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  Subjects -> CHEMISTRY (Total: 849 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (598 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (42 journals)
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    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (598 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: 32)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
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: 227)
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: 53)
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 Fluorine Science     Full-text available via subscription   (Followers: 8)
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: 14)
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: 67)
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: 13)
American Mineralogist     Hybrid Journal   (Followers: 13)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 159)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 210)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
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: 14)
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: 3)
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: 282)
Biochemistry Insights     Open Access   (Followers: 5)
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: 108)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 93)
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: 2)
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: 67)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
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: 7)
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: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
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: 172)
Chemical Science     Open Access   (Followers: 21)
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: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
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: 147)
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: 247)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
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)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
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: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
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  
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: 11)
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: 56)
Dalton Transactions     Full-text available via subscription   (Followers: 19)
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: 9)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Angewandte Chemie International Edition
  [SJR: 6.229]   [H-I: 397]   [210 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  [1584 journals]
  • Quantifying Hydrogen-Bond Populations in Dimethyl Sulfoxide/Water Mixtures
    • Authors: Kwang-Im Oh; Kavya Rajesh, John F. Stanton, Carlos R. Baiz
      Abstract: Water–dimethyl sulfoxide interactions are dissected using IR spectroscopy. In their Communication (
      DOI : 10.1002/anie.201704162, C. R. Baiz et al. show that hydrogen-bond populations in binary mixtures can be directly quantified and molecular ensembles can be correlated to macroscopic solution properties. The fishes represent DMSO molecules jumping out of the water in groups to portray the strong DMSO–DMSO self-interaction.
      PubDate: 2017-07-20T04:45:34.13216-05:0
       
  • Living and Conducting: Coating Individual Bacterial Cells with
           In Situ Formed Polypyrrole
    • Authors: Rong-Bin Song; YiChao Wu, Zong-Qiong Lin, Jian Xie, Chuan Hao Tan, Joachim Say Chye Loo, Bin Cao, Jian-Rong Zhang, Jun-Jie Zhu, Qichun Zhang
      Abstract: Coating individual bacteria cells with in situ formed polypyrrole is described by J. S. C. Loo, B. Cao, J. R. Zhang, J. J. Zhu, et al. in their Communication (
      DOI : 10.1002/anie.201704729). The coated polypyrrole can serve as a conductive medium as well as a protecting layer. Enhanced direct contact-based extracellular electron transfer and improved viability of bacterial cells are observed when polypyrrole-coated exoelectrogenic bacteria are employed as an anode in microbial fuel cells.
      PubDate: 2017-07-20T04:45:27.61107-05:0
       
  • Asymmetric Synthesis of Chiral Cyclopentanes Bearing an All-Carbon
           Quaternary Stereocenter via Zr-catalyzed Doubled Carboalumination
    • Authors: Shiqing Xu; Chuan Wang, Masato Komiyama, Yasuhiko Tomonari, Ei-ichi Negishi
      Abstract: Herein we report a Zr-catalyzed enantio- and diastereoselective inter-intramolecular doubled carboalumination of unactivated 2-substituted-1,5-dienes which provides an efficient and direct access to chiral cyclopentanes with generation of two stereocenters including an all-carbon quaternary stereocenter generally in excellent diastereomeric ratios and high enantiomeric excesses. This tandem carboalumination process creates two new C-C bonds as well as a C-Al bond which can be in-situ oxidized with O2 or hydrolyzed. Furthermore, the obtained chiral cyclopentanes can be readily functionalized to provide various chiral compounds.
      PubDate: 2017-07-20T00:34:37.800208-05:
      DOI: 10.1002/anie.201706198
       
  • Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers
           by Nickel-Catalyzed Asymmetric Suzuki-Miyaura Coupling of Secondary Benzyl
           Bromides
    • Authors: Weichen Huang; Xiaolong Wan, Qilong Shen
      Abstract: A method for the construction of trifluoromethoxy-containing stereogenic centers with high enantiometric excess via nickel-catalyzed Suzuki-Miyaura coupling of easily available -bromobenzyl trifluoromethylethers 1a-g with a variety of aryl pinacol boronates was described. The reaction conditions were mild and a variety of common functional groups such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino and vinyl group were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without erosion of the enantioselectivity.
      PubDate: 2017-07-20T00:13:38.100557-05:
      DOI: 10.1002/anie.201706868
       
  • Colossal Stability of Gas Phase Tri-anions: The Concept of
           Super-pnictogens
    • Authors: Tianshan Zhao; Jian Zhou, Qian Wang, Puru Jena
      Abstract: Multiply charged negative ions are ubiquitous in nature. In crystals, they are stable due to charge compensating cations while in solutions, solvent molecules protect them; but they are rarely stable in the gas phase due to strong electrostatic repulsion between the extra electrons. Understanding their stability without the influence of the environment, therefore, has been of great interest to scientists for decades. While much of the past work has focused on the di-anions, work on triply charged negative ions is sparse and the search for the smallest stable tri-anion against spontaneous electron emission or fragmentation continues. We show here that BeB₁₁(X)₁₂³- (X=CN, SCN, BO) tri-anions are all stable in the gas phase, with BeB₁₁(CN)₁₂³- exhibiting colossal stability against electron emission by 2.65 eV and against its neutral by 15.85 eV! The unusual stability of these tri-anions opens the door to a new class of super-pnictogens with potential applications in Al-ion batteries.
      PubDate: 2017-07-20T00:10:38.513808-05:
      DOI: 10.1002/anie.201706764
       
  • Crystalline π-Stack Containing Five Stereoisomers: Insights into
           Conformational Isomorphism, Chirality Inversion and Disorder
    • Authors: Agnieszka Nowak-Krol; Merle Röhr, David Schmidt, Frank Würthner
      Abstract: An unprecedented crystal packing arrangement of a tetramethoxy-bay-substituted perylene bisimide (PBI) consists of three crystallographically independent molecules, i.e. an achiral (AC) PBI of saddle-shaped geometry along with two pairs of propeller-like twisted (P) and (M)enantiomeric PBI frameworks. All these five conformations are observed within a single π-stack revealing an intriguing packing sequence with an inversion of chirality from P to M via AC. Nudged elastic band calculations for the isolated molecule show that AC is a local minimum of the P to M interconversion path. In addition, two minor conformations were observed in the crystal, one of which resembles a transition state molecule. Theoretical studies of dimeric and trimeric stacks reveal that the coexistence of all these structures in the crystal lattice is facilitated by the strong dispersion interactions between PBI cores and perfectly interdigitated dodecyl chains which stabilize energetically higher conformations.
      PubDate: 2017-07-19T09:10:50.327128-05:
      DOI: 10.1002/anie.201705445
       
  • Phosphaborenes: Accessible Reagents for the Synthesis of
           C−C/P−B Isosteres
    • Authors: Amy N. Price; Gary S. Nichol, Michael J. Cowley
      Abstract: Formal exchange of C=C units with isoelectronic B=N or B=P units can provide access to molecules with unique electronic or chemical properties. Herein, we report the simple solution-phase generation of highly reactive phosphaborenes, RP=BR, and demonstrate their use for the introduction of P=B units into organic systems. Ring opening of a P−B-containing cyclobutene isostere provided access to unique 1,4-boraphosphabutadiene systems with conjugated main-group multiple bonds.Captivating cousins: Transient phosphaborenes, RP=BR, can be generated in solution and used to introduce PB units into organic compounds as C=C isosteres (see scheme). A PB-containing cyclobutene analogue underwent ring opening to give conjugated systems with main-group multiple bonds.
      PubDate: 2017-07-19T08:16:07.246165-05:
      DOI: 10.1002/anie.201705050
       
  • Controlling Reaction Selectivity through the Surface Termination of
           Perovskite Catalysts
    • Authors: Felipe Polo-Garzon; Shi-Ze Yang, Victor Fung, Guo Shiou Foo, Elizabeth E. Bickel, Matthew F. Chisholm, De-en Jiang, Zili Wu
      Abstract: Although perovskites have been widely used in catalysis, tuning of their surface termination to control reaction selectivity has not been well established. In this study, we employed multiple surface-sensitive techniques to characterize the surface termination (one aspect of surface reconstruction) of SrTiO3 (STO) after thermal pretreatment (Sr enrichment) and chemical etching (Ti enrichment). We show, by using the conversion of 2-propanol as a probe reaction, that the surface termination of STO can be controlled to greatly tune catalytic acid/base properties and consequently the reaction selectivity over a wide range, which is not possible with single-metal oxides, either SrO or TiO2. Density functional theory (DFT) calculations explain well the selectivity tuning and reaction mechanism on STO with different surface termination. Similar catalytic tunability was also observed on BaZrO3, thus highlighting the generality of the findings of this study.It's what's on the surface that counts: Controlling the surface termination of SrTiO3 by thermal pretreatment (Sr enrichment) and chemical etching (Ti enrichment) enabled the catalytic selectivity for the conversion of 2-propanol to be tuned over a wide range. The findings have significant implications for catalysis by mixed oxides, the surface and bulk compositions of which can differ depending on treatment and reaction conditions.
      PubDate: 2017-07-19T08:15:56.561808-05:
      DOI: 10.1002/anie.201704656
       
  • Fluorinative Rearrangements of Substituted Phenylallenes Mediated by
           (Difluoroiodo)toluene: Synthesis of a-(Difluoromethyl)styrenes
    • Authors: Zhensheng Zhao; Léanne Racicot, Graham K. Murphy
      Abstract: Phenylallenes undergo a fluorinative rearrangement by the action of (difluoroiodo)toluene, in the presence of 20 mol% BF3*OEt2, to yield a-difluoromethyl styrenes. This unprecedented reaction was entirely chemoselective for the internal allene pi-bond, and showed remarkable regioselectivity during the fluorination event. Substituted phenylallenes, phenylallenes possessing both phenyl- and a-allenyl substituents, and diphenylallenes were investigated, and good functional group compatibility was observed throughout. The ease with which allenes can be prepared on large scale, and the operational simplicity of this reaction have allowed us to rapidly access fluorine-containing building blocks that have not been accessed by conventional deoxyfluorination strategies.
      PubDate: 2017-07-19T08:12:13.238753-05:
      DOI: 10.1002/anie.201706798
       
  • Phosphorene Co-catalyst Advancing Highly Efficient Visible-Light
           Photocatalytic Hydrogen Production
    • Authors: Jingrun Ran; Bicheng Zhu, Shi-Zhang Qiao
      Abstract: Transitional metals are widely used as co-catalysts boosting photocatalytic H2 production. However, metal-based co-catalysts suffer from high cost, limited abundance and detrimental environment impact. To date, metal-free co-catalyst is rarely reported. Here we for the first time utilized density functional calculations to guide the application of phosphorene as a high-efficiency metal-free co-catalyst for CdS, Zn0.8Cd0.2S or ZnS. Particularly, phosphorene modified CdS shows a high apparent quantum yield of 34.7 % at 420 nm. This outstanding activity arises from the strong electronic coupling between phosphorene and CdS, as well as the favorable band structure, high charge mobility and massive active sites of phosphorene, supported by computations and advanced characterizations, for example, synchrotron-based X-ray absorption near edge spectroscopy. This work brings new opportunities to prepare highly-active, cheap and green photocatalysts.Density functional calculations were used to direct the design of phosphorene as a metal-free co-catalyst promoting photocatalytic H2 production in metal sulfide photocatalyst systems. The enhanced photocatalytic performance arises from the pronounced electronic coupling between metal sulfides and phosphorene, together with its advantageous band structure and excellent charge carrier mobility.
      PubDate: 2017-07-19T07:51:11.788919-05:
      DOI: 10.1002/anie.201703827
       
  • Reactions of Donor–Acceptor Cyclopropanes with Naphthoquinones: Redox
           and Lewis Acid Catalysis Working in Concert
    • Authors: Alexander Lücht; Lukas J. Patalag, André U. Augustin, Peter G. Jones, Daniel B. Werz
      Abstract: Reactions of 2-arylcyclopropane dicarboxylates with naphthoquinones are reported. The key feature was the use of catalytic amounts of SnCl2, which acts as both an electron donor and a Lewis acid. By an in situ umpolung of naphthoquinone the formerly electrophilic species is converted into a nucleophile that is able to trigger the ring-opening of the three-membered ring with formation of a new C−C bond. Treatment of these products with base under oxidative conditions resulted—through loss of methyl formate—in cyclopentannulated products with fully conjugated π systems exhibiting intensive absorptions in the visible range.Electron power: Electrophilic naphthoquinone is converted by a catalytic amount of tin(II) into the corresponding nucleophilic species, which is able to open donor–acceptor cyclopropanes. Basic oxidative conditions lead to a [3+2]-cyclopentannulation resulting in a completely conjugated π system.
      PubDate: 2017-07-19T07:51:06.182616-05:
      DOI: 10.1002/anie.201703732
       
  • Unique Spectral Overlap and Resonant Energy Transfer between Europium(II)
           and Ytterbium(III) Cations: No Quantum Cutting
    • Authors: Lei Zhou; Peter A. Tanner, Weijie Zhou, Yeye Ai, Lixin Ning, Mingmei M. Wu, Hongbin Liang
      Abstract: Samples of the Ca3Sc2Si3O12 (CSS) host singly doped with Eu2+ or Yb3+, doubly doped with Eu2+ and Yb3+, and triply doped with Ce3+, Eu2+ and Yb3+ were synthesized by a sol–gel combustion process under reducing conditions. Unlike previous reports of Eu2+Yb3+ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb3+ is further enhanced by co-doping with Ce3+ in addition to Eu2+. The quantum efficiencies of the doped materials range between 9 % and 93 %.Harvesting solar energy: Eu2+ or Yb3+ singly, Eu2+ and Yb3+ doubly and Ce3+, Eu2+ and Yb3+ triply doped Ca3Sc2Si3O12 (CSS) host lattices were synthesized by a sol–gel combustion process under reducing conditions. The triply doped system is used for harvesting solar energy and converting it to Yb3+ near-infrared emission (dd=dipole–dipole and dq=dipole–quadrupole interactions, ET=electron transfer).
      PubDate: 2017-07-19T07:50:49.379907-05:
      DOI: 10.1002/anie.201703331
       
  • A Membrane-Free Redox Flow Battery with Two Immiscible Redox Electrolytes
    • Authors: Paula Navalpotro; Jesus Palma, Marc Anderson, Rebeca Marcilla
      Abstract: Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short-lifetimes, and expensive ion-selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane-free battery that relies on the immiscibility of redox electrolytes and where vanadium is replaced by organic molecules. We show that the biphasic system formed by one acidic solution and one ionic liquid, both containing quinoyl species, behaves as a reversible battery without any membrane. This proof-of-concept of a membrane-free battery has an open circuit voltage of 1.4 V with a high theoretical energy density of 22.5 Wh L−1, and is able to deliver 90 % of its theoretical capacity while showing excellent long-term performance (coulombic efficiency of 100 % and energy efficiency of 70 %).Without a membrane: The use of immiscible electrolytes makes possible the total removal of any membrane in a “proof-of-concept” battery. Moreover, the metallic pairs commonly used in redox flow batteries are replaced by organic molecules. The same molecule could be used in a symmetric battery design thanks to the different redox mechanisms occurring in each electrolyte.
      PubDate: 2017-07-19T07:46:04.150145-05:
      DOI: 10.1002/anie.201704318
       
  • Highly Ordered Self-Assembly of Native Proteins into 1D, 2D, and 3D
           Structures Modulated by the Tether Length of Assembly-Inducing Ligands
    • Authors: Guang Yang; Hong-ming Ding, Zdravko Kochovski, Rongting Hu, Yan Lu, Yu-qiang Ma, Guosong Chen, Ming Jiang
      Abstract: In nature, proteins are organized into highly ordered self-assembled structures with various morphologies and dimensions. In their Communication (
      DOI : 10.1002/anie.201703052), Y. Ma, G. Chen, and co-workers report the fabrication of protein assemblies by using native protein LecA as a building block through sugar–protein interactions and rhodamine dimerization. The morphologies and dimensions of the protein assemblies can be controlled by the length of the tether between the sugar and rhodamine.
      PubDate: 2017-07-19T07:45:29.708333-05:
       
  • Efficient Access to All-Carbon Quaternary and Tertiary α-Functionalized
           Homoallyl Aldehydes from Ketones
    • Authors: VITTORIO PACE; Laura Castoldi, Eugenia Mazzeo, Marta Rui, Thierry Langer, Wolfgang Holzer
      Abstract: Widely substituted all-carbon quaternary and tertiary α-homoallyl aldehydes are rapidly assembled through a unique synthetic operation from ketones consisting in: 1) C1-homologation; 2) epoxide-aldehyde Lewis acid mediated isomerization and, 3) electrophilic trapping. The synthetic equivalence between a vinyl oxirane and a β,γ-unsaturated aldehyde is the key concept for introducing such a previously undisclosed tactic. Mechanistic studies and labeled experiments suggest the intervention of an aldehyde enolate as the crucial intermediate. Significantly, the homologating carbenoid formation event (carbenoid precursor and organolithium) plays a critical role in determining the chemoselectivity.
      PubDate: 2017-07-19T07:11:58.706663-05:
      DOI: 10.1002/anie.201706236
       
  • From a Molecular 2Fe-2Se Precursor to a Highly Efficient Iron Diselenide
           Electrocatalyst for Overall Water Splitting
    • Authors: Chakadola Panda; Prashanth W. Menezes, Carsten Walter, Shenglai Yao, Matthias E. Miehlich, Vitaly Gutkin, Karsten Meyer, Matthias Driess
      Abstract: A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.Bridging the gap: A highly active iron diselenide electrocatalyst was prepared at low temperature from a bioinspired 2Fe-2Se molecular complex (Dep = diethylphenyl). The catalyst was applied to bifunctional oxygen and hydrogen evolution reactions, as well as overall water splitting. The nature of active sites and structure–activity relationships of the electrocatalyst were uncovered.
      PubDate: 2017-07-19T06:21:25.808777-05:
      DOI: 10.1002/anie.201706196
       
  • Sol–Gel-Derived Biohybrid Materials Incorporating Long-Chain DNA
           Aptamers
    • Authors: Carmen Carrasquilla; Emily Kapteyn, Yingfu Li, John D. Brennan
      Abstract: Functional DNA biohybrids of macroporous silica material incorporating megadalton mass amplicons of tandem–repeating DNA aptamers are shown in the picture. In their Communication (
      DOI : 10.1002/anie.201702859), Y. Li, J. D. Brennan et al. report that these materials can be used as flow-based biosensors for multiplexed detection of a wide range of targets, greatly expanding the utility of sol–gel–derived biohybrid materials.
      PubDate: 2017-07-19T06:21:11.073296-05:
       
  • Controlling Regioselectivity in the Enantioselective N-Alkylation of
           Indole Analogues Catalyzed by Dinuclear Zinc-ProPhenol
    • Authors: Barry M. Trost; Elumalai Gnanamani, Chao-I (Joey) Hung
      Abstract: The enantioselective N-alkylation of indole and its derivatives with aldimines is efficiently catalyzed by a zinc-ProPhenol dinuclear complex under mild conditions to afford N-alkylated indole derivatives in good yield (up to 86 %) and excellent enantiomeric ratio (up to 99.5:0.5 e.r.). This method tolerates a wide array of indoles, as well as pyrrole and carbazole, to afford the corresponding N-alkylation products. The reaction can be run on a gram scale with reduced catalyst loading without impacting the efficiency. The chiral aminals were further elaborated into various chiral polyheterocyclic derivatives. The surprising stability of the chiral N-alkylation products will open new windows for asymmetric catalysis and medicinal chemistry.Enantioselective N-alkylation of indole and its derivatives with aldimines is efficiently catalyzed by a zinc-ProPhenol dinuclear complex under mild conditions to afford N-alkylated indole derivatives in good yield (up to 86 %) and excellent enantiomeric ratio (up to 99.5:0.5 e.r.). This method tolerates a wide array of indoles, as well as pyrrole and carbazole, to afford the corresponding N-alkylation products.
      PubDate: 2017-07-19T06:20:57.444578-05:
      DOI: 10.1002/anie.201705315
       
  • Iridium-Catalyzed Enantioselective Synthesis of Pyrrole-Annulated
           Medium-Sized-Ring Compounds
    • Authors: Lin Huang; Yue Cai, Chao Zheng, Li-Xin Dai, Shu-Li You
      Abstract: Enantioselective synthesis of pyrrole-annulated medium-sized-ring compounds by an iridium-catalyzed allylic dearomatization/retro-Mannich/hydrolysis sequence is presented. Various substituted pyrrole-annulated seven- and eight-membered-ring products were obtained under mild reaction conditions with moderate to good yields and excellent enantioselectivity. Additionally, these products contain a scaffold widely distributed in natural products and biologically active compounds. The current method provides a convenient way for accessing such pyrrole-anuulated medium-sized-ring compounds.Life without ‘pyrrole’: Enantioselective synthesis of pyrrole-annulated medium-sized-ring compounds by an iridium-catalyzed allylic dearomatization/retro-Mannich/hydrolysis sequence is presented. Various substituted pyrrole-annulated seven- and eight-membered-ring products were obtained under mild reaction conditions with moderate to good yields and excellent enantioselectivity.
      PubDate: 2017-07-19T06:16:01.578935-05:
      DOI: 10.1002/anie.201705068
       
  • Bromination of Cycloparaphenylenes: Strain-Induced Site-Selective
           Bis-Addition and its Application for Late-Stage Functionalization
    • Authors: Eiichi Kayahara; Rui Qu, Shigeru Yamago
      Abstract: Bromination of [n]cycloparaphenylenes (CPPs) is herein reported. Small [n]CPPs (n
      PubDate: 2017-07-19T06:15:48.987441-05:
      DOI: 10.1002/anie.201704982
       
  • Size Dependence of Doping by a Vacancy Formation Reaction in Copper
           Sulfide Nanocrystals
    • Authors: Orian Elimelech; Jing Liu, Anna M. Plonka, Anatoly I. Frenkel, Uri Banin
      Abstract: Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sized NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.Vacancy formation and plasmon response were analyzed in Cu2S semiconducting nanocrystals (NCs) treated with iodine (I2). The redox reaction between Cu2S and I2 creates vacancies in the Cu2S phase that increase in number with NC size. The plasmonic response can be tuned either by the size of the NCs or by the doping level of holes, which is governed by the I/Cu ratio.
      PubDate: 2017-07-19T06:15:43.309803-05:
      DOI: 10.1002/anie.201702673
       
  • Pancake Bond Orders of a Series of π-Stacked Triangulene Radicals
    • Authors: Zhongyu Mou; Miklos Kertesz
      Abstract: Conjugated radicals are capable of forming π-stacking “pancake-bonded” dimers. Members of the family of triangulene hydrocarbons, non-Kekulé neutral multiradicals, can utilize more than one singly occupied molecular orbital (SOMO) to form multiple pancake-bonded dimers with formal bond orders of up to five. The resulting dimer binding energies can be quite high and the intermolecular contacts rather small compared to the respective van der Waals values. The preferred configurations are driven by the large stabilization energy of overlapping SOMOs.High spin ground states of triangular graphene flakes allow the formation of short and strong through-space multiple π-stacking pancake bonds.
      PubDate: 2017-07-19T06:15:36.35157-05:0
      DOI: 10.1002/anie.201704941
       
  • A Porphyrin Complex as a Self-Conditioned Electrode Material for
           High-Performance Energy Storage
    • Authors: Ping Gao; Zhi Chen, Zhirong Zhao-Karger, Jonathan E. Mueller, Christoph Jung, Svetlana Klyatskaya, Thomas Diemant, Olaf Fuhr, Timo Jacob, R. Jürgen Behm, Mario Ruben, Maximilian Fichtner
      Abstract: The novel functionalized porphyrin [5,15-bis(ethynyl)-10,20-diphenylporphinato]copper(II) (CuDEPP) was used as electrodes for rechargeable energy-storage systems with an extraordinary combination of storage capacity, rate capability, and cycling stability. The ability of CuDEPP to serve as an electron donor or acceptor supports various energy-storage applications. Combined with a lithium negative electrode, the CuDEPP electrode exhibited a long cycle life of several thousand cycles and fast charge–discharge rates up to 53 C and a specific energy density of 345 Wh kg−1 at a specific power density of 29 kW kg−1. Coupled with a graphite cathode, the CuDEPP anode delivered a specific power density of 14 kW kg−1. Whereas the capacity is in the range of that of ordinary lithium-ion batteries, the CuDEPP electrode has a power density in the range of that of supercapacitors, thus opening a pathway toward new organic electrodes with excellent rate capability and cyclic stability.Give and take: Electrodes based on a copper porphyrin showed excellent capacity retention over several thousand cycles and very fast charge–discharge rates, thus opening a pathway to organic electrode materials with the capacity of a lithium-ion battery and the rate capability of a good supercapacitor. The ability of the porphyrin complex to serve as an electron donor or acceptor is advantageous for various energy-storage applications (see picture).
      PubDate: 2017-07-19T06:15:31.556424-05:
      DOI: 10.1002/anie.201702805
       
  • RadH a Versatile Halogenase for Integration into Synthetic Pathways.
    • Authors: Binuraj Menon; Eileen Brandenburger, Humera Sharif, Ulrike Klemstein, Sarah Shepherd, Michael Greaney, Jason Micklefield
      Abstract: Flavin-dependent halogenases are useful enzymes providing halogenated molecules with improved biological activity or intermediates for synthetic derivatization. Here we demonstrate how the fungal halogenase RadH can be used to regioselectively halogenate a range of bioactive aromatic scaffolds. Site-directed mutagenesis of RadH was used to identify catalytic residues and provide insights into the mechanism of fungal halogenases. A high throughput fluorescence screen was also developed enabling a RadH mutant to be evolved with improved properties. Finally we demonstrate how biosynthetic genes from fungi, bacteria and plants can be combined, to encode a new pathway generating a novel chlorinated coumarin 'non-natural' product in E. coli.
      PubDate: 2017-07-19T05:11:10.164429-05:
      DOI: 10.1002/anie.201706342
       
