derivative or organic small molecule acceptors. We herein demonstrate a strategy to synthesize a high-performance polymer acceptor PZ1 by embedding an acceptor–donor–acceptor building block into the polymer main chain. PZ1 possesses broad absorption with a low band gap of 1.55 eV and high absorption coefficient (1.3×105 cm−1). The all-PSCs with the wide-band-gap polymer PBDB-T as donor and PZ1 as acceptor showed a record-high PCE of 9.19 % for the all-PSCs. The success of our polymerization strategy can provide a new way to develop efficient polymer acceptors for all-PSCs.Energy conversion: Embedding an acceptor–donor–acceptor-structured organic semiconductor building block into a polymer main chain creates an excellent low-band-gap polymer acceptor with red-shifted absorption and high absorption coefficient. The polymer acceptor provides a record-high power conversion efficiency of 9.19 % for all-polymer solar cells.
      PubDate: 2017-09-19T00:35:47.184736-05:
      DOI: 10.1002/anie.201707678
  • Polyamine-Mediated Stoichiometric Assembly of Ribonucleoproteins for
           Enhanced mRNA Delivery
    • Authors: Jiahe Li; Yanpu He, Wade Wang, Connie Wu, Celestine Hong, Paula T. Hammond
      Abstract: Messenger RNA (mRNA) represents a promising class of nucleic acid drugs. Although numerous carriers have been developed for mRNA delivery, the inefficient mRNA expression inside cells remains a major challenge. Inspired by the dependence of mRNA on 3′-terminal polyadenosine nucleotides (poly A) and poly A binding proteins (PABPs) for optimal expression, we complexed synthetic mRNA containing a poly A tail with PABPs in a stoichiometric manner and stabilized the ribonucleoproteins (RNPs) with a family of polypeptides bearing different arrangements of cationic side groups. We found that the molecular structure of these polypeptides modulates the degree of PABP-mediated enhancement of mRNA expression. This strategy elicits an up to 20-fold increase in mRNA expression in vitro and an approximately fourfold increase in mice. These findings suggest a set of new design principles for gene delivery by the synergistic co-assembly of mRNA with helper proteins.Although numerous carriers have been developed for mRNA delivery, the inefficient mRNA expression inside cells remains a major challenge. Inspired by the dependence of mRNA on 3′-terminal polyadenosine nucleotides (poly A) and poly A binding proteins (PABPs) for optimal expression, synthetic mRNA containing a poly A tail was complexed with PABPs in a stoichiometric manner.
      PubDate: 2017-09-19T00:35:25.802573-05:
      DOI: 10.1002/anie.201707466
  • Peroxidyme-Amplified Radical Chain Reaction (PARCR): Visible Detection of
           a Catalytic Reporter
    • Authors: John P. Goertz; Ian M. White
      Abstract: Peroxidyme Amplified Radical Chain Reaction (PARCR), a novel enzyme-free system that achieves exponential amplification of a visible signal, is presented. Typical enzyme-free amplification systems that produce a visible readout suffer from long reaction times, low sensitivity, and narrow dynamic range. PARCR employs photocatalyzed nonlinear signal generation, enabling unprecedented one-pot, naked-eye detection of a catalytic reporter from 1 μm down to 100 pm. In this reaction, hemin-binding peroxidase-mimicking DNAzymes (“peroxidymes”) mediate the NADH-driven oxidation of a colorless, nonfluorescent phenoxazine dye (Amplex Red) to a brightly colored, strongly fluorescent product (resorufin); illumination with green light initiates multiple radical-forming positive-feedback loops, rapidly producing visible levels of resorufin. Collectively, these results demonstrate the potential of PARCR as an easy-to-use readout for a range of detection schemes, including aptamer labels, hybridization assays, and nucleic acid amplification.A weakness becomes an asset: The oxidative activity of catalytic nucleic acids in tandem with the much-maligned photosensitivity of the phenoxazine dye Amplex Red is leveraged to engineer an exponentially propagating reaction which creates a visible readout via multiple positive-feedback loops. This novel assay enables visible detection of the catalytic reporter from 1 μm to 100 pm.
      PubDate: 2017-09-19T00:31:18.980587-05:
      DOI: 10.1002/anie.201706163
  • Conjugated Polymer with Intrinsic Alkyne Units for Synergistically
           Enhanced Raman Imaging in Living Cells
    • Authors: Shengliang Li; Tao Chen, Yunxia Wang, Libing Liu, Fengting Lv, Zhiliang Li, Yanyi Huang, Kirk S. Schanze, Shu Wang
      Abstract: Development of Raman-active materials with enhanced and distinctive Raman vibrations in the Raman-silent region (1800–2800 cm−1) is highly required for specific molecular imaging of living cells with high spatial resolution. Herein, water-soluble cationic conjugated polymers (CCPs), poly(phenylene ethynylene) (PPE) derivatives, are explored for use as alkyne-state-dependent Raman probes for living cell imaging due to synergetic enhancement effect of alkyne vibrations in Raman-silent region compared to alkyne-containing small molecules. The enhanced alkyne signals result from the integration of alkyne groups into the rigid backbone and the delocalized π-conjugated structure. PPE-based conjugated polymer nanoparticles (CPNs) were also prepared as Raman-responsive nanomaterials for distinct imaging application. This work opens a new way into the development of conjugated polymer materials for enhanced Raman imaging.Cell watching: Cationic poly(phenylene ethynylene) (PPE) derivatives are explored for use as Raman probes for living cell imaging due to a synergetic-enhancement effect of alkyne vibrations in Raman-silent regions. The enhanced alkyne signals result from the integration of alkyne groups into the rigid polymer backbone. PPE-based conjugated polymer nanoparticles were also prepared as Raman-responsive nanomaterials for distinct imaging application.
      PubDate: 2017-09-19T00:30:58.147896-05:
      DOI: 10.1002/anie.201707042
  • Enhanced Photoactivity from Single-crystalline SrTaO2N Nanoplates
           Synthesized by Topotactic Nitridation
    • Authors: Jie Fu; Sara Elizabeth Skrabalak
      Abstract: There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often render enhanced photoactivity. Here, single-crystalline SrTaO2N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, where single-crystalline SrTaO2N nanoplates form by topotactic nitridation of aerosol-prepared Sr2Ta2O7 nanoplates and SrTaO2N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO2N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1% for OER compared to the polyhedra (AQE: 1.6%) and SrTaO2N polycrystals (AQE: 0.6%). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides.
      PubDate: 2017-09-18T20:40:56.369484-05:
      DOI: 10.1002/anie.201708645
  • Catalytic Enantioselective Synthesis of Highly Functionalized
           Difluoromethylated Cyclopropanes
    • Authors: Maxence Bos; Wei-Sheng Huang, Thomas Poisson, Xavier Pannecoucke, André B. Charette, Philippe Jubault
      Abstract: The first catalytic asymmetric synthesis of highly functionalized difluoromethylated cyclopropanes is described. The method, based on a rhodium-catalyzed cyclopropanation of difluoromethylated olefins, gives access to a broad range of cyclopropanes bearing ester, ketone, or nitro functional groups. By using Rh2((S)-BTPCP)4 as a catalyst, the corresponding products were obtained in high yields and high diastereo- and enantioselectivities (up 20:1 d.r. and 99 % ee). This methodology allowed preparation of enantioenriched difluoromethylcyclopropanes for the first time.Small rings: The first catalytic asymmetric synthesis of difluorinated cyclopropanes is described. The methodology employs a rhodium catalyst and affords access to functionalized cyclopropanes in high yields with high diastereo- and enantioselectivities. PMP=para-methoxyphenyl.
      PubDate: 2017-09-18T11:39:39.13852-05:0
      DOI: 10.1002/anie.201707375
  • Discovery of a Novel Inhibitor of the Hedgehog Signaling Pathway through
           Cell-based Compound Discovery and Target Prediction
    • Authors: Lea Kremer; Carsten Schultz-Fademrecht, Matthias Baumann, Peter Habenberger, Axel Choidas, Bert Klebl, Susanne Kordes, Hans R. Schöler, Jared Sterneckert, Slava Ziegler, Gisbert Schneider, Herbert Waldmann
      Abstract: Cell-based assays enable monitoring of small-molecule bioactivity in a target-agnostic manner and help uncover new biological mechanisms. Subsequent identification and validation of the small-molecule targets, typically employing proteomics techniques, is very challenging and limited, in particular if the targets are membrane proteins. Herein, we demonstrate that the combination of cell-based bioactive-compound discovery with cheminformatic target prediction may provide an efficient approach to accelerate the process and render target identification and validation more efficient. Using a cell-based assay, we identified the pyrazolo-imidazole smoothib as a new inhibitor of hedgehog (Hh) signaling and an antagonist of the protein smoothened (SMO) with a novel chemotype. Smoothib targets the heptahelical bundle of SMO, prevents its ciliary localization, reduces the expression of Hh target genes, and suppresses the growth of Ptch+/− medulloblastoma cells.Better together: Joint application of chemical biology and computational target prediction enabled the identification of the pyrazolo-imidazole derivative smoothib as a novel inhibitor of hedgehog signaling and the membrane protein smoothened as its target.
      PubDate: 2017-09-18T11:39:21.60015-05:0
      DOI: 10.1002/anie.201707394
  • Osmium-Mediated Transformation of 4-Thiouridine to Cytidine as Key To
           Study RNA Dynamics by Sequencing
    • Authors: Christian Riml; Thomas Amort, Dietmar Rieder, Catherina Gasser, Alexandra Lusser, Ronald Micura
      Abstract: To understand the functional roles of RNA in the cell, it is essential to elucidate the dynamics of their production, processing and decay. A recent method for assessing mRNA dynamics is metabolic labeling with 4-thiouridine (4sU), followed by thio-selective attachment of affinity tags. Detection of labeled transcripts by affinity purification and hybridization to microarrays or by deep sequencing then reveals RNA expression levels. Here, we present a novel sequencing method (TUC-seq) that eliminates affinity purification and allows for direct assessment of 4sU-labeled RNA. It employs an OsO4-mediated transformation to convert 4sU into cytosine. We exemplify the utility of the new method for verification of endogenous 4sU in tRNAs and for the detection of pulse-labeled mRNA of seven selected genes in mammalian cells to determine the relative abundance of the new transcripts. The results prove TUC-seq as a straight-forward and highly versatile method for studies of cellular RNA dynamics.RNA modification: The osmium-mediated conversion of thiouridine (4sU) to cytidine (C) is a so far disregarded reaction with great potential for comparative sequencing approaches.
      PubDate: 2017-09-18T11:39:12.37625-05:0
      DOI: 10.1002/anie.201707465
  • Conformationally Flexible Bis(9-fluorenylidene)porphyrin Diradicaloids
    • Authors: Hejian Zhang; Hoa Phan, Tun Seng Herng, Tullimilli Y. Gopalakrishna, Wangdong Zeng, Jun Ding, Jishan Wu
      Abstract: A stable 5,10-bis(9-fluorenylidene)porphyrin (Por-Fl) diradicaloid was synthesized. It shows a quinoidal, saddle-shaped geometry in the single crystal but can be thermally populated to a triplet diradical both in solution and in the solid state. Coordination with the Ni2+ ion (Por-Fl-Ni) does not significantly change the contorted conformation but reduces the singlet–triplet gap. Heat-induced geometric change can explain the observed paramagnetic properties as well as unusual hysteresis in SQUID measurements. On the other hand, protonation (Por-Fl-2H+) dramatically changes the conformation while maintains the closed-shell electronic structure. Our studies demonstrate how heat, coordination, and protonation affect the geometry, diradical character, and physical properties of conformationally flexible open-shell singlet diradicaloids.Protonation with a twist! A quinoidal bis(9-fluorenylidene)porphyrin and its NiII complex showed closed-shell saddle-shaped geometry in the crystalline state but they can be thermally populated to paramagnetic triplet species through geometric change. Protonation also dramatically changes the conformation and physical properties.
      PubDate: 2017-09-18T11:39:00.080679-05:
      DOI: 10.1002/anie.201707480
  • 4,5,9,10-Pyrene Diimides: A Family of Aromatic Diimides Exhibiting High
           Electron Mobility and Two-Photon Excited Emission
    • Authors: Ze-Hua Wu; Zhuo-Ting Huang, Rui-Xue Guo, Chun-Lin Sun, Li-Chuan Chen, Bing Sun, Zi-Fa Shi, Xiangfeng Shao, Hanying Li, Hao-Li Zhang
      Abstract: The design and synthesis of high-performance n-type organic semiconductors are important for the development of future organic optoelectronics. Facile synthetic routes to reach the K-region of pyrene and produce 4,5,9,10-pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm2 V−1 s−1. The tert-butyl-substituted compounds (t-PyDI) also showed good one- and two-photon excited fluorescence properties. The PyDI derivatives are a new family of aromatic diimides that may exhibit both high electron mobility and good light-emitting properties, thus making them excellent candidates for future optoelectronics.Conductive and emissive: Facile synthetic routes to reach the K-region of pyrene and produce 4,5,9,10-pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm2 V−1 s−1. The tert-butyl-substituted compounds (t-PyDI) also showed good one- and two-photon excited fluorescence properties.
      PubDate: 2017-09-18T11:38:49.246633-05:
      DOI: 10.1002/anie.201707529
  • Tuning the Structure of Platinum Particles on Ceria In Situ for
           Enhancing the Catalytic Performance of Exhaust Gas Catalysts
    • Authors: Andreas M. Gänzler; Maria Casapu, Philippe Vernoux, Stéphane Loridant, Francisco J. Cadete Santos Aires, Thierry Epicier, Benjamin Betz, Rüdiger Hoyer, Jan-Dierk Grunwaldt
      Abstract: A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures (H2>C3H6). This dynamic nature of Pt on ceria at such low temperatures (250–500 °C) was additionally confirmed by in situ environmental transmission electron microscopy. A general concept is proposed to adjust the noble metal dispersion (size, structure), for example, during operation of an exhaust gas catalyst.Under control: The low temperature oxidation activity of diesel oxidation catalysts was improved by unraveling the dynamic structural behavior of Pt nanoparticles on ceria using operando X-ray absorption spectroscopy (XAS) and environmental transmission electron microscopy (ETEM). This led to a general concept to finely adjust the size and structure of noble metal particles on strongly interacting supports during real operation.
      PubDate: 2017-09-18T11:38:41.127549-05:
      DOI: 10.1002/anie.201707842
  • Discovery of Key Physicochemical, Structural, and Spatial Properties of
           RNA-Targeted Bioactive Ligands
    • Authors: Brittany S. Morgan; Jordan E. Forte, Rebecca N. Culver, Yuqi Zhang, Amanda E. Hargrove
      Abstract: While a myriad non-coding RNAs are known to be essential in cellular processes and misregulated in diseases, the development of RNA-targeted small molecule probes has met with limited success. To elucidate the guiding principles for selective small molecule/RNA recognition, we analyzed cheminformatic and shape-based descriptors for 104 RNA-targeted ligands with demonstrated biological activity (RNA-targeted BIoactive ligaNd Database, R-BIND). We then compared R-BIND to both FDA-approved small molecule drugs and RNA ligands without reported bioactivity. Several striking trends emerged for bioactive RNA ligands, including: 1) Compliance to medicinal chemistry rules, 2) distinctive structural features, and 3) enrichment in rod-like shapes over others. This work provides unique insights that directly facilitate the selection and synthesis of RNA-targeted libraries with the goal of efficiently identifying selective small molecule ligands for therapeutically relevant RNAs.A space for RNA: The curation and analysis of the RNA-targeted BIoactive ligaNd Database (R-BIND) uncovered distinguishing 2D and 3D molecular properties that support the existence of an RNA-privileged chemical space. These guiding principles can facilitate the future design of selective ligands targeted toward therapeutically relevant RNAs.
      PubDate: 2017-09-18T11:37:58.014707-05:
      DOI: 10.1002/anie.201707641
  • Sensuke Ogoshi
    • PubDate: 2017-09-18T11:37:17.130585-05:
      DOI: 10.1002/anie.201708270
  • Heavy-Atom Tunneling Calculations in Thirteen Organic Reactions: Tunneling
           Contributions are Substantial, and Bell's Formula Closely Approximates
           Multidimensional Tunneling at ≥250 K
    • Authors: Charles Doubleday; Randy Armas, Dana Walker, Christopher V. Cosgriff, Edyta M. Greer
      Abstract: Multidimensional tunneling calculations are carried out for 13 reactions, to test the scope of heavy-atom tunneling in organic chemistry, and to check the accuracy of one-dimensional tunneling models. The reactions include pericyclic, cycloaromatization, radical cyclization and ring opening, and SN2. When compared at the temperatures that give the same effective rate constant of 3×10−5 s−1, tunneling accounts for 25–95 % of the rate in 8 of the 13 reactions. Values of transmission coefficients predicted by Bell's formula, κBell , agree well with multidimensional tunneling (canonical variational transition state theory with small curvature tunneling), κSCT. Mean unsigned deviations of κBell vs. κSCT are 0.08, 0.04, 0.02 at 250, 300 and 400 K. This suggests that κBell is a useful first choice for predicting transmission coefficients in heavy-atom tunnelling.Several common reaction types were studied to assess the importance of heavy-atom tunneling in organic reactions. The results are consistent with the hypothesis that heavy-atom tunneling is widespread. The success of Bell's formula suggests it is a useful first choice for predicting transmission coefficients in heavy-atom tunnelling.
      PubDate: 2017-09-18T11:33:53.124255-05:
      DOI: 10.1002/anie.201708489
  • Chan Beum Park
    • PubDate: 2017-09-18T11:33:49.24239-05:0
      DOI: 10.1002/anie.201709297
  • Octacyanidotungstate(IV) Coordination Chains Demonstrate a Light-Induced
    • Authors: Michał Magott; Olaf Stefańczyk, Barbara Sieklucka, Dawid Pinkowicz
      Abstract: A huge increase in the magnetization of two coordination chains based on tetravalent octacyanidometalates (WIV and MoIV) is observed on irradiation with 436 nm light, while no such behavior is observed for the NbIV analogue. A photomagnetic response based solely on [WIV(CN)8]4− is demonstrated for the first time. The observed behavior is attributed to the light-induced excited spin state trapping (LIESST) effect at the octacyanidometalate, and to the resulting magnetic exchange ON/OFF photoswitching between the MnII center and the photoinduced high-spin (S=1) WIV or MoIV centers.Let it shine! Octacyanidotungstate(IV) demonstrates a light-induced excited spin state trapping photomagnetic effect that can be used to produce very strong magnetic exchange photoswitching functionality in various bimetallic coordination polymers.
      PubDate: 2017-09-18T11:33:46.706192-05:
      DOI: 10.1002/anie.201703934
  • Native Desorption Electrospray Ionization Liberates Soluble and Membrane
           Protein Complexes from Surfaces
    • Authors: Stephen Ambrose; Nicholas G. Housden, Kallol Gupta, Jieyuan Fan, Paul White, Hsin-Yung Yen, Julien Marcoux, Colin Kleanthous, Jonathan T. S. Hopper, Carol V. Robinson
      Abstract: Mass spectrometry (MS) applications for intact protein complexes typically require electrospray (ES) ionization and have not been achieved via direct desorption from surfaces. Desorption ES ionization (DESI) MS has however transformed the study of tissue surfaces through release and characterisation of small molecules. Motivated by the desire to screen for ligand binding to intact protein complexes we report the development of a native DESI platform. By establishing conditions that preserve non-covalent interactions we exploit the surface to capture a rapid turnover enzyme–substrate complex and to optimise detergents for membrane protein study. We demonstrate binding of lipids and drugs to membrane proteins deposited on surfaces and selectivity from a mix of related agonists for specific binding to a GPCR. Overall therefore we introduce this native DESI platform with the potential for high-throughput ligand screening of some of the most challenging drug targets including GPCRs.Folded soluble and membrane proteins can be released directly from surfaces using a desorption electrospray ionization source coupled to a high-resolution mass spectrometer. Desorbed protein complexes maintain non-covalent interactions enabling rapid measurement of subunit stoichiometries and capturing specific ligand binding to a GPCR.
      PubDate: 2017-09-18T11:33:42.257735-05:
      DOI: 10.1002/anie.201704849
  • Optimizing Optical Absorption, Exciton Dissociation, and Charge Transfer
           of a Polymeric Carbon Nitride with Ultrahigh Solar Hydrogen Production
    • Authors: Guigang Zhang; Guosheng Li, Zhi-An Lan, Lihua Lin, Aleksandr Savateev, Tobias Heil, Spiros Zafeiratos, Xinchen Wang, Markus Antonietti
      Abstract: Polymeric or organic semiconductors are promising candidates for photocatalysis but mostly only show moderate activity owing to strongly bound excitons and insufficient optical absorption. Herein, we report a facile bottom-up strategy to improve the activity of a carbon nitride to a level in which a majority of photons are really used to drive photoredox chemistry. Co-condensation of urea and oxamide followed by post-calcination in molten salt is shown to result in highly crystalline species with a maximum π–π layer stacking distance of heptazine units of 0.292 nm, which improves lateral charge transport and interlayer exciton dissociation. The addition of oxamide decreases the optical band gap from 2.74 to 2.56 eV, which enables efficient photochemistry also with green light. The apparent quantum yield (AQY) for H2 evolution of optimal samples reaches 57 % and 10 % at 420 nm and 525 nm, respectively, which is significantly higher than in most previous experiments.Free to dissociate: The simultaneous modification of the electronic band structures, layer-stacking geometry, and crystallinity of carbon nitride polymers enables the liberation of Frenkel exciton dissociation and magnification of the hot-charges yield, which dramatically enhances the visible-light photocatalytic activities.
      PubDate: 2017-09-18T11:33:33.725104-05:
      DOI: 10.1002/anie.201706870
  • Solvation Accounts for the Counterintuitive Nucleophilicity Ordering of
           Peroxide Anions
    • Authors: Robert J. Mayer; Takahiro Tokuyasu, Peter Mayer, Jérôme Gomar, Stéphane Sabelle, Benedetta Mennucci, Herbert Mayr, Armin R. Ofial
      Abstract: The nucleophilic reactivities (N, sN) of peroxide anions (generated from aromatic and aliphatic peroxy acids or alkyl hydroperoxides) were investigated by following the kinetics of their reactions with a series of benzhydrylium ions (Ar2CH+) in alkaline aqueous solutions at 20 °C. The second-order rate constants revealed that deprotonated peroxy acids (RCO3−), although they are the considerably weaker Brønsted bases, react much faster than anions of aliphatic hydroperoxides (ROO−). Substitution of the rate constants of their reactions with benzhydrylium ions into the linear free energy relationship lg k=sN(N+E) furnished nucleophilicity parameters (N, sN) of peroxide anions, which were successfully applied to predict the rates of Weitz–Scheffer epoxidations. DFT calculations with inclusion of solvent effects by means of the Integral Equation Formalism version of the Polarizable Continuum Model were performed to rationalize the observed reactivities.Weak bases, but strong nucleophiles: Peroxybenzoate ions can be generated in aqueous solution under much less basic conditions than alkyl peroxide anions. Nevertheless, their nucleophilic reactivities exceed those of the alkyl peroxide anions significantly. Quantum chemical calculations reveal solvation to be the origin of the unexpected ordering of reactivity.
      PubDate: 2017-09-18T11:33:30.626286-05:
      DOI: 10.1002/anie.201707086
  • Enantioselective [2,3]-Sigmatropic Rearrangements: Metal-Bound or Free
           Ylides as Reaction Intermediates'
    • Authors: Katharina J. Hock; Rene M. Koenigs
      Abstract: Out of bounds: Enantioselective rearrangement reactions are a long-standing challenge in organic synthesis. Recent advances are highlighted that led to the development of the first enantioselective Doyle–Kirmse reaction and enantioselective rearrangement reactions of iodonium ylides.
      PubDate: 2017-09-18T11:33:25.808575-05:
      DOI: 10.1002/anie.201707092
  • Biphasic Synergistic Gel Materials with Switchable Mechanics and
           Self-Healing Capacity
    • Authors: Ziguang Zhao; Yuxia Liu, Kangjun Zhang, Shuyun Zhuo, Ruochen Fang, Jianqi Zhang, Lei Jiang, Mingjie Liu
      Abstract: A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials.It's morphin’ time: Closely packed switchable micro-inclusions in a hydrogel matrix produce biphasic synergistic gel materials with switchable mechanics, self-healing capacity, and shape-memory properties.
      PubDate: 2017-09-18T11:33:03.120757-05:
      DOI: 10.1002/anie.201707239
  • An Active and Robust Bifunctional Oxygen Electrocatalyst through
           Carbon-Free Hierarchical Functionalization
    • Authors: Kevin Huang
      Abstract: A hierarchically functionalized hybrid electrode for Zn–air batteries is discussed that requires no carbon. Instead, an oxygen evolution reaction (OER)-active, porous, conductive, and corrosion-resistant nitride Ni3FeN is used as a support for oxygen reduction reaction (ORR)-active ordered intermetallic Fe3Pt NPs. The porosity in the Ni3FeN substrate is an important enabling factor for the high OER activity.
      PubDate: 2017-09-18T11:32:41.375911-05:
      DOI: 10.1002/anie.201707322
  • Copper-Catalyzed Borylacylation of Activated Alkenes with Acid Chlorides
    • Authors: Yuan Huang; Kevin B. Smith, M. Kevin Brown
      Abstract: A method for the copper-catalyzed borylacylation of activated alkenes is presented. The reaction involves borylcupration of the alkene, followed by capture of the generated alkyl–copper intermediate with an acid chloride. The reactions operated with low catalyst loading and generally occurre within 15 min at room temperature for a range of activated alkenes. In the case of vinyl arenes, enantioselective borylacylation was possible.Give 'em the new one, two: A range of activated alkenes underwent rapid copper-catalyzed borylacylation at room temperature at low catalyst loadings (see scheme). The reaction involves borylcupration of the alkene and capture of the resulting alkyl–copper intermediate with an acid chloride. In the case of vinyl arenes, the transformation could be carried out in an enantioselective manner.
      PubDate: 2017-09-18T11:32:26.134404-05:
      DOI: 10.1002/anie.201707323
  • Mass Production and Pore Size Control of Holey Carbon Microcages
    • Authors: Lei Zhang; Xiaoxiao Liu, Yuhai Dou, Binwei Zhang, Huiling Yang, Shixue Dou, Huakun Liu, Yunhui Huang, Xianluo Hu
      Abstract: Architectural control of porous solids, such as porous carbon cages, has received considerable attention for versatile applications because of their attractive ability to interact with liquids and gases not only at the surface, but throughout the bulk. Here we report a scalable, facile spray-pyrolysis route to synthesize holey carbon microcages with mosquito-net-like shells. Using the surfaces of water droplets as the growth templates, styrene-butadiene rubber macromolecules are controllably cross-linked, and size-tunable holes on the carbon shells are generated. The as-formed carbon microcages encapsulating Si nanoparticles exhibit enhanced lithium-storage performances for lithium-ion batteries. The scalable, inexpensive synthesis of porous carbon microcages with controlled porosity and the demonstration of outstanding electrochemical properties are expected to extend their uses in energy storage, molecular sieves, catalysis, adsorbents, water/air filters and biomedical engineering.
      PubDate: 2017-09-18T10:40:38.196791-05:
      DOI: 10.1002/anie.201708732
  • Asymmetric Iron-Catalyzed C−H Alkylation Enabled by Remote Ligand
    • Authors: Joachim Loup; Daniel Zell, Joao Carlos Agostinho de Oliveira, Helena Keil, Dietmar Stalke, Lutz Ackermann
      Abstract: Highly enantioselective iron-catalyzed C−H alkylations by inner-sphere C−H activation were accomplished with ample scope. High levels of enantiocontrol proved viable through a novel ligand design that exploits a remote meta-substitution on N-heterocyclic carbenes within a facile LLHT C−H cleavage.
      PubDate: 2017-09-18T09:41:38.38661-05:0
      DOI: 10.1002/anie.201709075
  • Structure and mechanism of the monoterpene cyclolavandulyl diphosphate
           synthase that catalyses consecutive condensation and cyclisation
    • Authors: Tomohisa Kuzuyama; Takeo Tomita, Masaya Kobayashi, Yuma Karita, Yoko Yasuno, Tetsuro Shinada, Makoto Nishiyama
      Abstract: Here, we report the three-dimensional structure of cyclolavandulyl diphosphate (CLPP) synthase (CLDS), which consecutively catalyses the condensation of two molecules of dimethylallyl diphosphate (DMAPP) followed by cyclisation to form a cyclic monoterpene, CLPP. The structures of apo-CLDS and CLDS in complex with Tris, pyrophosphate, and Mg2+ ion were refined at 2.00 Å resolution and 1.73 Å resolution, respectively. CLDS adopts a typical fold for cis-prenyl synthases and forms a homo-dimeric structure. An in vitro reaction using a regiospecifically 2H-substituted DMAPP substrate revealed the intramolecular proton transfer mechanism of the CLDS reaction. The CLDS structure and structure-based mutagenesis provide mechanistic insights into this unprecedented terpene synthase. The combination of structural and mechanistic insights advances the knowledge of intricate terpene synthase-catalysed reactions.
      PubDate: 2017-09-18T09:41:24.784734-05:
      DOI: 10.1002/anie.201708474
  • Encapsulation of Isolated Luminophores within Supramolecular Cages
    • Authors: Marcel Handke; Takuji Adachi, Chunhua Hu, Michael D. Ward
      Abstract: The sequestration of luminophores within supramolecular polyhedral compartments of a crystalline zeolite-like hydrogen-bonded framework illustrates a unique approach to limiting the self-quenching ordinarily exhibited at the high concentrations achievable in this framework. A range of differently sized luminescent guests, namely coumarin 1, coumarin 4, fluorescein, [Ru(bpy)3]Cl2, and rhodamine B, can be encapsulated in amounts of up to one molecule per cage, equivalent to a concentration of 0.175 m, which is significantly higher than the concentration at which aggregation-induced quenching occurs in other media. The luminescence spectra of the encapsulated guests are consistent with the presence of isolated monomers and the absence of self-quenching. The emission color of the single crystals can be tuned readily from blue to red through the choice of guest molecules. These observations promise an approach to organic solid-state lasing compounds if crystals of sufficient size and quality can be prepared.The supramolecular cages of a zeolite-like framework were used to encapsulate and isolate molecular luminophores with a range of sizes and emission wavelengths. The luminescence spectra of these host–guest systems were consistent with the presence of isolated monomers and the absence of self-quenching.
      PubDate: 2017-09-18T08:58:22.532345-05:
      DOI: 10.1002/anie.201707097
  • Ultrafast Vibrational Dynamics of Membrane-Bound Peptides at the Lipid
           Bilayer/Water Interface
    • Authors: Junjun Tan; Baixiong Zhang, Yi Luo, Shuji Ye
      Abstract: Vibrational energy transfer (VET) of proteins at cell membrane plays critical roles in controlling the protein functionalities, but its detection is very challenging. By using a surface-sensitive femtosecond time-resolved sum-frequency generation vibrational spectroscopy with infrared pump, the detection of the ultrafast VET in proteins at cell membrane has finally become possible. The vibrational relaxation time of the N−H groups is determined to be 1.70(±0.05) ps for the α-helix located in the hydrophobic core of the lipid bilayer and 0.9(±0.05) ps for the membrane-bound β-sheet structure. The N−H groups with strong hydrogen bonding gain faster relaxation time. By pumping the amide A band and probing amide I band, the vibrational relaxation from N−H mode to C=O mode through two pathways (direct coupling and through intermediate states) is revealed. The ratio of the pathways depends on the NH⋅⋅⋅O=C hydrogen-bonding strength. Strong hydrogen bonding favors the coupling through intermediate states.The energy transfer within amide bonds along the backbone of membrane peptides has been studied. Femtosecond infrared-pump sum-frequency generation (SFG) vibrational spectroscopy was used to track the energy transfer from the N−H group to the C=O group within the peptide backbone.
      PubDate: 2017-09-18T08:57:54.0459-05:00
      DOI: 10.1002/anie.201706996
  • An Icosidodecahedral Supramolecule Based on Pentaphosphaferrocene: From a
           Disordered Average Structure to Individual Isomers
    • Authors: Claudia Heindl; Eugenia Peresypkina, Alexander V. Virovets, Ivan S. Bushmarinov, Michael G. Medvedev, Barbara Krämer, Birger Dittrich, Manfred Scheer
      Abstract: Pentaphosphaferrocenes [CpRFe(η5-P5)] (1) and CuI halides are excellent building blocks for the formation of discrete supramolecules. Herein, we demonstrate the potential of Cu(CF3SO3) for the construction of the novel 2D polymer [{Cp*Fe(μ4,η5:1:1:1-P5)}{Cu(CF3SO3)}]n (2) and the unprecedented nanosphere (CH2Cl2)1.4@[{CpBnFe(η5-P5)}12{Cu(CF3SO3)}19.6] (3). The supramolecule 3 has a unique scaffold beyond the fullerene topology, with 20 copper atoms statistically distributed over the 30 vertices of an icosidodecahedron. Combinatorics was used to interpret the average disordered structure of the supramolecules. In this case, only two pairs of enantiomers with D5 and D2 symmetry are possible for bidentate bridging coordination of the triflate ligands. DFT calculations showed that differences in the energies of the isomers are negligible. The benzyl ligands enhance the solubility of 3, enabling NMR-spectroscopic and mass-spectrometric investigations.With the CF3SO3− anion as a spacer, a new type of giant supramolecule was obtained from pentaphosphaferrocene and Cu+. With 20 copper atoms distributed over the 30 vertices of a giant icosidodecahedron, its unprecedented scaffold contains intrinsic vacancies and exists as four isomers.
      PubDate: 2017-09-18T08:57:49.291701-05:
      DOI: 10.1002/anie.201706756
  • Carboxylation of Aromatic and Aliphatic Bromides and Triflates with CO2 by
           Dual Visible-Light–Nickel Catalysis
    • Authors: Qing-Yuan Meng; Shun Wang, Burkhard König
      Abstract: We report the efficient carboxylation of bromides and triflates with K2CO3 as the source of CO2 in the presence of an organic photocatalyst in combination with a nickel complex under visible light irradiation at room temperature. The reaction is compatible with a variety of functional groups and has been successfully applied to the synthesis and derivatization of biologically active molecules. In particular, the carboxylation of unactivated cyclic alkyl bromides proceeded well with our protocol, thus extending the scope of this transformation. Spectroscopic and spectroelectrochemical investigations indicated the generation of a Ni0 species as a catalytic reactive intermediate.Not only good for plants, CO2 (formed in situ from K2CO3) and light enabled the efficient and mild carboxylation of bromides and triflates in the presence of an organic fluorophore and a nickel complex (see scheme). A variety of functional groups were tolerated, and non-activated cyclic alkyl bromides reacted well. The synthesis and derivatization of biologically active molecules demonstrated the applicability of the method in multistep synthesis.
      PubDate: 2017-09-18T08:57:34.880472-05:
      DOI: 10.1002/anie.201706724
  • Role of the Adsorbed Oxygen Species in the Selective Electrochemical
           Reduction of CO2 to Alcohols and Carbonyls on Copper Electrodes
    • Authors: Cécile S. Le Duff; Matthew J. Lawrence, Paramaconi Rodriguez
      Abstract: The electrochemical reduction of CO2 into fuels has gained significant attention recently as source of renewable carbon-based fuels. The unique high selectivity of copper in the electrochemical reduction of CO2 to hydrocarbons has called much interest in discovering its mechanism. In order to provide significant information about the role of oxygen in the electrochemical reduction of CO2 on Cu electrodes, the conditions of the surface structure and the composition of the Cu single crystal electrodes were controlled over time. This was achieved using pulsed voltammetry, since the pulse sequence can be programmed to guarantee reproducible initial conditions for the reaction at every fraction of time and at a given frequency. In contrast to the selectivity of CO2 reduction using cyclic voltammetry and chronoamperometric methods, a large selection of oxygenated hydrocarbons was found under alternating voltage conditions. Product selectivity towards the formation of oxygenated hydrocarbon was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent.More oxygen, more oxygenation: Pulse voltammetry and copper single crystal electrodes were implemented to determine the influence of oxygen species adsorbed on copper electrodes in the electrochemical reduction of CO2. Product selectivity towards the formation of oxygenated hydrocarbons was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent.
      PubDate: 2017-09-18T08:57:27.503736-05:
      DOI: 10.1002/anie.201706463
  • “Isolated” DyO+ Embedded in a Ceramic Apatite Matrix Featuring
           Single-Molecule Magnet Behavior with a High Energy Barrier for
           Magnetization Relaxation
    • Authors: Pavel E. Kazin; Mikhail A. Zykin, Valentina V. Utochnikova, Oxana V. Magdysyuk, Alexander V. Vasiliev, Yan V. Zubavichus, Walter Schnelle, Claudia Felser, Martin Jansen
      Abstract: Meeting the challenges of Moore's Law, predicting ambitious miniaturization rates of integrated circuits, requires to go beyond the traditional top-down approaches, and to employ synthetic chemistry methods, to use bottom-up techniques. During the recent decades, it has been shown that open-shell coordination compounds may exhibit intramolecular spontaneous magnetization, thus offering promising prospects for storage and processing of digital information. Against this background we regarded it rewarding to implement similar magnetic centers into a ceramic material, which would provide better long-term mechanical and chemical durability. Here we present new robust inorganic compounds containing separate DyO+ ions in an apatite matrix, which behave like single-molecule magnets. The materials exhibit a blocking temperature of 11 K and an energy barrier for spin reversal of a thousand inverse centimeters which is among the highest values ever achieved.Dy2O3-doped apatites show low-temperature hysteresis magnetization with a blocking temperature of up to 11 K and slow relaxation of magnetization with an energy barrier (Ueff) of up to 1043 cm−1. The barrier was determined by an electron spin tunneling through the third and fourth exited Kramers doublet for calcium and strontium compounds, respectively.
      PubDate: 2017-09-18T08:57:21.023596-05:
      DOI: 10.1002/anie.201706391
  • Divergent C–H Annulation for Multifused N-Heterocycles: Regio- and
           Stereospecific Cyclizations of N-Alkynylindoles
    • Authors: Khyarul Alam; Sung Won Hong, Kyung Hwan Oh, Jin Kyoon Park
      Abstract: N-Alkynylindoles were divergently cyclized for the synthesis of multifused N-heterocycles. An ortho-aryl palladium species was added to the α position of an ynamine to generate (Z)-6-alkylidene/benzylidene-6H-isoindolo[2,1-a]indoles, while Pt-catalyzed β-addition through π-activation gave 5-alkyl/arylindolo[2,1-a]isoquinolines. Double cyclizations using PdCl2 and oxidant afforded bright yellow benzo[7,8]indolizino[2,3,4,5-ija]quinolines, the synthesis of which was also demonstrated in a different synthetic route.A short fuse: N-Alkynylindoles were divergently cyclized to give multifused N-heterocycles. The Pd(OAc)2-catalyzed reaction with PPh3 led to 5-exo-dig cycloisomerization, while the PtCl2-catalyzed reaction led to 6-endo-dig cycloisomerization. With PdCl2 and oxidant, β-addition and tandem α-addition, followed by a second ring closure provided bright yellow benzo[7,8]indolizino[2,3,4,5-ija]quinoline, which was also synthesized by a different synthetic route.
      PubDate: 2017-09-18T08:57:14.994929-05:
      DOI: 10.1002/anie.201705514
  • Catalytic Reductive Pinacol-Type Rearrangement of Unactivated 1,2-Diols
           through a Concerted, Stereoinvertive Mechanism
    • Authors: Nikolaos Drosos; Gui-Juan Cheng, Erhan Ozkal, Bastien Cacherat, Walter Thiel, Bill Morandi
      Abstract: A catalytic pinacol-type reductive rearrangement reaction of internal 1,2-diols is reported herein. Several scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary–secondary diols, undergo the transformation well without the need for prefunctionalization. The reaction uses a simple boron catalyst and two silanes and proceeds through a concerted, stereoinvertive mechanism that enables the preparation of highly enantiomerically enriched products. Computational studies have been used to rationalize the preference for migration over direct deoxygenation.Opportunities for insiders: A catalytic pinacol-type reductive rearrangement of 1,2-internal diols was developed by the use of a simple boron catalyst and two silanes (see scheme). The reaction occurs through a concerted, stereoinvertive mechanism and is applicable to several substrate scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary–secondary diols, without the need for prefunctionalization.
      PubDate: 2017-09-18T08:56:37.651555-05:
      DOI: 10.1002/anie.201704936
  • Total Synthesis of Crocagin A
    • Authors: Filip Bihelovic; Desiree Stichnoth, Frank Surup, Rolf Müller, Dirk Trauner
      Abstract: Crocagin A (1) combines an attractive molecular structure with an unusual biosynthesis and bioactivity. An efficient synthesis of crocagin A is presented that hinges on an early formation of the heterotricyclic core, an electrophilic amination, and the stereoselective hydrogenation of a tetrasubstituted double bond. This synthesis confirms the absolute configuration of crocagin A and provides access to the natural product and derivatives thereof for further biological testing.Let it RiPP: A concise synthesis of the ribosomally produced and post-translationally modified peptides (RiPP) crocagin A is presented. The approach hinges on early formation of the heterotricyclic core, an electrophilic amination, and the stereoselective hydrogenation of a tetrasubstituted double bond.
      PubDate: 2017-09-18T08:56:27.86203-05:0
      DOI: 10.1002/anie.201612641
  • The Quest for Mononuclear Gold(II) and its Potential Role in
           Photocatalysis and Drug Action
    • Authors: Katja Heinze
      Abstract: The chemistry of gold strongly focuses on the ubiquitousoxidation states +I and +III. The intermediate oxidation state +II isgenerally avoided in mononuclear gold species. In recent years,gold(II) has been increasingly suggested as key intermediate inartificial photosynthesis systems with gold(III) moieties as electronacceptors or in gold-catalyzed photoredox catalysis and radicalchemistry. This Minireview provides a concise summary onconfirmed and characterized mononuclear open-shell gold(II)complexes. Recent findings on structural motifs and reactivitypatterns will be discussed. Exciting developments in the fields ofphotosynthesis, photocatalysis and potential roles in medicinalchemistry will be outlined.
      PubDate: 2017-09-18T08:40:51.220359-05:
      DOI: 10.1002/anie.201708349
  • Redox Modulatory Mn3O4 Nanozyme with Multi-enzyme Activity Provides
           Efficient Cytoprotection to Human Cells in Parkinson's Disease Model
    • Authors: Govindasamy Mugesh; Namrata Singh, Mohammed Azharuddin Savanur, Shubhi Srivastava, Patrick D’Silva
      Abstract: Nanomaterials with enzyme-like activities (nanozymes) attracts significant interest due to their therapeutic potential for the treatment of various diseases. Herein, we report that a Mn3O4 nanozyme functionally mimic three major antioxidant enzymes, i.e. superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and the multienzyme activity is size as well as morphology-dependent. The redox modulatory effect of Mn3O4 plays a crucial role in protecting the cells from MPP+ induced cytotoxicity in a Parkinson disease (PD)-like cellular model, indicating that manganese-based nanomaterials having multi-enzyme activity can robustly rescue the cells from oxidative damage and thereby possess therapeutic potential to prevent ROS-mediated neurological disorders.
      PubDate: 2017-09-18T08:40:42.492209-05:
      DOI: 10.1002/anie.201708573
  • Borane-Stabilized Isomeric Dimers of the Phosphaethynolate Anion
    • Authors: Kevin Szkop; Andrew Jupp, Riccardo Suter, Hansjorg Gruetzmacher, Douglas Wade Stephan
      Abstract: The reactions of the phosphaethynolate anion ([PCO]-) with a range of boranes were explored. BPh3 and [PCO]- form a dimeric anion featuring P-B bonds and is prone to dissociation at room temperature. The more Lewis acidic borane B(C6F5)3 yields a less symmetric dimer of [PCO]- with P-B and P-O bonds. Less sterically demanding HB(C6F5)2 and H2B(C6F5) boranes form a third isomer with [PCO]- with both boranes bound to the same phosphorus atom. Despite the unexpected thermodynamic preference for P-coordination, computational data illustrate that electronic and steric features impact the binding modes of the resulting dianionic dimers.
      PubDate: 2017-09-18T08:40:21.248736-05:
      DOI: 10.1002/anie.201708646
  • Catalytic Enantioselective Carbopalladation/C-H Functionalization with
           Statistical Amplification of Product Enantiopurity: A Convertible Linker
    • Authors: Shuo Tong; Aurore Limouni, Qian Wang, Mei-Xiang Wang, Jieping Zhu
      Abstract: We demonstrated that combining a catalytic enantioselective reaction with dimerization in a single operation is an efficient way to upgrade the enantiomeric excesses (ee) of the product. Palladium-catalyzed reaction of N-(2-iodophenyl)-N-methyl methacrylamide derivatives with oxadiazole afforded, via a double enantioselective carbopalladation/intermolecular direct heteroarene C-H alkylation cascade, homodimers in good yields with excellent ee. The dimer was subsequently elaborated to the monomer in which the linker (oxadiazole) was incorporated into the target product
      PubDate: 2017-09-18T07:41:10.022023-05:
      DOI: 10.1002/anie.201709133
  • A Space-Charge Treatment of the Increased Concentration of Reactive
           Species at the Surface of a Ceria Solid Solution
    • Authors: Alexander F. Zurhelle; Xiaorui Tong, Andreas Klein, David S. Mebane, Roger A. De Souza
      Abstract: We apply a space-charge theory applicable to concentrated solid solutions—Poisson-Cahn theory—to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy (XPS) for the concentration of Ce3+ (the reactive species) at the surface of the oxide catalyst Ce0.8Sm0.2O1.9. In contrast to previous theoretical treatments, our calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space-charge zone. The high space-charge potential that develops at the surface (> 0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the space-charge layer. Our approach emphasizes the need to take into account defect interactions and to allow deviations from local charge neutrality when considering the surfaces of oxide catalysts.
      PubDate: 2017-09-18T07:40:57.20805-05:0
      DOI: 10.1002/anie.201708118
  • Stoichiometric Reactions of CO2 and Indium-Silylamides and Catalytic
           Synthesis of Ureas
    • Authors: Maotong Xu; Andrew Jupp, Douglas Wade Stephan
      Abstract: The indium compounds In(N(SiMe3)2)2Cl*THF (2) and In(N(SiMe3)2)Cl2*(THF)n¬ (3) were shown to react with CO2 to give [(Me3Si)2N)InX(-OSiMe3)]2 (X = N(SiMe3)2 4, Cl 5). 0.05-2.0 mol% of the species 3 acts as a pre-catalyst for the conversion of aryl and alkyl silylamines under CO2 (2-3 atm.) to give the corresponding ureas in 70-99% yields. A proposed mechanism is supported by experimental and computational data.
      PubDate: 2017-09-18T07:40:34.023834-05:
      DOI: 10.1002/anie.201708921
  • Structural characterization of a covalent monolayer sheet obtained by
           two-dimensional polymerization at an air/water interface
    • Authors: Vivian Müller; Feng Shao, Milos Baljozovic, Mina Moradi, Yao Zhang, Thomas Jung, William B. Thompson, Benjamin T. King, Renato Zenobi, A. Dieter Schlüter
      Abstract: This work describes a two-dimensional polymerization at an air/water interface and provides, for the first time, direct spectroscopic evidence for the kind of cross-links formed and for the conversion reached in a covalently bonded monolayer sheet. This is achieved by a combination of a variety of monolayer characterization techniques before and after transfer onto solid substrates in particular by tip-enhanced Raman spectroscopy (TERS) and TERS mapping after transfer of both the monomer and polymer monolayer onto Au(111). This is a major advance for the field of 2D polymers synthesized at the air/water interface as it in principle allows to estimate crystallinity via percolation theory and to locate regions with defects.