  • Control of Redox Events by Dye Encapsulation Applied to Light-driven
           Splitting of Hydrogen Sulfide
    • Authors: Xu Jing; Yang Yang, Cheng He, Zhiduo Chang, Joost N. H. Reek, Chunying Duan
      Abstract: Inspired by the pocket feature of enzymes, a synthetic platform to combine photocatalytic hydrogen evolution with sulfide oxidation in a one-pot process via control over the location of electron transfer steps is reported in this paper. The redox-active coordination vessel Ni-TFT, which exhibits an octahedral pocket, encapsulates an organic dye to pre-organize for photocatalytic proton reduction via an oxidative quenching pathway using the nickel corners as catalysts, generating molecular hydrogen and the oxidized dye. The oxidized dye is displaced by a neutral dye and oxidizes sulfide once outside the pocket to give element sulfur. The overall reaction constitutes hydrogen sulfide splitting, forming molecular hydrogen and elemental sulfur, which is analogous to the water-splitting reaction. The high efficiency, simple separation of hydrogen gas and sulfur solid from the reaction mixture, represent major advantages for potential applications.
      PubDate: 2017-07-19T04:16:45.313225-05:
      DOI: 10.1002/anie.201704327
       
  • Enantioselective Synthesis of Acyclic α-Quaternary Carboxylic Acid
           Derivatives via Iridium-Catalyzed Allylic Alkylation
    • Authors: Samantha Shockley; John Caleb Hethcox, Brian Stoltz
      Abstract: : The first highly enantioselective iridium-catalyzed allylic alkylation providing access to products bearing an allylic all-carbon quaternary stereogenic center has been developed. The reaction utilizes a masked acyl cyanide (MAC) reagent, which enables the one-pot preparation of α-quaternary carboxylic acids, esters, and amides with a high degree of enantioselectivity. The utility of these products is further explored via a series of diverse product transformations.
      PubDate: 2017-07-19T04:16:42.31666-05:0
      DOI: 10.1002/anie.201707015
       
  • Understanding the Role of Additive Leads to an Improved Synthetic Protocol
           Obviating Additive: Organocatalytic Synthesis of Chiral Diarylmethyl
           Alkynes
    • Authors: Min Chen; Jianwei Sun
      Abstract: The use of additives for organic synthesis has become a common tactic to improve organic reaction outcomes. In this report, using an organocatalytic process for the synthesis of chiral diarylmethyl alkynes as a platform, we describe how an additive is involved in the improvement of the process. The evolution of an excellent synthetic protocol has been achieved via three stages, from (1) initially no catalyst turnover to (2) good conversion and enantioselectivity with a superior additive, and eventually (3) even better efficiency and selectivity without using additive. It is an important and rare demonstration that understanding the role of additive can be so beneficial as to obviate using the additive.
      PubDate: 2017-07-19T04:16:36.653107-05:
      DOI: 10.1002/anie.201706579
       
  • Anti-Markovnikov Hydrofunctionalization of Alkenes - Use of a Benzyl Group
           as a Traceless Redox-active Hydrogen Donor
    • Authors: Geoffroy Hervé Lonca; Derek Yiren Ong, Thi Mai Huong Tran, Ciputra Tejo, Shunsuke Chiba, Fabien Gagosz
      Abstract: A protocol for the anti-Markovnikov hydrofunctionalization of alkenes, that utilizes a benzyl group as a traceless redox-active hydrogen donor, has been developed. Under copper catalysis and in the presence of CF3- or N3-containing hypervalent iodine reagents, a series of homoallylic alcohol derivatives could be regioselectivity hydrofunctionalized. A similar principle was also applied to the hydrofunctionalization of alkenols.
      PubDate: 2017-07-19T04:16:23.709968-05:
      DOI: 10.1002/anie.201705368
       
  • Metal-Free Nitrile Diboration through Activation by an Electron-Rich
           Diborane
    • Authors: Markus Frick; Elisabeth Kaifer, Hans-Jörg Himmel
      Abstract: Diboration of unsaturated organic compounds is an extremely useful reaction in synthetic chemistry. Herein we report the first diboration of a nitrile by an electron-rich diborane, mediated by an electrophilic borane. The reaction is metal-free, and all reagents are readily available.
      PubDate: 2017-07-19T03:05:38.951006-05:
      DOI: 10.1002/anie.201706001
       
  • Unusual Internal Electron Transfer in Conjugated Radical Polymers
    • Authors: Fei Li; Danielle N Gore, Shaoyang Wang, Jodie L Lutkenhaus
      Abstract: Nitroxide-containing organic radical polymers (ORPs) have captured attention for their high power and fast redox kinetics. Yet a major challenge is the polymer's aliphatic backbone, resulting in a low electronic conductivity. Recent attempts that replace the aliphatic backbone with a conjugated one have not met with success. The reason for this is not understood until now. We examine a family of polythiophenes bearing nitroxide radical groups, showing that while both species are electrochemically active, there exists an internal electron transfer mechanism that interferes with stabilization of the polymer's fully oxidized form. This finding directs the future design of conjugated radical polymers in energy storage and electronics, where careful attention to the redox potential of the backbone relative to the organic radical species is needed.Conjugated radical polymers: Evidence for the internal transfer of an electron from a nitroxide group to the polythiophene backbone explains the conductivity and redox activity of polythiophenes bearing pendant nitroxide radicals.
      PubDate: 2017-07-19T03:02:03.811429-05:
      DOI: 10.1002/anie.201705204
       
  • Frontispiece: Water Transport with Ultralow Friction through Partially
           Exfoliated g-C3N4 Nanosheet Membranes with Self-Supporting Spacers
    • Authors: Yanjie Wang; Libo Li, Yanying Wei, Jian Xue, Huang Chen, Li Ding, Jürgen Caro, Haihui Wang
      Abstract: Ultralow Friction MembranesIn their Communication on page 8974 ff., J. Caro et al. report a water purification membrane composed of 2D g-C3N4 nanosheets. Self-supporting spacers and intrinsic and artificial nanopores promote water transport with ultralow friction.
      PubDate: 2017-07-19T02:33:31.294438-05:
      DOI: 10.1002/anie.201783161
       
  • Stereospecific 1,3-Aminobromination of Donor-Acceptor Cyclopropanes
    • Authors: Saikat Das; Constantin Gabriel Daniliuc, Armido Studer
      Abstract: Sn(OTf)2-catalyzed 1,3-aminobromination of donor-acceptor cyclopropanes with various sulfonyl amides or electron poor anilines and N-bromosuccinimide is reported. Reactions which are experimentally easy to conduct, occur with complete regio- and stereospecificity (for anilines) resulting in γ-aminated α-brominated malonic diesters which are obtained in good to excellent yields (up to 98%). These compounds are valuable substrates for follow-up chemistry to provide substituted azetidines and γ-lactams in high yields.
      PubDate: 2017-07-19T02:30:32.718751-05:
      DOI: 10.1002/anie.201704092
       
  • Suppression of Oligomer Formation and Formation of Non-Toxic Fibrils upon
           Addition of Mirror-Image Aβ42 to the Natural l-Enantiomer
    • Authors: Subrata Dutta; Alejandro R. Foley, Christopher J. A. Warner, Xiaolin Zhang, Marco Rolandi, Benjamin Abrams, Jevgenij A. Raskatov
      Abstract: Racemates often have lower solubility than enantiopure compounds, and the mixing of enantiomers can enhance the aggregation propensity of peptides. Amyloid beta (Aβ) 42 is an aggregation-prone peptide that is believed to play a key role in Alzheimer's disease. Soluble Aβ42 aggregation intermediates (oligomers) have emerged as being particularly neurotoxic. We hypothesized that the addition of mirror-image d-Aβ42 should reduce the concentration of toxic oligomers formed from natural l-Aβ42. We synthesized l- and D-Aβ42 and found their equimolar mixing to lead to accelerated fibril formation. Confocal microscopy with fluorescently labeled analogues of the enantiomers showed their colocalization in racemic fibrils. Owing to the enhanced fibril formation propensity, racemic Aβ42 was less prone to form soluble oligomers. This resulted in the protection of cells from the toxicity of l-Aβ42 at concentrations up to 50 μm. The mixing of Aβ42 enantiomers thus accelerates the formation of non-toxic fibrils.The mixing of the two enantiomers of Aβ42 leads to a drastic acceleration of fibrillization. By using fluorescently labeled analogues, it was shown that the degree of enantiomer colocalization in racemic fibrils is high. The reduced propensity of the racemate to yield oligomeric aggregation intermediates resulted in inhibition of the toxicity of the natural l-Aβ42 enantiomer in the racemate.
      PubDate: 2017-07-19T02:17:22.595299-05:
      DOI: 10.1002/anie.201706279
       
  • Mineralized State of the Avian Influenza Virus in the Environment
    • Authors: Hangyu Zhou; Guangchuan Wang, Xiaoyu Wang, Zhiyong Song, Ruikang Tang
      Abstract: Although the circulation of avian influenza in humans is limited, they can be transmitted from Aves to humans, representing a great challenge. Herein, we suggest that influenza viruses from Aves might exist in a mineralized state due to the high calcium concentrations in the avian intestine. Using two typical influenza viruses as examples, we demonstrate these viruses can self-mineralize in simulated avian intestinal fluid, resulting in egg-like virus-mineral structured composites. The mineralized viruses are more robust, with enhanced infectivity and thermostability. More importantly, the mineral exterior of mineralized viruses can alter their cell internalization, expanding the possible tropisms. The discovery of a mineralized state of influenza highlights the integration of nanomaterials and viruses in the environment, which provides a new understanding of avian influenza infection and its control.
      PubDate: 2017-07-18T23:30:34.27042-05:0
      DOI: 10.1002/anie.201705769
       
  • Branched Aramid Nanofibers
    • Authors: Jian Zhu; Ming Yang, Ahmet Emre, Joong Hwan Bahng, Lizhi Xu, Jihyeon Yeom, Bongjun Yeom, Yoonseob Kim, Kyle Johnson, Peter Green, Nicholas Alexander Kotov
      Abstract: Interconnectivity of molecular or nanoscale components in three-dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network relies on weak short-range intermolecular interactions. The intrinsic stiffness and rod-like geometry of known nanofibers limits the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Here, we show that branched aramid nanofibers (BANFs) readily produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible with the number of branches controlled by the base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro- and aerogel monoliths with an order of magnitude less solid content than rod-like nanocomponents. Branching of the nanofibers also leads to improved mechanics of gels and nanocomposites
      PubDate: 2017-07-18T21:35:35.244894-05:
      DOI: 10.1002/anie.201703766
       
  • Rare Earth- and Uranium-Mesoionic Carbenes: A New Class of f-Block Carbene
           Complex Derived from an N-Heterocyclic Olefin
    • Authors: Stephen Liddle; John Seed, Matthew Gregson, Floriana Tuna, Nicholas Chilton, Ashley Wooles, Eric McInnes
      Abstract: Neutral mesoionic carbenes (MICs) have emerged as an important class of carbene, however they are found only in the free form or ligated to a few d-block ions. Here, we report unprecedented f-block MIC complexes [M(N'')3{CN(Me)C(Me)N(Me)CH}] (M = U, Y, La, Nd; N'' = N(SiMe3)2). These complexes were prepared by a formal 1,4-proton migration reaction when the metal-triamides [M(N'')3] were treated with the N-heterocyclic olefin H2C=C(NMeCH)2, which constitutes a new, general way to prepare MIC complexes. Quantum chemical calculations on the 5f3 uranium(III) complex suggest the presence of a U=C donor-acceptor bond, composed of a MICU σ-component and a U(5f)MIC(2p) π-back-bond, but for the d0f0 Y and La and 4f3 Nd congeners only MICM σ-bonding is found. Considering the generally negligible π-acidity of MICs, this is surprising and highlights that greater consideration should possibly be given to recognising MICs as potential π-acid ligands when coordinated to reducing metals.
      PubDate: 2017-07-18T11:30:41.623431-05:
      DOI: 10.1002/anie.201706546
       
  • Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10
           Two-dimensional Multilayered Perovskite Ferroelectric for High Performance
           Photodetectors
    • Authors: Junhua Luo; Lina Li, Zhihua Sun, Peng Wang, Weida Hu, Sasa Wang, Chengmin Ji, Maochun Hong
      Abstract: Two-dimensional (2D) layered hybrid perovskites have shown great potentials in optoelectronics. However, although great efforts have been made, 2D hybrid perovskite ferroelectrics remain rare. Here, we constructed the first ferroelectric with 2D multilayered perovskite framework, (C4H9NH3)2(CH3NH3)2Pb3Br10 (1), by tailored alloying mixed-organic-cations into the prototype of CH3NH3PbBr3. For the first time, concrete ferroelectricity was created by molecular reorientation and synergic ordering of organic cations, which is unprecedented for the known 2D hybrid perovskites. Besides, single-crystal photodetectors of 1 show fascinating behaviors, such as extremely low dark current (10-12 A), large on/off current ratio (2.5×103) and highly-fast response rate (150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH3NH3PbI3. This work paves a pathway to design new hybrid ferroelectrics for high-performance optoelectronic devices.
      PubDate: 2017-07-18T08:31:14.645461-05:
      DOI: 10.1002/anie.201705836
       
  • New Insight into Magnetic Interaction in Monodisperse Gd12Fe14 Metal
           Cluster
    • Authors: Xiu-Ying Zheng; Hui Zhang, Zhenxing Wang, Pengxin Liu, Ming-Hao Du, Ying-Zi Han, Rong-Jia Wei, Zhongwen Ouyang, Xiang-Jian Kong, Gui-Lin Zhuang, La-Sheng Long, Lan-Sun Zheng
      Abstract: Largest Ln-Fe metal cluster of [Gd12Fe14(μ3-OH)12(μ4-OH)6(μ4-O)12(TEOA)6(CH3COO)16(H2O)8]*(CH3COO)2(CH3CN)2* (H2O)20 (1) and core-shell monodisperse metal cluster of 1a@SiO2 (1a = [Gd12Fe14(μ3-OH)12(μ4-OH)6(μ4-O)12(TEOA)6(CH3COO)16 (H2O)8]2+) were prepared. Experimental and theoretical studies on the magnetic properties of 1 and 1a@SiO2 reveal that encapsulation of one cluster into one silica nanosphere not only effectively decreases intermolecular magnetic interaction but also significantly increases the zero-field splitting effect of the outer layer Fe3+ ions.
      PubDate: 2017-07-18T08:31:01.942411-05:
      DOI: 10.1002/anie.201705697
       
  • Development of new supramolecular lyotropic liquid crystals and their
           application as alignment media for organic compounds
    • Authors: Martin Leyendecker; Nils-Christopher Meyer, Christina Thiele
      Abstract: Most alignment media for the residual dipolar coupling (RDC) based molecular structure determination of small organic compounds consist of rod-like polymers dissolved in organic solvents or of swollen cross-linked polymer gels. So far the synthesis of polymer based alignment media is a challenging process which is often followed by a time consuming sample preparation. We propose the use of non-polymeric alignment media based on benzene-tricarboxamides (BTA) which self-assemble into rod-like supramolecules. Our newly found supramolecular lyotropic liquid crystals (LLC) are characterized for LLC properties and their suitability as alignment medium in NMR spectroscopy. Scalable enantiodifferentiating properties are introduced through a sergeant-and-soldier principle by blending achiral with chiral substituted BTAs.
      PubDate: 2017-07-18T08:30:42.438474-05:
      DOI: 10.1002/anie.201705642
       
  • Cesium's Off-the-Map Valence Orbital
    • Authors: Maarten G. Goesten; Martin Rahm, F. Matthias Bickelhaupt, Emiel J. M. Hensen
      Abstract: The Td-symmetric [CsO4]+ ion, featuring Cs in an oxidation state of 9, is computed to be a minimum. Cs uses outer core 5s and 5p orbitals to bind the oxygen atoms. The valence Cs 6s orbital lies too high to be involved in bonding, and contributes to Rydberg levels only. From a molecular orbital perspective, the bonding scheme is reminiscent of XeO4: an octet of electrons to bind electronegative ligands, and no low-lying acceptor orbitals on the central atom. In this sense, Cs+ resembles hypervalent Xe.Cesium seizes the initiative: The Td-symmetric [CsO4]+ ion, featuring cesium in an oxidation state of IX, is computed to be a minimum. Cs uses outer core 5s and 5p orbitals to bind the oxygen atoms. The valence Cs 6s orbital lies too high to be involved in bonding, and contributes to Rydberg levels only.
      PubDate: 2017-07-18T06:55:38.351327-05:
      DOI: 10.1002/anie.201704118
       
  • Unconventional Route to Uniform Hollow Semiconducting Nanoparticles with
           Tailorable Dimensions, Compositions, Surface Chemistry and Near-Infrared
           Absorption
    • Authors: Yanjie He; Xinchang Pang, Beibei Jiang, Chaowei Feng, Yeu Wei Harn, Yihuang Chen, Young Jun Yoon, Shuang Pan, Cheng-Hsin Lu, Yajing Chang, Mona Zebarjadi, Zhitao Kang, Naresh Thadhani, Juan Peng, Zhiqun Lin
      Abstract: Despite recent impressive advances in synthesizing lead chalcogenide solid nanoparticles, there are no demonstrations of lead chalcogenide hollow nanoparticles (HNPs) with controlled hollow diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with inability to precisely control the dimensions and restriction of applicable materials in scope. Herein, we report on an unconventional strategy for crafting uniform PbS and PbTe HNPs with tailorable size, surface chemistry, and near-IR absorption. Amphiphilic star-like PS-b-PAA-b-PS and PS-b-PAA-b-PEDOT triblock copolymers are rationally synthesized and exploited as nanoreactors to create uniform PbS and PbTe HNPs. Compared to solid NPs, the near-IR absorption of HNPs exhibits a blue-shift due to the presence of hollow interior. The star-like block copolymer nanoreactor strategy can be readily extended to create other types of intriguing low bandgap HNPs for diverse applications.
      PubDate: 2017-07-18T03:15:52.875948-05:
      DOI: 10.1002/anie.201706182
       
  • Stabilizing Otherwise Unstable Anions with Halogen Bonding
    • Authors: Xinxing Zhang; Gaoxiang Liu, Sandra Ciborowski, Kit Bowen
      Abstract: Both hydrogen bonding (HB) and halogen bonding (XB) are essentially electrostatic interactions, but whereas hydrogen bonding has a well-documented record of stabilizing unstable anions, little is known about halogen bonding's ability to do so. Herein, we present a combined anion photoelectron spectroscopic and density functional theory study of the halogen bond-stabilization of the pyrazine (Pz) anion, an unstable anion in isolation due to its neutral counterpart having a negative electron affinity (EA). The halogen bond formed between the σ-hole on bromobenzene (BrPh) and the lone pair(s) of Pz significantly lowers the energies of the Pz(BrPh)1− and Pz(BrPh)2− anions relative to the neutral molecule, resulting in the emergence of a positive EA for the neutral complexes. As seen through its charge distribution and electrostatic potential analyses, the negative charge on Pz− is diluted due to the XB. Thermodynamics reveals that the low temperature of the supersonic expansion plays a key role in forming these complexes.Anything you can do, I can do: Unlike hydrogen bonding (HB), halogen bonding (XB) has not been utilized in stabilizing unstable anions. XB was used for the first time to stabilize otherwise unstable pyrazine anions.
      PubDate: 2017-07-18T02:27:50.732515-05:
      DOI: 10.1002/anie.201705738
       
  • TMSCF3 as a Convenient Source of CF2=CF2 for Pentafluoroethylation,
           (Aryloxy)tetrafluoroethylation, and Tetrafluoroethylation
    • Authors: Lingchun Li; Chuanfa Ni, Qiqiang Xie, Mingyou Hu, Fei Wang, Jinbo Hu
      Abstract: A new method for the on-site preparation of tetrafluoroethylene (TFE) and a procedure for its efficient use in pentafluoroethylation by fluoride addition were developed by using a simple two-chamber system. The on-site preparation of TFE was accomplished by dimerization of difluorocarbene derived from (trifluoromethyl)trimethylsilane (TMSCF3) under mild conditions. Other fluoroalkylation reactions, such as (aryloxy)tetrafluoroethylation and tetrafluoroethylation processes, were also achieved using a similar approach. This work not only demonstrates a convenient and safe approach for the generation and use of TFE in academic laboratories, but also provides a new strategy for pentafluoroethylation.In your own lab: The on-site generation of CF2=CF2 from TMSCF3 under mild conditions is possible with a two-chamber system and can be used for per- or polyfluoroalkylation. This study describes a convenient and safe approach for the use of CF2=CF2 in standard laboratories, and provides a new method for pentafluoroethylation.
      PubDate: 2017-07-18T02:27:47.110458-05:
      DOI: 10.1002/anie.201705734
       
  • Unsupported Pt-Ni Aerogels with Enhanced High Current Performance and
           Durability in Fuel Cell Cathodes
    • Authors: Sebastian Henning; Hiroshi Ishikawa, Laura Kühn, Juan Herranz, Elisabeth Müller, Alexander Eychmüller, Thomas J. Schmidt
      Abstract: Highly active and durable oxygen reduction catalysts are needed to reduce the costs and enhance the service life of polymer electrolyte fuel cells (PEFCs). This can be accomplished by alloying Pt with a transition metal (for example Ni) and by eliminating the corrodible, carbon-based catalyst support. However, materials combining both approaches have seldom been implemented in PEFC cathodes. In this work, an unsupported Pt-Ni alloy nanochain ensemble (aerogel) demonstrates high current PEFC performance commensurate with that of a carbon-supported benchmark (Pt/C) following optimization of the aerogel's catalyst layer (CL) structure. The latter is accomplished using a soluble filler to shift the CL's pore size distribution towards larger pores which improves reactant and product transport. Chiefly, the optimized PEFC aerogel cathodes display a circa 2.5-fold larger surface-specific ORR activity than Pt/C and maintain 90 % of the initial activity after an accelerated stress test (vs. 40 % for Pt/C).An unsupported bimetallic ORR (oxygen reduction reaction) catalyst has been implemented in a polymer electrolyte fuel cell. This ORR catalyst leads to enhanced high current performance and superior durability in accelerated stress tests.
      PubDate: 2017-07-18T02:27:41.278708-05:
      DOI: 10.1002/anie.201704253
       
  • Microfluidic Formation of Monodisperse Coacervate Organelles in Liposomes
    • Authors: Nan-Nan Deng; Wilhelm T. S. Huck
      Abstract: Coacervates have been widely studied as model compartments in protocell research. Complex coacervates composed of disordered proteins and RNA have also been shown to play an important role in cellular processes. Herein, we report on a microfluidic strategy for constructing monodisperse coacervate droplets encapsulated within uniform unilamellar liposomes. These structures represent a bottom-up approach to hierarchically structured protocells, as demonstrated by storage and release of DNA from the encapsulated coacervates as well as localized transcription.Artificial organelles: Monodisperse liposomes containing monodisperse dynamic, functional compartments were achieved using microfluidics and employed as artificial/protocell models to imitate membrane-less intracellular organelle-based compartmentalization.
      PubDate: 2017-07-18T02:26:51.494552-05:
      DOI: 10.1002/anie.201703145
       
  • SN2 Reactions at Tertiary Carbon Centers in Epoxides
    • Authors: Yong-Qiang Zhang; Christina Poppel, Anastasia Panfilova, Fabian Bohle, Stefan Grimme, Andreas Gansäuer
      Abstract: Described herein is a novel concept for SN2 reactions at tertiary carbon centers in epoxides without activation of the leaving group. Quantum chemical calculations show why SN2 reactions at tertiary carbon centers are proceeding in these systems. The reaction allows flexible synthesis of 1,3-diol building blocks for natural product synthesis with excellent control of the relative and absolute configurations.Under attack: SN2 reactions at tertiary carbon centers in epoxides are possible when the angle of the “backside attack” is controlled. This control is achieved by binding of the reagent and its activation to hydride transfer by fluoride. The reaction proceeds with excellent regioselectivity and allows the synthesis of many acetate- and propionate-derived 1,3-diol units pertinent to natural product synthesis.
      PubDate: 2017-07-18T02:26:28.994394-05:
      DOI: 10.1002/anie.201702882
       
  • High-Field NMR Spectroscopy Reveals Aromaticity-Modulated Hydrogen Bonding
           in Heterocycles
    • Authors: Tayeb Kakeshpour; John P. Bailey, Madison R. Jenner, Darya E. Howell, Richard J. Staples, Daniel Holmes, Judy I. Wu, James E. Jackson
      Abstract: From DNA base pairs to drug–receptor binding, hydrogen (H-)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored. H-bond strength modulation due to enhancement or disruption of aromaticity of heterocycles is experimentally revealed by comparing homodimer H-bond energies of aromatic heterocycles with analogs that have the same H-bonding moieties but lack cyclic π-conjugation. NMR studies of dimerization in C6D6 find aromaticity-modulated H-bonding (AMHB) energy effects of approximately ±30 %, depending on whether they enhance or weaken aromatic delocalization. The attendant ring current perturbations expected from such modulation are confirmed by chemical shift changes in both observed ring C−H and calculated nucleus-independent sites. In silico modeling confirms that AMHB effects outweigh those of hybridization or dipole–dipole interaction.Fine-tuning of H-bonding: High-field NMR measurements show that the hydrogen bonding strength of heterocycles is effectively modulated by perturbation of their aromaticity upon hydrogen bonding in solution. Quantum chemical investigations show that these aromaticity perturbations are dominant, outweighing hybridization or dipole effects.
      PubDate: 2017-07-18T02:25:33.215174-05:
      DOI: 10.1002/anie.201705023
       
  • Arthur C. Cope Scholar Awards
    • PubDate: 2017-07-18T02:20:41.776806-05:
      DOI: 10.1002/anie.201706659
       
  • Isothermal Chirality Switching with Non-Polarized Light
    • Authors: Mohamed Alaasar; Silvio Poppe, Qingshu Dong, Feng Liu, Carsten Tschierske
      Abstract: Spontaneous mirror symmetry breaking is a fundamental process for development of chirality in natural and in artificial self-assembled systems. Here we report a new series of triple chain azobenzene based rod-like compounds, which for the first time show mirror symmetry breaking in an isotropic liquid occurring adjacent to a lamellar LC phase. The transition between the lamellar phase and the symmetry broken liquid is affected by trans-cis photoisomerization which allows a fast and reversible photoinduced switching between chiral and achiral states with non-polarized light.
      PubDate: 2017-07-18T02:15:35.991986-05:
      DOI: 10.1002/anie.201705559
       