      PubDate: 2017-09-18T06:40:34.892089-05:
      DOI: 10.1002/anie.201707140
  • Doubly N-Confused [36]Octaphyrin( Isomerization,
           Bis-Metal Coordination, and Topological Chirality
    • Authors: Hiroyuki Furuta; Koki Mitsuno, Takafumi Yoshino, Iti Gupta, Shigeki Mori, Satoru Karasawa, Masatoshi Ishida
      Abstract: A novel [36]octaphyrin analogue embedding two N-confused pyrrole units demonstrated unique prototropy-coupled isomerization between the figure-of-eight and dumbbell conformers. Upon bis-metal coordination, fixation of fully π-conjugated figure-of-eight structures were achieved as referred from the X-ray crystal structure. Chirogenesis of the helical enantiomers was proved by intense circular dichroism (CD) response in the near infrared (NIR) region.
      PubDate: 2017-09-18T05:41:53.198498-05:
      DOI: 10.1002/anie.201708253
  • Characterization of doubly ionic hydrogen bonds in protic ionic liquids by
           NMR deuteron quadrupole coupling constants - Differences to H-bonds in
           amides, peptides and proteins
    • Authors: Ralf Ludwig; Alexander E. Khudozhitkov, Peter Stange, Benjamin Golub, Dietmar Paschek, Alexander G. Stepanov, Daniil I. Kolokolov
      Abstract: We present the first deuteron quadrupole coupling constants (DQCC) for selected protic ionic liquids (PILs) measured by solid-state NMR spectroscopy. The experimental data are supported by dispersion-corrected density functional theory (DFT-D3) calculations and molecular dynamics (MD) simulations. The DQCCs of the N-D bond in the triethylammonium cations are the lowest reported for deuterons in PILs indicating strong doubly ionic hydrogen bonds. The NMR coupling parameters are compared to those in amides, peptides, and proteins. The DQCCs show characteristic behaviour with increasing interaction strength of the counterion and variation of the H-bond motifs. We report the similar presence of the quadrupolar splitting pattern and the narrow liquid line in the NMR spectra over large temperature ranges, indicating the heterogeneous nature of PILs. The knowledge of DQCC is a prerequisite for studying the rotational dynamics by means of NMR quadrupolar relaxation time experiments.
      PubDate: 2017-09-17T21:31:48.27565-05:0
      DOI: 10.1002/anie.201708340
  • Iridium-catalyzed direct C-H amidation polymerization: step-growth
           polymerization by C-N bond formation via C-H activation to give
           fluorescent polysulfonamides
    • Authors: Tae-Lim Choi; Jang Yoon-Jung, Soon-Hyeok Hwang
      Abstract: We report a powerful strategy for activation of C-H bonds to produce polysulfonamides by an atom-economical and green method using iridium-catalyzed direct C-H amidation polymerization (DCAP). After screening various directing groups, additives, silver salts, concentrations, and temperatures to optimize DCAP, high molecular-weight (up to 149 kDa) and defect-free polysulfonamides were synthesized from various bis-sulfonyl azides. Although these polymers do not have conventional fluorescent conjugated cores, they emit blue light with large Stokes shifts and high quantum yields upon photoexcitation, due to excited-state intramolecular proton transfer process.
      PubDate: 2017-09-15T23:31:22.243029-05:
      DOI: 10.1002/anie.201707446
  • Construction and Crystal Structure Analysis of Heme Acquisition Protein
           HasA Containing Iron(III)-5,15-Diphenylporphyrin and Derivatives Thereof
           as an Artificial Prosthetic Group
    • Authors: Hiromu Uehara; Yuma Shisaka, Tsubasa Nishimura, Hiroshi Sugimoto, Yoshitsugu Shiro, Yoshihiro Miyake, Hiroshi Shinokubo, Yoshihito Watanabe, Osami Shoji
      Abstract: Iron(III)-5,15-diphenylporphyrin (1) and its derivatives (2-7) were accommodated by the heme acquisition protein HasA secreted by Pseudomonas aeruginosa, despite possessing bulky substituents at the meso-position of the porphyrin. Crystal structure analysis revealed that the two phenyl groups at the meso-positions of porphyrin extend outside HasA. It was shown that growth of P. aeruginosa was inhibited in the presence of HasA coordinating the synthetic porphyrins under iron-limiting conditions, and that the structure of the synthetic porphyrins greatly affects the inhibition efficiency.
      PubDate: 2017-09-15T23:31:05.680221-05:
      DOI: 10.1002/anie.201707212
  • Enzymatic synthesis, amplification, and application of DNA with a
           functionalized backbone
    • Authors: Tingjian Chen; Floyd Eric Romesberg
      Abstract: The ability to amplify DNA along with its unprecedented sequence control has led to its use for different applications, but all are limited by the properties available to natural nucleotides. We previously reported the evolution of polymerase SFM4-3, which better tolerates 2'-modified substrates. To explore the utility of SFM4-3, we now report the characterization of its recognition of substrates with 2'-azido, 2'-chloro, 2'-amino, or arabinose sugars. We find that SFM4-3 can efficiently synthesize polymers composed of these nucleotides, and most interestingly, that SFM4-3 can also PCR amplify these modified oligonucleotides. When combined with post-amplification modification, the latter allows for the exponential amplification of polymers that may be functionalized with desired moieties arrayed in a controlled fashion, the utility of which we demonstrate with extensive small molecule functionalization and the production and initial characterization of a novel DNA hydrogel.
      PubDate: 2017-09-15T10:21:10.022421-05:
      DOI: 10.1002/anie.201707367
  • Wireless electrochemical actuation of conducting polymers
    • Authors: Bhavana Gupta; Bertrand Goudeau, Alexander Kuhn
      Abstract: Electrochemical actuation of conducting polymers usually requires a direct connection to an electric power supply. In this contribution, we suggest to overcome this issue by using the concept of bipolar electrochemistry. This allows changing the oxidation state of the polymer in a gradual and wireless way. Free standing polypyrrole films were synthesized with an intrinsic morphological asymmetry of their two faces in order to form a bilayer structure. Immersing such objects in an electrolyte solution and exposing them to a potential gradient leads to the asymmetric oxidation/reduction of the polymer, resulting in differential shrinking and swelling along the main axis. This additional asymmetry is responsible for a structural deformation. Optimization allowed highly efficient bending, which is expected to open up completely new directions in the field of actuation due to the wireless mode of action.
      PubDate: 2017-09-15T07:20:38.802574-05:
      DOI: 10.1002/anie.201709038
  • The thermodynamic basis of the fuzzy interaction of an intrinsically
           disordered protein
    • Authors: San Hadži; Andrej Mernik, Črtomir Podlipnik, Remy Loris, Jurij Lah
      Abstract: Many intrinsically disordered proteins (IDP) that fold upon binding retain conformational heterogeneity in IDP-target complexes. The thermodynamics of such fuzzy interactions is poorly understood. Here we introduce a thermodynamic framework, based on analysis of ITC and CD spectroscopy data, that provides experimental description of IDP association in terms of folding and binding contributions which can be predicted using sequence folding propensities and molecular modeling. We show how IDP can modulate the entropy and enthalpy by adapting their bound-state structural ensemble to achieve optimal binding. This is explained in terms of a free energy landscape that provides the relationship between free energy, sequence folding propensity and disorder. The observed "fuzzy" behavior is possible not only because of IDP flexibility but also because backbone and side chain interactions are, to some extent, energetically decoupled allowing IDP to minimize energetically unfavorable folding.
      PubDate: 2017-09-15T06:28:22.434074-05:
      DOI: 10.1002/anie.201707853
  • A Catalytic Microwave Process for Superfast Preparation of High Quality
           Reduced Graphene Oxide
    • Authors: Runze Liu; Yu Zhang, Zhenjian Ning, Yuxi Xu
      Abstract: Herein we report that a small amount of graphite can unexpectedly act as the catalyst to greatly promote the microwave exfoliation and reduction of graphite oxide in ambient air. The reaction can be finished in a few seconds in contrast to more than ten minutes without catalyst. Meanwhile, the catalytic microwave exfoliated graphite oxide (CMEGO) shows much better quality than the traditional microwave exfoliated graphite oxide, including a much higher exfoliation degree with thinner graphene sheets and higher specific surface area (886 m2/g vs 466 m2/g), a much larger C/O ratio (19.4 vs 6.3) and a higher lattice crystallinity as well as significantly improved electrical conductivity (53180 S/m vs 5140 S/m). With such prominent features, the CMEGO is further used as anode for lithium-ion battery (LIB) and sodium-ion battery (SIB), and delivers ultrahigh reversible capacities, remarkable rate capabilities, and superior cycling stabilities in both LIB and SIB.
      PubDate: 2017-09-15T06:28:09.220023-05:
      DOI: 10.1002/anie.201708714
  • Ethers on Si(001): A prime example for the common ground between surface
           science and molecular organic chemistry
    • Authors: Lisa Pecher; Slimane Laref, Marc Raupach, Ralf Ewald Tonner
      Abstract: Using computational chemistry, we show that the adsorption of ether molecules on Si(001) under ultra-high vacuum conditions can be understood with textbook organic chemistry. The two-step reaction mechanism of (1) dative bond formation between the ether oxygen and a Lewis acidic surface atom and (2) a nucleophilic attack of a nearby Lewis basic surface atom is analysed in detail and found to mirror the acid-catalysed ether cleavage in solution. The O-Si dative bond is found to be the strongest of its kind and reactivity from this state defies the Bell-Evans-Polanyi principle. Electron rearrangement during the C-O bond cleavage is visualized using a newly developed bonding analysis method, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular chemistry SN2 reactions. Our findings thus illustrate how the fields of surface science and molecular chemistry can mutually benefit and unexpected insight can be gained.
      PubDate: 2017-09-15T05:27:23.040222-05:
      DOI: 10.1002/anie.201707428
  • Fluorine Effects on Guiding Group Migration via Rh(V) Nitrenoid
    • Authors: Cheng-Qiang Wang; Yu Zhang, chao feng
      Abstract: An unprecedented Rh(III)-catalyzed hydroarylation of α,α-difluoromethylene alkynes with N-pivaloxyl aroylamides through sequential C−H activation and aryl migration was detailed herein. A large array of α,α-difluoromethylene alkynes and N-pivaloxyl aroylamides were well amenable to this transformation, thus providing a novel synthetic protocol for the construction of difluorinated 2-alkenylaniline derivatives in both high yields and excellent regioselectivity. Also of note, the unique fluorine effects were uncovered to underlie the thus unconventional reaction manifold.
      PubDate: 2017-09-15T05:27:12.032352-05:
      DOI: 10.1002/anie.201708505
  • A Freestanding SeS2 Cathode Based on CoS2-decorated Multichannel Carbon
           Fibers with Enhanced Lithium Storage Performance
    • Authors: Xiong-Wen (David) Lou
      Abstract: SeS2 shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root-like carbon fiber network decorated with CoS2 nanoparticles (denoted as CoS2@LRC) has been designed and prepared as the SeS2 host for enhancing the lithium storage performance. The integrated electrode is constructed by three-dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS2 (70 wt.%), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g-1 at 0.2 A g-1. What's more, there are numerous CoS2 nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g-1.
      PubDate: 2017-09-15T05:20:51.260898-05:
      DOI: 10.1002/anie.201708105
  • Selective electrochemical reduction of CO2 to ethanol on B and N codoped
    • Authors: Yanming Liu; Yujing Zhang, Kai Chen, Xie Quan, Xinfei Fan, Yan Su, Shuo Chen, Huimin Zhao, Yaobin Zhang, Hongtao Yu, Michael R. Hoffmann
      Abstract: Electrochemical reduction of CO2 to ethanol, a clean and renewable liquid fuel with high heating value, is an attractive strategy for global warming mitigation and resource utilization. However, converting CO2 to ethanol remains great challenge due to the low activity, poor product selectivity and stability of electrocatalysts. Here, B and N codoped nanodiamond (BND) was reported as an efficient and stable electrode for selective reduction of CO2 to ethanol. Good ethanol selectivity was achieved on BND with high Faradaic efficiency of 93.2% (-1.0 V vs RHE), which overcame the limitation of low selectivity for multicarbon or high heating value fuels. Its superior performance was mainly originated from the synergistic effect of B and N codoping, high N content and overpotential for hydrogen evolution. The possible pathway for CO2 reduction revealed by DFT computation was CO2 *COOH *CO *COCO *COCH2OH *CH2OCH2OH CH3CH2OH.
      PubDate: 2017-09-15T04:21:20.014704-05:
      DOI: 10.1002/anie.201706311
  • Strand Displacement in Coiled-Coil Structures − Controlled Induction
           and Reversal of Proximity
    • Authors: Katharina Gröger; Georgina Gavins, Oliver Seitz
      Abstract: Coiled-coil peptides are frequently used to create new function upon self-assembly of supramolecular complexes. A multitude of coil peptide sequences provides control over specificity and stability of coiled-coil complexes. However, comparably little attention has been paid to the development of methods that allow for the reversal of complex formation under non-denaturing conditions. Herein, we present a reversible 2-state switching system. The process involves two peptide molecules for formation of a size-mismatched coiled-coil duplex and a third, disruptor peptide which targets an overhanging end. A real-time fluorescence assay revealed that proximity between two chromophores can be switched on and off, repetitively if desired. Showcasing the advantages provided by non-denaturing conditions the method permitted control over the bivalent interactions of the tSH2 domain of Syk kinase with a phosphopeptide ligand.
      PubDate: 2017-09-15T03:20:52.613009-05:
      DOI: 10.1002/anie.201705339
  • Chemical functionalization strategies and intracellular applications of
    • Authors: Dominik Schumacher; Jonas Helma, Anselm F.L. Schneider, Heinrich Leonhardt, Christian Hackenberger
      Abstract: Nanobodies can be considered as next-generation life science tools for the recognition and modulation of antigens that are inaccessible to conventional antibodies. Due to their compact structure and high stability, nanobodies see frequent usage in basic research. Their chemical functionalization facilitates powerful diagnostic tools and opens the way towards promising therapeutic applications. In this review, central aspects of nanobody functionalization are given together with selected applications in molecular cell biology. While first-generation conjugation strategies rely on random modification of natural amino acids, more recent studies focus on a site-specific attachment of functional groups. Such techniques include chemoenzymatic approaches, expressed protein ligation and amber suppression in combination with bioorthogonal modification strategies. With an ever growing toolkit of protein synthesis and conjugation, functional applications are on the rise as well. Such recent applications range from sophisticated imaging and mass spectrometry to the delivery of nanobodies into living cells, enabling visualization and manipulation of intracellular antigens.
      PubDate: 2017-09-15T01:21:17.103468-05:
      DOI: 10.1002/anie.201708459
  • Merging [2 + 2] Cycloaddition with Radical 1,4-Addition: Metal-Free Access
           to Functionalized Cyclobuta[a]naphthalen-4-ols
    • Authors: Bo Jiang; Feng Liu, Jia-Yin Wang, Peng Zhou, guigen Li, Wen-Juan Hao, Shu-Jiang Tu
      Abstract: Metal-free [2 + 2] cycloaddition and S-centered radical-induced 1,4-addition cascades have been achieved by treating benzene-linked allene-ynes with aryldiazonium tetrafluoroborates and DABCO-bis(sulfur dioxide) in a one-pot operation; the reaction provides a greener and practical access to functionalized cyclobuta[a]naphthalen-4-ols of valuable applications. More than 50 examples were examined to achieve up to excellent diastereoselectivity and yields. The reaction pathway is proposed to proceed through the sequence of [2 + 2] cycloaddition, insertion of SO2, 1,4-addition, diazotization and tautomerization
      PubDate: 2017-09-14T22:21:35.335847-05:
      DOI: 10.1002/anie.201707615
  • Dynamic Molecular Invasion into Multiply Interlocked Catenane
    • Authors: Yasuyuki Yamada; Ryohei Ito, Sayaka Ogino, Tatsuhisa Kato, Kentaro Tanaka
      Abstract: A multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains. The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine is movable along the alkyl chains, it acts as an adjustable wall, permitting the invasion of large molecules to the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both the nanospaces with a high affinity. A photometric titration experiment revealed the two-step inclusion phenomenon. The multiply interlocked catenane complexed with three Cu2+ ions, and the spin-spin interaction was switched off by the intercalation of dianionic porphyrins.
      PubDate: 2017-09-14T21:36:46.597774-05:
      DOI: 10.1002/anie.201708248
  • Regioselective Intermolecular Allylic C-H Amination of Disubstituted
           Olefins via Rh-π-allyl Intermediates
    • Authors: Jacob S Burman; Simon B. Blakey
      Abstract: A method for catalytic intermolecular allylic C-H amination of trans-disubstituted olefins is reported. The reaction is efficient for a range of common nitrogen nucleophiles bearing electron withdrawing group and proceeds under mild conditions. Good levels of regioselectivity are observed for a wide range of electronically diverse trans-ß-alkyl styrene substrates.
      PubDate: 2017-09-14T21:36:17.162655-05:
      DOI: 10.1002/anie.201707021
  • A Chemical Disruptor of the ClpX Chaperone Complex Attenuates
           Multiresistant Staphylococcus aureus Virulence
    • Authors: Christian Fetzer; Vadim S Korotkov, Robert Thänert, Kyu Myung Lee, Martin Neuenschwander, Jens Peter von Kries, Eva Medina, Stephan Axel Sieber
      Abstract: The Staphylococcus aureus ClpXP protease is an important regulator of cell homeostasis and virulence. Here we utilize a high-throughput screen against the ClpXP complex and identify a specific inhibitor of the ClpX chaperone that disrupts its oligomeric state. Synthesis of 34 derivatives revealed that the molecular scaffold is restrictive for diversification with only minor changes tolerated. Subsequent analysis of the most active compound revealed strong attenuation of S. aureus toxin production which was quantified via a customized MS-based assay platform. Transcriptome and whole proteome studies further confirmed the global reduction of virulence and unraveled characteristic signatures of protein expression in compound treated cells. Although these partially matched the pattern of ClpX knockout cells, further depletion of toxins was observed leading to the intriguing perspective that additional virulence pathways may be directly or indirectly addressed by the small molecule.
      PubDate: 2017-09-14T07:22:13.20338-05:0
      DOI: 10.1002/anie.201708454
  • Because the Light is Better Here: Correlation-Time Analysis by NMR
    • Authors: Albert A. Smith; Matthias Ernst, Beat H. Meier
      Abstract: Relaxation data in NMR spectra are often used for dynamics analysis, by modeling motion in the sample with a correlation function consisting of one or more decaying exponential terms, each described by an order parameter, and a correlation time. This method has its origins in the Lipari–Szabo model-free approach, which originally considered overall tumbling plus one internal motion and was later expanded to several internal motions. Considering several of these cases in the solid state it is found that if the real motion is more complex than the assumed model, model fitting is biased towards correlation times where the relaxation data are most sensitive. This leads to unexpected distortions in the resulting dynamics description. Therefore dynamics detectors should be used, which characterize different ranges of correlation times and can help in the analysis of protein motion without assuming a specific model of the correlation function.Fighting bias: NMR Dynamics data are more sensitive to some correlation times than to others. Models of the correlation function tend to be biased towards where the light is better, that is, where the experiment is more sensitive, yielding an unreliable characterization of the motion. Replacing modeling by detectors that are sensitive to different ranges of correlation times could help to overcome this bias.
      PubDate: 2017-09-14T06:26:17.726482-05:
      DOI: 10.1002/anie.201707316
  • Cross-Coupling of α-Carbonyl Sulfoxonium Ylides with C−H Bonds
    • Authors: Manuel Barday; Christopher Janot, Nathan R. Halcovitch, James Muir, Christophe Aïssa
      Abstract: The functionalization of carbon–hydrogen bonds in non-nucleophilic substrates using α-carbonyl sulfoxonium ylides has not been so far investigated, despite the potential safety advantages that such reagents would provide over either diazo compounds or their in situ precursors. Described herein are the cross-coupling reactions of sulfoxonium ylides with C(sp2)−H bonds of arenes and heteroarenes in the presence of a rhodium catalyst. The reaction proceeds by a succession of C−H activation, migratory insertion of the ylide into the carbon–metal bond, and protodemetalation, the last step being turnover-limiting. The method is applied to the synthesis of benz[c]acridines when allied to an iridium-catalyzed dehydrative cyclization.A new alliance: The rhodium-catalyzed cross-coupling of sulfoxonium ylides with carbon–hydrogen bonds, in hexafluoroisopropanol at 60–90 °C, brings these reagents into the realm of C−H activation. When allied to an iridium-catalyzed dehydrative cyclization, this cross-coupling streamlines the synthesis of valuable heterocycles.
      PubDate: 2017-09-14T06:25:49.534279-05:
      DOI: 10.1002/anie.201706804
  • Enantioselective Light Harvesting with Perylenediimide Guests on
           Self-Assembled Chiral Naphthalenediimide Nanofibers
    • Authors: Ramarani Sethy; Jatish Kumar, Rémi Métivier, Marine Louis, Keitaro Nakatani, Nila Mohan Thazhe Mecheri, Akhila Subhakumari, K. George Thomas, Tsuyoshi Kawai, Takuya Nakashima
      Abstract: Self-assembling molecular systems often display amplified chirality compared to the monomeric state, which makes the molecular recognition more sensitive to chiral analytes. Herein, we report the almost absolute enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI-based host nanofibers to the guest PDI molecules. The excitation energy was successfully transferred to the guest molecule through efficient energy migration along the host nanofiber, thus demonstrating the light-harvesting capability of these hybrid systems. Furthermore, circularly polarized luminescence (CPL) was enantioselectively sensitized by the guest molecule as the wavelength band and sign of the CPL signal were switched in response to the chiral guest molecule.The enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative is described. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI nanofibers to the PDI molecules, which demonstrated the light-harvesting capability of these hybrid systems.
      PubDate: 2017-09-14T06:25:35.342029-05:
      DOI: 10.1002/anie.201707160
  • Fully automated quantum chemistry based computation of spin-spin coupled
           nuclear magnetic resonance spectra for molecules
    • Authors: Stefan Grimme; Christoph Bannwarth, Sebastian Dohm, Andreas Hansen, Jana Pisarek, Philipp Pracht, Jakob Seibert, Frank Neese
      Abstract: We present a composite procedure for the quantum chemical computation of spin-spin coupled 1H-NMR spectra for general, flexible molecules in solution. It is based on four main steps, namely, conformer/rotamer ensemble (CRE) generation by the fast tight-binding method GFN-xTB and a newly developed search algorithm,relative free energy and NMR parameter computation, and solution of the spin-Hamiltonian. In this way the NMR-specific nuclear permutation problem is solved and the correct spin-symmetries are obtained. Energies, shieldings, and spin-spin couplings are computed at state-of-the-art DFT levels employing continuumsolvation. A few (in)organic and transition metal complexes are presented and very good, unprecedented agreement between theoretical and experimental spectra is achieved. The approach isroutinely applicable to systems with up to 100-150 atoms and may open new avenues for a detailed (conformational) structure elucidation of e.g. natural products or drug molecules.
      PubDate: 2017-09-14T05:20:45.271223-05:
      DOI: 10.1002/anie.201708266
  • Colloidal Synthesis and Photophysics of M3Sb2I9 (M = Cs and Rb)
           Nanocrystals: Lead-Free Perovskites
    • Authors: Jaya Pal; Suman Manna, Anirban Mondal, Shyamashis Das, K V Adarsh, Angshuman Nag
      Abstract: Here we report the colloidal synthesis of Cs3Sb2I9 and Rb3Sb2I9 perovskite nanocrystals, and explore their prospect for optoelectronic applications. Different morphologies such as nanoplatelets and nanorods of Cs3Sb2I9, and spherical Rb3Sb2I9 nanocrystals were prepared. All these samples show band-edge emissions in the yellow-red region. Exciton many-body interactions studied by femtosecond transient absorption spectroscopy of Cs3Sb2I9 nanorods reveals characteristic second-derivative-type spectral features, suggesting red-shifted excitons by as much as 79 meV. A high absorption cross-section of ~10-15 cm2 was estimated. All these results suggest that colloidal Cs3Sb2I9 and Rb3Sb2I9 nanocrystals are potential candidates for optical and optoelectronic applications in the visible region, though a better control of defect chemistry is required for efficient applications.
      PubDate: 2017-09-14T05:20:37.051651-05:
      DOI: 10.1002/anie.201709040
  • Stabilization of Low-Valent Iron(I) in a High-Valent Vanadium(V) Oxide
    • Authors: Montaha Anjass; Katharina Kastner, Florian Naegele, Mark Ringenberg, John Boas, Jie Zhang, Alan Bond, Timo Jacob, Carsten Streb
      Abstract: Low valent iron centers are critical intermediates in chemical and bio-chemical processes. Here, we show the first example of a low-valent FeI center stabilized in a high-valent polyoxometalate framework. Electrochemical studies show that the FeIII-functionalized molecular vanadium(V) oxide (DMA)[FeIIIClVV12O32Cl]3- (DMA - dimethyl ammonium) features two well-defined, reversible, iron-based electrochemical reductions which cleanly yield the FeI species (DMA)[FeIClVV12O32Cl]5-. Experimental and theoretical studies including electron paramagnetic resonance spectroscopy and density functional theory computations verify the formation of the FeI species. The study presents the first example for the seemingly paradoxical embedding of low-valent metal species in high-valent metal oxide anions and opens new avenues for reductive electron transfer catalysis by polyoxometalates.
      PubDate: 2017-09-14T04:22:52.392344-05:
      DOI: 10.1002/anie.201706828
  • Ring Expansion, Photo-isomerization, and Retro-cyclization of
    • Authors: Bochao Su; Yongxin Li, Rekesh Ganguly, Rei Kinjo
      Abstract: Diverse skeletal transformations of 1,4,2-diazaboroles (4,12) have been achieved through ring expansion, photo-isomerization and retro-cyclization, leading to the isolation of various BN-dihydroindole (3, 6), 1,3-azaborolidin-2-imine (7) and 1,4,2-diazaborol-3-imine (11) derivatives. These newly formed BN-heterocycles have been fully characterized by multiple NMR spectroscopy and X-ray diffraction analysis, and computational studies reveal their electronic properties.
      PubDate: 2017-09-14T04:22:39.737001-05:
      DOI: 10.1002/anie.201708720
  • Distribution of amyloid-like and oligomeric species from protein
           aggregation kinetics
    • Authors: Alexandra Silva; Bruno Almeida, Joana Sofia Fraga, Pablo Taboada, Pedro Miguel Martins, Sandra Ribeiro
      Abstract: Amyloid fibrils and soluble oligomers are two types of protein aggregates associated with neurodegeneration. Classic therapeutic strategies try to prevent the nucleation and spread of amyloid fibrils, whilst diffusible oligomers have emerged as promising drug targets affecting downstream pathogenic processes. We developed a generic protein aggregation model and validate it against measured compositions of fibrillar and non-fibrillar assemblies of ataxin-3, a protein implicated in Machado-Joseph disease. The derived analytic rate-law equations can be used to (i) identify the presence of parallel aggregation pathways and (ii) estimate the critical sizes of amyloid fibrils. The discretized population balance supporting our model is the first to quantitatively fit time-resolved measurements of size and composition of both amyloid-like and oligomeric species. The new theoretical framework can be used to screen a new class of drugs specifically targeting toxic oligomers.
      PubDate: 2017-09-14T04:22:11.474774-05:
      DOI: 10.1002/anie.201707345
  • Cascades in Compartments: En Route to Machine-Assisted Biotechnology
    • Authors: Kersten S. Rabe; Joachim Müller, Marc Skoupi, Christof M. Niemeyer
      Abstract: Biological compartmentalization is a fundamental principle of life that allows cells to metabolize, propagate, or communicate with their environment. Much research is devoted to understanding this basic principle and to harness biomimetic compartments and catalytic cascades as tools for technological processes. This Review summarizes the current state-of-the-art of these developments, with a special emphasis on length scales, mass transport phenomena, and molecular scaffolding approaches, ranging from small cross-linkers over proteins and nucleic acids to colloids and patterned surfaces. We conclude that the future exploration and exploitation of these complex systems will largely benefit from technical solutions for the integrated, machine-assisted development and maintenance of a next generation of biotechnological processes. These goals should be achievable by implementing microfluidics, robotics, and added manufacturing techniques supplemented by theoretical simulations as well as computer-aided process modeling based on big data obtained from multiscale experimental analyses.Machine-generated multienzyme cascades: The machine-assisted development of biomimetic compartments and catalytic cascades will pave the way towards a novel generation of biotechnological processes. Molecular scaffolds with small cross-linkers, proteins, nucleic acids, colloids, and patterned surfaces can be used to arrange the catalytic units. S: substrate, P: product.
      PubDate: 2017-09-14T04:16:22.122478-05:
      DOI: 10.1002/anie.201703806
  • Construction of Quaternary Stereogenic Centers in the Total Synthesis of
           Natural Products
    • Authors: Evgeny V. Prusov
      Abstract: Total syntheses of the tetracyclic terpene waihoensene and the densely functionalized tetracyclic compound ryanodol have recently been reported. Both approaches constitute examples of the efficient and innovative construction of multiple quaternary centers.
      PubDate: 2017-09-14T04:15:59.258934-05:
      DOI: 10.1002/anie.201706629
  • Flavylium Polymethine Fluorophores for Near- and Shortwave Infrared
    • Authors: Emily D. Cosco; Justin R. Caram, Oliver T. Bruns, Daniel Franke, Rachael A. Day, Erik P. Farr, Moungi G. Bawendi, Ellen M. Sletten
      Abstract: Bright fluorophores in the near-infrared and shortwave infrared (SWIR) regions of the electromagnetic spectrum are essential for optical imaging in vivo. In this work, we utilized a 7-dimethylamino flavylium heterocycle to construct a panel of novel red-shifted polymethine dyes, with emission wavelengths from 680 to 1045 nm. Photophysical characterization revealed that the 1- and 3-methine dyes display enhanced photostability and the 5- and 7-methine dyes exhibit exceptional brightness for their respective spectral regions. A micelle formulation of the 7-methine facilitated SWIR imaging in mice. This report presents the first polymethine dye designed and synthesized for SWIR in vivo imaging.Moving beyond the NIR: A series of polymethine dyes containing a 7-dimethylamino flavylium heterocycle were designed and synthesized. These dyes display distinctly red-shifted absorption and emission. The flavylium heptamethine dye is a bright shortwave infrared (SWIR) emitter and was employed for in vivo SWIR imaging.
      PubDate: 2017-09-14T04:12:38.802094-05:
      DOI: 10.1002/anie.201706974
  • Divergent Reactivity of a Dinuclear (NHC)Nickel(I) Catalyst versus
           Nickel(0) Enables Chemoselective Trifluoromethylselenolation
    • Authors: Alexander B. Dürr; Henry C. Fisher, Indrek Kalvet, Khai-Nghi Truong, Franziska Schoenebeck
      Abstract: We herein showcase the ability of NHC-coordinated dinuclear NiI–NiI complexes to override fundamental reactivity limits of mononuclear (NHC)Ni0 catalysts in cross-couplings. This is demonstrated with the development of a chemoselective trifluoromethylselenolation of aryl iodides catalyzed by a NiI dimer. A novel SeCF3-bridged NiI dimer was isolated and shown to selectively react with Ar−I bonds. Our computational and experimental reactivity data suggest dinuclear NiI catalysis to be operative. The corresponding Ni0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3, over productive cross-coupling and is hence inactive.A nickel(I) dimer catalyzes the chemoselective trifluoromethylselenolation of aryl iodides, and computational and experimental reactivity data suggest dinuclear NiI catalysis to be operative. The corresponding Ni0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3, over productive cross-coupling and is hence inactive.
      PubDate: 2017-09-14T04:05:44.075307-05:
      DOI: 10.1002/anie.201706423
  • Correct Modeling of Cisplatin: a Paradigmatic Case
    • Authors: Nicola Tasinato; Cristina Puzzarini, Vincenzo Barone
      Abstract: Quantum chemistry is a useful tool in modern approaches to drug and material design, but only when the adopted model reflects a correct physical picture. Paradigmatic is the case of cis-diaminodichloroplatinum(II), cis-[Pt(NH3)2Cl2], for which the correct simulation of the structural and vibrational properties measured experimentally still remains an open question. By using this molecule as a proof of concept, it is shown that state-of-the-art quantum chemical calculations and a simple model, capturing the basic physical flavors, a cis-[Pt(NH3)2Cl2] dimer, can provide the accuracy required for interpretative purposes. The present outcomes have fundamental implications for benchmark studies aiming at assessing the accuracy of a given computational protocol.Two are needed for a valid prediction: A dimer of cis-[Pt(NH3)2Cl2] as a quantum chemical model for cisplatin provides the first quantitative agreement with experiment for structural and vibrational properties. This result points out that a reliable in-silico drug design requires a model capturing the essential physical picture of the system and a proper theoretical protocol.
      PubDate: 2017-09-14T04:05:32.839522-05:
      DOI: 10.1002/anie.201707683
  • Analytical Description of NMR Relaxation Highlights Correlated Dynamics in
           Intrinsically Disordered Proteins
    • Authors: Nicola Salvi; Anton Abyzov, Martin Blackledge
      Abstract: The dynamic fluctuations of intrinsically disordered proteins (IDPs) define their function. Although experimental nuclear magnetic resonance (NMR) relaxation reveals the motional complexity of these highly flexible proteins, the absence of physical models describing IDP dynamics hinders their mechanistic interpretation. Combining molecular dynamics simulation and NMR, we introduce a framework in which distinct motions are attributed to local libration, backbone dihedral angle dynamics and longer-range tumbling of one or more peptide planes. This model provides unique insight into segmental organization of dynamics in IDPs and allows us to investigate the presence and extent of the correlated motions that are essential for function.Conformational dynamics of intrinsically disordered proteins (IDPs) define their biological function but remain poorly understood. By combining MD simulation and NMR distinct contributions to this motion are identified, including backbone dihedral jumps and longer-range segmental dynamics.
      PubDate: 2017-09-14T04:03:08.449031-05:
      DOI: 10.1002/anie.201706740
  • Evolution of the Ligand Shell Morphology during Ligand Exchange Reactions
           on Gold Nanoparticles
    • Authors: Zhi Luo; Jing Hou, Laure Menin, Quy Khac Ong, Francesco Stellacci
      Abstract: Ligand exchange reactions are used to achieve nanoparticles coated with a mixture of ligand molecules. Currently, nothing is known on the evolution of the morphology of the ligand shell during the reaction. Here, we use a recently developed method (based on MALDI-TOF) to follow the evolution of the ligand shell composition and morphology during the reaction. We observe the expected evolution in composition and we find that the ligand shell starts as a random mixture and gradually evolves towards a patchy morphology. When the composition has reached a plateau (i.e. when the reaction is generally assumed to be finished), the ligand shell morphology keeps evolving for days, slowly approaching its equilibrium configuration.Patchy ligand distributions: The evolution of the ligand shell morphology during ligand exchange reactions on surfaces of nanoparticles is elucidated for the first time. Kinetics and thermodynamics both play important roles on the formation of patchy domains at different reaction stages.
      PubDate: 2017-09-14T04:02:54.090413-05:
      DOI: 10.1002/anie.201708190
  • Electrochemically Enabled, Nickel-Catalyzed Amination
    • Authors: Chao Li; Yu Kawamata, Hugh Nakamura, Julien C. Vantourout, Zhiqing Liu, Qinglong Hou, Denghui Bao, Jeremy T. Starr, Jinshan Chen, Ming Yan, Phil S. Baran
      Abstract: Along with amide bond formation, Suzuki cross-coupling, and reductive amination, the Buchwald–Hartwig–Ullmann-type amination of aryl halides stands as one of the most employed reactions in modern medicinal chemistry. The work herein demonstrates the potential of utilizing electrochemistry to provide a complementary avenue to access such critical bonds using an inexpensive nickel catalyst under mild reaction conditions. Of note is the scalability, functional-group tolerance, rapid rate, and the ability to employ a variety of aryl donors (Ar−Cl, Ar−Br, Ar−I, Ar−OTf), amine types (primary and secondary), and even alternative X−H donors (alcohols and amides).Amination electrified: Arguably one of the most important types of bonds, the C−N bond, can now be forged under nickel-catalysis with the aid of electrochemistry. Broad scope, scalability, sustainability, mildness, and rapid reacion rates are some highlights of this interesting new reaction. Tf=trifluoromethanesulfonyl.
      PubDate: 2017-09-14T04:00:44.829819-05:
      DOI: 10.1002/anie.201707906
  • Synthesis of Acylborons by Ozonolysis of Alkenylboronates: Preparation of
           an Enantioenriched Amino Acid Acylboronate
    • Authors: Jumpei Taguchi; Toshiki Ikeda, Rina Takahashi, Ikuo Sasaki, Yasushi Ogasawara, Tohru Dairi, Naoya Kato, Yasunori Yamamoto, Jeffrey W. Bode, Hajime Ito
      Abstract: A concise synthesis of acylborons was achieved by ozonolysis of alkenyl MIDA (N-methyliminodiacetic acid) boronates. This reaction exhibits excellent functional group tolerance and is applicable to various acyl MIDA boronates and potassium acyltrifluroborates (KATs) that could not be synthesized by previous methods. In addition, α-amino acylborons, which would be essential for peptide ligations, were prepared for the first time. The acylboron of L-alanine was obtained in high enantiopurity and found to be configurationally stable. Oligopeptide synthesis between the α-amino KATs and amino acid in dilute aqueous media was studied.
      PubDate: 2017-09-14T02:06:53.766297-05:
      DOI: 10.1002/anie.201707933
  • Intrinsic Broadband White-Light Emission from Ultrastable, Cationic Lead
           Halide Layered Materials
    • Authors: Zewen Zhuang; Chengdong Peng, Guiyang Zhang, Huimin Yang, Jinlin Yin, Honghan Fei
      Abstract: We report a family of cationic lead halide layered materials, formulated as [Pb2X2]2+[−O2C(CH)2CO2−] (X = F, Cl, and Br), exhibiting pronounced broadband white-light emission in bulk form. These well-defined PbX-based structures achieve an external quantum efficiency as high as 11.8%, which is comparable to the highest reported value (~9%) for broadband phosphors based on layered organolead halide perovskites. More importantly, our cationic materials are long-sought ultrastable lead halide materials, which overcome the air/moisture-sensitivity problems of lead perovskites. In contrast to the perovskites and other bulk emitters, the white-light emission intensity of our materials remains undiminished after continuous UV irradiation for 30 days under atmospheric conditions (~60% relative humidity). Our initial mechanistic studies confirm that the broadband emission is ascribed to short-range electron-phonon coupling in the strongly deformable lattice and generated self-trapped carriers.
      PubDate: 2017-09-14T01:49:31.769728-05:
      DOI: 10.1002/anie.201706660
  • Toward Cost-effective Manufacturing of Si Solar Cells: Electrodeposition
           of High Quality Si Films in a CaCl2-based Molten Salt
    • Authors: Xiao Yang; Li Ji, Xingli Zou, Taeho Lim, Ji Zhao, Edward T Yu, Allen J. Bard
      Abstract: Electrodeposition of Si films from a Si-containing electrolyte is a cost-effective approach for the manufacturing of solar cells. Proposals relying on molten salts have suffered from low product quality due to difficulties in impurity control. Here we demonstrate a novel approach to electrodeposit high quality Si films from a CaCl2-based molten salt. Soluble SiIV−O anions generated from solid SiO2 are electrodeposited onto a graphite substrate to form a uniform layer of crystalline Si. Impurities in the deposited Si film are controlled at low concentrations (both B and P are less than 1 ppm). In the photoelectrochemical measurements, the Si film shows p-type semiconductor character and large photocurrent. A p-n junction fabricated from the deposited Si film exhibits clear photovoltaic effects. This study represents a first step to the ultimate goal of developing a cost-effective manufacturing process for Si solar cells based on electrodeposition.
      PubDate: 2017-09-13T13:23:57.815383-05:
      DOI: 10.1002/anie.201707635
  • A Self-Assembled Oligopeptide as a Versatile NMR Alignment Medium for the
           Measurement of Residual Dipolar Couplings in Methanol
    • Authors: Xinxiang Lei; Feng Qiu, Han Sun, Liwen Bai, Wen-Xuan Wang, Wensheng Xiang, Hongping Xiao
      Abstract: Residual dipolar coupling (RDC) is a powerful structural parameter for the determination of the constitution, conformation, and configuration of organic molecules. Herein, we report the first liquid crystal-based orienting medium that is compatible with MeOH, thus enabling RDC acquisitions of a wide range of intermediate to polar organic molecules. The liquid crystals were produced from self-assembled oligopeptide nanotubes (AAKLVFF), which are stable at very low concentrations. The presented alignment medium is highly homogeneous, and the size of RDCs can be scaled with the concentration of the peptide. To assess the accuracy of the RDC measurement by employing this new medium, seven bioactive natural products from different classes were chosen and analyzed. The straightforward preparation of the anisotropic alignment sample will offer a versatile and robust protocol for the routine RDC measurement of natural products.Alignment medium: A novel, robust, versatile anisotropic medium composed of self-assembled peptides, which are stable at very low concentrations, is used for the measurement of residual dipolar couplings (RDCs) in MeOH. The presented alignment medium is highly homogeneous, and the size of RDCs can be scaled with the concentration of the peptide.
      PubDate: 2017-09-13T13:07:05.512986-05:
      DOI: 10.1002/anie.201705123
  • The First Gold(III) Formate: Evidence for β-Hydride Elimination
    • Authors: Roopender Kumar; Jean-Philippe Krieger, Enrique Gómez-Bengoa, Thomas Fox, Anthony Linden, Cristina Nevado
      Abstract: The first stable gold(III) formate and experimental evidence for its β-hydride elimination are described. A catalytic dehydrogenation of formic acid together with mechanistic studies shed light on potential pathways operating in fundamental gold-catalyzed transformations.An anionic ligand exchange reaction on [(N^C^C)AuIIIF] in the presence of formic acid delivered the first example of a stable gold(III) formate. Its ability to undergo β-hydride elimination and its reactivity in the dehydrogenation of formic acid (FA) have been experimentally and computationally demonstrated.
      PubDate: 2017-09-13T13:06:47.848241-05:
      DOI: 10.1002/anie.201705557
  • Enzyme Activity by Design: An Artificial Rhodium Hydroformylase for Linear
    • Authors: Amanda G. Jarvis; Lorenz Obrecht, Peter J. Deuss, Wouter Laan, Emma K. Gibson, Peter P. Wells, Paul C. J. Kamer
      Abstract: Artificial metalloenzymes (ArMs) are hybrid catalysts that offer a unique opportunity to combine the superior performance of natural protein structures with the unnatural reactivity of transition-metal catalytic centers. Therefore, they provide the prospect of highly selective and active catalytic chemical conversions for which natural enzymes are unavailable. Herein, we show how by rationally combining robust site-specific phosphine bioconjugation methods and a lipid-binding protein (SCP-2L), an artificial rhodium hydroformylase was developed that displays remarkable activities and selectivities for the biphasic production of long-chain linear aldehydes under benign aqueous conditions. Overall, this study demonstrates that judiciously chosen protein-binding scaffolds can be adapted to obtain metalloenzymes that provide the reactivity of the introduced metal center combined with specifically intended product selectivity.Artificial metalloenzymes are hybrid catalysts that offer a unique opportunity to combine the superior performance of natural protein structures with the unnatural reactivity of transition-metal catalytic centers. An artificial rhodium hydroformylase has been developed that displays remarkable activities and selectivities in the biphasic production of long-chain linear aldehydes.
      PubDate: 2017-09-13T13:06:41.674987-05:
      DOI: 10.1002/anie.201705753
  • HKOH-1: A Highly Sensitive and Selective Fluorescent Probe for Detecting
           Endogenous Hydroxyl Radicals in Living Cells
    • Authors: Xiaoyu Bai; Yueyang Huang, Mingyang Lu, Dan Yang
      Abstract: The hydroxyl radical (.OH), one of the most reactive and deleterious reactive oxygen species (ROS), has been suggested to play an essential role in many physiological and pathological scenarios. However, a reliable and robust method to detect endogenous .OH is currently lacking owing to its extremely high reactivity and short lifetime. Herein we report a fluorescent probe HKOH-1 with superior in vitro selectivity and sensitivity towards .OH. With this probe, we have calibrated and quantified the scavenging capacities of a wide range of reported .OH scavengers. Furthermore, HKOH-1r, which was designed for better cellular uptake and retention, has performed robustly in detection of endogenous .OH generation by both confocal imaging and flow cytometry. Furthermore, this probe has been applied to monitor .OH generation in HeLa cells in response to UV light irradiation. Therefore, HKOH-1 could be used for elucidating .OH related biological functions.Highly sensitive and selective probes for hydroxyl radical detection have been developed. The fluorescent probe HKOH-1 has been applied in the screening of antioxidant capacities of several reported hydroxyl radical scavengers. Endogenous hydroxyl radical generation in multiple cell types has been detected with HKOH-1r by both confocal imaging and flow cytometry.
      PubDate: 2017-09-13T13:06:28.636869-05:
      DOI: 10.1002/anie.201705873
  • The Hydrophobic Gap at High Hydrostatic Pressures
    • Authors: Florian J. Wirkert; Christoph Hölzl, Michael Paulus, Paul Salmen, Metin Tolan, Dominik Horinek, Julia Nase
      Abstract: We have gained new insight into the so-called hydrophobic gap, a molecularly thin region of decreased electron density at the interface between water and a solid hydrophobic surface, by X-ray reflectivity experiments and molecular dynamics simulations at different hydrostatic pressures. Pressure variations show that the hydrophobic gap persists up to a pressure of 5 kbar. The electron depletion in the interfacial region strongly decreases with an increase in pressure, indicating that the interfacial region is compressed more strongly than bulk water. The decrease is most significant up to 2 kbar; beyond that, the pressure response of the depletion is less pronounced.The hydrophobic gap, a thin layer of decreased electron density at the interface between water and a solid hydrophobic surface, was studied by X-ray reflectivity experiments and molecular dynamics simulations. The electron depletion in the interfacial region strongly decreases with increasing hydrostatic pressure, which indicates that the interfacial region is compressed more strongly than bulk water. OTS=octadecyltrichlorosilane.
      PubDate: 2017-09-13T13:06:17.487731-05:
      DOI: 10.1002/anie.201706662
  • Highly Efficient Nondoped OLEDs with Negligible Efficiency Roll-Off
           Fabricated from Aggregation-Induced Delayed Fluorescence Luminogens
    • Authors: Jian Huang; Han Nie, Jiajie Zeng, Zeyan Zhuang, Shifeng Gan, Yuanjing Cai, Jingjing Guo, Shi-Jian Su, Zujin Zhao, Ben Zhong Tang
      Abstract: Purely organic emitters that can efficiently utilize triplet excitons are highly desired to cut the cost of organic light-emitting diodes (OLEDs), but most of them require complicated doping techniques for their fabrication and suffer from severe efficiency roll-off. Herein, we developed novel luminogens with weak emission and negligible delayed fluorescence in solution but strong emission with prominent delayed components upon aggregate formation, giving rise to aggregation-induced delayed fluorescence (AIDF). The concentration-caused emission quenching and exciton annihilation are well-suppressed, which leads to high emission efficiencies and efficient exciton utilization in neat films. Their nondoped OLEDs provide excellent electroluminescence efficiencies of 59.1 cd A−1, 65.7 lm W−1, and 18.4 %, and a negligible current efficiency roll-off of 1.2 % at 1000 cd m−2. Exploring AIDF luminogens for the construction of nondoped OLEDs could be a promising strategy to advance device efficiency and stability.Neat films of luminogens with aggregation-induced delayed fluorescence (AIDF) were employed in nondoped OLEDs. These systems afford remarkable current, power, and external quantum efficiencies as the concentration-caused emission quenching and exciton annihilation are well suppressed, which leads to high emission efficiencies and efficient exciton utilization in the neat films.