  • One-Compound-Based Highly Efficient Deep-Red to Near-Infrared Thermally
           Activated Delayed Fluorescence Organic Solid Films and Electroluminescent
           Devices
    • Authors: Yue Wang; Chenglong Li, Ruihong Duan, Baoyan Liang, Guangchao Han, Shipan Wang, Kaiqi Ye, Yu Liu, Yuanping Yi
      Abstract: The design and synthesis of highly efficient deep red (DR) and near-infrared (NIR) organic emitting materials with characteristic of thermally activated delayed fluorescence (TADF) still remains a great challenge. In this contribution, we developed a strategy to construct TADF organic solid films with strong DR or NIR emission feature. The triphenylamine (TPA) and quinoxaline-6,7-dicarbonitrile (QCN) were respectively employed as electron donor (D) and acceptor (A) to synthesize a TADF compound, TPA-QCN. The TPA-QCN molecule with orange-red emission in solution was employed as a dopant to prepare DR and NIR luminescent solid thin films. The high doped concentration and neat films exhibited efficient DR and NIR emissions, respectively. The highly efficient DR and NIR organic light-emitting devices (OLEDs) were fabricated by regulating TPA-QCN dopant concentration in the emitting layers.
      PubDate: 2017-07-17T22:16:27.626298-05:
      DOI: 10.1002/anie.201706464
       
  • A Boron Alkylidene-Alkene Cycloaddition Reaction: Application to the
           Synthesis of Aphanamal
    • Authors: James Patrick Morken; Xun Liu, Timothy Maxwell Deaton, Fredrik Haeffner
      Abstract: We describe an unusual net 2+2 cycloaddition reaction between boron alkylidenes and unactivated alkenes. This reaction provides a new method for construction of carbocyclic ring systems bearing versatile organoboronic esters. In addition to surveying the scope of this reaction, we provide details about the mechanistic underpinnings of this process, and examine application to the synthesis of the natural product aphanamal.
      PubDate: 2017-07-17T22:16:18.301354-05:
      DOI: 10.1002/anie.201705720
       
  • Properties of water confined in periodic mesoporous organosilicas -
           nanoimprinting the local structure
    • Authors: Michael Fröba; J. Benedikt Mietner, Felix J. Brieler, Young Joo Lee
      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. Here, 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 directly probes the spatial arrangement of water inside the pores, demonstrating 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. Our study gives a molecular-level picture of the adsorbate-surface interaction, which helps understanding confinement effects and provides a new design concept of the pore structures with the desired properties
      PubDate: 2017-07-17T13:15:27.437542-05:
      DOI: 10.1002/anie.201705707
       
  • Ionophore-based anion-selective optode printed on cellulose paper
    • Authors: Xuewei Wang; Qi Zhang, Changwoo Nam, Michael Hickner, Mollie Mahoney, Mark Meyerhoff
      Abstract: We report a general anion sensing platform based on a portable and cost-effective ion-selective optode and a smartphone detector equipped with a color analysis app. In contrast to traditional anion-selective optodes using a hydrophobic polymer and/or plasticizer to dissolve hydrophobic sensing elements, the new optode relies on hydrophilic cellulose paper. The anion ionophore and a lipophilic pH indicator are inkjet-printed and adsorbed on paper and form a "dry" hydrophobic sensing layer. Porous cellulose sheets also allow the sensing site to be modified with dried buffer that prevents any sample pH dependence of the observed color change. A highly selective fluoride optode using an Al(III)-porphyrin ionophore is examined as an initial example of this new anion sensing platform for measurements of fluoride levels in drinking water samples. In addition to Lewis acid-base recognition, hydrogen bonding recognition is also shown to be compatible with this sensing platform.
      PubDate: 2017-07-17T12:15:46.054506-05:
      DOI: 10.1002/anie.201706147
       
  • Cyclodextrin cavity-induced mechanistic switch in copper-catalyzed
           hydroboration
    • Authors: Pinglu Zhang; Jorge Meijide Suarez, Thomas Driant, Etienne Derat, Yongmin Zhang, Mickaël Ménand, Sylvain Roland, Matthieu Sollogoub
      Abstract: NHC-capped cyclodextrin (ICyD) ligands, α-ICyD and β-ICyD derived from α- and β-cyclodextrin respectively give opposite regioselectivities in a copper-catalyzed hydroboration. The site-selectivity results from two different mechanisms: the conventional "parallel" one and a new "orthogonal" mechanism. The shape of the cavity was shown not only to induce a regioselectivity switch but also a mechanistic switch. The scope of interest of the encapsulation of a reactive center is therefore broadened by this study.
      PubDate: 2017-07-17T08:19:04.707861-05:
      DOI: 10.1002/anie.201705303
       
  • Nuclear Spin Isomers: Engineering a Et4N[DyPc2] Spin Qudit
    • Authors: Eufemio Moreno-Pineda; Marko Damjanović, Olaf Fuhr, Wolfgang Wernsdorfer, Mario Ruben
      Abstract: Two dysprosium isotopic isomers were synthesized: Et4N[163DyPc2] (1) with I=5/2 and Et4N[164DyPc2] (2) with I=0 (where Pc=phthalocyaninato). Both isotopologues are single-molecule magnets (SMMs); however, their relaxation times as well as their magnetic hystereses differ considerably. Quantum tunneling of the magnetization (QTM) at the energy level crossings is found for both systems via ac-susceptibility and μ-SQUID measurements. μ-SQUID studies of 1(I=5/2) reveal several nuclear-spin-driven QTM events; hence determination of the hyperfine coupling and the nuclear quadrupole splitting is possible. Compound 2(I=0) shows only strongly reduced QTM at zero magnetic field. 1(I=5/2) could be used as a multilevel nuclear spin qubit, namely qudit (d=6), for quantum information processing (QIP) schemes and provides an example of novel coordination-chemistry-discriminating nuclear spin isotopes. Our results show that the nuclear spin of the lanthanide must be included in the design principles of molecular qubits and SMMs.En route to quantum computers: The isotopologic lanthanide double-deckers Et4N[163DyPc2] and Et4N[164DyPc2] (Pc=phthalocyaninato, see figure) display quantum tunneling of the magnetization. Due to the quantum properties observed in Et4N[163DyPc2], this molecule could be considered as a plausible nuclear spin qudit (d=6) candidate for novel data search algorithms.
      PubDate: 2017-07-17T08:18:53.723545-05:
      DOI: 10.1002/anie.201706181
       
  • A Convergent Synthesis of Functionalized Alkenyl Halides through
           Cobalt(III)-Catalyzed Three-Component C−H Bond Addition
    • Authors: Jeffrey A. Boerth; Jonathan A. Ellman
      Abstract: A CoIII-catalyzed three-component coupling of C(sp2)−H bonds, alkynes, and halogenating agents to give alkenyl halides is reported. This transformation proceeds with high regio- and diastereoselectivity, and is effective for a broad range of aryl and alkyl terminal alkynes. Diverse C−H bond partners also exhibit good reactivity for a range of heteroaryl and aryl systems as well as synthetically useful secondary and tertiary amide, urea, and pyrazole directing groups. This multicomponent transformation is also compatible with allenes in place of alkynes to furnish tetrasubstituted alkenyl halides, showcasing the first halo-arylation of allenes.Triple Play: A convergent assembly of functionalized alkenyl halides through CoIII-catalyzed three-component C−H bond addition across alkynes and halogenating agents is reported. The reaction proceeds with high regio- and diastereoselectivity and is effective for a wide range of alkynes and C−H bond substrates. Allenes are also suitable substrates for the preparation of tetrasubstituted alkenyl halide products.
      PubDate: 2017-07-17T08:18:37.485388-05:
      DOI: 10.1002/anie.201705817
       
  • The Covalent Functionalization of Layered Black Phosphorus by Nucleophilic
           Reagents
    • Authors: Zdeněk Sofer; Jan Luxa, Daniel Bouša, David Sedmidubský, Petr Lazar, Tomáš Hartman, Hilde Hardtdegen, Martin Pumera
      Abstract: Layered black phosphorus has been attracting great attention due to its interesting material properties which lead to a plethora of proposed applications. Several approaches are demonstrated here for covalent chemical modifications of layered black phosphorus in order to form P−C and P-O-C bonds. Nucleophilic reagents are highly effective for chemical modification of black phosphorus. Further derivatization approaches investigated were based on radical reactions. These reagents are not as effective as nucleophilic reagents for the surface covalent modification of black phosphorus. The influence of covalent modification on the electronic structure of black phosphorus was investigated using ab initio calculations. Covalent modification exerts a strong effect on the electronic structure including the change of band-gap width and spin polarization.More than P's: Layered black phosphorus can be modified at the surface by the formation of covalent P−C and P-O-C bonds through nucleophilic substitution using halogen and hydroxyl derivatives.
      PubDate: 2017-07-17T08:18:18.067595-05:
      DOI: 10.1002/anie.201705722
       
  • Nickel-Catalyzed Intermolecular Carbosulfonylation of Alkynes via Sulfonyl
           Radicals
    • Authors: Andrés García-Domínguez; Simona Müller, Cristina Nevado
      Abstract: β,β-Disubstituted vinyl sulfones were obtained with complete regio- and stereocontrol in a multicomponent reaction involving alkynes, organoboronic acids, and sulfonyl chlorides in the presence of a nickel catalyst. The reaction proceeds via sulfonyl radicals generated in situ under mild reaction conditions.Running mild: Readily available alkynes, boronic acids, and sulfonyl chlorides can be combined in the presence of a Ni catalyst to produce β,β-disubstituted vinyl sulfones with complete regio- and stereocontrol. The reaction proceeds via sulfonyl radicals generated in situ under mild reaction conditions and with high functional-group tolerance.
      PubDate: 2017-07-17T08:18:12.652727-05:
      DOI: 10.1002/anie.201704862
       
  • Analyzing Reaction Rates with the Distortion/Interaction-Activation Strain
           Model
    • Authors: F. Matthias Bickelhaupt; Kendall N. Houk
      Abstract: The activation strain or distortion/interaction model is a tool to analyze activation barriers that determine reaction rates. For bimolecular reactions, the activation energies are the sum of the energies to distort the reactants into geometries they have in transition states plus the interaction energies between the two distorted molecules. The energy required to distort the molecules is called the activation strain or distortion energy. This energy is the principal contributor to the activation barrier. The transition state occurs when this activation strain is overcome by the stabilizing interaction energy. Following the changes in these energies along the reaction coordinate gives insights into the factors controlling reactivity. This model has been applied to reactions of all types in both organic and inorganic chemistry, including substitutions and eliminations, cycloadditions, and several types of organometallic reactions.The core concepts of a model are presented that explain reaction profiles and energy barrier heights in terms of reactant properties, in particular, the strain associated with distorting the reactants and the interaction between the distorted reactants (see picture). This model is known as both the activation strain model and the distortion/interaction model.
      PubDate: 2017-07-17T08:18:03.802232-05:
      DOI: 10.1002/anie.201701486
       
  • A Self-Sacrificing N-Methyltransferase Is the Precursor of the Fungal
           Natural Product Omphalotin
    • Authors: Sascha Ramm; Bartlomiej Krawczyk, Agnes Mühlenweg, Annette Poch, Eva Mösker, Roderich D. Süssmuth
      Abstract: Research on ribosomally synthesized and posttranslationally modified peptides (RiPPs) has led to an increasing understanding of biosynthetic mechanisms, mostly drawn from bacterial examples. In contrast, reports on RiPPs from fungal producers, apart from the amanitins and phalloidins, are still scarce. The fungal cyclopeptide omphalotin A carries multiple N-methylations on the peptide backbone, a modification previously known only from nonribosomal peptides. Mining the genome of the omphalotin-producing fungus for a precursor peptide led to the identification of two biosynthesis genes, one encoding a methyltransferase OphMA that catalyzes the automethylation of its C-terminus, which is then released and cyclized by the protease OphP. Our findings suggest a novel biosynthesis mechanism for a RiPP in which a modifying enzyme bears its own precursor peptide.Keep your tail up: The fungal cyclopeptide omphalotin A carries multiple N-methylations on the peptide backbone. Genome mining of the omphalotin-producing fungus for a precursor peptide identified two biosynthesis genes; a methyltransferase OphMA catalyzes the automethylation of its C-terminus, which is then released and cyclized by the protease OphP. These findings suggest a novel biosynthesis mechanism in which a modifying enzyme bears its own precursor.
      PubDate: 2017-07-17T08:17:46.857115-05:
      DOI: 10.1002/anie.201703488
       
  • Identification of a Stable ZnII–Oxyl Species Produced in an MFI Zeolite
           and Its Reversible Reactivity with O2 at Room Temperature
    • Authors: Akira Oda; Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda
      Abstract: Although a terminal oxyl species bound to certain metal ions is believed to be the intermediate for various oxidation reactions, such as O−O bond generation in photosystem II (PSII), such systems have not been characterized. Herein, we report a stable ZnII–oxyl species induced by an MFI-type zeolite lattice and its reversible reactivity with O2 at room temperature. Its intriguing characteristics were confirmed by in situ spectroscopic studies in combination with quantum-chemical calculations, namely analyses of the vibronic Franck–Condon progressions and the ESR signal features of both ZnII–oxyl and ZnII–ozonide species formed during this reversible process. Molecular orbital analyses revealed that the reversible reaction between a ZnII–oxyl species and an O2 molecule proceeds via a radical O–O coupling–decoupling mechanism; the unpaired electron of the oxyl species plays a pivotal role in the O−O bond generation process.Reversible radical formation: A ZnII−oxyl species was synthesized by utilizing a ZnII MFI-type zeolite as a subnanometer-sized reaction pot. This oxyl species reacts with O2 at room temperature. The unpaired electron of the oxyl moiety plays an important role during the central step of this reversible process.
      PubDate: 2017-07-17T08:17:42.437899-05:
      DOI: 10.1002/anie.201702570
       
  • Mechanistic Insight into Nanoparticle Surface Adsorption by Solution NMR
           Spectroscopy in an Aqueous Gel
    • Authors: Timothy K. Egner; Pranjali Naik, Nicholas C. Nelson, Igor I. Slowing, Vincenzo Venditti
      Abstract: Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found that the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. We believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.Gel for a while: The kinetics and thermodynamics of small-molecule adsorption on a nanoparticle surface were investigated by solution NMR spectroscopy in an aqueous gel (see picture), which prevented nanoparticle sedimentation for extended periods of time. A multistep binding mechanism was identified, in which a weakly associated encounter complex evolves into a tightly bound small-molecule–nanoparticle adduct.
      PubDate: 2017-07-17T08:17:35.204866-05:
      DOI: 10.1002/anie.201704471
       
  • Colorimetric Recognition of Aldehydes and Ketones
    • Authors: Zheng Li; Ming Fang, Maria K. LaGasse, Jon R. Askim, Kenneth S. Suslick
      Abstract: A colorimetric sensor array has been designed for the identification of and discrimination among aldehydes and ketones in vapor phase. Due to rapid chemical reactions between the solid-state sensor elements and gaseous analytes, distinct color difference patterns were produced and digitally imaged for chemometric analysis. The sensor array was developed from classical spot tests using aniline and phenylhydrazine dyes that enable molecular recognition of a wide variety of aliphatic or aromatic aldehydes and ketones, as demonstrated by hierarchical cluster, principal component, and support vector machine analyses. The aldehyde/ketone-specific sensors were further employed for differentiation among and identification of ten liquor samples (whiskies, brandy, vodka) and ethanol controls, showing its potential applications in the beverage industry.One Bourbon, One Scotch, One Brandy: A colorimetric sensor array has been designed for the vapor-phase identification of a wide range of aldehydes and ketones using pattern recognition techniques (e.g., by hierarchical cluster and support vector machine analyses). The aldehyde/ketone-specific sensors were also employed to differentiate among ten liquor samples (whiskies, brandy, vodka) and ethanol controls, showing its potential use in the beverage industry.
      PubDate: 2017-07-17T06:55:54.942727-05:
      DOI: 10.1002/anie.201705264
       
  • Structure of Human Tyrosinase Related Protein 1 Reveals a Binuclear Zinc
           Active Site Important for Melanogenesis
    • Authors: Xuelei Lai; Harry J. Wichers, Montserrat Soler-Lopez, Bauke W. Dijkstra
      Abstract: Tyrosinase-related protein 1 (TYRP1) is one of three tyrosinase-like glycoenzymes in human melanocytes that are key to the production of melanin, the compound responsible for the pigmentation of skin, eye, and hair. Difficulties with producing these enzymes in pure form have hampered the understanding of their activity and the effect of mutations that cause albinism and pigmentation disorders. Herein we show that the typical tyrosinase-like subdomain of TYRP1 contains two zinc ions in the active site instead of copper ions as found in tyrosinases, which explains why TYRP1 does not exhibit tyrosinase redox activity. In addition, the structures reveal for the first time that the Cys-rich subdomain, which is unique to vertebrate melanogenic proteins, has an epidermal growth factor-like fold and is tightly associated with the tyrosinase subdomain. Our structures suggest that most albinism-related mutations of TYRP1 affect its stability or activity.Let this zinc in: The first crystal structure of a mammalian enzyme involved in melanin biosynthesis reveals the structural basis of OCA3-albinism-related mutations. The typical tyrosinase-like subdomain of TYRP1 contains two zinc ions in the active site instead of copper ions as found in tyrosinases, which explains why TYRP1 does not exhibit tyrosinase redox activity.
      PubDate: 2017-07-17T06:55:49.380823-05:
      DOI: 10.1002/anie.201704616
       
  • Colloidal Rings by Site-Selective Growth on Patchy Colloidal Disc
           Templates
    • Authors: Yuanyuan Wu; Zhang Luo, Bing Liu, Zhenzhong Yang
      Abstract: Anisotropic colloidal building blocks are quite attractive as they enable the self-assembly towards new materials with designated hierarchical structures. Although many advances have been achieved in colloidal synthetic methodology, synthesis of colloidal rings with low polydispersity and on a large scale remains a challenge. To address this issue we introduce a new site-selective growth strategy, which relies on using patchy particles. For example, by using patchy discs as templates, silica can selectively be grown on only side surfaces, resulting in formation of silica rings. We demonstrate that shape parameters are tunable and find that these silica rings can be used as secondary template to synthesize other types of rings. This method for synthesizing ring-like colloids provides possibilities for studying their self-assembly and associated phase transitions, and this patchy particles template strategy paves a new route for fabricating other new colloidal particles.Monodisperse ring-like colloids have been synthesized by selectively growing SiO2 onto only the side surfaces of patchy disc-like colloids. The diameter and aspect ratio were tunable. The method makes possible the preparation on a large scale. The SiO2 rings have Janus character and can be used as secondary templates to synthesize other rings.
      PubDate: 2017-07-17T06:55:36.985431-05:
      DOI: 10.1002/anie.201704541
       
  • Structure of Amorphous Selenium by 2D 77Se NMR Spectroscopy: An End to the
           Dilemma of Chain versus Ring
    • Authors: Maxwell Marple; Jackson Badger, Ivan Hung, Zhehong Gan, Kirill Kovnir, Sabyasachi Sen
      Abstract: Amorphous selenium, owing to its tremendous technological importance and perhaps to its chemical simplicity, has been studied for nearly a century and yet an unequivocal structural description of this material remains lacking to date. The primary controversy regarding the structure of amorphous Se relates to the relative fraction of Se atoms residing in ∞1Se chains versus in Se8 rings. Herein we present the results of a two-dimensional solid-state 77Se nuclear magnetic resonance (NMR) spectroscopic study of the chain and ring crystalline allotropes of Se as well as of amorphous Se to unequivocally demonstrate that 1) the Se8 rings and the ∞1Se chains are characterized by their unique 77Se NMR signatures and 2) the structure of amorphous Se consists exclusively of ∞1Se chains.Se-ing is believing: Amorphous selenium has been studied for nearly a century and yet an unequivocal structural description of it is lacking. The main controversy regarding the structure relates to the fraction of Se atoms residing in ∞1Se chains versus in Se8 rings. 77Se MATPASS/CPMG NMR spectroscopy distinguishes the Se ring and chain environments and shows the structure consists exclusively of ∞1Se chains.
      PubDate: 2017-07-17T06:55:29.579673-05:
      DOI: 10.1002/anie.201704323
       
  • Copper-Catalyzed Enantio-, Diastereo-, and Regioselective
           [2,3]-Rearrangements of Iodonium Ylides
    • Authors: Bin Xu; Uttam K. Tambar
      Abstract: The first highly enantioselective, diastereoselective, and regioselective [2,3]-rearrangement of iodonium ylides has been developed as a general solution to catalytic onium ylide rearrangements. In the presence of a chiral copper catalyst, substituted allylic iodides couple with α-diazoesters to generate metal-coordinated iodonium ylides, which undergo [2,3]-rearrangements with high selectivities (up to>95:5 r.r., up to>95:5 d.r., and up to 97 % ee). The enantioenriched iodoester products can be converted stereospecifically into a variety of onium ylide rearrangement products, as well as compounds that are not accessible by classical onium ylide rearrangements.Making arrangements: The title reaction is reported as a general solution to catalytic onium ylide rearrangements. In the presence of a chiral copper catalyst, substituted allylic iodides couple with α-diazoesters to generate metal-coordinated iodonium ylides, which undergo [2,3]-rearrangements with high selectivities.
      PubDate: 2017-07-17T06:51:31.422079-05:
      DOI: 10.1002/anie.201705317
       
  • Heterocorrole Conformations: Little Saddling, Much Ruffling
    • Authors: Jörn Rösner; Birte Cordes, Stefanie Bahnmüller, Gabor Homolya, Dimitri Sakow, Peter Schweyen, Richard Wicht, Martin Bröring
      Abstract: 10-Heterocorrole complexes with oxygen, sulfur, and selenium at position 10 of the macrocycle and with the divalent ions of nickel, copper, and palladium were prepared and investigated. The focus was set on the size adaptation and matching mechanisms of cavity size versus ionic radius in corrole-type macrocycles. A full set of single-crystal X-ray analytical data revealed that in all but one case the N4 binding site of the ring-contracted tetrapyrrole was larger than necessary to bind the metal ion without deformation. In-plane size adaptation through M−N bond-length elongation by 2.5–3.2 % was effective, as well as pronounced out-of-plane ruffling of the macrocycle for those compounds with a more severe size mismatch. Such ruffling had been excluded for corroles previously, but is apparently the most efficient mechanism to adapt to small central ions.Yes, they can! Despite the presence of a direct pyrrole–pyrrole connection, 10-heterocorroles were found to adopt very efficient ruffling conformations when binding to central ions with small radii (see picture). Ruffling was observed to be the major out-of-plane distortion mode for the adaptation of the ligand cavity size in coordination compounds. This finding disproves the hypothesis that “corroles cannot ruffle”.
      PubDate: 2017-07-17T06:50:56.203017-05:
      DOI: 10.1002/anie.201705551
       
  • Fusing Dicarbollide Ions with N-Heterocyclic Carbenes
    • Authors: Jess Estrada; Vincent Lavallo
      Abstract: Discovered by Hawthorne in 1965, dicarbollide ions are an intriguing class of nido-carboranes that mimic the behavior of the cyclopentadienyl anion. Herein, we show that it is possible to directly link the dicarbollide ion to an N-heterocyclic carbene (NHC) to form an isolable N-dicarbollide-substituted NHC dianion. This molecule can be accessed by the sequential double deprotonation of a mono-nido-carboranyl imidazolium zwitterion. As revealed by a single-crystal X-ray diffraction study, the first deprotonation leads to a monoanionic dicarbollide ion that adopts a bis(dicarbollide) structure in the solid state. Subsequent deprotonation of this monoanion leads to the first N-dicarbollide NHC, which was fully characterized by multinuclear NMR spectroscopy as well as single-crystal X-ray diffraction.A happy marriage: Over 50 years after Hawthorne's seminal discovery of the dicarbollide ion, it is demonstrated that this classical cyclopentadienyl anion mimic can be directly fused to stable carbenes. The marriage of these two unusual classes of carbon-containing molecules introduces a new concept in NHC ligand design.
      PubDate: 2017-07-17T06:50:26.077093-05:
      DOI: 10.1002/anie.201705857
       
  • A General Mechanism of Photoconversion of Green-to-Red Fluorescent
           Proteins Based on Blue and Infrared Light Reduces Phototoxicity in
           Live-Cell Single-Molecule Imaging
    • Authors: Bartosz Turkowyd; Alexander Balinovic, David Virant, Haruko G. Gölz Carnero, Fabienne Caldana, MA Marc Endesfelder, Dominique Bourgeois, Ulrike Endesfelder
      Abstract: Photoconversion of fluorescent proteins by blue and complementary near-infrared light, termed primed conversion (PC), is a mechanism recently discovered for Dendra2. We demonstrate that controlling the conformation of arginine at residue 66 by threonine at residue 69 of fluorescent proteins from Anthozoan families (Dendra2, mMaple, Eos, mKikGR, pcDronpa protein families) represents a general route to facilitate PC. Mutations of alanine 159 or serine 173, which are known to influence chromophore flexibility and allow for reversible photoswitching, prevent PC. In addition, we report enhanced photoconversion for pcDronpa variants with asparagine 116. We demonstrate live-cell single-molecule imaging with reduced phototoxicity using PC and record trajectories of RNA polymerase in Escherichia coli cells.Photoconversion by illumination with blue and complementary near-IR light offers an alternative route to the UV-mediated photoconversion of green-to-red photoconvertible fluorescent proteins. This photoconversion pathway of Anthozoan fluorescent proteins with threonine at residue 69 shows efficient photoconversion and reduced phototoxicity when compared to UV-photoconversion in single-particle tracking imaging of Escherichia coli cells.
      PubDate: 2017-07-17T06:26:06.186659-05:
      DOI: 10.1002/anie.201702870
       
  • Biocatalysis with Unnatural Amino Acids: Enzymology Meets Xenobiology
    • Authors: Federica Agostini; Jan-Stefan Völler, Beate Koksch, Carlos G. Acevedo-Rocha, Vladimir Kubyshkin, Nediljko Budisa
      Abstract: The goal of xenobiology is to design biological systems endowed with unusual biochemical functions, whereas enzymology concerns the study of enzymes, the workhorses of biocatalysis. Biocatalysis employs enzymes and organisms to perform useful biotransformations in synthetic chemistry and biotechnology. During the past few years, the effects of incorporating noncanonical amino acids (ncAAs) into enzymes with potential applications in biocatalysis have been increasingly investigated. In this Review, we provide an overview of the effects of new chemical functionalities that have been introduced into proteins to improve various facets of enzymatic catalysis. We also discuss future research avenues that will complement unnatural mutagenesis with standard protein engineering to produce novel and versatile biocatalysts with applications in synthetic organic chemistry and biotechnology.Unnatural design: The goal of xenobiology is the design of biological systems endowed with unusual biochemical units. For example, engineering the genetic code of enzymes to contain unnatural amino acids and cofactors can lead to unique properties that make the enzymes useful biocatalysts.
      PubDate: 2017-07-17T06:25:48.528882-05:
      DOI: 10.1002/anie.201610129
       