      PubDate: 2017-09-13T13:06:13.179823-05:
      DOI: 10.1002/anie.201706752
  • Selective Ring-Opening Polymerization of Non-Strained γ-Butyrolactone
           Catalyzed by A Cyclic Trimeric Phosphazene Base
    • Authors: Na Zhao; Chuanli Ren, Huaike Li, Yunxin Li, Shaofeng Liu, Zhibo Li
      Abstract: A new superbase, the cyclic trimeric phosphazene base (CTPB), was prepared with high yield and purity. In the presence of alcohol, the CTPB serves as a highly efficient organocatalyst for ring-opening polymerization of the “non-polymerizable” γ-butyrolactone to offer well-defined poly(γ-butyrolactone) with high conversions (up to 98 %) at −60 °C. The produced polymers have high molecular weights (up to 22.9 kg mol−1) and low polydispersity distributions (1.27–1.50). NMR analysis of initiation process and the structural analysis of resulting polymers by MALDI-TOF suggest a mechanism involving an activating initiator which leads only to linear polymers with BnO/H chain ends.Superbase! Sustainable poly(γ-butyrolactone) was prepared by ring-opening polymerization using a metal-free superbase, that is, a cyclic trimeric phosphazene base. The reaction features high conversion (up to 98%), high molecular weights (up to 22.9 kDa), and selective synthesis of the linear polymer.
      PubDate: 2017-09-13T13:06:07.459335-05:
      DOI: 10.1002/anie.201707122
  • High-Fidelity Multistate Switching with Anion–Anion and Acid–Anion
           Dimers of Organophosphates in Cyanostar Complexes
    • Authors: Wei Zhao; Bo Qiao, Chun-Hsing Chen, Amar H. Flood
      Abstract: The acid–base switching of complexes formed from anti-electrostatic anion–anion homodimers of organophosphates and cyanostar macrocycles was investigated for the first time. High-fidelity 2:2 complexes were selected by using suitably sized organo substituents. Reversible and direct switching occurs with triflic acid and hydroxide base. An unexpected acid⋅⋅⋅anion heterodimer was discovered with weaker picric acid, which helped reveal some of the elementary steps. Switching can also proceed in a cooperative (strong anion then weak acid) or stepwise manner (weak acid then strong anion).On–off relationship: Anions in high-fidelity 2:2 complexes formed from phosphate homodimers and cyanostar macrocycles switch directly in and out of the macrocycles when a strong base and acid is added, respectively. An unexpected complex of an acid–anion heterodimer was discovered in step-wise switching with weaker acids.
      PubDate: 2017-09-13T13:06:03.377165-05:
      DOI: 10.1002/anie.201707869
  • Between Localization and Delocalization: Ru(cod)2+ Units in the Zintl
           Clusters [Bi9{Ru(cod)}2]3− and [Tl2Bi6{Ru(cod)}]2−
    • Authors: Niels Lichtenberger; Nils Spang, Andreas Eichhöfer, Stefanie Dehnen
      Abstract: Reactions of [K(crypt-222)]2(TlBi3)⋅0.5 en (1 b) with [Ru(cod)(H2CC(Me)CH2)2] (A) in 1,2-diaminoethane (en) led to the formation of two compounds with new bismuth-rich cluster anions, [K(crypt-222)]3[Bi9{Ru(cod)}2]⋅1.5 en (2) and [K(crypt-222)]2[Tl2Bi6{Ru(cod)}]⋅2 tol (3), alongside the salt of a binary nido cluster, [K(crypt-222)]3(Tl4Bi5)⋅2 en (4). The anions in 2 and 3 are two further examples of rare heterometallic clusters containing Ru atoms. As one cod ligand is retained on each Ru atom in both clusters, the anions may be viewed as intermediates on the way towards larger, ligand-free intermetalloid clusters. Quantum-chemical studies provided insight into the bonding situation in these clusters. According to these studies, the anion of 2 features both electron-precise and electron-deficient parts. Electrospray ionization mass spectrometry analysis indicated that the clusters undergo stepwise fragmentation.A little bit of each: DFT studies confirm a hybrid bonding situation in [Bi9{Ru(cod)}2]3− with both localized and delocalized bonds. This cluster and [Tl2Bi6{Ru(cod)}]2− were obtained upon reaction of the binary Zintl anion (TlBi3)2− with [Ru(cod)(H2CC(Me)CH2)2]. Both clusters are rare examples of Zintl anions comprising Ru atoms and illustrate the electronic flexibility of Group 15 polyanions with (pseudo)atoms of other groups.
      PubDate: 2017-09-13T13:05:49.975701-05:
      DOI: 10.1002/anie.201707632
  • Cationic Nitrogen Doped Helical Nanographenes
    • Authors: Kun Xu; Xinliang Feng, Reinhard berger, Alexey A Popov, Jan J Weigand, Ilka Vincon, Peter Machata, Felix Hennersdorf, Youjia Zhou, Yubin Fu
      Abstract: Herein, we report on the synthesis of a series of novel cationic nitrogen doped nanographenes (CNDN) by rhodium catalyzed annulation reactions. This powerful method allows for the synthesis of cationic nanographenes with non-planar, axial chiral geometries. Single-crystal X-ray analysis reveals helical and cove-edged structures. Compared to their all-carbon analogues, the CNDN exhibit energetically lower lying frontier orbitals with a reduced optical energy gap and an electron accepting behavior. All derivatives show quasi reversible reductions in cyclic voltammetry. Depending on the number of nitrogen dopant, in situ spectroelectrochemistry proves the formation of neutral radicals (one nitrogen dopant) or radical cations (two nitrogen dopants) upon reduction. The developed synthetic protocol paves the way for the design and synthesis of expanded nanographenes or even graphene nanoribbons containing cationic nitrogen doping.
      PubDate: 2017-09-13T11:15:32.323487-05:
      DOI: 10.1002/anie.201707714
  • Multidimensional Correlations in Asymmetric Catalysis via Parameterization
           of Uncatalyzed Transition States
    • Authors: Manuel Orlandi; F. Dean Toste, Matthew S. Sigman
      Abstract: The study of the chiral anion phase transfer (CAPT) catalyzed oxidative amination of tetrahydroisoquinolines via multidimensional correlation analysis (MCA) is revisited. The parameterization of the transition states (TSs) for the uncatalyzed reaction, the introduction of conformational descriptors, and the use of computed interaction energies and distances as parameters allowed access to a considerably simplified mathematical correlation of substrate and catalyst structure to enantioselectivity. The equation obtained is suggestive of key interactions occurring at the TS. Specifically, the CAPT catalyst is proposed to coordinate the intermediate iminium cation by P=O∙∙∙H-O hydrogen bond and by N∙∙∙H-C electrostatic interaction. The conformational freedom of the substrate's benzyl substituent is also found to be important in order to provide an efficient mode of molecular recognition.
      PubDate: 2017-09-13T10:15:25.727454-05:
      DOI: 10.1002/anie.201707644
  • Cover Picture: Diazirines as Potential Molecular Imaging Tags: Probing the
           Requirements for Efficient and Long-Lived SABRE-Induced Hyperpolarization
           (Angew. Chem. Int. Ed. 40/2017)
    • Authors: Kun Shen; Angus W. J. Logan, Johannes F. P. Colell, Junu Bae, Gerardo X. Ortiz, Thomas Theis, Warren S. Warren, Steven J. Malcolmson, Qiu Wang
      Pages: 12015 - 12015
      Abstract: Diazirines are an attractive class of potential molecular tags for magnetic resonance imaging owing to their biocompatibility and ease of incorporation into a large variety of molecules. In their Communication on page 12112 ff., W. S. Warren, S. J. Malcolmson, Q. Wang, and co-workers show with a 15N2-diazirine-containing choline derivative that 15N2-diazirine motifs are capable of supporting long-lasting polarization by the simple SABRE-SHEATH hyperpolarization method, making then promising as tags for NMR/MRI imaging.
      PubDate: 2017-08-01T08:41:45.794772-05:
      DOI: 10.1002/anie.201707296
  • Inside Cover: Capturing Elusive Cobaltacycle Intermediates: A Real-Time
           Snapshot of the Cp*CoIII-Catalyzed Oxidative Alkyne Annulation (Angew.
           Chem. Int. Ed. 40/2017)
    • Authors: Jesús Sanjosé-Orduna; Daniel Gallego, Alèria Garcia-Roca, Eddy Martin, Jordi Benet-Buchholz, Mónica H. Pérez-Temprano
      Pages: 12016 - 12016
      Abstract: Over the past few years, Cp*CoIII complexes have demonstrated their potential to catalyze C−H functionalization. However, these systems remain in their infancy, especially concerning the lack of information on the mechanisms of these processes. In their Communication on page 12137 ff., M. H. Pérez-Temprano et al. describe the use of MeCN to capture highly reactive cobalt species and unravel previously inaccessible mechanistic features of Cp*CoIII-catalyzed C−H oxidative alkyne annulation.
      PubDate: 2017-08-03T05:01:22.175759-05:
      DOI: 10.1002/anie.201707433
  • Graphical Abstract: Angew. Chem. Int. Ed. 40/2017
    • Pages: 12019 - 12035
      PubDate: 2017-09-20T02:00:12.652192-05:
      DOI: 10.1002/anie.201784011
  • Spotlights on our sister journals: Angew. Chem. Int. Ed. 40/2017
    • Pages: 12038 - 12041
      PubDate: 2017-09-20T02:00:22.701813-05:
      DOI: 10.1002/anie.201784013
  • Andrey P. Antonchick
    • Pages: 12042 - 12042
      Abstract: “The secret of being a successful scientist is patience. My favorite name reaction is the Belousov–Zhabotinsky reaction ...” This and more about Andrey P. Antonchick can be found on page 12042.
      PubDate: 2017-05-10T07:36:17.910288-05:
      DOI: 10.1002/anie.201704212
  • Royal Society of Chemistry Prizes and Awards 2017
    • Pages: 12043 - 12044
      PubDate: 2017-08-28T12:40:48.411535-05:
      DOI: 10.1002/anie.201708393
  • Lewis Base Catalysis in Organic Synthesis. 3 Volume Set. Edited by Edwin
           Vedejs and Scott E. Denmark.
    • Authors: Marialuisa Aufiero; Ryan Gilmour
      Pages: 12045 - 12045
      Abstract: Wiley-VCH, Weinheim 2016. 1488 pp., hardcover, € 449.00.—ISBN 978-3527336180
      PubDate: 2017-08-18T01:20:20.482103-05:
      DOI: 10.1002/anie.201707836
  • Inhibition of Protein–Protein Interactions: New Options for Developing
           Drugs against Neglected Tropical Diseases
    • Authors: Thorsten Berg
      Pages: 12048 - 12050
      Abstract: Wake up! Sleeping sickness and Chagas disease are neglected tropical diseases caused by trypanosome infections. Small molecules that disrupt a crucial protein–protein interaction in the parasites offer a new approach to drug development for these diseases.
      PubDate: 2017-08-02T04:05:24.012665-05:
      DOI: 10.1002/anie.201706479
  • A Challenging Pie to Splice: Drugging the Spliceosome
    • Authors: Brian León; Manoj K. Kashyap, Warren C. Chan, Kelsey A. Krug, Januario E. Castro, James J. La Clair, Michael D. Burkart
      Pages: 12052 - 12063
      Abstract: Since its discovery in 1977, the study of alternative RNA splicing has revealed a plethora of mechanisms that had never before been documented in nature. Understanding these transitions and their outcome at the level of the cell and organism has become one of the great frontiers of modern chemical biology. Until 2007, this field remained in the hands of RNA biologists. However, the recent identification of natural product and synthetic modulators of RNA splicing has opened new access to this field, allowing for the first time a chemical-based interrogation of RNA splicing processes. Simultaneously, we have begun to understand the vital importance of splicing in disease, which offers a new platform for molecular discovery and therapy. As with many natural systems, gaining clear mechanistic detail at the molecular level is key towards understanding the operation of any biological machine. This minireview presents recent lessons learned in this emerging field of RNA splicing chemistry and chemical biology.Over the last decade, considerable effort has been directed at developing drugs that target the spliceosome. The resulting synthetic and natural product splice modulators have opened new avenues for the interrogation of disease-associated splicing events. In this Minireview, an overview is provided of the recent advances in addressing the chemistry and chemical biology of the spliceosome and modulating its action with small molecules.
      PubDate: 2017-08-15T02:17:16.035205-05:
      DOI: 10.1002/anie.201701065
  • Fervent Hype behind Magnesium Batteries: An Open Call to Synthetic
           Chemists—Electrolytes and Cathodes Needed
    • Authors: John Muldoon; Claudiu B. Bucur, Thomas Gregory
      Pages: 12064 - 12084
      Abstract: Magnesium metal is a superior anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of −2.37 V vs. the standard hydrogen electrode. A major benefit of magnesium is the apparent lack of dendrite formation during charging which is one of the crucial concerns of using a lithium metal anode. In this Review, we highlight the foremost research in the development of electrolytes and cathodes and discuss some of the significant challenges which must be overcome in realizing a practical magnesium battery.100 years after Grignard's Nobel Prize: Magnesium chemistry has been resurrected by the promise of a magnesium battery to rival the lithium battery. This Review is an invitation to synthetic chemists to enter and boost this hot energy storage field to the next level.
      PubDate: 2017-08-10T10:39:45.573063-05:
      DOI: 10.1002/anie.201700673
  • Facile One-Pot Synthesis of Functional Giant Polymeric Vesicles Controlled
           by Oscillatory Chemistry
    • Authors: Bishnu Prasad Bastakoti; Juan Perez-Mercader
      Pages: 12086 - 12091
      Abstract: We introduce a novel application of an oscillatory chemical reaction to the synthesis of block copolymers. The Belousov–Zhabotinsky (B-Z) reaction is coupled with the polymerization of an amphiphilic block copolymer. Radicals generated in the B-Z reaction initiate the polymerization between a polyethylene glycol (PEG) macroreversible addition-fragmentation chain-transfer agent and butyl acrylate monomers. The attachment of a hydrophobic block on PEG leads to self-assembly and formation of spherical micelles. The nanoscale micelles transform into submicrometer vesicles and grow to giant vesicles as a consequence of the oscillatory behavior of the B-Z reaction. The one-pot synthesis of an amphiphilic di-block copolymer and retention of oscillatory behavior for the B-Z reaction with the formation of giant vesicles bring a new insight into possible pathways for the synthesis of active functional microreactors in the range from hundreds of nanometers to tens of micrometers.Get into the swing of things: An oscillatory chemical reaction is used to synthesize self-assembling active giant polymeric vesicles in one pot. The hydrophobic block on polyethylene glycol (PEG) undergoes self-assembly to form vesicles. The green squiggly line represents the PEG, the red star is the chain transfer agent (CTA), the yellow diamonds are components of the Belousov-Zhabotinsky reaction, and the purple spheres are monomer units.
      PubDate: 2017-07-24T03:36:58.027883-05:
      DOI: 10.1002/anie.201703816
  • Ultrafast Light-Driven Substrate Expulsion from the Active Site of a
           Photoswitchable Catalyst
    • Authors: Manuel D. Pescher; Luuk J. G. W. van Wilderen, Susanne Grützner, Chavdar Slavov, Josef Wachtveitl, Stefan Hecht, Jens Bredenbeck
      Pages: 12092 - 12096
      Abstract: The photoswitchable piperidine general base catalyst is a prototype structure for light control of catalysis. Its azobenzene moiety moves sterically shielding groups to either protect or expose the active site, thereby changing the basicity and hydrogen-bonding affinity of the compound. The reversible switching dynamics of the catalyst is probed in the infrared spectral range by monitoring hydrogen bond (HB) formation between its active site and methanol (MeOH) as HB donor. Steady-state infrared (IR) and ultrafast IR and UV/Vis spectroscopies are used to uncover ultrafast expulsion of MeOH from the active site within a few picoseconds. Thus, the force generated by the azobenzene moiety even in the final phase of its isomerization is sufficient to break a strong HB within 3 ps and to shut down access to the active site.Light-controlled catalysis: Switching of the azobenzene moiety moves the steric shielding groups on an ultrafast time scale, expelling a strongly hydrogen-bonded binding partner from the active site. The catalyst is deactivated by blocking access to the binding site.
      PubDate: 2017-08-23T12:37:20.545062-05:
      DOI: 10.1002/anie.201702861
  • Porphyrin Antennas on Carbon Nanodots: Excited State Energy and Electron
    • Authors: Francesca Arcudi; Volker Strauss, Luka Đorđević, Alejandro Cadranel, Dirk M. Guldi, Maurizio Prato
      Pages: 12097 - 12101
      Abstract: We report the synthesis and electron donor–acceptor features of a novel nanohybrid, in which the light-harvesting and electron-donating properties of a meso-tetraarylporphyrin (TArP) are combined with the electron-accepting features of nitrogen-doped carbon nanodots (NCNDs). In particular, in an ultrafast process (>1012 s−1), visible-light excitation transforms the strongly quenched porphyrin singlet excited states into short-lived (225 ps) charge-separated states. On the other hand, ultraviolet light excitation triggers a non-resolvable transduction of singlet excited state energy from the NCNDs to the porphyrins, followed by the same charge separation observed upon visible light excitation.Antennas up! The synthesis and electron donor–acceptor features of a novel hybrid nanomaterial are reported. The nanohybrid combines the light-harvesting and electron-donating properties of a meso-tetraarylporphyrin (TArP) with the electron-accepting features of nitrogen-doped carbon nanodots (NCNDs).
      PubDate: 2017-08-24T03:52:57.908229-05:
      DOI: 10.1002/anie.201704544
  • Nanoscale Metal–Organic Layers for Deeply Penetrating X-ray-Induced
           Photodynamic Therapy
    • Authors: Guangxu Lan; Kaiyuan Ni, Ruoyu Xu, Kuangda Lu, Zekai Lin, Christina Chan, Wenbin Lin
      Pages: 12102 - 12106
      Abstract: We report the rational design of metal–organic layers (MOLs) that are built from [Hf6O4(OH)4(HCO2)6] secondary building units (SBUs) and Ir[bpy(ppy)2]+- or [Ru(bpy)3]2+-derived tricarboxylate ligands (Hf-BPY-Ir or Hf-BPY-Ru; bpy=2,2′-bipyridine, ppy=2-phenylpyridine) and their applications in X-ray-induced photodynamic therapy (X-PDT) of colon cancer. Heavy Hf atoms in the SBUs efficiently absorb X-rays and transfer energy to Ir[bpy(ppy)2]+ or [Ru(bpy)3]2+ moieties to induce PDT by generating reactive oxygen species (ROS). The ability of X-rays to penetrate deeply into tissue and efficient ROS diffusion through ultrathin 2D MOLs (ca. 1.2 nm) enable highly effective X-PDT to afford superb anticancer efficacy.Ultrathin: Heavy Hf atoms in the secondary building units (SBUs) of ultrathin metal–organic layers (MOLs) efficiently absorb X-rays and transfer energy to the Ir[bpy(ppy)2]+ or [Ru(bpy)3]2+ moieties to induce photodynamic therapy (PDT) by generating reactive oxygen species (ROS). Deep tissue penetration of X-rays, high 1O2 quantum yields, and efficient ROS diffusion allow for regression of tumors via MOL-mediated, X-ray-induced PDT treatments.
      PubDate: 2017-08-25T05:26:27.870459-05:
      DOI: 10.1002/anie.201704828
  • Chemical Origin of the Stability Difference between Copper(I)- and
           Silver(I)-Based Halide Double Perovskites
    • Authors: Zewen Xiao; Ke-Zhao Du, Weiwei Meng, David B. Mitzi, Yanfa Yan
      Pages: 12107 - 12111
      Abstract: Recently, CuI- and AgI-based halide double perovskites have been proposed as promising candidates for overcoming the toxicity and instability issues inherent within the emerging Pb-based halide perovskite absorbers. However, up to date, only AgI-based halide double perovskites have been experimentally synthesized; there are no reports on successful synthesis of CuI-based analogues. Here we show that, owing to the much higher energy level for the Cu 3d10 orbitals than for the Ag 4d10 orbitals, CuI atoms energetically favor 4-fold coordination, forming [CuX4] tetrahedra (X=halogen), but not 6-fold coordination as required for [CuX6] octahedra. In contrast, AgI atoms can have both 6- and 4-fold coordinations. Our density functional theory calculations reveal that the synthesis of CuI halide double perovskites may instead lead to non-perovskites containing [CuX4] tetrahedra, as confirmed by our material synthesis efforts.Tetrahedra preferred: Owing to the high-energy level for the Cu 3d10 orbitals, CuI atoms energetically do not favor the 6-fold coordination required for [CuX6] octahedra. DFT and experimental studies reveal that the CuI halide double perovskites are thermodynamically unstable against decomposition into products containing [CuX4] tetrahedra.
      PubDate: 2017-08-23T12:40:26.655589-05:
      DOI: 10.1002/anie.201705113
  • Diazirines as Potential Molecular Imaging Tags: Probing the Requirements
           for Efficient and Long-Lived SABRE-Induced Hyperpolarization
    • Authors: Kun Shen; Angus W. J. Logan, Johannes F. P. Colell, Junu Bae, Gerardo X. Ortiz, Thomas Theis, Warren S. Warren, Steven J. Malcolmson, Qiu Wang
      Pages: 12112 - 12116
      Abstract: Diazirines are an attractive class of potential molecular tags for magnetic resonance imaging owing to their biocompatibility and ease of incorporation into a large variety of molecules. As recently reported, 15N2-diazirine can be hyperpolarized by the SABRE-SHEATH method, sustaining both singlet and magnetization states, thus offering a path to long-lived polarization storage. Herein, we show the generality of this approach by illustrating that the diazirine tag alone is sufficient for achieving excellent signal enhancements with long-lasting polarization. Our investigations reveal the critical role of Lewis basic additives, including water, on achieving SABRE-promoted hyperpolarization. The application of this strategy to a 15N2-diazirine-containing choline derivative demonstrates the potential of 15N2-diazirines as molecular imaging tags for biomedical applications.Tag team: 15N2-diazirine motifs are demonstrated to be capable of supporting long-lasting polarization by the experimentally simple and cost-effective hyperpolarization method of SABRE-SHEATH, presenting promising potential as molecular tags for NMR/MRI imaging.
      PubDate: 2017-07-24T14:52:22.371211-05:
      DOI: 10.1002/anie.201704970
  • Perfluoroaryl Azide Staudinger Reaction: A Fast and Bioorthogonal Reaction
    • Authors: Madanodaya Sundhoro; Seaho Jeon, Jaehyeung Park, Olof Ramström, Mingdi Yan
      Pages: 12117 - 12121
      Abstract: We report a fast Staudinger reaction between perfluoroaryl azides (PFAAs) and aryl phosphines, which occurs readily under ambient conditions. A rate constant as high as 18 m−1 s−1 was obtained between methyl 4-azido-2,3,5,6-tetrafluorobenzoate and methyl 2-(diphenylphosphanyl)benzoate in CD3CN/D2O. Furthermore, the iminophosphorane product was stable toward hydrolysis and aza-phosphonium ylide reactions. This PFAA Staudinger reaction proved to be an excellent bioothorgonal reaction. PFAA-derivatized mannosamine and galactosamine were successfully transformed into cell-surface glycans and efficiently labeled with phosphine-derivatized fluorophore-conjugated bovine serum albumin.Better, faster, stronger: Perfluoroaryl azides (PFAAs) react with aryl phosphines in a fast Staudinger reaction under ambient conditions to yield kinetically stable iminophosphorane products. This PFAA Staudinger reaction proved to be an excellent bioorthogonal reaction and was successfully applied to cell-surface labeling.