  • Antimonene Quantum Dots: Synthesis and Application as Near-Infrared
           Photothermal Agents for Effective Cancer Therapy
    • Authors: Wei Tao; Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid C. Farokhzad
      Abstract: Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium. The PEG-coated AMQDs showed a PTCE of 45.5 %, which is higher than many other NMs-based PTAs such as graphene, Au, MoS2, and black phosphorus (BP). The AMQDs-based PTAs also exhibited a unique feature of NIR-induced rapid degradability. Through both in vitro and in vivo studies, the PEG-coated AMQDs demonstrated notable NIR-induced tumor ablation ability. This work is expected to expand the utility of 2D antimonene (AM) to biomedical applications through the development of an entirely novel PTA platform.Antimonene quantum dots (AMQDs) were synthesized through a liquid exfoliation method. The poly(ethylene glycol)-coated AMQDs were shown to have high photothermal conversion efficiency (45.5 %), near-infrared-induced degradability, and biocompatibility, making them a new generation of ideal photothermal agents for effective cancer treatment. The study opens up an exciting and novel research direction of AM for biomedical applications.
      PubDate: 2017-07-17T06:25:33.24265-05:0
      DOI: 10.1002/anie.201703657
       
  • From Borane to Borylene without Reduction: Ambiphilic Behavior of a
           Monovalent Silylisonitrile Boron Species
    • Authors: Merle Arrowsmith; Dominic Auerhammer, Rüdiger Bertermann, Holger Braunschweig, Mehmet Ali Celik, Julian Erdmannsdörfer, Ivo Krummenacher, Thomas Kupfer
      Abstract: Deprotonation of [(cAAC)BH2(CN)] provided clean access to the stable boryl anion, [(cAAC)BH(CN)]−. Whereas the addition of soft electrophiles occurred at the nucleophilic boron center, harder silyl electrophiles added to the harder terminal cyano nitrogen. The resulting [(cAAC)BH(CNSiPh3)] species behaved like a silylium boryl nucleophile as well as a neutral silylisonitrile borylene.Whereas the salt metathesis of soft electrophiles with the (cyano)hydroboryl anion [(cAAC)B(CN)H]− occurs at the nucleophilic boron center, comparatively harder silyl electrophiles add to the harder terminal cyano nitrogen. The resulting [(cAAC)BH(CNSiR3)] species behave as both zwitterionic silylium boryl and neutral silylisonitrile borylene, a BI compound accessed through simple deprotonation and salt metathesis. cAAC=cyclic (alkyl)(amino)carbene.
      PubDate: 2017-07-17T06:22:11.083362-05:
      DOI: 10.1002/anie.201705561
       
  • Associating and Dissociating Nanodimer Analysis for Quantifying Ultrasmall
           Amounts of DNA
    • Authors: Keunsuk Kim; Jeong-Wook Oh, Young Kwang Lee, Jiwoong Son, Jwa-Min Nam
      Abstract: The amplification- and enzyme-free quantification of DNA at ultralow concentrations, on the order of 10–1000 targets, is highly beneficial but extremely challenging. To address this challenge, true detection signals must be reliably discriminated from false or noise signals. Herein, we describe the development of associating and dissociating nanodimer analysis (ADNA) as a method that enables a maximum number of detection signals to be collected from true target-binding events while keeping nonspecific signals at a minimum level. In the ADNA assay for ultralow target concentrations, Au nanoprobes on a lipid micropattern were monitored and analyzed in situ, and newly defined dissociating dimers, which are eventually decoupled into monomers again, were incorporated into the detection results. Tens to thousands of DNA copies can be reliably quantified with excellent single-base-mismatch differentiation capability by this non-enzymatic, amplification-free ADNA method.How low can you go' Associating and dissociating nanodimer analysis (ADNA) based on DNA recognition by plasmonic nanoprobes on a lipid micropattern has been developed as a method for DNA quantification. The detection and quantification of dimers that form but dissociate again as well as bound dimers enabled the reliable quantification of ultrasmall amounts of biomolecules (as few as 47 copies of DNA) without amplification steps (see picture).
      PubDate: 2017-07-17T06:22:03.81499-05:0
      DOI: 10.1002/anie.201705330
       
  • A Carbene Catalysis Strategy for the Synthesis of Protoilludane Natural
           Products
    • Authors: M. Todd Hovey; Daniel T. Cohen, Daniel M. Walden, Paul H.-Y. Cheong, Karl A. Scheidt
      Abstract: The Armillaria and Lactarius genera of fungi produce the antimicrobial and cytotoxic mellolide, protoilludane, and marasmane sesquiterpenoids. We report a unified synthetic strategy to access the protoilludane, mellolide, and marasmane families of natural products. The key features of these syntheses are 1) the organocatalytic, enantioselective construction of key chiral intermediates from a simple achiral precursor, 2) the utility of a key 1,2-cyclobutanediol intermediate to serve as a precursor to each natural product class, and 3) a direct chemical conversion of a protoilludane to a marasmane through serendipitous ring contraction, which provides experimental support for their proposed biosynthetic relationships.First proto-type: The first total syntheses of the protoilludanes armillaridin and echinochidins B and D are reported. Notable features include: 1) enantioselective NHC-catalyzed annulation to establish the critical cis-cyclopentane core; 2) a late-stage VII/ZnII-promoted reductive pinacol coupling to give an advanced cis-cyclobutanediol intermediate; and 3) a potentially biomimetic ring-contraction of the protoilludane skeleton to give the marasmane core.
      PubDate: 2017-07-17T06:21:32.236372-05:
      DOI: 10.1002/anie.201705308
       
  • Effect of Selective CF3 Substitution on the Physical and Chemical
           Properties of Gold Corroles
    • Authors: Kolanu Sudhakar; Amir Mizrahi, Monica Kosa, Natalia Fridman, Boris Tumanskii, Magal Saphier, Zeev Gross
      Abstract: Gold corroles are not readily accessible and they display no interesting physical or chemical properties. A facile methodology has now been developed for obtaining selectively CF3-substituted gold(III) corroles and the introduction of these groups has been found to have an immense effect on the structures of the complexes, their photophysical and redox properties, and on their ability to participate in catalytic processes.Tweaking the electronics: Trifluoromethylation of inert gold corroles dramatically changes their structural, optical, and electrochemical properties, as was proven by a combination of analytical methods. The tetra-CF3-substituted gold complex serves as an electrocatalyst for proton reduction to hydrogen gas.
      PubDate: 2017-07-17T06:20:44.668391-05:
      DOI: 10.1002/anie.201705007
       
  • Two-Dimensional Metal–Organic Framework Nanosheets for
           Membrane-Based Gas Separation
    • Authors: Yuan Peng; Yanshuo Li, Yujie Ban, Weishen Yang
      Abstract: Metal–organic framework (MOF) nanosheets could serve as ideal building blocks of molecular sieve membranes owing to their structural diversity and minimized mass-transfer barrier. To date, discovery of appropriate MOF nanosheets and facile fabrication of high performance MOF nanosheet-based membranes remain as great challenges. A modified soft-physical exfoliation method was used to disintegrate a lamellar amphiprotic MOF into nanosheets with a high aspect ratio. Consequently sub-10 nm-thick ultrathin membranes were successfully prepared, and these demonstrated a remarkable H2/CO2 separation performance, with a separation factor of up to 166 and H2 permeance of up to 8×10−7 mol m−2 s−1 Pa−1 at elevated testing temperatures owing to a well-defined size-exclusion effect. This nanosheet-based membrane holds great promise as the next generation of ultrapermeable gas separation membrane.MOF nanosheet membranes: Layered Zn2(benzimidazole)3(OH)(H2O) precursors were exfoliated into nanosheets with high aspect ratio. These were further assembled on anisotropic α-Al2O3 substrates for the construction of high-performance molecular-sieve membranes. The membranes feature high H2/CO2 selectivity and excellent H2 permeance. Zn green, N orange, C gray, O red.
      PubDate: 2017-07-17T06:20:32.271994-05:
      DOI: 10.1002/anie.201703959
       
  • Material-Efficient Microfluidic Platform for Exploratory Studies of
           Visible-Light Photoredox Catalysis
    • Authors: Connor W. Coley; Milad Abolhasani, Hongkun Lin, Klavs F. Jensen
      Abstract: We present an automated microfluidic platform for in-flow studies of visible-light photoredox catalysis in liquid or gas–liquid reactions at the 15 μL scale. An oscillatory flow strategy enables a flexible residence time while preserving the mixing and heat transfer advantages of flow systems. The adjustable photon flux made possible with the platform is characterized using actinometry. Case studies of oxidative hydroxylation of phenylboronic acids and dimerization of thiophenol demonstrate the capabilities and advantages of the system. Reaction conditions identified through droplet screening translate directly to continuous synthesis with minor platform modifications.Glow with the flow: An automated photochemistry platform built around a microfluidic oscillatory flow reactor enables efficient investigation of photocatalyzed liquid and gas–liquid reactions in individual 15 μL droplets. The conditions identified through screening are directly adapted to continuous flow synthesis.
      PubDate: 2017-07-17T06:20:25.255434-05:
      DOI: 10.1002/anie.201705148
       
  • Annulated 1,3,4-azadiphospholides: Heterocycles with widely tunable
           optical properties
    • Authors: Hansjörg Grützmacher; Riccardo Suter, Zoltán Benkö, Mark Bispinghoff
      Abstract: Phosphorus heterocycles find applications in the synthesis of π-conjugated compounds and as precursors for optoelectronic materials such as organic light emitting diodes (OLEDs), electronic switches, and transistors. We report a high yield, one pot synthesis of anionic annulated 1,3,4-azadiphospholides from Na(OCP) and 2-chloro pyridines. The synthesis proceeds without the use of transition metals and tolerates a wide range of substrates. Cyano-substituted compounds are especially deeply colored and have absorption maxima which range from λmax = 525 to 596 nm. The optical properties are dominated by the spatial separation of an electron acceptor and donor unit within one molecule (push-pull chromophore). The anionic 1,3,4-azadiphospholides are silylated to neutral siloxy compounds with a strong blue-shifted absorption. This reaction can be reversed by addition of fluoride ions, which allows to detect optically fluoride in low concentrations.
      PubDate: 2017-07-17T06:16:06.867825-05:
      DOI: 10.1002/anie.201705473
       
  • LiTMP Trans-Metal-Trapping of Fluorinated Aromatic Molecules: A
           Comparative Study of Aluminum and Gallium Carbanion Traps
    • Authors: Ross McLellan; Marina Uzelac, Alan R. Kennedy, Eva Hevia, Robert E. Mulvey
      Abstract: Fluoroaromatic scaffolds pose a challenge to lithiation due to low stability of lithiated intermediates. Here we apply trans-metal-trapping (TMT) to a series of key fluorinated aromatics. In TMT, LiTMP performs the metalation, while an organometallic trap intercepts the emergent carbanion. This study contrasts the trapping abilities of iBu2AlTMP and Ga(CH2SiMe3)3, structurally mapping their TMT reactions and probing relative stabilities of metalated fluoroaromatic intermediates by NMR studies. Results show the installed Al−C(aryl) bonds are more prone to decomposition by benzyne formation and Li-F liberation, than the Ga−C(aryl) species. The latter are thus better for onward reactivity as demonstrated in cross-coupling reactions with benzoyl chloride that produce ketones.Coping with the Flu: The highly sensitive intermediates produced via lithiation of synthetically important fluorinated aromatic molecules are best stabilized for onward reactions via the gallium tris-alkyl Ga(CH2SiMe3)3 carbanion trap rather than by the related aluminum trap iBu2AlTMP.
      PubDate: 2017-07-17T06:15:29.443198-05:
      DOI: 10.1002/anie.201706064
       
  • Manganese-Catalyzed C−H Functionalizations: Hydroarylations and
           Alkenylations Involving an Unexpected Heteroaryl Shift
    • Authors: Chengming Wang; Ai Wang, Magnus Rueping
      Abstract: A manganese-catalyzed regio- and stereoselective hydroarylation of allenes is reported. The C−H functionalization method provides access to various alkenylated indoles in excellent yields. Moreover, a hydroarylation/cyclization cascade involving an unexpected C−N bond cleavage and aryl shift has been developed, which provides a new synthetic approach to substituted pyrroloindolones.Which way to go: An efficient, scalable, regio-, and stereoselective manganese-catalyzed C−H arylation of allenes is reported. When trisubstituted allenes are used, a C−H functionalization/C−N bond cleavage/cyclization cascade affords pyrroloindolones. Mechanistic studies suggest that a manganacycle is formed during the catalytic cycle.
      PubDate: 2017-07-17T04:10:52.884111-05:
      DOI: 10.1002/anie.201704682
       
  • Polyladderane Constructed from Gemini Monomer via Photoreaction
    • Authors: Zhihan Wang; Benjamin Miller, Jonathan Butz, Katelyn Randazzo, Zijun D. Wang, Qianli Rick Chu
      Abstract: Polyladderane, the first polymer to contain the ladderane functional group, was successfully synthesized from 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.
      PubDate: 2017-07-17T03:16:02.608581-05:
      DOI: 10.1002/anie.201705937
       
  • Pd(II)-Catalyzed Site-Selective C(sp3)-H Alkynylation of Oligopeptides: A
           Linchpin Approach for Oligopeptide-Drug Conjugation
    • Authors: Tao Liu; Jennifer X Qiao, Michael A Poss, Jin-Quan Yu
      Abstract: The palladium(II)-catalyzed C(sp3)-H alkynylation of oligopeptides was developed with tetrabutylammonium acetate as a key additive. Through molecular design, the acetylene motif serves as a linchpin to introduce a broad range of carbonyl-containing pharmacophores onto oligopeptides, thus providing a chemical tool for the synthesis and modification of novel oligopeptide-pharmacophore conjugates via C-H functionalization. Dipeptide conjugates with coprostanol and estradiol has been synthesized using this method for potential application in targeted drug delivery to tumor cells with overexpressed nuclear hormone receptors.
      PubDate: 2017-07-17T03:15:46.559905-05:
      DOI: 10.1002/anie.201706367
       
  • Intermediate product regulation in tandem solid catalysts with multimodal
           porosity for high-yield synthetic fuel production
    • Authors: Nicolas Duyckaerts; Mathias Bartsch, Ioan-Teodor Trotus, Norbert Pfänder, Axel Lorke, Ferdi Schüth, Gonzalo Prieto
      Abstract: Tandem catalysis is an attractive strategy to intensify chemical processes but simultaneous control over the individual and concerted catalyst performances poses a challenge. We show that enhanced pore transport within a Co/Al2O3 Fischer-Tropsch (FT) catalyst with a hierarchical porosity enables its tandem integration with a Pt/ZSM-5 zeolitic hydrotreating catalyst in a spatially distant fashion ‒ permitting a catalyst-specific temperature adjustment ‒ albeit resembling a close active site proximity ‒ by mitigating secondary reactions of primary FT α-olefin products. This approach enables the conciliation of in situ de-waxing with a minimum production of gases (18 wt%) and an up to two-fold higher (50 wt%) selectivity to middle-distillates compared to benchmark mesoporous FT catalysts. An overall 80% selectivity to liquid hydrocarbons from syngas is attained in one step, attesting for the potential of this strategy to increase the efficiency in intensified gas-to-liquid technologies.
      PubDate: 2017-07-16T21:21:34.678335-05:
      DOI: 10.1002/anie.201705714
       
  • Bioinspired, size-tunable self-assembly of polymer-lipid bilayer nanodiscs
    • Authors: Thirupathi Ravula; Sudheer Ramadugu, Giacomo Di Mauro, Ayyalusamy Ramamoorthy
      Abstract: Polymer-based nanodiscs are valuable tools in biomedical research that can offer a detergent-free solubilization of membrane proteins maintaining their native lipid environment. Here, we introduce a novel ~1.6 kDa SMA-based polymer with styrene:maleic acid moieties that can form nanodiscs containing a planar lipid bilayer which are useful to reconstitute membrane proteins for structural and functional studies. The physicochemical properties and the mechanism of formation of polymer-based nanodiscs are characterized by light scattering, NMR, FT-IR, and TEM imaging experiments. A remarkable feature is that nanodiscs of different sizes, from nanometer to sub micrometer diameter, can be produced only by varying the lipid-to-polymer ratio. As demonstrated, the small size nanodiscs (up to ~30 nm diameter) can be used for solution NMR studies whereas the magnetic-alignment of macro-nanodiscs (diameter of>~40 nm) can be exploited for solid-state NMR studies on membrane proteins.
      PubDate: 2017-07-16T21:21:01.466358-05:
      DOI: 10.1002/anie.201705569
       
  • Carbonitride Aerogels for the Photoredox Conversion of Water
    • Authors: Honghui Ou; Pengju Yang, Lihua Lin, Masakazu Anpo, Xinchen Wang
      Abstract: Aerogel structures have attracted increasing research interest in energy storage and conversion owing to their unique structural features, and a variety of matters has been engineered into aerogels, including carbons, metal oxides, linear polymers and even metal chalcogenides. However, manufacturing of aerogels from nitride-based materials, particularly the emerging light-weight carbonitride (CN) is rarely reported. Here, we develop a facile method based on self-assembly chemistry to produce self-supported CN aerogels, without using any cross-linking agents. The combination of the large surface area, the incorporated functional group and the 3D network structure, endow the resulting freestanding aerogels with high photoreactiveity for hydrogen evolution and H2O2 production under visible light irradiation. This work presents a simple colloid chemistry strategy to construct 3D CN aerogel network that shows great potentials for solar to chemical conversion by artificial photosynthesis.
      PubDate: 2017-07-15T04:25:28.619498-05:
      DOI: 10.1002/anie.201705926
       
  • Rational Control on the Selectivity of Ru Catalyst for Hydrogenation of
           4-Nitrostyrene via Strain Regulation
    • Authors: Yadong Li; Junjie Mao, Wenxing Chen, Wenming Sun, Zheng Chen, Jiajing Pei, Dongsheng He, Chunlin Lv, Dingsheng Wang
      Abstract: Tuning the selectivity of metal catalysts is of paramount importance, yet a great challenge. Here, a new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is reported. In this approach, we introduce a certain amount of Co atoms into Ru catalysts to compress the Ru lattice, as confirmed by aberration corrected high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS) measurements. We discover that, the lattice strain of Ru catalysts can greatly affect their selectivity and Ru with 3% lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene compared to pristine Ru (99% Vs. 66%). The theoretical studies prove that the optimized lateral compressive strain facilitates hydrogenation of nitro-group but impedes the hydrogenation of vinyl-group. This study provides a new guideline for designing metal catalysts with high selectivity.
      PubDate: 2017-07-14T23:30:33.993489-05:
      DOI: 10.1002/anie.201706645
       
  • Enhanced carbon dioxide electroreduction to carbon monoxide over defect
           rich plasma-activated silver catalysts
    • Authors: Hemma Mistry; Yong-Wook Choi, Alexander Bagger, Fabian Scholten, Cecile Bonifacio, Ilya Sinev, Nuria J. Divins, Ioannis Zegkinoglou, Hyo Sang Jeon, Kim Kisslinger, Eric A. Stach, Judith C. Yang, Jan Rossmeisl, Beatriz Roldán Cuenya
      Abstract: Efficient, stable catalysts with high selectivity for a single product are essential to making the electroreduction of CO2 a viable route to the synthesis of industrial feedstocks and fuels. We reveal how a plasma oxidation pre-treatment can lead to an enhanced content of low-coordinated active sites which dramatically lower the overpotential and increase the activity of CO2 electroreduction to CO. At -0.6 V vs. RHE, more than 90% Faradaic efficiency towards CO could be achieved on a pre-oxidized silver foil. While transmission electron microscopy and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulk of the catalyst during the reaction, in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. DFT calculations show how the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields results in a drastic decrease in the overpotential for the electroreduction of CO2.
      PubDate: 2017-07-14T23:30:24.0276-05:00
      DOI: 10.1002/anie.201704613
       
  • Total Syntheses of the Reported Structures of Curcusone I and J via Tandem
           Gold Catalysis
    • Authors: Yong Li; Mingji Dai
      Abstract: Total syntheses of the reported structures of the rhamnofolane diterpene natural products curcusone I and J in racemic forms have been achieved. The synthetic strategy features a novel tandem gold-catalyzed furan formation and furan-allene [4+3] cycloaddition to build the 5,7-fused ring system with an oxa-bridge in one step and a stereoselective exo-Diels-Alder reaction to form the 6-membered ring. The newly developed tandem gold catalysis is quite general and can be scaled up. Our syntheses suggested that structural revisions of curcusone I and J are needed.
      PubDate: 2017-07-14T10:25:55.591659-05:
      DOI: 10.1002/anie.201706845
       
  • Pd-Catalyzed Spirocyclization via C-H Activation and Regioselective Alkyne
           Insertion
    • Authors: Hyung Yoon; Martin Rolz, Felicitas Landau, Mark Lautens
      Abstract: A Pd-catalyzed spirocyclization involving a sequential carbopalladation, intramolecular C-H activation and a highly regioselective alkyne insertion to afford spirooxindoles and spirodihydrobenzofurans has been achieved. The spirocyclic products were generated in good to excellent yields with complete regiocontrol in a readily scalable procedure.
      PubDate: 2017-07-14T09:25:45.116564-05:
      DOI: 10.1002/anie.201706325
       
  • Palladium Catalyzed Suzuki-Miyaura Cross-Coupling of Secondary
           α-(Trifluoromethyl)benzyl Tosylates
    • Authors: Marta Brambilla; Matthew Tredwell
      Abstract: A palladium catalyzed C(sp3)-C(sp2) Suzuki-Miyaura cross-coupling of aryl boronic acids and α-(trifluoromethyl)benzyl tosylates is reported. The reaction uses a readily available, air-stable palladium catalyst to access a wide range of functionalized 1,1-diaryl-2,2,2-trifluoroethanes. Enantioenriched α-(trifluoromethyl)benzyl tosylates were found to undergo cross-coupling to give the corresponding enantioenriched cross-coupled products with an overall inversion in configuration. The crucial role of the CF3 group in promoting this transformation is demonstrated by comparison with non-fluorinated derivatives.
      PubDate: 2017-07-14T08:25:52.779763-05:
      DOI: 10.1002/anie.201706631
       
  • Catalytic Nitrene Transfer To Alkynes: A Novel and Versatile Route for the
           Synthesis of Sulfinamides and iso-Thiazoles
    • Authors: Pedro J. Pérez; M. Mar Diaz-Requejo, Manuel R. Rodríguez, Álvaro Beltrán, Eleuterio Alvarez, Angel Mudarra, Feliu Maseras
      Abstract: A novel transformation is reported for the reaction of terminal or internal alkynes with the nitrene precursor PhI=NTs (Ts = p-toluenesulfonyl) in the presence of catalytic amounts of TpBr3Cu(NCMe) (TpBr3 = hydrotris(3,4,5-tribromo-pyrazolylborate). Two products containing an imine functionality have been isolated from the reaction mixtures, identified as sulfinamides and iso-thiazoles. The former correspond to the formal reduction of the sulfone group into sulfoxide, whereas the latter involves the insertion of an alkyne carbon atom into the aromatic ring of the N-tosyl moiety.
      PubDate: 2017-07-14T07:25:31.872263-05:
      DOI: 10.1002/anie.201705664
       
  • Catalytic Regio- and Enantioselective [4+2] Annulation Reactions of
           Non-activated Allenes by a Chiral Cationic Indium Complex
    • Authors: Le Wang; Jian Lv, Long Zhang, Sanzhong Luo
      Abstract: Regio- and enantioselective [4+2] annulation between ,γ-unsaturated -keto esters and non-activated allenes has been achieved by a chiral cationic indium(III)/phosphate catalyst. The reaction affords the corresponding C3-selective dihydropyrans in good yields and with high enantioselectivities (up to 99% ee).
      PubDate: 2017-07-14T05:25:40.788616-05:
      DOI: 10.1002/anie.201704020
       
  • Supramolecular Nanotubules as Catalytic Regulator for Pd Cation and Their
           Application in Selective Catalysis
    • Authors: Zhegang Huang; Shanshan Wu, Yongguang Li, Siying Xie, Cong Ma, Joonwon Lim, Jiong Zhao, Dae Seok Kim, Minyong Yang, Doong Ki Yoon, Myongsoo Lee, Sang Ouk Kim
      Abstract: Despite recent development of highly efficient and stable metal catalysts, conferral of regulatory characteristic to the catalytic reaction in heterogeneous system remains a challenge. Herein, novel supramolecular nanotubules were prepared by alternative stacking from trimeric macrocycles, which was found to be able to coordinate with Pd cations. The Pd complexes exhibited a high catalytic performance for C-C coupling reaction. Notably, the tubular catalyst was observed to be controlled by supramolecular reversible assembly and showed superior heterogeneous catalytic activity maintained for a number of recycles or reuse under aerobic environment. Furthermore, the supramolecular catalyst showed unprecedented selectivity for the multi-functional coupling reaction and was able to serve as a new construction of asymmetrical compounds.
      PubDate: 2017-07-14T04:25:32.056747-05:
      DOI: 10.1002/anie.201706373
       
  • Selective Pd(II)-Catalyzed Carbonylation of Methylene beta-C-H Bonds in
           Aliphatic Amines
    • Authors: Matthew James Gaunt; Jaime Cabrera-Pardo, Aaron Trowbridge, Manuel Nappi, Kyohei Ozaki
      Abstract: Pd(II)-catalyzed C-H carbonylation of methylene C-H bonds in secondary aliphatic amines leads to the formation trans-disubstituted beta-lactams in excellent yields and selectivities. The generality of the C-H carbonylation process is aided by the action of xantphos-based ligands and is important in securing good yields of the beta-lactam products.
      PubDate: 2017-07-14T03:26:19.193672-05:
      DOI: 10.1002/anie.201706303
       
  • Facile Synthesis of Azetidine Nitrones and Diastereoselective Conversion
           to Densely-Substituted Azetidines
    • Authors: Tyler W Reidl; Jongwoo Son, Donald J Wink, Laura L Anderson
      Abstract: Discovery of an electrocyclization route to azetidine nitrones from N-alkenylnitrones has been shown to provide facile access to these unsaturated strained heterocycles. Reactivity studies have shown that these compounds undergo a variety of reduction, cycloaddition, and nucleophilic addition reactions to form highly-substituted azetidines with excellent diastereoselectivity. Taken together, these transformations provide a fundamentally different approach to azetidine synthesis than traditional cyclization by nucleophilic displacement and provide novel access to a variety of underexplored, strained heterocyclic compounds.
      PubDate: 2017-07-14T00:36:59.389098-05:
      DOI: 10.1002/anie.201705681
       