      PubDate: 2017-09-01T03:56:16.754366-05:
      DOI: 10.1002/anie.201705346
  • Functional Molecular Junctions Derived from Double Self-Assembled
    • Authors: Sohyeon Seo; Eunhee Hwang, Yunhee Cho, Junghyun Lee, Hyoyoung Lee
      Pages: 12122 - 12126
      Abstract: Information processing using molecular junctions is becoming more important as devices are miniaturized to the nanoscale. Herein, we report functional molecular junctions derived from double self-assembled monolayers (SAMs) intercalated between soft graphene electrodes. Newly assembled molecular junctions are fabricated by placing a molecular SAM/(top) electrode on another molecular SAM/(bottom) electrode by using a contact-assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions. Robust contact-assembled molecular junctions can act as platforms for the development of equivalent contact molecular junctions between top and bottom electrodes, which can be applied independently to different kinds of molecules to enhance either the structural complexity or the assembly properties of molecules.Mind the gap: Functional molecular junctions derived from double self-assembled monolayers (SAMs) intercalated between soft graphene electrodes are fabricated by using a contact-assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions.
      PubDate: 2017-08-24T03:52:43.748435-05:
      DOI: 10.1002/anie.201705518
  • Microfluidic Lithography of Bioinspired Helical Micromotors
    • Authors: Yunru Yu; Luoran Shang, Wei Gao, Ze Zhao, Huan Wang, Yuanjin Zhao
      Pages: 12127 - 12131
      Abstract: Considerable efforts have been devoted to developing artificial micro/nanomotors that can convert energy into movement. A flow lithography integrated microfluidic spinning and spiraling system is developed for the continuous generation of bioinspired helical micromotors. Because the generation processes could be precisely tuned by adjusting the flow rates and the illuminating frequency, the length, diameter, and pitch of the helical micromotors were highly controllable. Benefiting from the fast online gelation and polymerization, the resultant helical micromotors could be imparted with Janus, triplex, and core–shell cross-sectional structures that have never been achieved by other methods. Owing to the spatially controlled encapsulation of functional nanoparticles in the microstructures, the helical micromotors can perform locomotion not only by magnetically actuated rotation or corkscrew motion but also through chemically powered catalytic reaction.Bioinspired helical micromotors with Janus, triplex, and core–shell cross-sectional structures were precisely generated from a flow lithography integrated microfluidic spinning and spiraling system. The helical micromotors can perform locomotion not only by magnetically actuated rotation or corkscrew motion but also through chemically powered catalytic reaction.
      PubDate: 2017-08-23T12:41:24.061799-05:
      DOI: 10.1002/anie.201705667
  • Hydrogels with Reversible Mechanics to Probe Dynamic Cell
    • Authors: Adrianne M. Rosales; Sebastián L. Vega, Frank W. DelRio, Jason A. Burdick, Kristi S. Anseth
      Pages: 12132 - 12136
      Abstract: The relationship between ECM mechanics and cell behavior is dynamic, as cells remodel and respond to changes in their local environment. Most in vitro substrates are static and supraphysiologically stiff; thus, platforms with dynamic and reversible mechanical changes are needed. Herein, we developed hyaluronic acid-based substrates capable of sequential photodegradation and photoinitiated crosslinking reactions to soften and then stiffen the hydrogels over a physiologically relevant range of moduli. Reversible mechanical signaling to adhered cells was demonstrated with human mesenchymal stem cells. In situ hydrogel softening (from ca. 14 to 3.5 kPa) led to a decrease in the cell area and nuclear localization of YAP/TAZ, and subsequent stiffening (from ca. 3.5 to 28 kPa) increased the cell area and nuclear localization of YAP/TAZ. Each photoreaction was cytocompatible and tunable, rendering this platform amenable to studies of dynamic mechanics on cell behavior across many cell types and contexts.Hydrogels with reversible mechanics have been developed from hyaluronic acid polymers capable of photodegradation and photopolymerization, capturing dynamic aspects of native microenvironments. Cellular mechanosensing was demonstrated with human mesenchymal stem cells as the substrate mechanics changed in situ.
      PubDate: 2017-09-01T03:50:38.728875-05:
      DOI: 10.1002/anie.201705684
  • Capturing Elusive Cobaltacycle Intermediates: A Real-Time Snapshot of the
           Cp*CoIII-Catalyzed Oxidative Alkyne Annulation
    • Authors: Jesús Sanjosé-Orduna; Daniel Gallego, Alèria Garcia-Roca, Eddy Martin, Jordi Benet-Buchholz, Mónica H. Pérez-Temprano
      Pages: 12137 - 12141
      Abstract: Despite Cp*CoIII catalysts having emerged as a very attractive alternative to noble transition metals for the construction of heterocyclic scaffolds through C−H activation, the structure of the reactive species remains uncertain. Herein, we report the identification and unambiguous characterization of two long-sought cyclometalated Cp*CoIII complexes that have been proposed as key intermediates in C−H functionalization reactions. The addition of MeCN as a stabilizing ligand plays a crucial role, allowing the access to otherwise highly reactive species. Mechanistic investigations demonstrate the intermediacy of these species in oxidative annulations with alkynes, including the direct observation, under catalytic conditions, of a previously elusive post-migratory insertion seven-membered cobaltacycle.Cyclic Co complex caught: The first direct observation and full characterization of elusive cobaltacycle species in Cp*CoIII-catalyzed C−H oxidative alkyne annulation is reported. The exceptional ability of MeCN to stabilize otherwise highly reactive intermediates has paved the way to uncover previously inaccessible mechanistic features of these transformations.
      PubDate: 2017-06-28T06:47:03.701606-05:
      DOI: 10.1002/anie.201704744
  • Neodymium(III) Complexes Capable of Multi-Electron Redox Chemistry
    • Authors: Ezra J. Coughlin; Matthias Zeller, Suzanne C. Bart
      Pages: 12142 - 12145
      Abstract: A family of neodymium complexes featuring a redox-active ligand in three different oxidation states has been synthesized, including the iminoquinone (L0) derivative, (dippiq)2NdI3 (1-iq), the iminosemiquinone (L1−) compound, (dippisq)2NdI(THF) (1-isq), and the amidophenolate (L2−) [K(THF)2][(dippap)2Nd(THF)2] (1-ap) and [K(18-crown-6)][(dippap)2Nd(THF)2] (1-ap crown) species. Full spectroscopic and structural characterization of each derivative established the +3 neodymium oxidation state with redox chemistry occurring at the ligand rather than the neodymium center. Oxidation with elemental chalcogens showed the reversible nature of the ligand-mediated reduction process, forming the iminosemiquinone metallocycles, [K(18-crown-6)][(dippisq)2Nd(S5)] (2-isq crown) and [K(18-crown-6)(THF)][(dippisq)2Nd(Se5)] (3-isq crown), which are characterized to contain a 6-membered twist-boat ring.A twist on Ln3+ chemistry: A family of neodymium complexes featuring a redox-active ligand in three different oxidation states has been synthesized. Spectroscopic and structural characterization established NdIII centers with redox chemistry occurring at the ligand. Oxidation with elemental chalcogens showed the reversible nature of the ligand-mediated reduction process.
      PubDate: 2017-08-30T11:13:01.018916-05:
      DOI: 10.1002/anie.201705423
  • Fast Adsorption of Soft Hydrogel Microspheres on Solid Surfaces in Aqueous
    • Authors: Shusuke Matsui; Takuma Kureha, Seina Hiroshige, Mikihiro Shibata, Takayuki Uchihashi, Daisuke Suzuki
      Pages: 12146 - 12149
      Abstract: The real-time adsorption behavior of polymeric colloidal microspheres onto solid surfaces in aqueous solution was visualized for the first time using high-speed atomic force microscopy (HS-AFM) to reveal how the softness of the microspheres affects their dynamic adsorption. Studies that focus on the deformability of microspheres upon dynamic adsorption have not yet been reported, most likely on account of a lack of techniques that appropriately depict the dynamic adsorption and deformation behavior of individual microspheres at the nanoscale in real time. In this study, the deformability of microspheres plays a crucial role on the adsorption kinetics, that is, soft hydrogel microspheres adsorb faster than harder elastomeric or rigid microspheres. These results should provide insight towards development of new colloidal nanomaterials that exhibit effective adsorption on specific sites in aqueous solution.A soft landing: The detailed adsorption and deformation kinetics of polymeric colloidal microspheres on solid surfaces in aqueous solution under flow conditions were examined by high-speed atomic force microscopy (HS-AFM). The elasticity (deformability) of the microspheres crucially affects their adsorption kinetics.
      PubDate: 2017-08-25T05:23:10.609281-05:
      DOI: 10.1002/anie.201705808
  • Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10
           Two-Dimensional Multilayered Perovskite Ferroelectric for a
           High-Performance Photodetector
    • Authors: Lina Li; Zhihua Sun, Peng Wang, Weida Hu, Sasa Wang, Chengmin Ji, Maochun Hong, Junhua Luo
      Pages: 12150 - 12154
      Abstract: Two-dimensional (2D) layered hybrid perovskites have shown great potential in optoelectronics, owing to their unique physical attributes. However, 2D hybrid perovskite ferroelectrics remain rare. The first hybrid ferroelectric with unusual 2D multilayered perovskite framework, (C4H9NH3)2(CH3NH3)2Pb3Br10 (1), has been constructed by tailored alloying of the mixed organic cations into 3D prototype of CH3NH3PbBr3. Ferroelectricity is created through molecular reorientation and synergic ordering of organic moieties, which are unprecedented for the known 2D multilayered hybrid perovskites. Single-crystal photodetectors of 1 exhibit fascinating performances, including extremely low dark currents (ca. 10−12 A), large on/off current ratios (ca. 2.5×103), and very fast response rate (ca. 150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH3NH3PbI3.A 2D multilayered perovskite hybrid ferroelectric was constructed by alloying mixed organic cations into the 3D perovskite prototype of CH3NH3PbBr3. Ferroelectric single-crystal photodetectors show exceptional behavior, including extremely low dark current (ca. 10−12 A), large on/off current ratio (ca. 2.5×103), and a very fast response rate (ca. 150 μs).
      PubDate: 2017-09-05T06:30:36.398045-05:
      DOI: 10.1002/anie.201705836
  • Polyladderane Constructed from a Gemini Monomer through Photoreaction
    • Authors: Zhihan Wang; Benjamin Miller, Jonathan Butz, Katelyn Randazzo, Zijun D. Wang, Qianli R. Chu
      Pages: 12155 - 12159
      Abstract: Polyladderane, the first polymer to contain the ladderane functional group, was synthesized from a gemini monomer through photoreaction in the solid state. The modular design of the gemini monomers used to create polyladderane allowed specific structural modification, resulting in the formation of two distinct polymer products. Monomers were synthesized by connecting two photoreactive units, either sorbic acids (monomer I) or 2-furanacrylic acids (monomer II), with a 1,4-butanediol linker. Single-crystal X-ray diffraction analysis of the monomers confirmed that they packed in the desired head-to-tail orientation and within a viable distance for photoreaction by electronically complementary interaction. Pre-organized gemini monomers were irradiated with UV light and monitored by FT-IR. Two polyladderanes with cis,anti,cis-[3]-ladderane as a characteristic functional group were constructed stereospecifically in 24–36 hours.Two polyladderanes with cis,anti,cis-[3]-ladderane as a characteristic functional group were synthesized from a gemini monomer through photoreaction in the solid state. A key intermediate captured in single-crystal-to-single-crystal experiments, and the isolation and characterization of a ladderane dimer provided direct evidence of newly formed cyclobutane rings.
      PubDate: 2017-08-25T05:22:32.308384-05:
      DOI: 10.1002/anie.201705937
  • Organic Nanocrystals with Bright Red Persistent Room-Temperature
           Phosphorescence for Biological Applications
    • Authors: S. M. Ali Fateminia; Zhu Mao, Shidang Xu, Zhiyong Yang, Zhenguo Chi, Bin Liu
      Pages: 12160 - 12164
      Abstract: Persistent room-temperature phosphorescence (RTP) in pure organic materials has attracted great attention because of their unique optical properties. The design of organic materials with bright red persistent RTP remains challenging. Herein, we report a new design strategy for realizing high brightness and long lifetime of red-emissive RTP molecules, which is based on introducing an alkoxy spacer between the hybrid units in the molecule. The spacer offers easy Br−H bond formation during crystallization, which also facilitates intermolecular electron coupling to favor persistent RTP. As the majority of RTP compounds have to be confined in a rigid environment to quench nonradiative relaxation pathways for bright phosphorescence emission, nanocrystallization is used to not only rigidify the molecules but also offer the desirable size and water-dispersity for biomedical applications.Nevertheless, RTP persisted: A bright pure organic compound with red persistent room-temperature phosphorescence (RTP) is synthesized. Its nanocrystals show excellent biocompatibility, water dispersity, and retention of bright phosphorescence in aqueous media, which show great potential for bioimaging.
      PubDate: 2017-08-23T12:38:08.462922-05:
      DOI: 10.1002/anie.201705945
  • On-Surface Formation of Cumulene by Dehalogenative Homocoupling of Alkenyl
    • Authors: Qiang Sun; Bay V. Tran, Liangliang Cai, Honghong Ma, Xin Yu, Chunxue Yuan, Meike Stöhr, Wei Xu
      Pages: 12165 - 12169
      Abstract: The on-surface activation of carbon–halogen groups is an efficient route to produce radicals for constructing various hydrocarbons and carbon nanostructures. To date, the employed halide precursors have only one halogen attached to a carbon atom. It is thus of interest to study the effect of attaching more than one halogen atom to a carbon atom with the aim of producing multiple unpaired electrons. By introducing an alkenyl gem-dibromide, cumulene products were fabricated on a Au(111) surface by dehalogenative homocoupling reactions. The reaction products and pathways were unambiguously characterized by a combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy measurements together with density functional calculations. This study further supplements the database of on-surface synthesis strategies and provides a facile manner for incorporation of more complicated carbon scaffolds into surface nanostructures.A gem of a reaction: Cumulene products have been sucessfully fabricated on a Au(111) surface by introducing dehalogenative homocoupling reactions of alkenyl gem-dibromides.
      PubDate: 2017-08-28T12:42:25.762014-05:
      DOI: 10.1002/anie.201706104
  • Enzyme-Responsive LipoCEST Agents: Assessment of MMP-2 Activity by
           Measuring the Intra-liposomal Water 1H NMR Shift
    • Authors: Giuseppe Ferrauto; Enza Di Gregorio, Marta Ruzza, Valeria Catanzaro, Sergio Padovan, Silvio Aime
      Pages: 12170 - 12173
      Abstract: Mobile proton-containing solutes can be detected by MRI by the chemical exchange saturation transfer (CEST) method. CEST sensitivity is dramatically enhanced by using, as exchanging protons, the water molecules confined inside liposomes, shifted by a paramagnetic shift reagent. The chemical shift of the intraliposomal water resonance (δIL) is affected by the overall shape of the supramolecular system. δIL of a spherical LipoCEST acts as a sensitive reporter of the distribution of streptavidin proteins anchored at the liposome surface by biotinylated phospholipids. This finding prompted the design of a MMP-2 responsive LipoCEST agent as the streptavidin moieties can be released from the liposome surfaces when a properly tailored enzyme-cleavable peptide is inserted on the phospholipids before the terminal biotin residues. δIL reports on the overall changes in the supramolecular architecture associated to the cleavage carried out by MMP-2.Biotinylated LipoCEST agents change the chemical shift of the intraliposomal water resonance when bound to streptavidin (see picture; gray). Upon introducing a MMP-2 cleavable moiety in the biotinylated substrate, an enzyme-responsive LipoCEST agent is generated. The change in the intraliposomal water chemical shift reports on the MMP-2 activity. Biotin: blue, Tm-HPDO3A shift agent: yellow spheres.
      PubDate: 2017-08-25T05:22:15.336193-05:
      DOI: 10.1002/anie.201706271
  • Self-Assembled Luminescent Quantum Dots To Generate Full-Color and White
           Circularly Polarized Light
    • Authors: Shengwei Huo; Pengfei Duan, Tifeng Jiao, Qiuming Peng, Minghua Liu
      Pages: 12174 - 12178
      Abstract: The design and fabrication of quantum dots (QDs) with circularly polarized luminescence (CPL) has been a great challenge in developing chiroptical materials. We herein propose an alternative to the use of chiral capping reagents on QDs for the fabrication of CPL-active QDs that is based on the supramolecular self-assembly of achiral QDs with chiral gelators. Full-color-tunable CPL-active QDs were obtained by simple mixing or gelation of a chiral gelator and achiral 3-mercaptopropionic acid capped QDs. In addition, the handedness of the CPL can be controlled by the supramolecular chirality of the gels. Moreover, QDs with circularly polarized white light emission were fabricated for the first time by tuning the blending ratio of colorful QDs in the gel. The chirality transfer in the co-assembly of the achiral QDs with the gelator and the spacer effect of the capping reagents on the QD surface are also discussed. This work provides new insight into the design of functional chiroptical materials.Circularly polarized luminescence (CPL) was observed for various co-gels with nanotube structures that had been assembled from achiral quantum dots (QDs) and a chiral lipid gelator. Full-color and white CPL was achieved through mixing several QDs with different colors with the chiral gelator.
      PubDate: 2017-08-24T13:05:39.054064-05:
      DOI: 10.1002/anie.201706308
  • β-Lactam Synthesis through Diodomethane Addition to Amide Dianions
    • Authors: Alaa Zidan; Julian Garrec, Marie Cordier, Abeer M. El-Naggar, Nour E. A. Abd El-Sattar, Ali Khalil Ali, Mohamed Ali Hassan, Laurent El Kaim
      Pages: 12179 - 12183
      Abstract: We present a novel route for the quick and easy synthesis of a broad range of β-lactams. The synthesis involves a [3+1] cyclization of amide dianions with diiodomethane. In contrast to the seminal work of Hirai et al. from 1979, the reaction proved to be a general and efficient approach towards azetidinones. The ease of the process was confirmed by DFT calculations and its power demonstrated by a diversity-oriented synthesis of β-lactams with four points of diversity determined by the choice of Ugi adducts as starting materials.Old dog new tricks: A facile synthesis of a broad range of β-lactams through [3+1] cyclization of amide dianions with diiodomethane was developed. In contrast to the seminal work of Hirai et al. from 1979, the reaction proved to be a general and efficient approach towards azetidinones. The utility of the process was demonstrated by a diversity-oriented synthesis of β-lactams with four points of diversity determined by the choice of Ugi adducts as starting materials.
      PubDate: 2017-08-24T03:51:44.394424-05:
      DOI: 10.1002/anie.201706315
  • Highly Regioselective Alkylation of Hexabenzocoronenes: Fundamental
           Insights into the Covalent Chemistry of Graphene
    • Authors: Johannes Holzwarth; Konstantin Yu. Amsharov, Dmitry I. Sharapa, David Reger, Kateryna Roshchyna, Dominik Lungerich, Norbert Jux, Frank Hauke, Timothy Clark, Andreas Hirsch
      Pages: 12184 - 12190
      Abstract: Hexa-peri-hexabenzocoronides (HBC) was successfully used as a model system for investigating the complex mechanism of the reductive functionalization of graphene. The well-defined molecular HBC system enabled deeper insights into the mechanism of the alkylation of reductively activated nanographenes. The separation and complete characterization of alkylation products clearly demonstrate that nanographene functionalization proceeds with exceptionally high regio- and stereoselectivities on the HBC scaffold. Experimental and theoretical studies lead to the conclusion that the intact basal graphene plane is chemically inert and addend binding can only take place at either preexisting defects or close to the periphery.In ‘plane' view: Experimental and theoretical studies lead to the conclusion that the intact basal graphene plane is chemically inert and addend binding can only take place at either preexisting defects or close to the periphery. The free movement of alkyl radicals (see picture) in the neutral van der Waals complex HBC-R. is a key step of the entire sequence. HBC=hexa-peri-hexabenzocoronide.
      PubDate: 2017-08-23T12:37:59.65692-05:0
      DOI: 10.1002/anie.201706437
  • Atomic-Level Insight into Optimizing the Hydrogen Evolution Pathway over a
           Co1-N4 Single-Site Photocatalyst
    • Authors: Yuanjie Cao; Si Chen, Qiquan Luo, Huan Yan, Yue Lin, Wei Liu, Linlin Cao, Junling Lu, Jinlong Yang, Tao Yao, Shiqiang Wei
      Pages: 12191 - 12196
      Abstract: Knowledge of the photocatalytic H2 evolution mechanism is of great importance for designing active catalysts toward a sustainable energy supply. An atomic-level insight, design, and fabrication of single-site Co1-N4 composite as a prototypical photocatalyst for efficient H2 production is reported. Correlated atomic characterizations verify that atomically dispersed Co atoms are successfully grafted by covalently forming a Co1-N4 structure on g-C3N4 nanosheets by atomic layer deposition. Different from the conventional homolytic or heterolytic pathway, theoretical investigations reveal that the coordinated donor nitrogen increases the electron density and lowers the formation barrier of key Co hydride intermediate, thereby accelerating H–H coupling to facilitate H2 generation. As a result, the composite photocatalyst exhibits a robust H2 production activity up to 10.8 μmol h−1, 11 times higher than that of pristine counterpart.A good Co single site: A single-site Co1-N4 structure grafted on polymeric g-C3N4 was prepared for efficient and stable photocatalytic H2 generation. Atomic-level characterization and calculations provide insight into a nitrogen-optimized H2 evolution pathway occurring on an active Co site.
      PubDate: 2017-08-28T12:41:24.125143-05:
      DOI: 10.1002/anie.201706467
  • C−H Activation from Iron(II)-Nitroxido Complexes
    • Authors: Claudia Kleinlein; Andrew J. Bendelsmith, Shao-Liang Zheng, Theodore A. Betley
      Pages: 12197 - 12201
      Abstract: The reaction of nitroxyl radicals TEMPO (2,2′,6,6′-tetramethylpiperidinyloxyl) and AZADO (2-azaadamantane-N-oxyl) with an iron(I) synthon affords iron(II)-nitroxido complexes (ArL)Fe(κ1-TEMPO) and (ArL)Fe(κ2-N,O-AZADO) (ArL=1,9-(2,4,6-Ph3C6H2)2-5-mesityldipyrromethene). Both high-spin iron(II)-nitroxido species are stable in the absence of weak C−H bonds, but decay via N−O bond homolysis to ferrous or ferric iron hydroxides in the presence of 1,4-cyclohexadiene. Whereas (ArL)Fe(κ1-TEMPO) reacts to give a diferrous hydroxide [(ArL)Fe]2(μ-OH)2, the reaction of four-coordinate (ArL)Fe(κ2-N,O-AZADO) with hydrogen atom donors yields ferric hydroxide (ArL)Fe(OH)(AZAD). Mechanistic experiments reveal saturation behavior in C−H substrate and are consistent with rate-determining hydrogen atom transfer.Nitroxyl radicals react with iron(I) synthon (ArL)Fe to afford iron(II)-nitroxido complexes. The high-spin iron(II) compounds are stable in the absence of weak C−H bonds, but decay via N−O bond homolysis to ferrous or ferric iron hydroxides in the presence of labile C−H bonds.
      PubDate: 2017-08-25T11:06:14.693895-05:
      DOI: 10.1002/anie.201706594
  • Hierarchical Nanotubes Constructed by Carbon-Coated Ultrathin SnS
           Nanosheets for Fast Capacitive Sodium Storage
    • Authors: Peilei He; Yongjin Fang, Xin-Yao Yu, Xiong Wen (David) Lou
      Pages: 12202 - 12205
      Abstract: Tin(II) sulfide (SnS) has been an attractive anode material for sodium ion batteries. Herein, an elegant templating method has been developed for the rational design and synthesis of hierarchical SnS nanotubes composed of ultrathin nanosheets. In order to enhance the electrochemical performance, carbon coated hierarchical SnS nanotubes (denoted as SnS@C nanotubes) have also been obtained by simply adding glucose into the reaction system. Benefiting from their unique structural merits, the SnS@C nanotubes exhibit enhanced sodium storage properties in terms of good cycling performance and superior rate capability.A facile templating method provides hierarchical nanotubes constructed by carbon-coated ultrathin SnS nanosheets. Benefiting from the unique structural merits, the hierarchical SnS@C nanotubes manifest enhanced sodium storage performance in terms of long cycle life and excellent rate capability.