  • Synthesis and Reactivity of Fluoroalkyl Copper Complexes by the
           Oxycupration of Tetrafluoroethylene
    • Authors: Masato Ohashi; Takuya Adachi, Naoyoshi Ishida, Kotaro Kikushima, Sensuke Ogoshi
      Abstract: The copper(I)-mediated generation of -OCF2CF2- moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2-aryloxy-1,1,2,2-tetrafluoroethyl and 2-alkoxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE, and their structures in solution and in the solid state were unambiguously determined by multinuclear NMR spectroscopy and X-ray diffraction analysis. These copper complexes subsequently reacted with aryl iodides (ArI) to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.The copper(I)-mediated generation of -OCF2CF2- moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2-aryloxy- and 2-alkyloxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE. These copper complexes subsequently reacted with aryl iodides to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.
      PubDate: 2017-07-14T00:36:16.639611-05:
      DOI: 10.1002/anie.201703923
       
  • Colloidal Synthesis of Silicon@Carbon Composite Materials for Lithium-Ion
           Batteries
    • Authors: Haiping Su; Alejandro A Barragan, Linxiao Geng, Donghui Long, Licheng Ling, Krassimir N Bozhilov, Lorenzo Mangolini, Juchen Guo
      Abstract: We report colloidal routes to synthesize silicon@carbon composites for the first time. Surface-functionalized Si nanoparticles (SiNPs) dissolved in styrene and hexadecane are used as the dispersed phase in oil-in-water emulsions, from which yolk-shell and dual-shell hollow SiNPs@C composites are produced via polymerization and subsequent carbonization. As anode materials for Li-ion batteries, the SiNPs@C composites demonstrate excellent cycling stability and rate performance, which is ascribed to the uniform distribution of SiNPs within the carbon hosts. The Li-ion anodes composed of 46 wt.% of dual-shell SiNPs@C, 46 wt.% of graphite, 5 wt.% of acetylene black, and 3 wt.% of carboxymethyl cellulose with> 3 mg cm-2 areal loading achieve an overall specific capacity of> 600 mAh g-1, which is>100% improvement from the pure graphite anode. These new colloidal routes present a promising general method to produce viable Si-C composites for Li-ion batteries.
      PubDate: 2017-07-14T00:30:21.873184-05:
      DOI: 10.1002/anie.201705200
       
  • Fine Tuning of MOF-505 Analogues to Reduce Low Pressure Methane Uptake and
           Enhance Methane Working Capacity
    • Authors: Junfeng Bai; Mingxing Zhang, Wei Zhou, Tony Pham, Katherine A Forrest, Wenlong Liu, Yabing He, Hui Wu, Taner Yildirim, banglin chen, Brian Space, Yi Pan, Michael J Zaworotko
      Abstract: We present a crystal engineering strategy to fine tune the pore chemistry and CH4 storage performance of a family of isomorphous MOFs based upon PCN-14. These MOFs exhibit similar pore size, pore surface and surface area (around 3000 m2 g-1) and were prepared with the goal to enhance CH4 working capacity. [Cu2(L2)(H2O)2]n (NJU-Bai 41: NJU-Bai for Nanjing University Bai's group), [Cu2(L3)(H2O)2]n (NJU-Bai 42) and [Cu2(L4)(DMF)2]n (NJU-Bai 43) were prepared and we observed that the CH4 volumetric working capacity and volumetric uptake values are impacted by subtle changes in structure and chemistry. In particular, the CH4 working capacity of NJU-Bai 43 reaches 198 cm3 (STP: 273.15 K, 1 atm) cm-3 at 298 K and 65 bar, which is amongst the highest reported for MOFs under these conditions and is much higher than the corresponding value for PCN-14 (157 cm3 (STP) cm-3).
      PubDate: 2017-07-13T22:25:29.462047-05:
      DOI: 10.1002/anie.201704974
       
  • Rhodium-Catalyzed Enantioselective Reductive Arylation: Convenient Access
           to 3,3-Disubstituted Oxindoles
    • Authors: Mark Lautens; Young Jin Jang, Egor Mikhailovich Larin
      Abstract: A rhodium-Josiphos(L*) catalyzed enantioselective intramolecular hydroarylation reaction is described. The reductive cyclization of o-bromoaniline-derived acrylamides provides convenient access to 3,3-disubstituted oxindoles in good yields and with excellent enantioselectivity across a range of substrates. We propose that the key cyclization proceeds via a rhodium(III) intermediate. Overall, this method represents an unusual mode of reactivity for rhodium catalysis and is complementary to palladium(0)-catalyzed α-arylation protocols.
      PubDate: 2017-07-13T13:25:43.43932-05:0
      DOI: 10.1002/anie.201704922
       
  • Unveiling the target promiscuity of pharmacologically active compounds in
           silico
    • Authors: Petra Schneider; Gisbert Schneider
      Abstract: Drug discovery is governed by the desire to find ligands with defined modes of action. It has been realized that even designated selective drugs may have more macromolecular targets than is commonly thought. Consequently, it will be mandatory to consider multi-target activity for the design of future medicines. Computational models assist medicinal chemists in this effort by helping to eliminate unsuitable lead structures and spot undesired drug effects early in the discovery process. Here, we present a straightforward computational method to find previously unknown targets of pharmacologically active compounds. Validation experiments revealed hitherto unknown targets of the natural product resveratrol and the nonsteroidal anti-inflammatory drug celecoxib. The obtained results advocate machine-learning for polypharmacology-based molecular design, drug re-purposing, and the "de-orphaning" of phenotypic drug effects.
      PubDate: 2017-07-13T11:26:08.086631-05:
      DOI: 10.1002/anie.201706376
       
  • A Bulky m-Terphenyl Cyclopentadienyl Ligand and its Alkali Metal Complexes
           (Li, Na, K, Rb, and Cs)
    • Authors: Alex J. Veinot; Angela D.K. Todd, Jason Masuda
      Abstract: The synthesis of the new m-terphenyl substituted cyclopentadienyl ligand precursor 1-cyclopentadiene-2,6-bis(2,4,6-trimethylphenyl)benzene (TerMesCpH) is described. Synthesis proceeds through the reaction of TerMesLi with cobaltocenium iodide, followed by oxidation of the intermediate cobalt(I) species to give the corresponding cyclopentadiene as a mixture of isomers. The preparation and spectroscopic properties of the alkali metal salts (Li-Cs) is described, as well as structural information obtained by X-ray diffraction studies for the lithium, potassium, and caesium analogues. Crystallographic data demonstrates the utility of these new ligands to act as monoanionic chelates by forming metal complexes with Cp-M-Ar bonding environments.
      PubDate: 2017-07-13T08:25:41.653714-05:
      DOI: 10.1002/anie.201706398
       
  • Polly L. Arnold Made Officer of the Order of the British Empire/Robert
           Koch Gold Medal for Christopher T. Walsh/Inhoffen Medal for Helma
           Wennemers/OMCOS Award for Rubén Martín
    • PubDate: 2017-07-13T08:00:23.284418-05:
      DOI: 10.1002/anie.201706735
       
  • Palladium-Catalyzed Fluoroarylation of gem-Difluoroalkenes
    • Authors: Hai-Jun Tang; Ling-Zhi Lin, Chao Feng, Teck-Peng Loh
      Abstract: A Pd-catalyzed fluoroarylation of gem-difluoroalkenes with aryl halides is reported. By taking advantage of the in situ generated α-CF3-benzylsilver intermediates derived from the nucleophilic addition of silver fluoride to gem-difluoroalkenes, this strategy bypasses the use of a strong base, thus enabling a mild and general synthetic method for ready access to non-symmetric α,α-disubstituted trifluoroethane derivatives.Two is company: By taking advantage of the in situ generation of α-trifluoromethyl benzylsilver intermediates, a general synthetic method for the preparation of 1,1,1-trifluoro-2-arylalkane derivatives through palladium-catalyzed fluoroarylation of gem-difluoroalkenes is reported. This work represents a rare example of the introduction of α-trifluoromethylated alkyl segments through a two-electron transmetalation process.
      PubDate: 2017-07-13T07:56:38.762633-05:
      DOI: 10.1002/anie.201705321
       
  • Phosphonium Salts as Pseudohalides: Regioselective Nickel-Catalyzed
           Cross-Coupling of Complex Pyridines and Diazines
    • Authors: Xuan Zhang; Andrew McNally
      Abstract: Heterobiaryls are important pharmacophores that are challenging to prepare by traditional cross-coupling methods. An alternative approach is presented where pyridines and diazines are converted into heteroaryl phosphonium salts and coupled with aryl boronic acids. Nickel catalysts are unique for selective heteroaryl transfer, and the reaction has a broad substrate scope that includes complex pharmaceuticals. Phosphonium ions also display orthogonal reactivity in cross-couplings compared to halides, enabling chemoselective palladium- and nickel-catalyzed coupling sequences.Pyridines and diazines can be selectively converted into heterocyclic phosphonium salts that function as generic alternatives to heteroaryl halides in a nickel-catalyzed Suzuki–Miyaura coupling reaction. Complex pyridines, drug-like fragments, and pharmaceuticals can be arylated according to this two-step method.
      PubDate: 2017-07-13T07:56:33.474694-05:
      DOI: 10.1002/anie.201704948
       
  • Selenium-Doped Carbon Quantum Dots for Free Radical Scavenging
    • Authors: Feng Li; Tianyu Li, Chenxing Sun, Jiahao Xia, Yang Jiao, Huaping Xu
      Abstract: Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium-doped carbon dots have rarely been reported, even though selenium has unique chemical properties such as redox-responsive properties owing to its special electronegativity. Herein, a facile and high-output strategy to fabricate selenium-doped carbon quantum dots (Se-CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions. Selenium heteroatoms endow the Se-CQDs with redox-dependent reversible fluorescence. Furthermore, free radicals such as .OH can be effectively scavenged by the Se-CQDs. Once Se-CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are decreased. This property makes the Se-CQDs capable of protecting biosystems from oxidative stress.Using hydrothermal treatment of selenocystine, selenium-doped carbon quantum dots (Se-CQDs) with redox-dependent reversible fluorescence and free radical-scavenging capability were fabricated. Once Se-CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are decreased. This property makes the Se-CQDs capable of protecting biosystems from oxidative stress.
      PubDate: 2017-07-13T07:56:14.331915-05:
      DOI: 10.1002/anie.201705989
       
  • Highly Bent 1,3-Digerma-2-silaallene
    • Authors: Tomohiro Sugahara; Takahiro Sasamori, Norihiro Tokitoh
      Abstract: A 1,3-digerma-2-silacyclopenta-1,2-diene, that is, a 1,3-digerma-2-silaallene incorporated into a five-membered ring system, was synthesized and obtained as a stable orange solid. Owing to incorporation into a cyclic framework, the 1,3-digerma-2-silaallene moiety is highly bent, exhibiting a Si0 character for the central silicon moiety.The bends: A 1,3-digerma-2-silacyclopenta-1,2-diene, that is, a 1,3-digerma-2-silaallene incorporated into a five-membered ring system, was synthesized and obtained as a stable orange solid. Owing to incorporation into a cyclic framework, the 1,3-digerma-2-silaallene moiety is highly bent, exhibiting a Si0 character for the central silicon moiety.
      PubDate: 2017-07-13T07:55:53.930743-05:
      DOI: 10.1002/anie.201706297
       
  • B(C6F5)3: Stoichiometric and Catalytic C-C and C-H Bond Formation via
           Cationic Intermediates
    • Authors: Yashar Soltani; Lewis Charles Wilkins, Rebecca Melen
      Abstract: This work showcases a new method of catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C-H or C-C bond formation. Activation of alkyne containing substrates using B(C6F5)3 allows catalytic intramolecular cyclizations of carboxylic acid substrates to be achieved for the first time using this Lewis acid. In addition, intramolecular cyclizations of esters enables C-C bond formation in which catalytic B(C6F5)3 is used to effect formal 1,5-alkyl migrations from ester functionalities to unsaturated carbon-carbon frameworks. Using this new methodology, the catalytic formation of complex dihydropyrones and coumarins in extremely good yields under relatively mild conditions with excellent atom efficiency can be achieved in a metal-free manner.
      PubDate: 2017-07-13T05:37:39.638891-05:
      DOI: 10.1002/anie.201704789
       
  • Building Morphan Derivatives by Nitroso-Ene Cyclization: Mechanistic
           Insights and Total Synthesis of (±)-Kopsone
    • Authors: Ran Hong; Li Zhai, Xuechao Tian, Chao Wang, Wenhua Li, Zhi-Xiang Yu, Sha-Hua Huang, Qi Cui
      Abstract: A type II nitroso-ene cyclization was developed for the construction of morphan derivatives with a good functional group tolerance. DFT calculations revealed the nitroso-ene reaction is stepwise involving diradical or zwitterionic intermediates. The rate-determining step is the C-N bond formation, following by a rapid hydrogen transfer step with a chair-conformation transition state. The current approach was also successfully applied in the first total synthesis of (±)-kopsone, a highly strained yet simple morphan-type alkaloid isolated from Kopsia macrophylla.
      PubDate: 2017-07-13T05:37:13.668529-05:
      DOI: 10.1002/anie.201706018
       
  • A Second-coordination-sphere Strategy to Modulate Nickel- and
           Palladium-catalyzed Olefin Polymerization and Copolymerization
    • Authors: Min Li; Xingbao Wang, Yi Luo, Changle Chen
      Abstract: Transition-metal-catalyzed copolymerizations of olefins with polar functionalized comonomers are highly important and also highly challenging. We introduce a second-coordination-sphere strategy to address some of the difficulties encountered in these copolymerization reactions. A series of α-diimine ligands bearing nitrogen-containing second coordination spheres were prepared and characterized. The properties of the corresponding nickel and palladium catalysts in ethylene polymerizations and copolymerizations were investigated. In the nickel system, significant reduction in polymer branching density was observed, while lower polymer branching densities as well as wider range of polar monomer substrates were achieved in the palladium system. Control experiments and computational results reveal the critical role of the metal-nitrogen interaction in these polymerization and copolymerization reactions.
      PubDate: 2017-07-13T05:31:39.101728-05:
      DOI: 10.1002/anie.201706249
       
  • Discovery of Small Molecules that Induce Degradation of Huntingtin
    • Authors: Shusuke Tomoshige; Sayaka Nomura, Kenji Ohgane, Yuichi Hashimoto, Minoru Ishikawa
      Abstract: Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by aggregation of mutant huntingtin (mHtt), and removal of toxic mHtt is expected to be an effective therapeutic approach. We designed two small hybrid molecules 1 and 2, by linking a ligand for ubiquitin ligase (cellular inhibitor of apoptosis protein 1; cIAP1) with probes for mHtt aggregates, anticipating that these compounds would recruit cIAP1 to mHtt and induce selective degradation via the ubiquitin-proteasome system. The synthesized compounds reduced mHtt levels in HD patients' fibroblasts, and appear to be promising candidates for treatment of HD.
      PubDate: 2017-07-13T04:26:02.77361-05:0
      DOI: 10.1002/anie.201706529
       
  • Two-Dimensional Seeded Self-Assembly of a Complex Hierarchical
           Heterostructure
    • Authors: Yin Liu; Cheng Peng, Wei Xiong, Yifan Zhang, Yanjun Gong, Yanke Che, Jincai Zhao
      Abstract: In this work, a complex two-dimensional (2D) hierarchical heterostructure was fabricated via a sequential two-dimensional seeded self-assembly, which consisted of laterally grown nanotubes from 1 and terminally elongated nanocoils from 2 on microribbon seed from 3. Because monomers 1 and 2 can form kinetically trapped off-pathway aggregates to prevent self-nucleation and have similar molecular organizations to different facets of the seeds from 3, monomers 1 and 2 preferentially nucleated and grew on the seed sides and terminal ends, respectively, to form a complex 2D hierarchical heterostructure. The strategy used in this work can be extended to fabricate other complex nanoarchitectures from small molecules, which remains a great challenge.
      PubDate: 2017-07-13T00:45:57.055101-05:
      DOI: 10.1002/anie.201704015
       
  • Fluorescent Probes with Multiple Binding Sites to Distinguish Cys, Hcy and
           GSH
    • Authors: Cai-Xia Yin; Kang-Ming Xiong, Fang-Jun Huo, James C. Salamanca, Robert Michael Strongin
      Abstract: Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play crucial roles in maintaining redox homeostasis in biological systems. This Mini Review summarizes the most significant current challenges in the field of thiol-reactive probes for biomedical research and diagnostics, emphasizing needs and opportunities that have been under-investigated by chemists in the selective probe and sensor field. Progress on multiple binding site probes to distinguish Cys, Hcy and GSH is highlighted as a creative new direction in the field that can enable simultaneous, accurate ratiometric monitoring. New probe design strategies and researcher priorities can better help address current challenges, including the monitoring of disease states such as autism and chronic diseases involving oxidative stress that are characterized by divergent levels of GSH, Cys and Hcy.
      PubDate: 2017-07-12T20:46:07.67232-05:0
      DOI: 10.1002/anie.201704084
       
  • Diastereo- and Enantioselective Synthesis of β-Aminoboronate Esters by
           Copper(I)-Catalyzed 1,2-Addition of 1,1-Bis[(pinacolato)boryl]alkanes to
           Imines
    • Authors: Jeongho Kim; Kwangwook Ko, Seung Hwan Cho
      Abstract: We report an efficient Cu(I)-catalytic system for the diastereo- and enantioselective 1,2-addition of 1,1-bis[(pinacolato)boryl]alkanes to protected imines to afford synthetically valuable enantioenriched ß-aminoboron compounds bearing contiguous stereogenic centers. The reaction exhibits a broad scope with respect to protected imines and 1,1-bis[(pinacolato)boryl]alkanes, providing ß-aminoboronate esters with excellent diastereo- and enantioselectivity. The synthetic utility of the obtained ß-aminoboronate ester was also demonstrated.
      PubDate: 2017-07-12T12:40:32.091669-05:
      DOI: 10.1002/anie.201705829
       
  • A Novel Esterase-sensitive Prodrug Approach for Controllable Delivery of
           Persulfide Species
    • Authors: Yueqin Zheng; Bingchen Yu, Zhen Li, Zhengnan Yuan, David J. Lefer, Binghe Wang, Siming Wang, Chelsea L. Organ, Rishi K. Trivedi
      Abstract: A new strategy to deliver a well-defined persulfide species in a biological medium is described herein. Under near physiological conditions, the persulfide prodrug can be activated by an esterase to generate a "hydroxyl methyl persulfide" intermediate, which rapidly collapses to form a defined persulfide. Such persulfide prodrugs can be used either as chemical tools to study persulfide chemistry and biology or for future development as H2S-based therapeutic reagents. Using the persulfide prodrugs developed in this study, the reactivity between S-methyl methanethiosulfonate (MMTS) with persulfide was unambiguously demonstrated. In addition, a representative prodrug exhibited potent cardioprotective effects in a murine model of myocardial ischemia-reperfusion (MI/R) injury with a bell shape therapeutic profile.
      PubDate: 2017-07-12T11:40:44.432796-05:
      DOI: 10.1002/anie.201704117
       
  • Crystallization of a Two-Dimensional Hydrogen-Bonded Molecular Assembly:
           Evolution of the Local Structure Resolved by Atomic Force Microscopy
    • Authors: Laerte L. Patera; Xunshan Liu, Nico Mosso, Silvio Decurtins, Shi-Xia Liu, Jascha Repp
      Abstract: Surface-assisted self-assembly structures of the aromatic N-heterocyclic hexaazatriphenylene (HAT) molecular synthon were determined with sub-Å resolution by means of noncontact Atomic Force Microscopy (nc-AFM), both in the kinetically trapped amorphous state and in the thermodynamically stable crystalline phase. These results reveal how, for non-flexible molecular species, the crystallization governs the length-scale of the network order, without affecting the local bonding schemes. The capability of nc-AFM to accurately resolve structural relaxations will be highly relevant for the characterization of vitreous structure of 2-dimensional supramolecular materials.
      PubDate: 2017-07-12T10:40:24.933683-05:
      DOI: 10.1002/anie.201705338
       
  • Copper-alkyne complexation is responsible for the Nucleolar Localisation
           of Quadruplex Nucleic Acid Drugs Labelled by Click Chemistry
    • Authors: Marie-Paule Teulade-Fichou; Joël Lefebvre, Corinne Guetta, florent Poyer, florence Mahuteau-Betzer
      Abstract: G-quadruplex(es) (G4) are non-canonical nucleic acid structures found in guanine-rich sequences. They can be targeted with small molecules (G4-ligands) acting as reporters, for tracking both in vitro and in cells. We explored the cellular localisation of PhenDC3, one of the most powerful G4 ligands, by synthesising two clickable azide and alkyne derivatives (PhenDC3-alk, PhenDC3-az) and labelling them in situ with the corresponding Cy5 click partners. A careful comparison of the results obtained for the copper-based CuAAC and copper-free SPAAC methodologies in fixed cells implicated Cu(I) /alkyne intermediates in the non-specific localisation of ligands (and fluorophores) to the nucleoli. By contrast, SPAAC yielded similar nucleoplasmic labelling patterns in fixed and live cells. Our findings demonstrate the need for great care when using CuAAC to localise drugs in cells, and show that SPAAC gives results that are more consistent between fixed and live cells.
      PubDate: 2017-07-12T09:40:23.194883-05:
      DOI: 10.1002/anie.201703783
       
  • Catalytic intermolecular dicarbofunctionalization of styrenes with CO2 and
           radical precursors
    • Authors: Ruben Martin; Veera Reddy Yatham, Yangyang Shen
      Abstract: A redox-neutral intermolecular dicarbofunctionalization of styrenes with CO2 at atmospheric pressure and carbon-centered radicals is described. This mild protocol results in multiple C-C bond-forming reactions from simple precursors in the absence of stoichiometric reductants, thus exploiting a previously unrecognized opportunity that complements existing catalytic carboxylation events
      PubDate: 2017-07-12T08:40:42.353034-05:
      DOI: 10.1002/anie.201706263
       
  • Dynamic Equilibrium of the Aurora-A Kinase Activation Loop Revealed by
           Single Molecule Spectroscopy
    • Authors: James A H Gilburt; Hajrah Sarkar, Peter Sheldrake, Julian Blagg, Liming Ying, Charlotte Dodson
      Abstract: The conformation of the activation loop (T-loop) of protein kinases underlies enzymatic activity and influences the binding of small molecule inhibitors. Using single molecule fluorescence spectroscopy, we have determined that phosphorylated Aurora-A kinase is in dynamic equilibrium between a DFG-in-like active T-loop conformation and a DFG-out-like inactive conformation and have measured the rate constants of interconversion. Addition of the Aurora-A activating protein TPX2 shifts the equilibrium towards an active T-loop conformation, whereas addition of the inhibitors MLN8054 and CD532 favors an inactive T-loop. We show that Aurora-A binds TPX2 and MLN8054 simultaneously and provide a new model for kinase conformational behaviour. Our approach will enable conformation-specific effects to be integrated into inhibitor discovery across the kinome and we outline some immediate consequences for structure-based drug discovery.
      PubDate: 2017-07-12T07:40:29.290018-05:
      DOI: 10.1002/anie.201704654
       
  • Gold-Triggered Uncaging Chemistry in Living Systems
    • Authors: Ana M. Pérez-López; Belén Rubio-Ruiz, Víctor Sebastián, Lloyd Hamilton, Catherine Adam, Thomas L. Bray, Silvia Irusta, Paul M. Brennan, Guy Lloyd-Jones, Dirk Sieger, Jesús Santamaría, Asier Unciti-Broceta
      Abstract: Recent advances in bioorthogonal catalysis are increasing our capacity to manipulate the fate of molecules in complex biological systems. Herein we report a novel bioorthogonal uncaging strategy that is triggered by heterogeneous gold catalysis and facilitates the activation of a structurally-diverse range of therapeutics in cancer cell culture. Furthermore, this solid supported catalytic system enabled —for the first time— the locally-controlled release of a fluorescent dye in the brain of a zebrafish, offering a novel way to modulate the activity of bioorthogonal reagents in the most fragile and complex organs.
      PubDate: 2017-07-12T04:42:02.303887-05:
      DOI: 10.1002/anie.201705609
       
  • Molecular Magnetic Resonance Imaging of Lung Fibrogenesis with an Oxyamine
           Based Probe
    • Authors: Philip A. Waghorn; Chloe M. Jones, Nicholas J. Rotile, Steffi K. Koerner, Diego S. Ferreira, Howard H. Chen, Clemens K. Probst, Andrew M. Tager, Peter Caravan
      Abstract: Fibrogenesis is the active production of extracellular matrix in response to tissue injury. In many chronic diseases persistent fibrogenesis results in the accumulation of scar tissue, which can lead to organ failure and death. However no non-invasive technique exists to assess this key biological process. All tissue fibrogenesis results in the formation of allysine, which enables collagen cross-linking and leads to tissue stiffening and scar formation. We report here a novel allysine-binding gadolinium chelate (GdOA), that can non-invasively detect and quantify the extent of fibrogenesis using magnetic resonance imaging (MRI). We demonstrate that GdOA signal enhancement correlates with extent of disease and is sensitive to therapeutic response.
      PubDate: 2017-07-05T06:21:04.453558-05:
      DOI: 10.1002/anie.201704773
       
  • Cover Picture: A Twisted Nanographene Consisting of 96 Carbon Atoms
           (Angew. Chem. Int. Ed. 31/2017)
    • Authors: Kwan Yin Cheung; Chi Kit Chan, Zhifeng Liu, Qian Miao
      Pages: 8905 - 8905
      Abstract: Three-dimensional nanocarbon structures with negative curvature produced by embedding heptagons or octagons in the graphitic lattice have been proposed, but are yet to be synthesized. In their Communication on page 9003 ff., Q. Miao et al. describe a new type of twisted nanographene, which can be regarded as a segment containing structural information of such negatively curved nanocarbon structures. Consisting of 96 sp2 carbon atoms, this nanographene is twisted along two directions in the crystal.
      PubDate: 2017-06-08T07:15:20.127103-05:
      DOI: 10.1002/anie.201704990
       
  • Inside Cover: Natural Abundance 17O DNP NMR Provides Precise O−H
           Distances and Insights into the Brønsted Acidity of Heterogeneous
           Catalysts (Angew. Chem. Int. Ed. 31/2017)
    • Authors: Frédéric A. Perras; Zhuoran Wang, Pranjali Naik, Igor I. Slowing, Marek Pruski
      Pages: 8906 - 8906
      Abstract: Brønsted acidic sites on catalyst surfaces are observed by 17O dynamic nuclear-polarization-enhanced NMR spectroscopy, which hyperpolarizes nuclei by microwave-induced saturation of electrons. In their Communication on page 9165 ff., M. Pruski et al. report the measurement of O−H distances with sub-picometer precision. The length of the O−H bond is directly related to the Brønsted acidity of the sites and is also a reporter of the formation of intermolecular hydrogen-bonding interactions.
      PubDate: 2017-06-09T04:00:54.799487-05:
      DOI: 10.1002/anie.201704989
       
  • Graphical Abstract: Angew. Chem. Int. Ed. 31/2017
    • Pages: 8909 - 8924
      PubDate: 2017-07-19T02:33:25.872606-05:
      DOI: 10.1002/anie.201783111
       
  • Spotlights on our sister journals: Angew. Chem. Int. Ed. 31/2017
    • Pages: 8926 - 8929
      PubDate: 2017-07-19T02:33:22.166292-05:
      DOI: 10.1002/anie.201783113
       
  • Takeaki Iwamoto
    • Pages: 8930 - 8930
      Abstract: “My favorite place on earth is Bora Bora in Tahiti. The most important thing I learned from my parents is kindness. ...” This and more about Takeaki Iwamoto can be found on page 8930.
      PubDate: 2017-03-21T04:10:49.264308-05:
      DOI: 10.1002/anie.201702167
       
  • Dreyfus Prize in the Chemical Sciences: M. Parrinello / FCI Dozentenpreis:
           J. Strunk / Stifterverband Science Prize: P. H. Seeberger / Günther
           Laukien Prize: B. Reif / Humboldt, Siemens, and Bessel Research Awards
           2016/2017
    • Pages: 8931 - 8932
      PubDate: 2017-07-05T07:22:58.345279-05:
      DOI: 10.1002/anie.201706380
       
  • Form Follows Function: Designer Chemistry at the 52nd Bürgenstock
           Conference
    • Authors: Philipp Heretsch
      Pages: 8933 - 8936
      Abstract: The 52nd Bürgenstock Conference on Stereochemistry took place from April 30–May 4, 2017, and showed how chemistry and design go hand-in-hand (as reflected in the image of the Bauhausarchiv in Berlin). In this Conference Report, Philipp Heretsch outlines the program.
      PubDate: 2017-07-04T04:50:22.305538-05:
      DOI: 10.1002/anie.201705476
       
  • Illuminating Iron: Mesoionic Carbenes as Privileged Ligands in
           Photochemistry
    • Authors: Biprajit Sarkar; Lisa Suntrup
      Pages: 8938 - 8940
      Abstract: The new iron age: The stabilization of an iron(III) complex with mesoionic carbenes has been shown to lead to record-breaking excited-state lifetimes and an unprecedented spin-allowed radiative decay from a 2LMCT state. These results set the stage for a sustainable future in the new “iron age”.
      PubDate: 2017-06-01T13:11:36.556104-05:
      DOI: 10.1002/anie.201704522
       
  • Enantioselective Chemo- and Biocatalysis: Partners in Retrosynthesis
    • Authors: Moritz Hönig; Philipp Sondermann, Nicholas J. Turner, Erick M. Carreira
      Pages: 8942 - 8973
      Abstract: Recent developments of stereoselective biocatalytic and chemocatalytic methods are discussed. The review provides a guide to the use of biocatalytic methods in the area of chemical synthesis with focused attention on retrosynthetic considerations and analysis. The transformations presented are organized according to bond disconnections and attendant synthetic methods. The review is expected to lead to better understanding of the characteristics and distinctions of the two complementary approaches. It depicts for researchers in bio- and chemocatalysis a road map of challenges and opportunities for the evolution (and at times revolution) in chemical synthesis.Partners in synthesis: This Review provides a guide to the use of biocatalytic methods in the area of chemical synthesis with focus on retrosynthetic considerations and analysis. It is expected to lead to better understanding of the characteristics and distinctions of the two complementary approaches by depicting a road map of challenges and opportunities for the evolution in chemical synthesis.
      PubDate: 2017-06-26T02:28:52.962586-05:
      DOI: 10.1002/anie.201612462
       
  • Water Transport with Ultralow Friction through Partially Exfoliated g-C3N4
           Nanosheet Membranes with Self-Supporting Spacers
    • Authors: Yanjie Wang; Libo Li, Yanying Wei, Jian Xue, Huang Chen, Li Ding, Jürgen Caro, Haihui Wang
      Pages: 8974 - 8980
      Abstract: Two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C3N4 nanosheets in a stack with elaborate structures. In water purification the g-C3N4 membrane shows a better separation performance than commercial membranes. The g-C3N4 membrane has a water permeance of 29 L m−2 h−1 bar−1 and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C3N4 nanosheets and the spacers between the partially exfoliated g-C3N4 nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C3N4 membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3N4 nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.A g-C3N4 membrane assembled from two-dimensional g-C3N4 nanosheets demonstrates good chemical and mechanical stability, as well as ultralow water friction when applied in water purification. The nanosheets contain intrinsic (P1) and artificial (P2) nanopores, as well as self-supporting spacers (S) formed by adhered unstripped fragments.
      PubDate: 2017-06-07T06:24:47.067012-05:
      DOI: 10.1002/anie.201701288
       
  • Suppression of the Charge Density Wave State in Two-Dimensional 1T-TiSe2
           by Atmospheric Oxidation
    • Authors: Lifei Sun; Chuanhui Chen, Qinghua Zhang, Christian Sohrt, Tianqi Zhao, Guanchen Xu, Jinghui Wang, Dong Wang, Kai Rossnagel, Lin Gu, Chenggang Tao, Liying Jiao
      Pages: 8981 - 8985
      Abstract: Two-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe2, have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe2 undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase-transition behavior. We comprehensively investigate the oxidation process of 2D TiSe2 by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium-assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices.The oxidation behavior and the effect of the oxidation on the charge density wave transition behavior of two-dimensional TiSe2 is revealed (see picture; Ti purple, Se yellow, O blue). This provides important insights into the oxidation mechanism of ultrathin layered materials, and paves the way for exploiting the unusual properties of these materials.
      PubDate: 2017-06-27T06:57:56.243201-05:
      DOI: 10.1002/anie.201612605
       
  • Thermally Stable and Regenerable Platinum–Tin Clusters for Propane
           Dehydrogenation Prepared by Atom Trapping on Ceria
    • Authors: Haifeng Xiong; Sen Lin, Joris Goetze, Paul Pletcher, Hua Guo, Libor Kovarik, Kateryna Artyushkova, Bert M. Weckhuysen, Abhaya K. Datye
      Pages: 8986 - 8991
      Abstract: Ceria (CeO2) supports are unique in their ability to trap ionic platinum (Pt), providing exceptional stability for isolated single atoms of Pt. The reactivity and stability of single-atom Pt species was explored for the industrially important light alkane dehydrogenation reaction. The single-atom Pt/CeO2 catalysts are stable during propane dehydrogenation, but are not selective for propylene. DFT calculations show strong adsorption of the olefin produced, leading to further unwanted reactions. In contrast, when tin (Sn) is added to CeO2, the single-atom Pt catalyst undergoes an activation phase where it transforms into Pt–Sn clusters under reaction conditions. Formation of small Pt–Sn clusters allows the catalyst to achieve high selectivity towards propylene because of facile desorption of the product. The CeO2-supported Pt–Sn clusters are very stable, even during extended reaction at 680 °C. Coke formation is almost completely suppressed by adding water vapor to the feed. Furthermore, upon oxidation the Pt–Sn clusters readily revert to the atomically dispersed species on CeO2, making Pt–Sn/CeO2 a fully regenerable catalyst.Isolated platinum single atoms are active but not selective for alkane dehydrogenation. Platinum single atoms self-assemble into subnanometer platinum–tin clusters during reaction. The spent catalyst readily reverts to an atomically dispersed state after oxidation treatment without the need for added chlorine.
      PubDate: 2017-06-28T06:11:33.357694-05:
      DOI: 10.1002/anie.201701115
       
  • Bioorthogonal Labeling of Human Prostate Cancer Tissue Slice Cultures for
           Glycoproteomics
    • Authors: David R. Spiciarich; Rosalie Nolley, Sophia L. Maund, Sean C. Purcell, Jason Herschel, Anthony T. Iavarone, Donna M. Peehl, Carolyn R. Bertozzi
      Pages: 8992 - 8997
      Abstract: Sialylated glycans are found at elevated levels in many types of cancer and have been implicated in disease progression. However, the specific glycoproteins that contribute to the cancer cell-surface sialylation are not well characterized, specifically in bona fide human disease tissue. Metabolic and bioorthogonal labeling methods have previously enabled the enrichment and identification of sialoglycoproteins from cultured cells and model organisms. Herein, we report the first application of this glycoproteomic platform to human tissues cultured ex vivo. Both normal and cancerous prostate tissues were sliced and cultured in the presence of the azide-functionalized sialic acid biosynthetic precursor Ac4ManNAz. The compound was metabolized to the azidosialic acid and incorporated into cell surface and secreted sialoglycoproteins. Chemical biotinylation followed by enrichment and mass spectrometry led to the identification of glycoproteins that were found at elevated levels or uniquely in cancerous prostate tissue. This work therefore extends the use of bioorthogonal labeling strategies to problems of clinical relevance.Glycoprotein in a haystack: The metabolic labeling of human prostate cancer tissue slice cultures was employed to introduce azide-labeled sialic acid into cell-surface and secreted glycoproteins. Chemical biotinylation followed by enrichment and mass spectrometry led to the identification of glycoproteins that were found at elevated levels or uniquely in cancerous prostate tissue.
      PubDate: 2017-06-26T02:09:05.641366-05:
      DOI: 10.1002/anie.201701424
       
  • A Binary Bivalent Supramolecular Assembly Platform Based on
           Cucurbit[8]uril and Dimeric Adapter Protein 14-3-3
    • Authors: Pim J. de Vink; Jeroen M. Briels, Thomas Schrader, Lech-Gustav Milroy, Luc Brunsveld, Christian Ottmann
      Pages: 8998 - 9002
      Abstract: Interactions between proteins frequently involve recognition sequences based on multivalent binding events. Dimeric 14-3-3 adapter proteins are a prominent example and typically bind partner proteins in a phosphorylation-dependent mono- or bivalent manner. Herein we describe the development of a cucurbit[8]uril (Q8)-based supramolecular system, which in conjunction with the 14-3-3 protein dimer acts as a binary and bivalent protein assembly platform. We fused the phenylalanine–glycine–glycine (FGG) tripeptide motif to the N-terminus of the 14-3-3-binding epitope of the estrogen receptor α (ERα) for selective binding to Q8. Q8-induced dimerization of the ERα epitope augmented its affinity towards 14-3-3 through a binary bivalent binding mode. The crystal structure of the Q8-induced ternary complex revealed molecular insight into the multiple supramolecular interactions between the protein, the peptide, and Q8.Binary bivalent binding: The combination of a bivalent cucurbit[8]uril (Q8) host–guest complex with the bivalent protein 14-3-3 generated a binary assembly platform. Supramolecular induced switching between mono- and bivalent protein modes was observed and the elucidation of the first Q8-protein cocrystal structure reported.
      PubDate: 2017-06-29T07:47:13.6597-05:00
      DOI: 10.1002/anie.201701807
       
  • A Twisted Nanographene Consisting of 96 Carbon Atoms
    • Authors: Kwan Yin Cheung; Chi Kit Chan, Zhifeng Liu, Qian Miao
      Pages: 9003 - 9007
      Abstract: Herein we report synthesis, structure and properties of a new type of twisted nanographene, which contains an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms. The key steps in this synthesis are the Diels–Alder reaction of a macrocyclic diyne and the subsequent Scholl reaction forming the [8]circulene moiety. Two incompletely cyclized products were isolated from the Scholl reaction, providing insight into the cyclization of the strained octagon. This nanographene is twisted along two directions with end-to-end twists of 142.4° and 140.2° as revealed by X-ray crystallography, and is flexible at room temperature as found from the computational and experimental studies.A new type of twisted nanographene containing an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms was synthesized from a macrocyclic diyne (see picture). Its structure was studied with X-ray crystallography and DFT calculations.
      PubDate: 2017-05-16T03:40:35.663359-05:
      DOI: 10.1002/anie.201703754
       
  • Differences between G-Protein-Stabilized Agonist–GPCR Complexes and
           their Nanobody-Stabilized Equivalents
    • Authors: Noureldin Saleh; Passainte Ibrahim, Timothy Clark
      Pages: 9008 - 9012
      Abstract: Protein nanobodies have been used successfully as surrogates for unstable G-proteins in order to crystallize G-protein-coupled receptors (GPCRs) in their active states. We used molecular dynamics (MD) simulations, including metadynamics enhanced sampling, to investigate the similarities and differences between GPCR–agonist ternary complexes with the α-subunits of the appropriate G-proteins and those with the protein nanobodies (intracellular binding partners, IBPs) used for crystallization. In two of the three receptors considered, the agonist-binding mode differs significantly between the two alternative ternary complexes. The ternary-complex model of GPCR activation entails enhancement of ligand binding by bound IBPs: Our results show that IBP-specific changes can alter the agonist binding modes and thus also the criteria for designing GPCR agonists.Strike a pose: Molecular dynamics (MD) simulations indicate that the protein nanobodies often used to obtain crystals of G-protein coupled receptors lead to slightly different poses for bound ligands and changes in the orthosteric binding site relative to the native G-protein. Currently, MD simulations are the only way to determine such differences.
      PubDate: 2017-07-03T08:07:39.179354-05:
      DOI: 10.1002/anie.201702468
       
  • Inorganic-Macroion-Induced Formation of Bicontinuous Block Copolymer
           Nanocomposites with Enhanced Conductivity and Modulus
    • Authors: Liying Zhang; Tingting Cui, Xiao Cao, Chengji Zhao, Quan Chen, Lixin Wu, Haolong Li
      Pages: 9013 - 9017
      Abstract: A facile and electrostatically driven approach has been developed to prepare bicontinuous polymer nanocomposites that is based on the polyoxometalate (POM) macroion induced phase transition of PS-b-P2VP from an initial lamellar phase to a stable bicontinuous phase. The multi-charged POMs can electrostatically cross-link P2VP blocks and give rise to bicontinuous phases in which the POM hybrid conductive domains occupy a large volume fraction of more than 50 %. Furthermore, the POMs can give rise to high proton conductivity and serve as nanoenhancers, endowing the bicontinuous nanocomposites with a conductivity of 0.1 mS cm−1 and a Young's modulus of 7.4 GPa at room temperature; these values are greater than those of pristine PS-b-P2VP by two orders of magnitude and a factor of 1.8, respectively. This approach can provide a new concept based on electrostatic control to design functional bicontinuous polymer materials.Polymer nanocomposites: Bicontinuous nanocomposites were prepared from block copolymers through a phase transition induced by polyoxometalate macroions. The resulting nanocomposites exhibit a large conductive volume fraction of greater than 50 %, an increased conductivity of up to 0.1 mS cm−1, and an enhanced Young's modulus of 7.4 GPa at room temperature.
      PubDate: 2017-06-30T02:02:16.998745-05:
      DOI: 10.1002/anie.201702785
       
  • Low-Dimensional Organic Tin Bromide Perovskites and Their Photoinduced
           Structural Transformation
    • Authors: Chenkun Zhou; Yu Tian, Mingchao Wang, Alyssa Rose, Tiglet Besara, Nicholas K. Doyle, Zhao Yuan, Jamie C. Wang, Ronald Clark, Yanyan Hu, Theo Siegrist, Shangchao Lin, Biwu Ma
      Pages: 9018 - 9022
      Abstract: Hybrid organic–inorganic metal halide perovskites possess exceptional structural tunability, with three- (3D), two- (2D), one- (1D), and zero-dimensional (0D) structures on the molecular level all possible. While remarkable progress has been realized in perovskite research in recent years, the focus has been mainly on 3D and 2D structures, with 1D and 0D structures significantly underexplored. The synthesis and characterization of a series of low-dimensional organic tin bromide perovskites with 1D and 0D structures is reported. Using the same organic and inorganic components, but at different ratios and reaction conditions, both 1D (C4N2H14)SnBr4 and 0D (C4N2H14Br)4SnBr6 can be prepared in high yields. Moreover, photoinduced structural transformation from 1D to 0D was investigated experimentally and theoretically in which photodissociation of 1D metal halide chains followed by structural reorganization leads to the formation of a more thermodynamically stable 0D structure.Synthetic control of low-dimensional organic tin bromide perovskites with 1D and 0D structures is reported. The non-emissive 1D structure is a kinetically favored product that can undergo photoinduced structural transformation to form a more thermodynamically stable 0D structure with exceptional luminescence.
      PubDate: 2017-07-03T07:16:16.665336-05:
      DOI: 10.1002/anie.201702825
       
  • Switching Between Giant Positive and Negative Thermal Expansions of a
           YFe(CN)6-based Prussian Blue Analogue Induced by Guest Species
    • Authors: Qilong Gao; Jun Chen, Qiang Sun, Dahu Chang, Qingzhen Huang, Hui Wu, Andrea Sanson, Ruggero Milazzo, He Zhu, Qiang Li, Zhanning Liu, Jinxia Deng, Xianran Xing
      Pages: 9023 - 9028
      Abstract: The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K+) and molecules (H2O) can substantially switch thermal expansion of YFe(CN)6 from negative (αv=−33.67×10−6 K−1) to positive (αv=+42.72×10−6 K−1)—a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests.Guest of honor: Thermal expansion of an open YFe(CN)6 framework is switched from strongly negative to positive by introducing guest potassium ions or H2O molecules. Guests have a damping effect on the transverse vibrations of nitrogen and carbon atoms, thus inhibiting negative thermal expansion.
      PubDate: 2017-06-23T03:40:30.88633-05:0
      DOI: 10.1002/anie.201702955
       
  • Initiator-Loaded Gold Nanocages as a Light-Induced Free-Radical Generator
           for Cancer Therapy
    • Authors: Xiao-Qiang Wang; Fan Gao, Xian-Zheng Zhang
      Pages: 9029 - 9033
      Abstract: Tumor hypoxia greatly suppresses the therapeutic efficacy of photodynamic therapy (PDT), mainly because the generation of toxic reactive oxygen species (ROS) in PDT is highly oxygen-dependent. In contrast to ROS, the generation of oxygen-irrelevant free radicals is oxygen-independent. A new therapeutic strategy based on the light-induced generation of free radicals for cancer therapy is reported. Initiator-loaded gold nanocages (AuNCs) as the free-radical generator were synthesized. Under near-infrared light (NIR) irradiation, the plasmonic heating effect of AuNCs can induce the decomposition of the initiator to generate alkyl radicals (R.), which can elevate oxidative-stress (OS) and cause DNA damages in cancer cells, and finally lead to apoptotic cell death under different oxygen tensions. As a proof of concept, this research opens up a new field to use various free radicals for cancer therapy.A therapeutic strategy using gold nanocages loaded with initiator as a light-induced free-radical generator is presented. The generation of free radicals is oxygen-independent. The therapeutic mechanism of the generated free radicals was revealed.
      PubDate: 2017-06-28T06:12:25.159551-05:
      DOI: 10.1002/anie.201703159
       
  • Energy Transfer between Spatially Separated Entangled Molecules
    • Authors: Xiaolan Zhong; Thibault Chervy, Lei Zhang, Anoop Thomas, Jino George, Cyriaque Genet, James A. Hutchison, Thomas W. Ebbesen
      Pages: 9034 - 9038
      Abstract: Light–matter strong coupling allows for the possibility of entangling the wave functions of different molecules through the light field. We hereby present direct evidence of non-radiative energy transfer well beyond the Förster limit for spatially separated donor and acceptor cyanine dyes strongly coupled to a cavity. The transient dynamics and the static spectra show an energy transfer efficiency approaching 37 % for donor–acceptor distances ≥100 nm. In such systems, the energy transfer process becomes independent of distance as long as the coupling strength is maintained. This is consistent with the entangled and delocalized nature of the polaritonic states.Non-radiative energy transfer occurs between spatially separated entangled molecules in the vacuum field of an optical cavity. In such systems, the energy transfer process becomes independent of distance as long as the coupling strength is maintained. This behavior is consistent with the entangled and delocalized nature of the polaritonic states.
      PubDate: 2017-06-28T06:40:49.517976-05:
      DOI: 10.1002/anie.201703539
       
  • Direct Mechanism of the First Carbon–Carbon Bond Formation in the
           Methanol-to-Hydrocarbons Process
    • Authors: Xinqiang Wu; Shutao Xu, Wenna Zhang, Jindou Huang, Jinzhe Li, Bowen Yu, Yingxu Wei, Zhongmin Liu
      Pages: 9039 - 9043
      Abstract: In the past two decades, the reaction mechanism of C−C bond formation from either methanol or dimethyl ether (DME) in the methanol-to-hydrocarbons (MTH) process has been a highly controversial issue. Described here is the first observation of a surface methyleneoxy analogue, originating from the surface-activated DME, by in situ solid-state NMR spectroscopy, a species crucial to the first C−C bond formation in the MTH process. New insights into the first C−C bond formation were provided, thus suggesting DME/methanol activation and direct C−C bond formation by an interesting synergetic mechanism, involving C−H bond breakage and C−C bond coupling during the initial methanol reaction within the chemical environment of the zeolite catalyst.In a fine state: A crucial surface methyleneoxy analogue group originating from surface-activated dimethyl ether (DME) was directly observed by in situ solid-state NMR spectroscopy. New insights into the first C−C bond formation for the methanol-to-hydrocarbons process are provided.
      PubDate: 2017-05-31T03:01:08.878101-05:
      DOI: 10.1002/anie.201703902
       
  • Temperature-Dependence of the Rates of Reaction of Trifluoroacetic Acid
           with Criegee Intermediates
    • Authors: Rabi Chhantyal-Pun; Max R. McGillen, Joseph M. Beames, M. Anwar H. Khan, Carl J. Percival, Dudley E. Shallcross, Andrew J. Orr-Ewing
      Pages: 9044 - 9047
      Abstract: The rate coefficients for gas-phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240–340 K. The rate coefficients k(CH2OO + CF3COOH)=(3.4±0.3)×10−10 cm3 s−1 and k((CH3)2COO + CF3COOH)=(6.1±0.2)×10−10 cm3 s−1 at 294 K exceed estimates for collision-limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre-reactive complex. Fits to a model incorporating this complex formation give k [cm3 s−1]=(3.8±2.6)×10−18 T2 exp((1620±180)/T) + 2.5×10−10 and k [cm3 s−1]=(4.9±4.1)×10−18 T2 exp((1620±230)/T) + 5.2×10−10 for the CH2OO + CF3COOH and (CH3)2COO + CF3COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates.Criegee intermediates produced by ozonolysis of alkenes in the Earth's troposphere are potentially important oxidizers of trace constituent gases. Studies of the rates of reaction of trifluoroacetic acid with two Criegee intermediates, formaldehyde oxide and acetone oxide, suggest an important atmospheric sink for this persistent pollutant.
      PubDate: 2017-06-29T01:40:31.730886-05:
      DOI: 10.1002/anie.201703700
       
  • (NHC)NiH-Catalyzed Intermolecular Regio- and Diastereoselective
           Cross-Hydroalkenylation of Endocyclic Dienes with α-Olefins
    • Authors: Xiaoyan Lian; Weihao Chen, Liang Dang, Yuchen Li, Chun-Yu Ho
      Pages: 9048 - 9052
      Abstract: Highly selective cross-hydroalkenylations of endocyclic 1,3-dienes at the least substituted site with α-olefins were achieved with a set of neutral (NHC)NiIIH(OTf) catalysts and cationic NiII catalysts with a novel NHC ligand. Under heteroatom assistance, skipped dienes were obtained in good yields, often from equal amounts of the two substrates and at a catalyst loading of 2–5 mol %. Rare 4,3-product selectivity (i.e., with the H atom at C4 and the alkenyl group at C3 of the diene) was observed, which is different from the selectivity of known dimerizations of α-olefins with both acyclic Co and Fe systems. The influence of the various substituents on the NHC, 1,3-diene, and α-olefin on the chemo-, regio-, and diastereoselectivity was studied. High levels of chirality transfer were observed with chiral cyclohexadiene derivatives.Heteroatom effects: Skipped dienes with exo-methylene groups were prepared by nickel-catalyzed cross-hydroalkenylation in high yields. Endocyclic 1,3-dienes easily accessible from natural sources with built-in chiral centers are now compatible with α-olefins. Isomerization is prevented by steric effects of the NHC ligands and products. DIPP=2,6-diisopropylphenyl.
      PubDate: 2017-06-16T03:15:55.55437-05:0
      DOI: 10.1002/anie.201703706
       
  • A Simple Nanocellulose Coating for Self-Cleaning upon Water Action:
           Molecular Design of Stable Surface Hydrophilicity
    • Authors: Shu Huang; Dayang Wang
      Pages: 9053 - 9057
      Abstract: Coating solid surfaces with cellulose nanofibril (CNF) monolayers via physical deposition was found to keep the surfaces free of a variety of oils, ranging from viscous engine oil to polar n-butanol, upon water action. The self-cleaning function was well correlated with the unique molecular structure of the CNF, in which abundant surface carboxyl and hydroxy groups are uniformly, densely, and symmetrically arranged to form a polar corona on a crystalline nanocellulose strand. This isotropic core–corona configuration offers new and easily adoptable guidance to design self-cleaning surfaces at the molecular level. Thanks to its excellent self-cleaning behavior, the CNF coating converted conventional meshes into highly effective membranes for oil–water separation with no prior surface treatment required.Simple coating of cellulose nanofibril (CNF) monolayers brings about excellent self-cleaning surface behavior. Thanks to its isotropic molecular configuration, the orientation of each CNF with respect to the surface plane hardly affects water wetting on the CNF coating, thus making the coating surfaces clean of a variety of oils upon simple water action.
      PubDate: 2017-06-28T06:42:12.448107-05:
      DOI: 10.1002/anie.201703913
       