      PubDate: 2017-08-24T01:01:38.736164-05:
      DOI: 10.1002/anie.201706652
  • Enantioselective Tandem Cyclization of Alkyne-Tethered Indoles Using
           Cooperative Silver(I)/Chiral Phosphoric Acid Catalysis
    • Authors: Yugen Zhu; Wei He, Wei Wang, Chloe E. Pitsch, Xiaotai Wang, Xiang Wang
      Pages: 12206 - 12209
      Abstract: Reported is the enantioselective synthesis of tetracyclic indolines using silver(I)/chiral phosphoric acid catalysis. A variety of alkyne-tethered indoles are suitable for this process. Mechanistic studies suggest that the in situ generated silver(I) chiral phosphate activates both the alkyne and the indole nucleophile in the initial cyclization step through an intermolecular hydrogen bond and the phosphate anion promotes proton transfer. In addition, further modifications of the cyclization products enabled stereochemistry–function studies of a series of bioactive indolines.Duality: Highly enantioselective synthesis of tetracyclic indolines was realized using cooperative silver(I)/chiral phosphoric acid catalysis. Mechanistic studies identified the dual role of the chiral phosphate. M.S.=molecular sieves.
      PubDate: 2017-08-23T12:37:37.840932-05:
      DOI: 10.1002/anie.201706694
  • Photochemical Intramolecular C−H Addition of
           Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement
    • Authors: Naoki Ando; Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, Shuhei Itoyama, Kazunari Yoshizawa, Yasunori Matsui, Yutaro Kuramoto, Hiroshi Ikeda, Shigehiro Yamaguchi
      Pages: 12210 - 12214
      Abstract: A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl-substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C−H bonds in the ortho-methyl groups of the mesityl substituents was formally added in a syn fashion to a C−C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis measurements indicated that the reaction proceeds through a [1,6]-sigmatropic rearrangement. This behavior is reminiscent of the photochemical reaction mode of arylalkenylketones, thus demonstrating the isosteric relation between tricoordinate organoboron compounds and the corresponding pseudo-carbocationic species in terms of pericyclic reactions. Despite the disrupted π-conjugation, the resulting spirocyclic boraindanes exhibited a characteristic absorption band at relatively long wavelengths (λ=370—400 nm).Set in motion: The photoinduced isomerization of dimesitylboryl-substituted (hetero)arenes to afford spirocyclic boraindanes is disclosed. It proceeds through a [1,6]-sigmatropic rearrangement, followed by an intramolecular C−C coupling. The former process is characterized by the participation of the vacant p orbital on boron, and thus constitutes a new reaction mode for triarylboranes. The obtained spirocyclic boraindanes showed characteristic absorption properties.
      PubDate: 2017-08-23T12:37:08.009136-05:
      DOI: 10.1002/anie.201706929
  • Beyond Bleaney's Theory: Experimental and Theoretical Analysis of Periodic
           Trends in Lanthanide-Induced Chemical Shift
    • Authors: Elizaveta A. Suturina; Kevin Mason, Carlos F. G. C. Geraldes, Ilya Kuprov, David Parker
      Pages: 12215 - 12218
      Abstract: A detailed analysis of paramagnetic NMR shifts in a series of isostructural lanthanide complexes relavant to PARASHIFT contrast agents reveals unexpected trends in the magnetic susceptibility anisotropy that cannot be explained by the commonly used Bleaney's theory. Ab initio calculations reveal that the primary assumption of Bleaney's theory—that thermal energy is larger than the ligand field splitting—does not hold for the lanthanide complexes in question, and likely for a large fraction of lanthanide complexes in general. This makes the orientation of the magnetic susceptibility tensor differ significantly between complexes of different lanthanides with the same ligand: one of the most popular assumptions about isostructural lanthanide series is wrong.Theory and practice: Assignment and fitting of paramagnetic proton NMR spectra of isostructural series of lanthanide(III) complexes reveal significant deviations from the commonly employed Bleaney's theory. Calculations show that the primary assumption of Bleaney's theory—that thermal energy is larger than the ligand field splitting—does not hold for the lanthanide complexes in question.
      PubDate: 2017-08-24T03:51:22.257306-05:
      DOI: 10.1002/anie.201706931
  • Exclusive Formation of Formic Acid from CO2 Electroreduction by a Tunable
           Pd-Sn Alloy
    • Authors: Xiaofang Bai; Wei Chen, Chengcheng Zhao, Shenggang Li, Yanfang Song, Ruipeng Ge, Wei Wei, Yuhan Sun
      Pages: 12219 - 12223
      Abstract: Conversion of carbon dioxide (CO2) into fuels and chemicals by electroreduction has attracted significant interest, although it suffers from a large overpotential and low selectivity. A Pd-Sn alloy electrocatalyst was developed for the exclusive conversion of CO2 into formic acid in an aqueous solution. This catalyst showed a nearly perfect faradaic efficiency toward formic acid formation at the very low overpotential of −0.26 V, where both CO formation and hydrogen evolution were completely suppressed. Density functional theory (DFT) calculations suggested that the formation of the key reaction intermediate HCOO* as well as the product formic acid was the most favorable over the Pd-Sn alloy catalyst surface with an atomic composition of PdSnO2, consistent with experiments.The right mix: Pd-Sn alloy supported electrocatalysts were synthesized for the electrochemical conversion of CO2 in an aqueous solution. A nearly perfect faradaic efficiency toward formic acid formation at a very low overpotential of −0.26 V was achieved over PdSn/C, which was attributed to the optimal surface oxide configuration.
      PubDate: 2017-08-24T03:51:16.272963-05:
      DOI: 10.1002/anie.201707098
  • Rapid Access to Nanographenes and Fused Heteroaromatics by
           Palladium-Catalyzed Annulative π-Extension Reaction of Unfunctionalized
           Aromatics with Diiodobiaryls
    • Authors: Wataru Matsuoka; Hideto Ito, Kenichiro Itami
      Pages: 12224 - 12228
      Abstract: Efficient and rapid access to nanographenes and π-extended fused heteroaromatics is important in materials science. Herein, we report a palladium-catalyzed efficient one-step annulative π-extension (APEX) reaction of polycyclic aromatic hydrocarbons (PAHs) and heteroaromatics, producing various π-extended aromatics. In the presence of a cationic Pd complex, triflic acid, silver pivalate, and diiodobiaryls, diverse unfunctionalized PAHs and heteroaromatics were directly transformed into larger PAHs, nanographenes, and π-extended fused heteroaromatics in a single step. In the reactions that afford [5]helicene substructures, simultaneous dehydrogenative ring closures occur at the fjord regions to form unprecedented larger nanographenes. This successive APEX reaction is notable as it stiches five aryl–aryl bonds by C−H functionalization in a single operation. Moreover, the unique molecular structures, crystal-packing structures, photophysical properties, and frontier molecular orbitals of the thus-formed nanographenes were elucidated.Meet me at the APEX: A novel π-extension reaction provides rapid access to polycyclic aromatic hydrocarbons, fused heteroaromatics and nanographenes. In the presence of a palladium catalyst, silver pivalate and trifluoromethanesulfonic acid the unfunctionalized aromatic templates were π-extended with a variety of diiodobiaryls as π-extending agents in good yields and regioselectivity.
      PubDate: 2017-08-24T03:51:09.589936-05:
      DOI: 10.1002/anie.201707486
  • A Stereoselective [3+1] Ring Expansion for the Synthesis of Highly
           Substituted Methylene Azetidines
    • Authors: Steven C. Schmid; Ilia A. Guzei, Jennifer M. Schomaker
      Pages: 12229 - 12233
      Abstract: The reaction of rhodium-bound carbenes with strained bicyclic methylene aziridines results in a formal [3+1] ring expansion to yield highly substituted methylene azetidines with excellent regio- and stereoselectivity. The reaction appears to proceed through an ylide-type mechanism, where the unique strain and structure of the methylene aziridine promotes a ring-opening/ring-closing cascade that efficiently transfers chirality from substrate to product. The resultant products can be elaborated into new azetidine scaffolds containing vicinal tertiary-quaternary and even quaternary-quaternary stereocenters.A tale of two rings: A one carbon ring expansion of methylene aziridines to methylene azetidines occurs upon reaction with a rhodium-bound carbene. This 3+1 ring expansion efficiently delivers substituted azetidines in high yields and stereoselectivities.
      PubDate: 2017-09-01T03:45:33.543105-05:
      DOI: 10.1002/anie.201705202
  • Enzymatic C−H Oxidation–Amidation Cascade in the Production of Natural
           and Unnatural Thiotetronate Antibiotics with Potentiated Bioactivity
    • Authors: Jie Li; Xiaoyu Tang, Takayoshi Awakawa, Bradley S. Moore
      Pages: 12234 - 12239
      Abstract: The selective activation of unreactive hydrocarbons by biosynthetic enzymes has inspired new synthetic methods in C−H bond activation. Herein, we report the unprecedented two-step biosynthetic conversion of thiotetromycin to thiotetroamide C involving the tandem oxidation and amidation of an unreactive ethyl group. We detail the genetic and biochemical basis for the terminal amidation in thiotetroamide C biosynthesis, which involves a uniquely adapted cytochrome P450–amidotransferase enzyme pair and highlights the first oxidation–amidation enzymatic cascade reaction leading to the selective formation of a primary amide group from a chemically inert alkyl group. Motivated by the ten-fold increase in antibiotic potency of thiotetroamide C ascribed to the acetamide group and the unusual enzymology involved, we enzymatically interrogated diverse thiolactomycin analogues and prepared an unnatural thiotetroamide C analogue with potentiated bioactivity compared to the parent molecule.Enzymatic oxidation–amidation cascade: Uncovering the biochemical genesis of the terminal amide group of thiotetroamide C illuminated a uniquely adapted cytochrome P450–amidotransferase enzyme pair that selectively and sequentially oxidizes and amidates an unreactive ethyl group, leading to a significant increase in antibiotic potency. Substrate promiscuity of this enzyme pair provides an opportunity in chemoenzymatic synthesis.
      PubDate: 2017-09-01T03:51:03.050918-05:
      DOI: 10.1002/anie.201705239
  • Band-Gap Opening in Metallic Single-Walled Carbon Nanotubes by
           Encapsulation of an Organic Salt
    • Authors: Belén Nieto-Ortega; Julia Villalva, Mariano Vera-Hidalgo, Luisa Ruiz-González, Enrique Burzurí, Emilio M. Pérez
      Pages: 12240 - 12244
      Abstract: The encapsulation of viologen derivatives into metallic single-walled carbon nanotubes (SWNTs) results in the opening of a band gap, making the SWNTs semiconducting. Raman spectroscopy, thermogravimetric analysis, and aberration-corrected high-resolution transmission electron microscopy confirm the encapsulation process. Through the fabrication of field-effect transistor devices, the change of the electronic structure of the tubes from metallic to semiconducting upon the encapsulation is confirmed. The opening of a gap in the band structure of the tubes was not detected in supramolecular controls.Bandgap, be opened! Viologen salts were encapsulated within single-walled carbon nanotubes (SWNTs). This encapsulation tunes the electronic band gap of the tube from metallic to a high-quality semiconductor.
      PubDate: 2017-08-24T03:52:52.359613-05:
      DOI: 10.1002/anie.201705258
  • Activation of Remote meta-C−H Bonds in Arenes with Tethered Alcohols: A
           Salicylonitrile Template
    • Authors: Lanlan Zhang; Chaoyue Zhao, Yang Liu, Jiancong Xu, Xiufang Xu, Zhong Jin
      Pages: 12245 - 12249
      Abstract: Palladium-catalyzed activation of remote meta-C−H bonds in arenes containing tethered alcohols was achieved with high regioselectivity by using a nitrile template. Computational studies on the macrocyclic transition state of the regioselectivity-determining C−H activation steps revealed that both the C-N-Ag angles and gauche comformations of phenyl ether play an extremely important role in the meta selectivity.From a distance: Palladium-catalyzed activation of remote C−H bonds arenes containing long-chain alcohols is achieved with high meta regioselectivity by using a salicylonitrile template. DFT calculations show that the regioselectivity of products greatly depends on both the C-N-Ag angle and gauche comformation of phenyl ether in the macrocyclic transition state.
      PubDate: 2017-08-23T12:41:03.749775-05:
      DOI: 10.1002/anie.201705495
  • An Asymmetric Pathway to Dendrobine by a Transition-Metal-Catalyzed
           Cascade Process
    • Authors: Yujin Lee; Elise M. Rochette, Junyong Kim, David Y.-K. Chen
      Pages: 12250 - 12254
      Abstract: An asymmetric pathway to the caged tetracyclic pyrrolidine alkaloid, dendrobine, is reported. The successful synthetic strategy features a one-pot, sequential palladium-catalyzed enyne cycloisomerization and rhodium-catalyzed diene-assisted pyrrolidine formation by allylic CH activation. The developed transition-metal-catalyzed cascade process permits rapid access to the dendrobine core structure and circumvents the handling of labile intermediates. An intramolecular aldol condensation under carefully defined reaction conditions takes place with a concomitant detosylation, followed by reductive amine methylation, to afford a late-stage intermediate (previously identified by several prior dendrobine syntheses) in only 10 synthetic steps overall.An asymmetric pathway to polycyclic alkaloid dendrobine was developed comprising a one-pot palladium-catalyzed enyne cycloisomerization, and rhodium-catalyzed diene-assisted pyrrolidine formation by allylic CH activation. Intramolecular aldol condensation with concomitant detosylation, followed by reductive amination, afforded an advanced intermediate in only 10 synthetic steps.
      PubDate: 2017-08-24T03:52:10.860902-05:
      DOI: 10.1002/anie.201705713
  • Photochemical Dual-Catalytic Synthesis of Alkynyl Sulfides
    • Authors: Jeffrey Santandrea; Clémentine Minozzi, Corentin Cruché, Shawn K. Collins
      Pages: 12255 - 12259
      Abstract: A photochemical dual-catalytic cross-coupling to form alkynyl sulfides via C(sp)−S bond formation is described. The cross-coupling of thiols and bromoalkynes is promoted by a soluble organic carbazole-based photocatalyst using continuous flow techniques. Synthesis of alkynyl sulfides bearing a wide range of electronically and sterically diverse aromatic alkynes and thiols can be achieved in good to excellent yields (50–96 %). The simple continuous flow setup also allows for short reaction times (30 min) and high reproducibility on gram scale. In addition, we report the first application of photoredox/nickel dual catalysis towards macrocyclization, as well as the first example of the incorporation of an alkynyl sulfide functional group into a macrocyclic scaffold.Catalytic partnership: A photochemical dual-catalytic cross-coupling to form alkynyl sulfides through C(sp)−S bond formation is promoted by a carbazole-based photocatalyst using continuous flow techniques in short reaction times (50–96 %, 30 min). In addition, incorporation of an alkynyl sulfide functional group into a macrocyclic scaffold was demonstrated as the first application of photoredox/nickel dual catalysis towards macrocyclization.
      PubDate: 2017-08-24T03:52:04.023084-05:
      DOI: 10.1002/anie.201705903
  • Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with
           Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
    • Authors: Hoi-Ki Kwong; Po-Kam Lo, Shek-Man Yiu, Hajime Hirao, Kai-Chung Lau, Tai-Chu Lau
      Pages: 12260 - 12263
      Abstract: The OsVI nitrido complex, OsVI(N)(quin)2(OTs) (1, quin=2-quinaldinate, OTs=tosylate), is a highly selective and efficient catalyst for the ring hydroxylation of alkylbenzenes with H2O2 at room temperature. Oxidation of various alkylbenzenes occurs with ring/chain oxidation ratios ranging from 96.7/3.3 to 99.9/0.1, and total product yields from 93 % to 98 %. Moreover, turnover numbers up to 6360, 5670, and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene, and mesitylene, respectively. Density functional theory calculations suggest that the active intermediate is an OsVIII nitrido oxo species.The ring and chain trick: The OsVI nitrido complex OsVI(N)(2-quin)2(OTs) (quin=2-quinaldinate, OTs=tosylate) catalyzes hydroxylation of alkylbenzenes with H2O2, reaching a ring/chain ratio of up to 99.9/0.1 and turnover numbers (TON) in excess of 6300.
      PubDate: 2017-08-23T12:38:03.595892-05:
      DOI: 10.1002/anie.201705986
  • A Nucleophilic Gold(III) Carbene Complex
    • Authors: Anthony Pujol; Mathieu Lafage, Feriel Rekhroukh, Nathalie Saffon-Merceron, Abderrahmane Amgoune, Didier Bourissou, Noel Nebra, Marie Fustier-Boutignon, Nicolas Mézailles
      Pages: 12264 - 12267
      Abstract: The first AuIII carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated AuIII precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high-energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the AuIII carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS2), resulting in two types of C=C coupling reactions.Sitting on a gold mine: A AuIII carbene complex was assembled from a geminal dianion and a (P,C) cyclometalated AuIII precursor. In contrast to AuI carbene complexes, the title complex possesses nucleophilic character and participates in C=C coupling with electrophiles.
      PubDate: 2017-08-24T03:51:59.175725-05:
      DOI: 10.1002/anie.201706197
  • Group 6 Transition-Metal/Boron Frustrated Lewis Pair Templates Activate
           N2 and Allow its Facile Borylation and Silylation
    • Authors: Antoine Simonneau; Raphaël Turrel, Laure Vendier, Michel Etienne
      Pages: 12268 - 12272
      Abstract: The reaction of trans-[M(N2)2(dppe)2] (M=Mo, 1Mo, M=W, 1W) with B(C6F5)3 (2) provides the adducts [(dppe)2M=N=N-B(C6F5)3] (3) which can be regarded as M/B transition-metal frustrated Lewis pair (TMFLP) templates activating dinitrogen. Easy borylation and silylation of the activated dinitrogen ligands in complexes 3 with a hydroborane and hydrosilane occur by splitting of the B−H and Si−H bonds between the N2 moiety and the perfluoroaryl borane. This reactivity of 3 is reminiscent of conventional frustrated Lewis pair chemistry and constitutes an unprecedented approach for the functionalization of dinitrogen.Dinitrogen is one of the missing small-molecule targets of the frustrated Lewis pair (FLP) chemistry. The use of a Group 6 metal (Mo or W)/boron comound allows activation of N2 that is reminiscent of conventional FLPs. This mode of activation allows its mild and easy borylation and silylation, under a mechanism in which coordinated N2 acts as the Lewis base component of an FLP.
      PubDate: 2017-08-29T04:36:58.797114-05:
      DOI: 10.1002/anie.201706226
  • Iminyl-Radicals by Oxidation of α-Imino-oxy Acids: Photoredox-Neutral
           Alkene Carboimination for the Synthesis of Pyrrolines
    • Authors: Heng Jiang; Armido Studer
      Pages: 12273 - 12276
      Abstract: The visible-light-promoted decarboxylation of α-imino-oxy propionic acids for the generation of iminyl radicals has been accomplished through the use of Ir(dFCF3ppy)2(dtbbpy)PF6 as a photoredox catalyst. Different from visible-light-promoted homolysis and single-electron reduction of oxime derivatives, this strategy provides a novel catalytic cycle for alkene carboimination through a sequence comprising N-radical generation, iminyl radical cyclization, intermolecular conjugate addition to a Michael acceptor, and single-electron reduction to afford various pyrroline derivatives in an overall redox-neutral process. The indolizidine alkaloid skeleton could be easily constructed from a pyrroline derivative prepared by this synthetic method.Radical closure: A redox-neutral radical reaction cascade of α-imino-oxy propionic acids with various Michael acceptors, using iridium-photoredox catalysis, delivers valuable pyrrolines. These reaction cascades comprise oxidative iminyl radical generation, carboimination cyclization, and subsequent intermolecular radical conjugate addition.
      PubDate: 2017-09-05T06:31:22.308481-05:
      DOI: 10.1002/anie.201706270
  • Total Synthesis of Actinophyllic Acid
    • Authors: Yu Yoshii; Hidetoshi Tokuyama, David Y.-K. Chen
      Pages: 12277 - 12281
      Abstract: Herein we report a total synthesis of the indolohydroazocine natural product actinophyllic acid. The target molecule was retrosynthetically deconvoluted to render a greatly simplified and symmetrical [4.4.1] bicyclic trienone, the desymmetrization of which was carefully examined under a variety of conditions, including oxidative, reductive, and transition-metal-catalyzed transformations. Ultimately, the successful synthetic strategy featured chemoselective catalytic dihydroxylation, desymmetrizing nitrile oxide dipolar cycloaddition, and palladium-catalyzed aminoarylation to sequentially modify the three olefins within the trienone, followed by a late-stage reductive cascade indolization and alkylation to complete the target molecule.Find a mirror to break: The indolohydroazocine natural product actinophyllic acid was synthesized by an expedient route based on the desymmetrization of a trienone precursor. The developed synthesis features chemoselective catalytic dihydroxylation of the trienone, desymmetrizing dipolar cycloaddition with a nitrile oxide, and palladium-catalyzed aminoarylation as key steps.
      PubDate: 2017-08-24T03:51:51.588058-05:
      DOI: 10.1002/anie.201706312
  • Aryloxide-Facilitated Catalyst Turnover in Enantioselective
           α,β-Unsaturated Acyl Ammonium Catalysis
    • Authors: Anastassia Matviitsuk; Mark D. Greenhalgh, Diego-Javier Barrios Antúnez, Alexandra M. Z. Slawin, Andrew D. Smith
      Pages: 12282 - 12287
      Abstract: A new general concept for α,β-unsaturated acyl ammonium catalysis is reported that uses p-nitrophenoxide release from an α,β-unsaturated p-nitrophenyl ester substrate to facilitate catalyst turnover. This method was used for the enantioselective isothiourea-catalyzed Michael addition of nitroalkanes to α,β-unsaturated p-nitrophenyl esters in generally good yield and with excellent enantioselectivity (27 examples, up to 79 % yield, 99:1 er). Mechanistic studies identified rapid and reversible catalyst acylation by the α,β-unsaturated p-nitrophenyl ester, and a recently reported variable-time normalization kinetic analysis method was used to delineate the complex reaction kinetics.Turnover a new leaf: A new concept in α,β-unsaturated acyl ammonium catalysis uses aryloxide release from an α,β-unsaturated aryl ester substrate to facilitate catalyst turnover. Enantioselective isothiourea-catalyzed Michael addition of nitroalkanes to α,β-unsaturated p-nitrophenyl esters was achieved in good yield and with excellent enantioselectivity. Kinetic analysis was used to probe the reaction mechanism.
      PubDate: 2017-08-25T05:22:06.534553-05:
      DOI: 10.1002/anie.201706402
  • Palladium-Catalyzed Alkylation with Alkyl Halides by C(sp3)−H
    • Authors: Zhuo Wu; Ding Ma, Bo Zhou, Xiaoming Ji, Xiaotian Ma, Xiaoling Wang, Yanghui Zhang
      Pages: 12288 - 12291
      Abstract: Utilizing halogens as traceless directing goups represents an attractive strategy for C−H functionalization. A two C−H alkylation system, initiated by the oxidative addition of organohalides to Pd0, has been developed. The first reaction involves an intermolecular alkylation of palladacycles to form C(sp3)−C(sp2) bonds followed by C(sp2)−H activation/cyclization to deliver alkylated benzocyclobutenes as the final products. In the second reaction, two C−C bonds are formed by the reaction of palladacycles with CH2Br2, and provides a facile and efficient method for the synthesis of indanes. The alkylated benzocyclobutene products can be transformed into tricyclic hyrocarbons, and the indane derivatives are essential structural motifs in bioactive and odorant molecules.A twofer: Palladium-catalyzed intermolecular alkylation reactions with alkyl halides proceed by C(sp3)−H activation of aryl halides. The reactions involve a tandem process and two C(sp2)−C(sp3) bonds are formed and yield alkylated benzocyclobutenes as the final products. A catalytic route for the reaction with CH2Br2 was also developed, and provides access to indanes.