  • Highly Stable, Low Gas Crossover, Proton-Conducting Phenylated
           Polyphenylenes
    • Authors: Michael Adamski; Thomas J. G. Skalski, Benjamin Britton, Timothy J. Peckham, Lukas Metzler, Steven Holdcroft
      Pages: 9058 - 9061
      Abstract: Two classes of novel sulfonated phenylated polyphenylene ionomers are investigated as polyaromatic-based proton exchange membranes. Both types of ionomer possess high ion exchange capacities yet are insoluble in water at elevated temperatures. They exhibit high proton conductivity under both fully hydrated conditions and reduced relative humidity, and are markedly resilient to free radical attack. Fuel cells constructed with membrane-electrode assemblies containing each ionomer membrane yield high in situ proton conductivity and peak power densities that are greater than obtained using Nafion reference membranes. In situ chemical stability accelerated stress tests reveal that this class of the polyaromatic membranes allow significantly lower gas crossover and lower rates of degradation than Nafion benchmark systems. These results point to a promising future for molecularly designed sulfonated phenylated polyphenylenes as proton-conducting media in electrochemical technologies.Passing stress test: Two classes of novel sulfonated polyphenylene ionomers were investigated as proton exchange membranes. Both possess high ion-exchange capacities yet are insoluble in water. They exhibit high proton conductivity under both fully hydrated conditions and reduced relative humidity, and are markedly resilient to free-radical attack.
      PubDate: 2017-06-27T06:30:50.96903-05:0
      DOI: 10.1002/anie.201703916
       
  • Synthesis and Characterization of a Metallacyclic Framework with Three
           Fused Five-membered Rings
    • Authors: Congqing Zhu; Jingjing Wu, Shenyan Li, Yuhui Yang, Jun Zhu, Xin Lu, Haiping Xia
      Pages: 9067 - 9071
      Abstract: Polycyclic complexes containing a bridgehead transition metal are interesting species because the transition metal is shared by all the rings simultaneously. In this study, we present a novel osmium–bridgehead system with three fused five-membered rings. This novel framework can be viewed as a 10-atom carbon chain coordinating to the osmium center. In sharp contrast to the nonplanar organic analogue, this unique metallacycle exhibits good planarity, which was unambiguously verified by means of X-ray diffraction. Interestingly, preliminary DFT calculations show that the aromaticity in the three 5MRs of these osmatricycles can be easily tuned by the ligand substitution. Finally, the broad UV/Vis absorption spectra of these novel polycyclic complexes were also reported.Missing link: A metallacyclic framework with three fused five-membered rings (5MRs) was constructed (dotted box) from a 10-atom carbon chain coordinating with a transition metal in the equatorial plane. This structure can be viewed as the missing link between a metallapentalyne, metallapentalene-fused 3MR, metallapentalene-fused 4MR, and metallapentalene-fused 6MR.
      PubDate: 2017-07-19T02:33:21.889377-05:
      DOI: 10.1002/anie.201704057
       
  • Gluing Ionic Liquids to Oxide Surfaces: Chemical Anchoring of
           Functionalized Ionic Liquids by Vapor Deposition onto Cobalt(II) Oxide
    • Authors: Tao Xu; Tobias Waehler, Julia Vecchietti, Adrian Bonivardi, Tanja Bauer, Johannes Schwegler, Peter S. Schulz, Peter Wasserscheid, Joerg Libuda
      Pages: 9072 - 9076
      Abstract: Ionic liquids (IL) hold a great potential as novel electrolytes for applications in electronic materials and energy technology. The functionality of ILs in these applications relies on their interface to semiconducting nanomaterials. Therefore, methods to control the chemistry and structure of this interface are the key to assemble new IL-based electronic and electrochemical materials. Here, we present a new method to prepare a chemically well-defined interface between an oxide and an IL film. An imidazolium-based IL, which is carrying an ester group, is deposited onto cobalt oxide surface by evaporation. The IL binds covalently to the surface by thermally activated cleavage of the ester group and formation of a bridging carboxylate. The anchoring reaction shows high structure sensitivity, which implies that the IL film can be adhered selectively to specific oxide surfaces.On the surface of it: A functionalized imidazolium-based ionic liquid is covalently anchored to an oxide surface by deposition from the gas phase. In a highly structure-sensitive reaction, the ionic liquid binds to the surface by thermally activated cleavage of an ester group and formation of a bridging carboxylate.
      PubDate: 2017-06-28T06:42:24.46715-05:0
      DOI: 10.1002/anie.201704107
       
  • Rational Engineering of a Dynamic, Entropy-Driven DNA Nanomachine for
           Intracellular MicroRNA Imaging
    • Authors: Cheng-Pin Liang; Pei-Qiang Ma, Hui Liu, Xinggang Guo, Bin-Cheng Yin, Bang-Ce Ye
      Pages: 9077 - 9081
      Abstract: We rationally engineered an elegant entropy-driven DNA nanomachine with three-dimensional track and applied it for intracellular miRNAs imaging. The proposed nanomachine is activated by target miRNA binding to drive a walking leg tethered to gold nanoparticle with a high density of DNA substrates. The autonomous and progressive walk on the DNA track via the entropy-driven catalytic reaction of intramolecular toehold-mediated strand migration leads to continuous disassembly of DNA substrates, accompanied by the recovery of fluorescence signal due to the specific release of a dye-labeled substrate from DNA track. Our nanomachine outperforms the conventional intermolecular reaction-based gold nanoparticle design in the context of an improved sensitivity and kinetics, attributed to the enhanced local effective concentrations of working DNA components from the proximity-induced intramolecular reaction. Moreover, the nanomachine was applied for miRNA imaging inside living cells.Walk on a DNA track: An elegant entropy-driven DNA nanomachine with a three-dimensional track was rationally engineered (see picture). The nanomachine was applied for microRNA imaging inside living cells.
      PubDate: 2017-06-28T06:46:44.253255-05:
      DOI: 10.1002/anie.201704147
       
  • Proton Transport in the Outer-Membrane Flavocytochrome Complex Limits the
           Rate of Extracellular Electron Transport
    • Authors: Akihiro Okamoto; Yoshihide Tokunou, Shafeer Kalathil, Kazuhito Hashimoto
      Pages: 9082 - 9086
      Abstract: The microbial transfer of electrons to extracellularly located solid compounds, termed extracellular electron transport (EET), is critical for microbial electrode catalysis. Although the components of the EET pathway in the outer membrane (OM) have been identified, the role of electron/cation coupling in EET kinetics is poorly understood. We studied the dynamics of proton transport associated with EET in an OM flavocytochrome complex in Shewanella oneidensis MR-1. Using a whole-cell electrochemical assay, a significant kinetic isotope effect (KIE) was observed following the addition of deuterated water (D2O). The removal of a flavin cofactor or key components of the OM flavocytochrome complex significantly increased the KIE in the presence of D2O to values that were significantly larger than those reported for proton channels and ATP synthase, thus indicating that proton transport by OM flavocytochrome complexes limits the rate of EET.It electrifying: Direct electron transport via an electron circuit composed of multiheme and flavin in an integral outer-membrane (OM) flavocytochrome complex is critical for microbial electrode catalysis. Electrochemical study of the solvent kinetic isotope effect revealed that proton transport by the OM flavocytochrome limits the rate of electron transport in the iron-reducing bacterium Shewanella oneidensis MR-1.
      PubDate: 2017-06-29T07:50:27.102368-05:
      DOI: 10.1002/anie.201704241
       
  • A Modular Approach to Inorganic Phosphazane Macrocycles
    • Authors: Alex J. Plajer; Raúl García-Rodríguez, Callum G. M. Benson, Peter D. Matthews, Andrew D. Bond, Sanjay Singh, Lutz H. Gade, Dominic S. Wright
      Pages: 9087 - 9090
      Abstract: Inorganic macrocycles, based on non-carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host–guest and supramolecular chemistry. Here we demonstrate a new high-yielding modular approach to a broad range of trimeric and hexameric S- and Se-bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(μ-NR)]2. The method involves the in situ generation of the key intermediate [E....._(S....._)P(μ-NR)]22−(E=S, Se) dianion, which can be reacted with electrophilic [ClP(μ-NR)]2 to give PIII/PV hexameric rings or reacted with I2 to give trimeric PV variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air-stable and chiral inorganic macrocycles.Give me a ring: A range of new S- or Se-bridged phosphazane macrocycles can be obtained using the dimeric dianions [S=(Se)P(μ-NtBu)]22−, either through reactions with the dichlorophosphazane dimers [ClP(μ-NR)]2 or by oxidation with I2. This approach allows variation of the organic substituents in this class of inorganic macromolecule for the first time, and the introduction of chirality.
      PubDate: 2017-04-21T02:56:39.616832-05:
      DOI: 10.1002/anie.201702558
       
  • Facile and Reversible Formation of Iron(III)–Oxo–Cerium(IV) Adducts
           from Nonheme Oxoiron(IV) Complexes and Cerium(III)
    • Authors: Apparao Draksharapu; Waqas Rasheed, Johannes E. M. N. Klein, Lawrence Que
      Pages: 9091 - 9095
      Abstract: Ceric ammonium nitrate (CAN) or CeIV(NH4)2(NO3)6 is often used in artificial water oxidation and generally considered to be an outer-sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)FeIII-O-CeIV(OH2)(NO3)4]+ (3), a complex obtained from the reaction of [(N4Py)FeII(NCMe)]2+ with 2 equiv CAN or [(N4Py)FeIV=O]2+ (2) with CeIII(NO3)3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the FeIV and CeIV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S=1 FeIV in 2 to S=5/2 in 3, which is found to be facile despite the formal spin-forbidden nature of this process. This observation suggests that FeIV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier.Cerium caught in the redox act: CeIII reacts with FeIV(O) complexes in acetonitrile to form inner-sphere FeIII-O-CeIV adducts. The transformation is easily reversed by adding water. The facile equilibrium is tuned by the ligands on the Ce center, and its existence shows that the CeIV/III and FeIV/III potentials must fall within a range of 0.9–1.1 V measured against a saturated calomel electrode.
      PubDate: 2017-06-27T06:31:01.469637-05:
      DOI: 10.1002/anie.201704322
       
  • Unified Asymmetric Total Syntheses of (−)-Alotaketals A–D and
           (−)-Phorbaketal A
    • Authors: Hang Cheng; Zhihong Zhang, Hongliang Yao, Wei Zhang, Jingxun Yu, Rongbiao Tong
      Pages: 9096 - 9100
      Abstract: The novel tricyclic spiroketal alotane-type sesterterpenoids showed strikingly different biological activities and potency with subtle structural alterations. Asymmetric total syntheses of the tricyclic sesterterpenoids (−)-alotaketals A–D and (−)-phorbaketal A were accomplished [29–31 steps from (−)-malic acid] in a collective way for the first time. The key features of the strategy included 1) a new cascade cyclization of vinyl epoxy δ-keto-alcohols to forge the common tricyclic spiroketal intermediate, 2) a late-stage allylic C−H oxidation, and 3) olefin cross-metathesis to install the different side chains.All-in-one: Unified total syntheses of the tricyclic sesterterpenoids (−)-alotaketals A–D and (−)-phorbaketal A were accomplished (29–31 steps from (−)-malic acid) in a collective way for the first time. The syntheses feature a new cascade cyclization of vinyl epoxy δ-keto-alcohols, late-stage C−H oxidation, and olefin cross-metathesis.
      PubDate: 2017-06-26T02:29:18.013335-05:
      DOI: 10.1002/anie.201704628
       
  • Automated Quantum Mechanical Predictions of Enantioselectivity in a
           Rhodium-Catalyzed Asymmetric Hydrogenation
    • Authors: Yanfei Guan; Steven E. Wheeler
      Pages: 9101 - 9105
      Abstract: A computational toolkit (AARON: An automated reaction optimizer for new catalysts) is described that automates the density functional theory (DFT) based screening of chiral ligands for transition-metal-catalyzed reactions with well-defined reaction mechanisms but multiple stereocontrolling transition states. This is demonstrated for the Rh-catalyzed asymmetric hydrogenation of (E)-β-aryl-N-acetyl enamides, for which a new C2-symmetric phosphorus ligand is designed.The computational toolkit AARON (an automated reaction optimizer for new catalysts) automates the quantum mechanical optimization of the hundreds of transition-state structures needed to reliably predict the stereochemical outcome of transition-metal-catalyzed reactions, as demonstrated for a Rh-catalyzed asymmetric hydrogenation of (E)-β-aryl-N-acetyl enamides.
      PubDate: 2017-06-28T06:46:28.221809-05:
      DOI: 10.1002/anie.201704663
       
  • Pentagon-Embedded Cycloarylenes with Cylindrical Shapes
    • Authors: Shunpei Hitosugi; Sota Sato, Taisuke Matsuno, Takashi Koretsune, Ryotaro Arita, Hiroyuki Isobe
      Pages: 9106 - 9110
      Abstract: Cylinder-shaped graphitic networks in carbon nanotubes have attracted interest from scientists in various disciplines. The chemical synthesis of segments thereof is considered as a challenging and appealing subject in chemistry, and deepens our understanding of curved and conjugated arrays of hexagons. We herein report the synthesis of cylinder-shaped molecules containing non-hexagon bridges in their conjugated systems. Multiple pentagon units were embedded in the cylinder-shaped discrete molecules, and the stereoisomerism originating from their helical carbon arrangements was studied. Structural analysis by NMR, UV/Vis absorption spectroscopy, and single-crystal X-ray diffraction provided fundamental experimental information on the curved systems with conjugation across the pentagons. This study provides the first experimental guide for further explorations of anomalous non-hexagon arrays of graphitic carbon materials with cylindrical shapes.Multiple pentagons were synthetically embedded in cylinder-shaped molecules to obtain segments of haeckelite nanotubes with imperfect honeycomb arrays. In these cylinder-shaped molecules, conjugation was observed over the pentagon bridges. These compounds also provide intermediate structures for retrosynthetic analysis and inspiration for novel defective carbon nanotubes.
      PubDate: 2017-06-29T07:50:48.474145-05:
      DOI: 10.1002/anie.201704676
       
  • Antimony Complexes for Electrocatalysis: Activity of a Main-Group Element
           in Proton Reduction
    • Authors: Jianbing Jiang; Kelly L. Materna, Svante Hedström, Ke R. Yang, Robert H. Crabtree, Victor S. Batista, Gary W. Brudvig
      Pages: 9111 - 9115
      Abstract: Main-group complexes are shown to be viable electrocatalysts for the H2-evolution reaction (HER) from acid. A series of antimony porphyrins with varying axial ligands were synthesized for electrocatalysis applications. The proton-reduction catalytic properties of TPSb(OH)2 (TP=5,10,15,20-tetra(p-tolyl)porphyrin) with two axial hydroxy ligands were studied in detail, demonstrating catalytic H2 production. Experiments, in conjunction with quantum chemistry calculations, show that the catalytic cycle is driven via the redox activity of both the porphyrin ligand and the Sb center. This study brings insight into main group catalysis and the role of redox-active ligands during catalysis.Antimony–porphyrin complexes were prepared and studied for catalytic proton reduction. The catalysts were found to produce hydrogen gas electrochemically, and provide a basis for the development of new main-group catalysts.
      PubDate: 2017-07-04T04:55:51.436678-05:
      DOI: 10.1002/anie.201704700
       
  • Catalysis of Extracellular Deamination by a FAD-Linked Oxidoreductase
           after Prodrug Maturation in the Biosynthesis of Saframycin A
    • Authors: Li-Qiang Song; Ying-Ying Zhang, Jin-Yue Pu, Man-Cheng Tang, Chao Peng, Gong-Li Tang
      Pages: 9116 - 9120
      Abstract: The biosynthesis of antibiotics in bacteria is usually believed to be an intracellular process, at the end of which the matured compounds are exported outside the cells. The biosynthesis of saframycin A (SFM-A), an antitumor antibiotic, requires a cryptic fatty acyl chain to guide the construction of a pentacyclic tetrahydroisoquinoline scaffold; however, the follow-up deacylation and deamination steps remain unknown. Herein we demonstrate that SfmE, a membrane-bound peptidase, hydrolyzes the fatty acyl chain to release the amino group; and SfmCy2, a secreted oxidoreductase covalently associated with FAD, subsequently performs an oxidative deamination extracellularly. These results not only fill in the missing steps of SFM-A biosynthesis, but also reveal that a FAD-binding oxidoreductase catalyzes an unexpected deamination reaction through an unconventional extracellular pathway in Streptmyces bacteria.Take it outside! A secreted protein, SfmCy2, that binds covalently to FAD was found to catalyze extracellular oxidative deamination as the last tailoring step in saframycin A biosynthesis, following prodrug maturation by the membrane-bound peptidase SfmE (see scheme; saframycin A has a cyano group in place of the hydroxy group in precursor saframycin S).
      PubDate: 2017-07-04T04:56:00.784373-05:
      DOI: 10.1002/anie.201704726
       
  • Carbon Dioxide Electroreduction into Syngas Boosted by a Partially
           Delocalized Charge in Molybdenum Sulfide Selenide Alloy Monolayers
    • Authors: Jiaqi Xu; Xiaodong Li, Wei Liu, Yongfu Sun, Zhengyu Ju, Tao Yao, Chengming Wang, Huanxin Ju, Junfa Zhu, Shiqiang Wei, Yi Xie
      Pages: 9121 - 9125
      Abstract: Structural parameters of ternary transition-metal dichalcogenide (TMD) alloy usually obey Vegard law well, while interestingly it often exhibits boosted electrocatalytic performances relative to its two pristine binary TMDs. To unveil the underlying reasons, we propose an ideal model of ternary TMDs alloy monolayer. As a prototype, MoSeS alloy monolayers are successfully synthesized, in which X-ray absorption fine structure spectroscopy manifests their shortened Mo−S and lengthened Mo−Se bonds, helping to tailor the d-band electronic structure of Mo atoms. Density functional theory calculations illustrate an increased density of states near their conduction band edge, which ensures faster electron transfer confirmed by their lower work function and smaller charge-transfer resistance. Energy calculations show the off-center charge around Mo atoms not only benefits for stabilizing COOH* intermediate confirmed by its most negative formation energy, but also facilitates the rate-limiting CO desorption step verified by CO temperature programmed desorption and electro-stripping tests. As a result, MoSeS alloy monolayers attain the highest 45.2 % Faradaic efficiency for CO production, much larger than that of MoS2 monolayers (16.6 %) and MoSe2 monolayers (30.5 %) at −1.15 V vs. RHE. This work discloses how the partially delocalized charge in ternary TMDs alloys accelerates electrocatalytic performances at atomic level, opening new horizons for manipulating CO2 electroreduction properties.CO2 conversion: MoSeS alloy monolayers have been synthesized by a liquid–liquid interface-mediated strategy, in which X-ray absorption fine structure spectroscopy manifested shortened Mo−S and lengthened Mo−Se bonds. Calculations show that the off-center charge around Mo atoms not only stabilizes the COOH* intermediate, but also facilitates the rate-limiting CO desorption step.
      PubDate: 2017-06-29T07:55:49.991679-05:
      DOI: 10.1002/anie.201704928
       
  • A Rechargeable Li-CO2 Battery with a Gel Polymer Electrolyte
    • Authors: Chao Li; Ziyang Guo, Bingchang Yang, Yao Liu, Yonggang Wang, Yongyao Xia
      Pages: 9126 - 9130
      Abstract: The utilization of CO2 in Li-CO2 batteries is attracting extensive attention. However, the poor rechargeability and low applied current density have remained the Achilles’ heel of this energy device. The gel polymer electrolyte (GPE), which is composed of a polymer matrix filled with tetraglyme-based liquid electrolyte, was used to fabricate a rechargeable Li-CO2 battery with a carbon nanotube-based gas electrode. The discharge product of Li2CO3 formed in the GPE-based Li-CO2 battery exhibits a particle-shaped morphology with poor crystallinity, which is different from the contiguous polymer-like and crystalline discharge product in conventional Li-CO2 battery using a liquid electrolyte. Accordingly, the GPE-based battery shows much improved electrochemical performance. The achieved cycle life (60 cycles) and rate capability (maximum applied current density of 500 mA g−1) are much higher than most of previous reports, which points a new way to develop high-performance Li-CO2 batteries.En route to high-performance batteries: A gel polymer electrolyte (GPE) is used to fabricate a rechargeable Li-CO2 battery. This battery has a high rate capability (maximum applied current density of 500 mA g−1) and long cycle life (60 cycles).
      PubDate: 2017-06-30T02:03:43.028851-05:
      DOI: 10.1002/anie.201705017
       
  • Water-Catalyzed Oxidation of Few-Layer Black Phosphorous in a Dark
           Environment
    • Authors: Zehua Hu; Qiang Li, Bo Lei, Qionghua Zhou, Du Xiang, Zhiyang Lyu, Fang Hu, Junyong Wang, Yinjuan Ren, Rui Guo, Eda Goki, Li Wang, Cheng Han, Jinlan Wang, Wei Chen
      Pages: 9131 - 9135
      Abstract: Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.A new oxidation mechanism of black phosphorus (BP), namely water-catalyzed oxidation in the dark, has been revealed by comprehensive in situ experiments. DFT calculations reveal that the polarization effect of water lowers the energy level of oxygen, thus catalyzing the oxidation process.
      PubDate: 2017-06-30T02:02:40.879284-05:
      DOI: 10.1002/anie.201705012
       
  • Anion Exchange Renders Hydrophobic Capsules and Cargoes Water-Soluble
    • Authors: Edmundo G. Percástegui; Jesús Mosquera, Jonathan R. Nitschke
      Pages: 9136 - 9140
      Abstract: Control over the solubility properties of container molecules is a central challenge in host–guest chemistry. Herein we present a simple anion-exchange protocol that allows the dissolution in water of various hydrophobic metal–organic container molecules prepared by iron(II)-templated subcomponent self-assembly. Our process involved the exchange of less hydrophilic trifluoromethanesulfonate anions for hydrophilic sulfate; the resulting water-soluble cages could be rendered water-insoluble through reverse anion exchange. Notably, this strategy allowed cargoes within capsules, including polycyclic aromatic compounds and complex organic drugs, to be brought into water. Hydrophobic effects appeared to enhance binding, as many of these cargoes were not bound in non-aqueous media. Studies of the scope of this method revealed that cages containing tetratopic and tritopic ligands were more stable in water, whereas cages with ditopic ligands disassembled.Let's jump in the water: Anion exchange enabled a variety of large and hydrophobic self-assembled capsules to be dissolved in water, where they encapsulated a wide range of guests that may not be bound in acetonitrile. The resulting water-soluble cages could be rendered water-insoluble through reverse anion exchange (see scheme).
      PubDate: 2017-06-27T06:34:20.889688-05:
      DOI: 10.1002/anie.201705093
       
  • An Intrinsically Stretchable and Compressible Supercapacitor Containing a
           Polyacrylamide Hydrogel Electrolyte
    • Authors: Yan Huang; Ming Zhong, Fukuan Shi, Xiaoying Liu, Zijie Tang, Yukun Wang, Yang Huang, Haoqing Hou, Xuming Xie, Chunyi Zhi
      Pages: 9141 - 9145
      Abstract: Stretchability and compressibility of supercapacitors is an essential element of modern electronics, such as flexible, wearable devices. Widely used polyvinyl alcohol-based electrolytes are neither very stretchable nor compressible, which fundamentally limits the realization of supercapacitors with high stretchability and compressibility. A new electrolyte that is intrinsically super-stretchable and compressible is presented. Vinyl hybrid silica nanoparticle cross-linkers were introduced into polyacrylamide hydrogel backbones to promote dynamic cross-linking of the polymer networks. These cross-linkers serve as stress buffers to dissipate energy when strain is applied, providing a solution to the intrinsically low stretchability and compressibility shortcomings of conventional supercapacitors. The newly developed supercapacitor and electrolyte can be stretched up to an unprecedented 1000 % strain with enhanced performance, and compressed to 50 % strain with good retention of the initial performance.S-T-R-E-T-C-H: An easily fabricated polyacrylamide hydrogel electrolyte incorporated into a supercapacitor instills the device with intrinsic and unprecedented super-stretchability (1000 % strain with enhanced performance) and high compressibility (50 % strain with retained capacitance).
      PubDate: 2017-06-29T07:55:28.058425-05:
      DOI: 10.1002/anie.201705212
       
  • An Interconnected Ternary MIn2S4 (M=Fe, Co, Ni) Thiospinel Nanosheet
           Array: A Type of Efficient Platinum-Free Counter Electrode for
           Dye-Sensitized Solar Cells
    • Authors: Wenjing Hou; Yaoming Xiao, Gaoyi Han
      Pages: 9146 - 9150
      Abstract: The ternary iron-group thiospinels of metal diindium sulfides (MIn2S4, M=Fe, Co, Ni) with a vertically aligned nanosheet array structure are fabricated through an in situ solvothermal method on F-doped tin oxide (FTO) substrates, which are employed as one type of platinum (Pt)-free counter electrodes (CEs) in structure-dependent dye-sensitized solar cells (DSSCs). A DSSC assembled with ternary CoIn2S4 CE achieves an photoelectric conversion efficiency (PCE) of 8.83 %, outperforming than that of FeIn2S4 (7.18 %) and NiIn2S4 (8.27 %) CEs under full sunlight illumination (100 mW cm−2, AM 1.5 G), which is also comparable with that of the Pt CE (8.19 %). Putting aside that the interconnected nanosheet array provides fast electron transfer and electrolyte diffusion channels, the highest PCE of CoIn2S4 based DSSC results from its largest specific surface area (144.07 m2 g−1), providing abundant active sites and the largest electron injection efficiency from CE to electrolyte.Ternary sulfides (MIn2S4, M=Fe, Co, Ni) with a vertically aligned nanosheet array structure are fabricated on F-doped tin oxide (FTO) substrates by a simple in situ solvothermal method. Abundant active sites and fast electron-transfer channels for I3− reduction are present in the structure.
      PubDate: 2017-07-04T04:50:56.821974-05:
      DOI: 10.1002/anie.201705399
       
  • The Existence of an Isolated Hydronium Ion in the Interior of Proteins
    • Authors: Takuya Ikeda; Keisuke Saito, Ryo Hasegawa, Hiroshi Ishikita
      Pages: 9151 - 9154
      Abstract: Neutron diffraction analysis studies reported an isolated hydronium ion (H3O+) in the interior of d-xylose isomerase (XI) and phycocyanobilin-ferredoxin oxidoreductase (PcyA). H3O+ forms hydrogen bonds (H-bonds) with two histidine side-chains and a backbone carbonyl group in PcyA, whereas H3O+ forms H-bonds with three acidic residues in XI. Using a quantum mechanical/molecular mechanical (QM/MM) approach, we analyzed stabilization of H3O+ by the protein environment. QM/MM calculations indicated that H3O+ was unstable in the PcyA crystal structure, releasing a proton to an H-bond partner His88, producing H2O and protonated His88. On the other hand, H3O+ was stable in the XI crystal structure. H-bond partners of isolated H3O+ would be practically limited to acidic residues such as aspartic and glutamic acids in the protein environment.Hydronium alone: H3O+ is often proposed to play a role in enzymatic reactions. To understand how the protein environment can stabilize an isolated H3O+, the potential energy profiles of H-bonds in the proposed H3O+ binding moieties were analyzed by adopting a QM/MM approach based on the neutron diffraction structures of phycocyanobilin-ferredoxin oxidoreductase (PcyA) and d-xylose isomerase (XI).
      PubDate: 2017-06-30T03:50:25.978481-05:
      DOI: 10.1002/anie.201705512
       
  • Dendronized Semiconducting Polymer as Photothermal Nanocarrier for Remote
           Activation of Gene Expression
    • Authors: Yan Lyu; Dong Cui, He Sun, Yansong Miao, Hongwei Duan, Kanyi Pu
      Pages: 9155 - 9159
      Abstract: Regulation of transgene systems is needed to develop innovative medicines. However, noninvasive remote control of gene expression has been rarely developed and remains challenging. We herein synthesize a near-infrared (NIR) absorbing dendronized semiconducting polymer (DSP) and utilize it as a photothermal nanocarrier not only to efficiently deliver genes but also to spatiotemporally control gene expression in conjunction with heat-inducible promoter. DSP has a high photothermal conversion efficiency (44.2 %) at 808 nm, permitting fast transduction of NIR light into thermal signals for intracellular activation of transcription. Such a DSP-mediated remote activation can rapidly and safely result in 25- and 4.5-fold increases in the expression levels of proteins in living cells and mice, respectively. This study thus provides a promising approach to optically regulate transgene systems for on-demand therapeutic transgene dosing.Gene genie: A near-infrared (NIR) absorbing dendronized semiconducting polymer (DSP) is synthesized and utilized as a photothermal nanocarrier not only to efficiently deliver genes but also to photothermally control gene expression at designated location and time.
      PubDate: 2017-07-03T07:16:50.510266-05:
      DOI: 10.1002/anie.201705543
       
  • Bright, Multi-responsive, Sky-Blue Platinum(II) Phosphors Based on a
           Tetradentate Chelating Framework
    • Authors: Lijie Liu; Xiang Wang, Nan Wang, Tai Peng, Suning Wang
      Pages: 9160 - 9164
      Abstract: A new class of highly efficient and stable, blue-phosphorescent PtII complexes based on a tetradentate chelating framework has been found to exhibit highly sensitive and reversible responses to multiple external stimuli including temperature, pressure, and UV irradiation with distinct phosphorescent color switching—from blue to red or white. Intermolecular excimer formation is the main origin of this intriguing multi-response phenomenon. Highly efficient singlet-oxygen sensitization by the PtII compounds yields UV-light-induced phosphorescence enhancement and color switching.Platinum gets the blues: Structural rigidification of PtII complexes has been found to be highly effective in achieving highly efficient and stable, dual emissive phosphorescent species that switch color and intensity in response to temperature, pressure, and UV light/oxygen.
      PubDate: 2017-06-27T06:34:31.657154-05:
      DOI: 10.1002/anie.201705785
       
  • Natural Abundance 17O DNP NMR Provides Precise O−H Distances and
           Insights into the Brønsted Acidity of Heterogeneous Catalysts
    • Authors: Frédéric A. Perras; Zhuoran Wang, Pranjali Naik, Igor I. Slowing, Marek Pruski
      Pages: 9165 - 9169
      Abstract: Heterogeneous Brønsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Brønsted acid sites can be directly observed at natural abundance by 17O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O−H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material. Experiments performed on materials impregnated with pyridine also allow for the direct detection of intermolecular hydrogen bonding interactions through the lengthening of O−H bonds.The lonely reporter: Dynamic nuclear polarization surface-enhanced oxygen-17 NMR spectroscopy is applied to enable natural-abundance 17O–1H distance measurements in silica and silica–alumina materials with a sub-picometer precision. The highly precise measurement of O−H bond lengths was used to probe the Brønsted acidity of oxide surfaces as well as detect the formation of intermolecular hydrogen bonding interactions.
      PubDate: 2017-06-06T08:25:21.10959-05:0
      DOI: 10.1002/anie.201704032
       
  • A Strategy for Creating Organisms Dependent on Noncanonical Amino Acids
    • Authors: Weimin Xuan; Peter G. Schultz
      Pages: 9170 - 9173
      Abstract: The use of noncanonical amino acids (ncAAs) to control the viability of an organism provides a strategy for the development of conditional “kill switches” for live vaccines or engineered human cells. We report an approach inspired by the posttranslational acetylation/deacetylation of lysine residues, in which a protein encoded by a gene with an in-frame nonsense codon at an essential lysine can be expressed in its native state only upon genetic incorporation of N-ϵ-acetyl-l-Lys (AcK), and subsequent enzymatic deacetylation in the host cell. We applied this strategy to two essential E. coli enzymes: the branched-chain aminotransferase BCAT and the DNA replication initiator protein DnaA. We also devised a barnase-based conditional suicide switch to further lower the escape frequency of the host cells. This strategy offers a number of attractive features for controlling host viability, including a single small-molecule-based kill switch, low escape frequency, and unaffected protein function.There's no escape: A PTM-inspired strategy for creating organisms dependent on noncanonical amino acids was developed in which a protein encoded by a gene with an in-frame nonsense codon at an essential lysine can be expressed in its native state only upon genetic incorporation of N-ϵ-acetyl-l-Lys (AcK) and subsequent enzymatic deacetylation in the host cell. A barnase-based conditional suicide switch was also devised to further lower the escape frequency.
      PubDate: 2017-06-27T06:30:39.819771-05:
      DOI: 10.1002/anie.201703553
       
  • DOSY Analysis of Micromolar Analytes: Resolving Dilute Mixtures by SABRE
           Hyperpolarization
    • Authors: Indrek Reile; Ruud L. E. G. Aspers, Jean-Max Tyburn, James G. Kempf, Martin C. Feiters, Floris P. J. T. Rutjes, Marco Tessari
      Pages: 9174 - 9177
      Abstract: DOSY is an NMR spectroscopy technique that resolves resonances according to the analytes’ diffusion coefficients. It has found use in correlating NMR signals and estimating the number of components in mixtures. Applications of DOSY in dilute mixtures are, however, held back by excessively long measurement times. We demonstrate herein, how the enhanced NMR sensitivity provided by SABRE hyperpolarization allows DOSY analysis of low-micromolar mixtures, thus reducing the concentration requirements by at least 100-fold.How low can DOSY go' DOSY analysis of a low-micromolar mixture is achieved by combining DOSY with nuclear spin hyperpolarization. SABRE hyperpolarization enhances NMR signals by two orders of magnitude, resolving six dilute analytes in a 35 min SABRE-DOSY experiment.
      PubDate: 2017-06-28T06:40:22.335253-05:
      DOI: 10.1002/anie.201703577
       
  • Poly(oligo(ethylene glycol) vinyl acetate)s: A Versatile Class of
           Thermoresponsive and Biocompatible Polymers
    • Authors: Guillaume G. Hedir; Maria C. Arno, Marvin Langlais, Jonathan T. Husband, Rachel K. O'Reilly, Andrew P. Dove
      Pages: 9178 - 9182
      Abstract: Polymers with a thermally triggered phase transition are important in the design of materials for biological applications, where their behavior can be used to trigger release or (dis)assembly events. Despite their advantages, a system with tunable thermal response, end-group reactive sites, low toxicity, and controlled main-chain degradability has not been realized, yet this would be a significant advance. The versatile new poly(oligo(ethylene glycol) vinyl acetate)s are presented with excellent control over their molecular properties obtained through RAFT/MADIX polymerization. Furthermore, we demonstrate structure-controlled thermal transitions, conjugation to human lysozyme through the retained end-group, and moreover show that this class of polymers can uniquely be copolymerized with 2-methylene-1,3-dioxepane (MDO) to generate polymers in which the degradability and cloud point can be independently tuned to create materials that display the same cloud point but degrade differently.Smart acetates: The controlled polymerization of a family of PEGylated vinyl acetates is reported. These polymers display a thermal response that can be tuned by (co)monomer choice and enables the independent tuning of response and degradation behavior. High end-group retention also enables new opportunities in protein–polymer conjugation.
      PubDate: 2017-06-30T03:45:22.912483-05:
      DOI: 10.1002/anie.201703763
       
  • Synthesis of [5,6]-Bicyclic Heterocycles with a Ring-Junction Nitrogen
           Atom: Rhodium(III)-Catalyzed C−H Functionalization of Alkenyl Azoles
    • Authors: Kim Søholm Halskov; Howard S. Roth, Jonathan A. Ellman
      Pages: 9183 - 9187
      Abstract: The first syntheses of privileged [5,6]-bicyclic heterocycles, with ring-junction nitrogen atoms, by transition metal catalyzed C−H functionalization of C-alkenyl azoles is disclosed. Several reactions are applied to alkenyl imidazoles, pyrazoles, and triazoles to provide products with nitrogen incorporated at different sites. Alkyne and diazoketone coupling partners give azolopyridines with various substitution patterns. In addition, 1,4,2-dioxazolone coupling partners yield azolopyrimidines. Furthermore, the mechanisms for the reactions are discussed and the utility of the developed approach is demonstrated by iterative application of C−H functionalization for the rapid synthesis of a patented drug candidate.Ride that bicycle: A wide range of [5,6]-bicyclic heterocycles with a ring-junction nitrogen atom were accessed by the title reaction. Alkenyl imidazoles, pyrazoles, and triazoles as C−H activation substrates, in combination with either alkynes, diazoketones, or 1,4,2-dioxazolones as reaction partners, allow formation of this privileged class of heterocycles with rich diversity in substitution patterns and nitrogen-atom incorporation.
      PubDate: 2017-07-05T12:32:56.068774-05:
      DOI: 10.1002/anie.201703967
       
  • Synthesis and Structural Characterization of Butadienylcalcium-based Heavy
           Grignard Reagents and a Ca4[O] Inverse Crown Ether Complex
    • Authors: Baosheng Wei; Liang Liu, Wen-Xiong Zhang, Zhenfeng Xi
      Pages: 9188 - 9192
      Abstract: The structure elucidation of heavy Grignard reagents (RAeX, Ae=Ca, Sr, and Ba, X=halides) has been greatly strived after, mainly because of their inaccessibility and remarkable instability. The synthesis of a series of butadienylcalcium compounds is presented, including 1-calcio-4-lithio-1,3-butadiene, 1,4-dicalcio-1,3-butadiene, and a Ca4[O] inverse crown ether complex, via the reaction between 1,4-dilithio-1,3-butadienes and calcium iodide in THF. Single-crystal X-ray analysis of these unprecedented heavy Grignard reagents revealed unique structural characteristics and bonding modes. Preliminary reaction chemistry was investigated. This study provides a novel class of alkenyl heavy Grignard reagents and a useful synthetic strategy for otherwise unavailable reactive organometallic compounds.Ca makes it: A series of butadienylcalcium compounds were synthesized by transmetalation of 1,4-dilithio-1,3-butadienes with calcium iodide in THF. Single-crystal X-ray analysis of these heavy Grignard reagents revealed their unique structural characteristics and bonding modes. A Ca4[O] inverse crown ether complex was also discovered.
      PubDate: 2017-06-29T07:45:25.034526-05:
      DOI: 10.1002/anie.201704176
       
  • Nitrogen–Carbon Bond Formation by Reactions of a Titanium–Potassium
           Dinitrogen Complex with Carbon Dioxide, tert-Butyl Isocyanate, and
           Phenylallene
    • Authors: Yusuke Nakanishi; Yutaka Ishida, Hiroyuki Kawaguchi
      Pages: 9193 - 9197
      Abstract: Nitrogen–carbon bond-forming reactions at coordinated dinitrogen in a bifunctional titanium–potassium system are reported. A titanium atrane complex with a tris(aryloxide)methyl ligand (1) was treated with two equivalents of potassium naphthalenide under N2 atmosphere to generate a bifunctional complex (2) in which N2 binds end-on to two titanium centers and side-on to three potassium cations. Dinitrogen complex 2 reacted with carbon dioxide, tert-butyl isocyanate, and phenylallene, forming nitrogen–carbon bonds and affording diverse N-functionalized products. The reaction of 2 with CO2 followed by addition of Me3SiCl resulted in the formation of the starting complex 1 with concomitant release of silylated carboxyl hydrazines while the reaction with two equivalents of tert-butyl isocyanate proceeded by insertion into the Ti−N bonds. Treatment of 2 with phenylallene afforded vinyl-substituted hydrazido complexes.A titanium atrane complex supported by a tris(aryloxide) ligand was reduced with potassium naphthalenide under N2 atmosphere to afford a complex with N2 binding end-on to titanium and side-on to potassium. This dinitrogen complex reacted with CO2, tBuNCO, and phenylallene, forming nitrogen–carbon bonds and affording diverse N-functionalized products.
      PubDate: 2017-06-14T06:45:23.260922-05:
      DOI: 10.1002/anie.201704286
       
  • Reversible Photothermal Isomerization of Carborane-Fused Azaborole to
           Borirane: Synthesis and Reactivity of Carbene-Stabilized Carborane-Fused
           Borirane
    • Authors: Hao Wang; Jiji Zhang, Zuowei Xie
      Pages: 9198 - 9201
      Abstract: A fully reversible photothermal isomerization between carborane-fused trigonal-planar azaborole (dark-purple) and tetrahedral borirane (pale-yellow) has been observed, leading to the isolation and structural characterization of the first example of carborane-fused borirane. DFT calculations indicate that the azaborole is thermodynamically more stable than the borirane by 11.2 kcal mol−1, and the energy barrier for the thermal conversion from azaborole to borirane is 35.5 kcal mol−1. The reactivity studies show that the B−C(cage) bond in borirane can be broken in the reaction with CuCl, HCl, or elemental sulfur.Boriranes in the spotlight: A completely reversible photothermal isomerization between carborane-fused trigonal-planar azaborole (dark-purple) and borirane (pale-yellow) has been observed, leading to the isolation and structural characterization of the first example of carborane-fused borirane. It can react with CuCl, HCl, and elemental sulfur to give the C(cage)−B bond cleavage products.
      PubDate: 2017-06-26T02:08:52.881642-05:
      DOI: 10.1002/anie.201704642
       
  • Frustrated Lewis Pair Mediated 1,2-Hydrocarbation of Alkynes
    • Authors: Valerio Fasano; Liam D. Curless, James E. Radcliffe, Michael J. Ingleson
      Pages: 9202 - 9206
      Abstract: Frustrated Lewis pair (FLP) chemistry enables a rare example of alkyne 1,2-hydrocarbation with N-methylacridinium salts as the carbon Lewis acid. This 1,2-hydrocarbation process does not proceed through a concerted mechanism as in alkyne syn-hydroboration, or through an intramolecular 1,3-hydride migration as operates in the only other reported alkyne 1,2-hydrocarbation reaction. Instead, in this study, alkyne 1,2-hydrocarbation proceeds by a novel mechanism involving alkyne dehydrocarbation with a carbon Lewis acid based FLP to form the new C−C bond. Subsequently, intermolecular hydride transfer occurs, with the Lewis acid component of the FLP acting as a hydride shuttle that enables alkyne 1,2-hydrocarbation.Serving up a rare treat: A rare alkyne 1,2-hydrocarbation reaction was developed on the basis of frustrated Lewis pair (FLP) chemistry (see picture). The reaction proceeded through a novel mechanism involving FLP-mediated dehydrocarbation of the alkyne, followed by hydride transfer enabled by an intermolecular hydride shuttle, and finally protonation.
      PubDate: 2017-07-04T04:56:44.070548-05:
      DOI: 10.1002/anie.201705100
       
  • Asymmetric Yttrium-Catalyzed C(sp3)−H Addition of 2-Methyl Azaarenes
           to Cyclopropenes
    • Authors: Yong Luo; Huai-Long Teng, Masayoshi Nishiura, Zhaomin Hou
      Pages: 9207 - 9210
      Abstract: An enantioselective C−H addition to a C=C bond represents the most atom-efficient route for the construction of chiral carbon–carbon skeletons, a central research topic in organic synthesis. We herein report the enantioselective yttrium-catalyzed C(sp3)−H bond addition of 2-methyl azaarenes, such as 2-methyl pyridines, to various substituted cyclopropenes and norbornenes. This process efficiently afforded a new family of chiral pyridylmethyl-functionalized cyclopropane and norbornane derivatives in high yields and high enantioselectivities (up to 97 % ee).Enantioselective C(sp3)−H bond additions of 2-methyl azaarenes, such as 2-methylpyridines, to substituted cyclopropenes and norbornenes have been achieved by using a chiral half-sandwich yttrium catalyst. This process afforded a series of chiral pyridylmethyl-functionalized cyclopropane and norbornane derivatives in good yields, high enantioselectivity, and 100 % atom efficiency.
      PubDate: 2017-07-04T00:36:39.86693-05:0
      DOI: 10.1002/anie.201705431
       
  • Palladium-Catalyzed Asymmetric Synthesis of Silicon-Stereogenic
           5,10-Dihydrophenazasilines via Enantioselective 1,5-Palladium Migration
    • Authors: Yosuke Sato; Chihiro Takagi, Ryo Shintani, Kyoko Nozaki
      Pages: 9211 - 9216
      Abstract: A palladium-catalyzed asymmetric synthesis of silicon-stereogenic 5,10-dihydrophenazasilines was developed that proceeds via an unprecedented enantioselective 1,5-palladium migration. High enantioselectivity was achieved by employing 4,4′-bis(trimethylsilyl) (R)-Binap as the chiral ligand, and a series of mechanistic investigations were carried out to probe the catalytic cycle of this process.A palladium-catalyzed asymmetric synthesis of silicon-stereogenic 5,10-dihydrophenazasilines was developed that proceeds via a highly enantioselective 1,5-palladium migration. Mechanistic investigations were carried out to probe the catalytic cycle.
      PubDate: 2017-07-04T00:37:17.733891-05:
      DOI: 10.1002/anie.201705500
       
  • Catalytic Enantioselective Aza-pinacol Rearrangement
    • Authors: Yuanyuan Yu; Jingwen Li, Long Jiang, Jing-Ren Zhang, Liansuo Zu
      Pages: 9217 - 9221
      Abstract: The first catalytic enantioselective asymmetric aza-pinacol rearrangement is reported. The reactions are catalyzed by a chiral phosphoric acid and proceed via a highly organized transition state involving a cyclic aza-ortho-xylylene intermediate to afford the indoline structures with good to excellent enantioselectivity. The synthetic utility of this method is demonstrated by the asymmetric synthesis of a key intermediate to the natural product minfiensine and the identification of a chiral lead compound to repress antibiotic resistance.I did it my way: The first catalytic enantioselective aza-pinacol rearrangement is reported. This reaction, which is catalyzed by a chiral phosphoric acid and proceeds via a highly organized transition state, was used to provide direct access to the indoline core of a variety of natural products and to identify a simplified lead compound to repress antibiotic resistance.
      PubDate: 2017-06-29T08:10:56.92327-05:0
      DOI: 10.1002/anie.201705539
       
  • Thermal Disproportionation of Oxo-Functionalized Graphene
    • Authors: Fabian Grote; Christoph Gruber, Felix Börrnert, Ute Kaiser, Siegfried Eigler
      Pages: 9222 - 9225
      Abstract: Graphene production by wet chemistry is an ongoing scientific challenge. Controlled oxidation of graphite introduces oxo functional groups; this material can be processed and converted back to graphene by reductive defunctionalization. Although thermal processing yields conductive carbon, a ruptured and undefined carbon lattice is produced as a consequence of CO2 formation. This thermal process is not understood, but it is believed that graphene is not accessible. Here, we thermally process oxo-functionalized graphene (oxo-G) with a low (4–6 %) and high degree of functionalization (50–60 %) and find on the basis of Raman spectroscopy and transmission electron microscopy performed at atomic resolution (HRTEM) that thermal processing leads predominantly to an intact carbon framework with a density of lattice defects as low as 0.8 %. We attribute this finding to reorganization effects of oxo groups. This finding holds out the prospect of thermal graphene formation from oxo-G derivatives.Losing O's: Graphene can be prepared by heating oxo-functionalized graphene. Defunctionalization resulting in graphene formation (path I) is the dominant process.
      PubDate: 2017-06-30T06:07:05.479282-05:
      DOI: 10.1002/anie.201704419
       
  • Ring-Opening 1-Amino-3-aminomethylation of Donor–Acceptor
           Cyclopropanes via 1,3-Diazepanes
    • Authors: Lennart K. B. Garve; Peter G. Jones, Daniel B. Werz
      Pages: 9226 - 9230
      Abstract: The first ring-opening reaction of donor–acceptor cyclopropanes to give diamines is reported. For this reaction, a 1,3-bisfunctionalization was developed using cyclopropanes, triazinanes, and Sc(OTf)3 as the catalyst, followed by treatment with acid. The reaction proceeds under very mild conditions and tolerates many functional groups. Moreover, a library of various 1,3-diazepanes, which arise as intermediates of the first formal aza-[4+3]-cycloaddition reaction with donor–acceptor cyclopropanes, was synthesized.Double Amination: Donor–acceptor cyclopropanes can be selectively opened with triazinanes to give diamines under scandium catalysis and mild acidic conditions. Moreover, a library of various 1,3-diazepanes, which arise as intermediates of these formal aza-[4+3]-cycloaddition reactions, was synthesized.
      PubDate: 2017-06-28T06:13:00.201898-05:
      DOI: 10.1002/anie.201704619
       
  • 1,4-Diphosphinines from Imidazole-2-thiones
    • Authors: Abhishek Koner; Gregor Pfeifer, Zsolt Kelemen, Gregor Schnakenburg, László Nyulászi, Takahiro Sasamori, Rainer Streubel
      Pages: 9231 - 9235
      Abstract: 1,4-Diphosphinines that are fused to two thiourea units were synthesized from the corresponding tricyclic 1,4-dichloro-1,4-dihydro-1,4-diphosphinines, and their structures and spectroscopic features are described. Electrochemical studies revealed very low oxidation potentials, which are due to the effective π-interaction between the 1,4-diphosphinine ring and the orbitals of the two ylidic C=S bonds. In accordance with the low-lying LUMO, which is largely localized at the two phosphorus centers, dianion formation is strongly preferred. Despite the small HOMO–LUMO gap, which is in accordance with the red color of the title compounds, theoretical calculations suggest considerable aromaticity for the 1,4-diphosphinine ring.Tricyclic 1,4-diphosphinines (II), with two fused thiourea units, have been synthesized from the corresponding 1,4-dichloro-1,4-dihydro-1,4-diphosphinines (I). Their structures and spectroscopic features were studied, and the electrochemical properties suggest that their very low oxidation potentials are due to cyclic π-conjugation. The spectroscopic properties and theoretical calculations indicate considerable aromaticity.
      PubDate: 2017-06-28T06:12:32.704911-05:
      DOI: 10.1002/anie.201704070
       
  • Preparation of Solid Polyfunctional Alkynylzinc Pivalates with Enhanced
           Air and Moisture Stability for Organic Synthesis
    • Authors: Yi-Hung Chen; Carl Phillip Tüllmann, Mario Ellwart, Paul Knochel
      Pages: 9236 - 9239
      Abstract: We report the preparation of solid and air-stable polyfunctionalized alkynylzinc pivalates from the corresponding alkynes using TMPZnOPiv (TMP=2,2,6,6-tetramethylpiperidyl) as base. These organozinc pivalates are obtained as powders under mild conditions in excellent yields and can be manipulated in air for several hours without significant decomposition. These zinc reagents show an excellent reactivity in various carbon–carbon bond- forming reactions and 1,3-dipolar cycloadditions. An alkynylzinc pivalate has been used to prepare a carboxyamidotriazole with potential antineoplastic activity in eight steps and 38 % overall yield.Think positive: zinc pivalate. Functionalized solid alkynylzinc pivalates with enhanced air and moisture stability are reported to undergo Pd-catalyzed Negishi cross-couplings and Fukuyama acylations as well as Cu-catalyzed allylations and 1,3-dipolar cycloadditions to afford trisubstituted triazoles. A four-component transformation leads to a potential antineoplastic agent (eight steps and 38 % overall yield).
      PubDate: 2017-06-27T06:33:44.09553-05:0
      DOI: 10.1002/anie.201704400
       
  • Inside Back Cover: Direct Mechanism of the First Carbon–Carbon Bond
           Formation in the Methanol-to-Hydrocarbons Process (Angew. Chem. Int. Ed.
           31/2017)
    • Authors: Xinqiang Wu; Shutao Xu, Wenna Zhang, Jindou Huang, Jinzhe Li, Bowen Yu, Yingxu Wei, Zhongmin Liu
      Pages: 9241 - 9241
      Abstract: The first carbon–carbon bond formation in the methanol to hydrocarbons (MTH) reaction over zeolite catalysts has been a highly controversial issue and has puzzled scientists for 30 years. In their Communication on page 9039 ff. Z. Liu, Y. Wei et al. propose a direct mechanism for the formation of the first C−C bond in the MTH reaction, based on the detection of the crucial intermediate, a surface methyleneoxy analogue species originating from activated DME or methanol, by in situ solid-state NMR spectroscopy.
      PubDate: 2017-06-16T03:16:00.103228-05:
      DOI: 10.1002/anie.201705757
       
  • Back Cover: A Modular Approach to Inorganic Phosphazane Macrocycles
           (Angew. Chem. Int. Ed. 31/2017)
    • Authors: Alex J. Plajer; Raúl García-Rodríguez, Callum G. M. Benson, Peter D. Matthews, Andrew D. Bond, Sanjay Singh, Lutz H. Gade, Dominic S. Wright
      Pages: 9242 - 9242
      Abstract: The union of organic and macrocyclic chemistry: The formation of large inorganic macrocycles containing phosphazane units linked by sulfur or selenium becomes straightforward with the method described by D. S. Wright et al. in their Communication on page 9087 ff.This allows the introduction of a range of organic substituents, facilitating the tuning of the steric and electronic host environment, and marks a significant step towards the development of synthetic tools in macromolecular inorganic assembly that mirror those in organic synthesis.
      PubDate: 2017-06-20T07:44:14.464133-05:
      DOI: 10.1002/anie.201705956
       
 
 
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