      PubDate: 2017-08-24T03:51:37.099419-05:
      DOI: 10.1002/anie.201706418
  • Catalytic Divergent [3+3]- and [3+2]-Cycloaddition by Discrimination
           Between Diazo Compounds
    • Authors: Yongming Deng; Lynée A. Massey, Yeray A. Rodriguez Núñez, Hadi Arman, Michael P. Doyle
      Pages: 12292 - 12296
      Abstract: Highly selective divergent cycloaddition reactions of enoldiazo compounds and α-diazocarboximides catalyzed by copper(I) or dirhodium(II) have been developed. With tetrakis(acetonitrile)copper(I) tetrafluoroborate as the catalyst epoxypyrrolo[1,2-a]azepine derivatives were prepared in good yields and excellent diastereoselectivities through the first reported [3+3]-cycloaddition of a carbonyl ylide. Use of Rh2(pfb)4 or Rh2(esp)2 directs the reactants to regioselective [3+2]-cycloaddition generating cyclopenta[2,3]pyrrolo[2,1-b]oxazoles with good yields and excellent diastereoselectivities.Catalytic divergence: Using copper(I) or dirhodium(II) catalysts, the title reaction of enoldiazo compounds and α-diazocarboximides was achieved with high diastereocontrol and cross-selectivity. Three different heterocyclic products, containing multicyclic azepine, pyrrolizine, and oxazole skeletons, were synthesized from the same diazo compounds.
      PubDate: 2017-08-24T03:51:28.966157-05:
      DOI: 10.1002/anie.201706639
  • Formation of Binuclear Zigzag Hexapentaene Titanium Complexes via a
           Titanacumulene [Ti=C=C=CH2] Intermediate
    • Authors: Tim Oswald; Tina Gelert, Christian Lasar, Marc Schmidtmann, Thorsten Klüner, Rüdiger Beckhaus
      Pages: 12297 - 12301
      Abstract: The reaction of bis(η5:η1-pentafulvene)titanium complexes with an allylidenephosphorylide Ph3P=C(H)- C(H)=CH2 leads to binuclear zigzag hexapentaene titanium complexes (Ti2a, Ti2b). The formation of the central C6H4 unit can be described as a spontaneous double C−H bond activation process, leading to an R3P=C=C=CH2 intermediate, as a synthon for a titanabutatriene fragment [(CpR)2Ti=C=C=CH2] (R: 2-adamantyl, CH(p-tol)2). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single-crystal X-ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations.Not only in the atmosphere of Saturn's moon Titan but also in the coordination sphere of titanium, the unusual hexapentaene H2C=C=C=C=C=CH2 can be formed. Double C−H bond activation of a phosphorus ylide generates a phosphacumulene intermediate which reacts with a titanocene fragment to [Cp′2Ti=C=C=CH2], by PPh3 elimination, leading to titanium-hexapentaene complexes by dimerization.
      PubDate: 2017-08-23T12:37:42.430488-05:
      DOI: 10.1002/anie.201706674
  • Sono-RAFT Polymerization in Aqueous Medium
    • Authors: Thomas G. McKenzie; Enrico Colombo, Qiang Fu, Muthupandian Ashokkumar, Greg G. Qiao
      Pages: 12302 - 12306
      Abstract: The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition–fragmentation chain transfer (RAFT) agent. This allows for a highly “green” method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.Make some noise: A sonochemically induced RAFT polymerization with efficient temporal control is demonstrated using high-frequency ultrasound. Unlike the low frequencies used in mechanically induced polymerizations the high frequency employed produces very little shear force, potentially avoiding chain-breaking “depolymerization” events.
      PubDate: 2017-09-01T06:30:45.140738-05:
      DOI: 10.1002/anie.201706771
  • Selective α-Oxyamination and Hydroxylation of Aliphatic Amides
    • Authors: Xinwei Li; Fengguirong Lin, Kaimeng Huang, Jialiang Wei, Xinyao Li, Xiaoyang Wang, Xiaoyu Geng, Ning Jiao
      Pages: 12307 - 12311
      Abstract: Compared to the α-functionalization of aldehydes, ketones, even esters, the direct α-modification of amides is still a challenge because of the low acidity of α-CH groups. The α-functionalization of N−H (primary and secondary) amides, containing both an unactived α-C−H bond and a competitively active N−H bond, remains elusive. Shown herein is the general and efficient oxidative α-oxyamination and hydroxylation of aliphatic amides including secondary N−H amides. This transition-metal-free chemistry with high chemoselectivity provides an efficient approach to α-hydroxy amides. This oxidative protocol significantly enables the selective functionalization of inert α-C−H bonds with the complete preservation of active N−H bond.Active duty: A general and efficient oxidative α-oxyamination of aliphatic amides, including secondary N−H amides, was developed. This transition-metal-free chemistry, with high chemoselectivity, provides an efficient approach to α-hydroxy amides. This oxidative route enables the selective functionalization of inert α-C−H bonds with complete preservation of the active N−H bond.
      PubDate: 2017-09-05T06:32:22.184174-05:
      DOI: 10.1002/anie.201706963
  • Synergistic Cu/Pd Catalysis for Enantioselective Allylic Alkylation of
           Aldimine Esters: Access to α,α-Disubstituted α-Amino Acids
    • Authors: Liang Wei; Shi-Ming Xu, Qiao Zhu, Chao Che, Chun-Jiang Wang
      Pages: 12312 - 12316
      Abstract: An unprecedented enantioselective allylic alkylation of readily available aldimine esters has been developed, and is catalyzed by a synergistic Cu/Pd catalyst system. This strategy provides facile access to nonproteinogenic α,α-disubstituted α-amino acids in high yield with excellent enantioselectivity. The more challenging double allylic alkylation of glycinate-derived imine esters was also realized. Furthermore, this methodology was applied for the construction of the key intermediate of PLG peptidomimetics.Double duty: An enantioselective allylic alkylation of aldimine esters has been developed by using a synergistic Cu/Pd catalyst system. This strategy provides access to nonproteinogenic α,α-disubstituted α-amino acids in high yield with excellent enantioselectivity. The more challenging double allylic alkylation of glycinate-derived imine esters was also realized. LG=leaving group.
      PubDate: 2017-08-23T12:36:28.993152-05:
      DOI: 10.1002/anie.201707019
  • A meso–meso β-β β-β Triply Linked Subporphyrin
    • Authors: Yasuhiro Okuda; Norihito Fukui, Jinseok Kim, Taeyeon Kim, Hua-Wei Jiang, Graeme Copley, Masaaki Kitano, Dongho Kim, Atsuhiro Osuka
      Pages: 12317 - 12321
      Abstract: A meso–meso β-β β-β triply linked subporphyrin dimer 6 was synthesized by stepwise reductive elimination of β-to-β doubly PtII-bridged subporphyrin dimer 9. Dimer 6 was characterized by spectroscopic and electrochemical measurements, theoretical calculations, and picosecond time-resolved transient absorption spectroscopy. X-ray diffraction analysis reveals that 6 has a bowl-shaped structure with a positive Gaussian curvature. Despite the curved structure, 6 exhibits a remarkably red-shifted absorption band at 942 nm and a small electrochemical HOMO–LUMO gap (1.35 eV), indicating an effectively conjugated π-electronic network.A triply linked subporphyrin dimer was synthesized by stepwise reductive elimination of a β-to-β doubly PtII-bridged subporphyrin dimer with the concurrent formation of the meso–meso bond. Despite the curved structure, the triply linked dimer displayed a remarkably red-shifted absorption spectrum and narrow electrochemical HOMO–LUMO gap because of the effectively conjugated π-electronic network.
      PubDate: 2017-08-23T12:36:12.310832-05:
      DOI: 10.1002/anie.201707123
  • Strategic Construction of Directly Linked Porphyrin–BODIPY Hybrids
    • Authors: Lei Xu; Bin Wen, Gakhyun Kim, Taeyeon Kim, Fei Cheng, Mingbo Zhou, Ling Xu, Takayuki Tanaka, Bangshao Yin, Atsuhiro Osuka, Dongho Kim, Jianxin Song
      Pages: 12322 - 12326
      Abstract: A powerful and concise synthesis of directly linked porphyrin-BODIPY hybrids has been demonstrated, which consists of condensation of directly linked meso-pyrroyl NiII-porphyrin with arylaldehyde, oxidation with p-chloranil, and complexation with BF3⋅Et2O. Synthesized hybrids include porphyrin dimer 6Ni, trimers 8Ni, 9Ni, tetramer 12Ni, pentamer 16Ni, hexamer 13Ni, and nonamers 17Ni and 18Ni. The structures of 6Ni, 9Ni and 12Ni were unambiguously confirmed by X-ray diffraction analysis. Some NiII porphyrins were effectively converted to the corresponding ZnII porphryins. In these hybrids, the pigments are three-dimensionally arranged with a face-to-face dimeric porphyrin unit in a well-defined manner, featuring their potential as light-harvesting antenna and functional hosts.Directly linked NiII porphyrin–BODIPY oligomeric hybrids (n-mers: n=2–6, 9), were formed by a powerful and concise synthesis. Some NiII porphyrins were converted into the corresponding ZnII porphyrins. The pigment moities are three-dimensionally arranged with a face-to-face dimeric porphyrin unit in a well-defined manner, showing their potential as light-harvesting antenna and functional hosts.
      PubDate: 2017-08-25T11:05:31.816043-05:
      DOI: 10.1002/anie.201707237
  • Total Synthesis of (−)-Vindorosine
    • Authors: Wen Chen; Xiao-Dong Yang, Wen-Yun Tan, Xiang-Yang Zhang, Xia-Li Liao, Hongbin Zhang
      Pages: 12327 - 12331
      Abstract: Outlined herein is a novel and scalable synthesis of (−)-vindorosine based on two key transformations. A highly diastereoselective vinylogous Mannich addition of dioxinone-derived lithium dienolates with indolyl N-tert-butanesulfinyl imines has been developed. In addition, an intramolecular Heathcock/aza-Prins cyclization was introduced to construct both the C, and the highly substituted E rings for the synthesis of (−)-vindorosine and related alkaloids.In total: A new strategy for the synthesis of (−)-vindorosine and related alkaloids features an asymmetric vinylogous Mannich addition of dioxinone-derived lithium dienolates to indolyl N-tert-butanesulfinyl imines, and an intramolecular Heathcock/aza-Prins cyclization to construct the C and E rings. Tf=trifluoromethanesulfonyl, THF=tetrahydrofuran.
      PubDate: 2017-08-24T03:50:39.737844-05:
      DOI: 10.1002/anie.201707249
  • Biomimetic Synthesis of Complex Flavonoids Isolated from Daemonorops
           “Dragon's Blood”
    • Authors: Matthias Schmid; Dirk Trauner
      Pages: 12332 - 12335
      Abstract: The dragonbloodins are a pair of complex flavonoid trimers that have been isolated from the palm tree Daemonorops draco, one of the sources of the ancient resin known as “dragon's blood”. We present a short synthesis that clarifies their relative configurations and sheds light on their origin in Nature. This synthesis features biomimetic cascade reactions that involve both ionic and radical intermediates. The biogenetic relationships between dracorhodin, the dracoflavans C, and the dragonbloodins A1 and A2 are discussed.Dragonbloodin A1 and A2 are two flavonoid trimers that have been isolated from the palm tree Daemonorops draco, one of the sources of “dragon's blood”. Their relative configurations were clarified through an efficient synthesis, which also suggests that the complex molecules form spontaneously from the red colorants of dragon's blood in air.
      PubDate: 2017-08-16T02:30:37.841954-05:
      DOI: 10.1002/anie.201705390
  • Deaminative Strategy for the Visible-Light-Mediated Generation of Alkyl
    • Authors: Felix J. R. Klauck; Michael J. James, Frank Glorius
      Pages: 12336 - 12339
      Abstract: A deaminative strategy for the visible-light-mediated generation of alkyl radicals from redox-activated primary amine precursors is described. Abundant and inexpensive primary amine feedstocks, including amino acids, were converted in a single step into redox-active pyridinium salts and subsequently into alkyl radicals by reaction with an excited-state photocatalyst. The broad synthetic potential of this protocol was demonstrated by the alkylation of a number of heteroarenes under mild conditions.Radical cut: In the title reaction alkyl radicals are generated from redox-activated primary amine precursors. Abundant and inexpensive primary amine feedstocks, including amino acids, were converted in a single step into redox-active pyridinium salts and subsequently into alkyl radicals by reaction with an excited-state photocatalyst. The potential of this method was demonstrated by the alkylation of a number of heteroarenes.
      PubDate: 2017-08-29T11:21:13.958335-05:
      DOI: 10.1002/anie.201706896
  • Multiple Metal–Metal Bond or No Bond' The Electronic Structure
           of V2O2
    • Authors: Olaf Hübner; Hans-Jörg Himmel
      Pages: 12340 - 12343
      Abstract: Detailed knowledge of the electronic structure of vanadium oxide clusters provides the basis for understanding and tuning their significant catalytic properties. However, already for the simple four-atom V2O2 molecule, there are contradictory reports in the literature regarding the electronic ground state and a possible vanadium–vanadium bond. We herein show through a combination of experimental (matrix isolation) studies and theoretical results that there is a multiple vanadium–vanadium bond in this benchmark vanadium oxide molecule.Where to put the electrons' A thorough combined experimental and theoretical study was required to elucidate the electronic structure of the seemingly simple V2O2 molecule, a benchmark compound for catalytically active vanadium oxides.
      PubDate: 2017-08-24T03:51:54.591631-05:
      DOI: 10.1002/anie.201706266
  • Structural and Electronic Flexibility in Hydrides of Zintl Phases with
           Tetrel–Hydrogen and Tetrel–Tetrel Bonds
    • Authors: Henry Auer; Robert Schlegel, Oliver Oeckler, Holger Kohlmann
      Pages: 12344 - 12347
      Abstract: The hydrogenation of Zintl phases enables the formation of new structural entities with main-group-element–hydrogen bonds in the solid state. The hydrogenation of SrSi, BaSi, and BaGe yields the hydrides SrSiH5/3−x, BaSiH5/3−x and BaGeH5/3−x. The crystal structures show a sixfold superstructure compared to the parent Zintl phase and were solved by a combination of X-ray, neutron, and electron diffraction and the aid of DFT calculations. Layers of connected HSr4 (HBa4) tetrahedra containing hydride ions alternate with layers of infinite single- and double-chain polyanions, in which hydrogen atoms are covalently bound to silicon and germanium. The idealized formulae AeTtH5/3 (Ae=alkaline earth, Tt=tetrel) can be rationalized with the Zintl–Klemm concept according to (Ae2+)3(TtH−)(Tt2H2−)(H−)3, where all Tt atoms are three-binding. The non-stoichiometry (SrSiH5/3−x, x=0.17(2); BaGeH5/3−x, x=0.10(3)) can be explained by additional π-bonding of the Tt chains.The Zintl phases SrSi, BaSi, and BaGe form hydrides AeTtH5/3−x, (alkaline earth Ae=Sr, Ba; tetrel Tt=Si, Ge), with new single- and double-chain polyanions characterized by additional tetrel–hydrogen and tetrel–tetrel bonds.
      PubDate: 2017-08-25T05:22:02.349579-05:
      DOI: 10.1002/anie.201706523
  • Properties of Water Confined in Periodic Mesoporous Organosilicas:
           Nanoimprinting the Local Structure
    • Authors: J. Benedikt Mietner; Felix J. Brieler, Young Joo Lee, Michael Fröba
      Pages: 12348 - 12351
      Abstract: The properties of materials confined in porous media are important in scientific and technological aspects. Topology, size, and surface polarity of the pores play a critical role in the confinement effects, however, knowledge regarding the guest–pore interface structure is still lacking. Herein, we show that the molecular mobility of water confined in periodic mesoporous organosilicas (PMOs) is influenced by the polarity of the organic moiety. Multidimensional solid-state NMR spectroscopy directly probes the spatial arrangement of water inside the pores, showing that water interacts either with only the silicate layer or with both silicate and organic layers depending on the alternating surface polarity. A modulated and a uniform pore filling mode are proposed for different types of PMOs.The shape of water: Topology, size, and surface polarity of nanopores play a critical role in the confinement effects. Molecular mobility and the spatial arrangement of water confined in periodic mesoporous organosilicas (PMOs), are probed by multidimensional solid-state NMR spectroscopy, demonstrating that water interacts either with the silicate layer only or with the organic layers as well.
      PubDate: 2017-08-23T12:38:36.259333-05:
      DOI: 10.1002/anie.201705707
  • Enzymatic Synthesis of Psilocybin
    • Authors: Janis Fricke; Felix Blei, Dirk Hoffmeister
      Pages: 12352 - 12355
      Abstract: Psilocybin is the psychotropic tryptamine-derived natural product of Psilocybe carpophores, the so-called “magic mushrooms”. Although its structure has been known for 60 years, the enzymatic basis of its biosynthesis has remained obscure. We characterized four psilocybin biosynthesis enzymes, namely i) PsiD, which represents a new class of fungal l-tryptophan decarboxylases, ii) PsiK, which catalyzes the phosphotransfer step, iii) the methyltransferase PsiM, catalyzing iterative N-methyl transfer as the terminal biosynthetic step, and iv) PsiH, a monooxygenase. In a combined PsiD/PsiK/PsiM reaction, psilocybin was synthesized enzymatically in a step-economic route from 4-hydroxy-l-tryptophan. Given the renewed pharmaceutical interest in psilocybin, our results may lay the foundation for its biotechnological production.Psychoactive psilocybin: The tryptamine derivative psilocybin constitutes the psychoactive principle of Psilocybe species, the so-called “magic mushrooms”. The decarboxylase PsiD, the kinase PsiK, and the methyltransferase PsiM were identified as biosynthetic enzymes in Psilocybe cubensis and used to enzymatically synthesize psilocybin in a one-pot reaction.
      PubDate: 2017-08-25T05:25:46.001534-05:
      DOI: 10.1002/anie.201705489
  • From Fenestrindane towards Saddle-Shaped Nanographenes Bearing a
           Tetracoordinate Carbon Atom
    • Authors: Wai-Shing Wong; Chun-Fai Ng, Dietmar Kuck, Hak-Fun Chow
      Pages: 12356 - 12360
      Abstract: Two saddle-shaped polycyclic aromatic compounds (8 a and 8 b) bearing an all-cis-[]fenestrane core surrounded by an o,p,o,p,o,p,o,p-cyclooctaphenylene belt were synthesized and characterized by NMR spectroscopy and mass spectrometry. The key step of this synthesis involves the formation of four cycloheptatriene rings from the corresponding electron-rich 1,4,9,12-tetraarylfenestrindane derivatives 7 a and 7 b in Scholl-type cyclizations. The structural details of the D2d-symmetric saddle compound 8 a were determined by X-ray crystallography, and the properties of 8 a and 8 b were studied by UV/Vis and fluorescence spectroscopy and cyclic voltammetry.Warped nanographene: Two fourfold bay-bridged fenestrindane derivatives were prepared in good yields through a non-classical Scholl-type cyclization, paving the way to saddle-shaped nanographenes.
      PubDate: 2017-08-29T04:36:24.554869-05:
      DOI: 10.1002/anie.201707505
  • Cyanide-Free and Broadly Applicable Enantioselective Synthetic Platform
           for Chiral Nitriles through a Biocatalytic Approach
    • Authors: Tobias Betke; Philipp Rommelmann, Keiko Oike, Yasuhisa Asano, Harald Gröger
      Pages: 12361 - 12366
      Abstract: A cyanide-free platform technology for the synthesis of chiral nitriles by biocatalytic enantioselective dehydration of a wide range of aldoximes is reported. The nitriles were obtained with high enantiomeric excess of>90 % ee (and up to 99 % ee) in many cases, and a “privileged substrate structure” with respect to high enantioselectivity was identified. Furthermore, a surprising phenomenon was observed for the enantiospecificity that is usually not observed in enzyme catalysis. Depending on whether the E or Z isomer of the racemic aldoxime substrate was employed, one or the other enantiomer of the corresponding nitrile was formed preferentially with the same enzyme.A cyanide-free approach based on the biocatalytic enantioselective dehydration of a wide range of readily available aldoximes provides access to chiral nitriles with high enantioselectivities of>90 % ee (and up to 99 % ee) in many cases. This study also reveals a “privileged substrate structure” with respect to good activity and high enantioselectivity.
      PubDate: 2017-08-29T04:37:29.548106-05:
      DOI: 10.1002/anie.201702952
  • Calcium Hydride Cation [CaH]+ Stabilized by an NNNN-type Macrocyclic
           Ligand: A Selective Catalyst for Olefin Hydrogenation
    • Authors: Danny Schuhknecht; Carolin Lhotzky, Thomas P. Spaniol, Laurent Maron, Jun Okuda
      Pages: 12367 - 12371
      Abstract: Reaction of dibenzyl calcium complex [Ca(Me4TACD)(CH2Ph)2], containing the neutral NNNN-type macrocyclic ligand Me4TACD (Me4TACD=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane), with triphenylsilane gave the cationic dinuclear calcium hydride [Ca2H2(Me4TACD)2](PhCHSiPh3)2 which was characterized by NMR spectroscopy and single-crystal X-ray diffraction. The cation can be regarded as the ligand-stabilized dimeric form of hypothetical [CaH]+. Hydrogenolysis of benzyl calcium cation [Ca(Me4TACD)(CH2Ph)(thf)]+ gave dicationic calcium hydrides [Ca2H2(Me4TACD)2][BAr4]2 (Ar=C6H4-4-tBu; C6H3-3,5-Me2) containing weakly coordinating anions. In THF, they catalyzed the isotope exchange of H2 and D2 to give HD and the hydrogenation of unactivated 1-alkenes.The solution is calcium hydride: The cationic dinuclear calcium hydride [Ca2H2(Me4TACD)2]2+ was characterized by NMR spectroscopy and single-crystal X-ray diffraction. The complex catalyzes the HD exchange between H2 and D2 as well as the hydrogenation of unactivated 1-alkenes.
      PubDate: 2017-08-29T04:36:36.387745-05:
      DOI: 10.1002/anie.201706848
  • Inside Back Cover: Biomimetic Synthesis of Complex Flavonoids Isolated
           from Daemonorops “Dragon's Blood” (Angew. Chem. Int. Ed. 40/2017)
    • Authors: Matthias Schmid; Dirk Trauner
      Pages: 12373 - 12373
      Abstract: An oxidative cascade reaction reveals the origin of the complex flavonoids dragonbloodin A1 and A2 isolated from Daemonorops draco or “dragon's blood". In their Communication on page 12332 ff., D. Trauner and M. Schmid present a concise synthesis of these complex flavonoids that features a biomimetic trimerization and an autoxidative radical cyclization reaction and clarifies their relative and absolute stereochemistry.
      PubDate: 2017-08-23T12:28:46.158572-05:
      DOI: 10.1002/anie.201708380
  • Back Cover: Cyanide-Free and Broadly Applicable Enantioselective Synthetic
           Platform for Chiral Nitriles through a Biocatalytic Approach (Angew. Chem.
           Int. Ed. 40/2017)
    • Authors: Tobias Betke; Philipp Rommelmann, Keiko Oike, Yasuhisa Asano, Harald Gröger
      Pages: 12374 - 12374
      Abstract: A cyanide-free platform technology for the synthesis of chiral nitriles through biocatalytic enantioselective dehydration of a wide range of aldoximes leads to the nitrile products with high enantioselectivity in many cases. In their Communication on page 12361 ff., Y. Asano, H. Gröger, and co-workers also describe an interesting phenomenon with regard to the enantiospecificity: Depending on whether the E or Z isomer of the racemic substrate is used, the other enantiomer of the nitrile is obtained with the same enzyme.
      PubDate: 2017-09-01T03:55:58.122933-05:
      DOI: 10.1002/anie.201707179
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
Home (Search)
Subjects A-Z
Publishers A-Z
Your IP address:
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016