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  Subjects -> CHEMISTRY (Total: 852 journals)
    - ANALYTICAL CHEMISTRY (52 journals)
    - CHEMISTRY (598 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (46 journals)
    - PHYSICAL CHEMISTRY (69 journals)

CHEMISTRY (598 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 10)
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: 38)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 24)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 251)
ACS Photonics     Full-text available via subscription   (Followers: 12)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 23)
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 Chimica Slovenica     Open Access  
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: 8)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 51)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 57)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 15)
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: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 21)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
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)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
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: 66)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 15)
American Journal of Chemistry     Open Access   (Followers: 27)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 39)
Angewandte Chemie     Hybrid Journal   (Followers: 177)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 229)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 16)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 22)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 325)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 122)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 84)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 68)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 15)
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: 25)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 21)
Chemical Reviews     Full-text available via subscription   (Followers: 183)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 24)
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: 146)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 20)
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: 42)
Chemistry of Materials     Full-text available via subscription   (Followers: 246)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 10)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 6)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 19)
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: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 18)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 64)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
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: 3)
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  

        1 2 3 | Last

Journal Cover Angewandte Chemie International Edition
  [SJR: 6.229]   [H-I: 397]   [229 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  [1589 journals]
  • An Efficient Method for the Conjugation of Hydrophilic and Hydrophobic
           Components by Solid-Phase-Assisted Disulfide Ligation
    • Authors: Kyohei Muguruma; Takuya Shirasaka, Daichi Akiyama, Kentarou Fukumoto, Akihiro Taguchi, Kentaro Takayama, Atsuhiko Taniguchi, Yoshio Hayashi
      Abstract: Chemical conjugation between hydrophilic and hydrophobic components is difficult because of their extremely different solubility. Herein, we report a new versatile method with a solid-phase-assisted disulfide ligation to overcome the difficulty of conjugation attributed to solubility. The method involves two steps in a one-pot process: 1) loading of a hydrophobic molecule onto a resin in an organic solvent, and 2) release of the solid-supported hydrophobic molecule as a conjugate with a hydrophilic molecule into an aqueous solvent. This strategy allows the use of a suitable solvent system for the substrates in each step. Conjugates of a water-insoluble drug, plinabulin, with hydrophilic carriers that could not be prepared by solution-phase reactions were obtained in moderate yields (29–45 %). This strategy is widely applicable to the conjugation of compounds with solubility problems.Solid-phase-assisted disulfide ligation has been developed to overcome the difficulty of conjugation between hydrophilic and hydrophobic components attributed to solubility. Conjugates of a poorly water-soluble model drug, plinabulin, with various hydrophilic carriers were obtained in moderate yields.
      PubDate: 2018-01-19T04:41:23.884089-05:
      DOI: 10.1002/anie.201712324
       
  • Surface-Confined Dynamic Covalent System Driven by Olefin Metathesis
    • Authors: Chunhua Liu; Eunsol Park, Yinghua Jin, Jie Liu, Yanxia Yu, Wei Zhang, Shengbin Lei, Wenping Hu
      Abstract: Understanding how the constitutional dynamics of a dynamic combinatorial library (DCL) adapts to surfaces (compared to bulk solution) is of fundamental importance to the design of adaptive materials. Submolecular resolved scanning tunneling microscopy (STM) can provide detailed insights into olefin metathesis at the interface. Analysis of the distribution of products has revealed the important role of environmental pressure, reaction temperature, and substituent effects in surface-confined olefin metathesis. We also report an unprecedented preferred deposition and assembly of linear polymers, and some specific oligomers, on the surface that are hard to obtain otherwise.Surface-confined olefin metathesis was studied by scanning tunneling microscopy to determine the effects of substituents, reaction temperature, and pressure. Surface confinement significantly enhances the formation of linear polymers and allows selective synthesis of specific oligomers that are difficult to obtain by solution-phase synthesis. DCC=Dynamic covalent chemistry.
      PubDate: 2018-01-19T04:41:11.205773-05:
      DOI: 10.1002/anie.201711040
       
  • Cobalt(II)-based Metalloradical Activation of 2-(Diazomethyl)pyridines for
           Radical Transannulation and Cyclopropanation
    • Authors: Satyajit Roy; Sandip Kumar Das, Buddhadeb Chattopadhyay
      Abstract: A new catalytic method for the denitrogenative transannulation/cyclopropanation of in-situ-generated 2-(diazomethyl)pyridines is described using a cobalt-catalyzed radical-activation mechanism. The method takes advantage of the inherent properties of a CoIII-carbene radical intermediate and is the first report of denitrogenative transannulation/cyclopropanation by a radical-activation mechanism, which is supported by various control experiments. The synthetic benefits of the metalloradical approach are showcased with a short total synthesis of (±)-monomorine.Denitrogenative transannulation/cyclopropanation of in-situ-generated 2-(diazomethyl)pyridine is presented, which involves a cobalt-catalyzed radical-activation mechanism. A cobalt(II)-metalloradical undergoes radical addition to alkynes during denitrogenative transannulation, or to alkenes during cyclopropanation; forming indolizines and cyclopropanes, respectively
      PubDate: 2018-01-19T04:40:38.968371-05:
      DOI: 10.1002/anie.201711209
       
  • Palladium/Copper Dual Catalysis for the Cross-Coupling of
           Aryl(trialkyl)silanes with Aryl Bromides
    • Authors: Takeshi Komiyama; Yasunori Minami, Yuki Furuya, Tamejiro Hiyama
      Abstract: Whereas aryl(trialkyl)silanes are considered to be ideal organometallic reagents for cross-coupling reactions owing to their stability, low toxicity, solubility, and easy accessibility, they are generally inert under typical cross-coupling conditions. Disclosed herein is a palladium/copper catalytic system that enables the cross-coupling of trimethyl, triethyl, tert-butyldimethyl, and triisopropyl aryl silanes with aryl bromides. This process is applicable to the sequential C−H and C−Si bond arylation of thiophenes and the synthesis of poly(thiophene–fluorene)s.The practical cross-coupling of aryl(trialkyl)silanes with aryl bromides to give biaryls and teraryls is enabled by palladium/copper catalysis. A wide variety of silyl and aryl groups are compatible with these reaction conditions. This process can be used for cross-coupling polymerization as well as sequential C−H arylation/cross-coupling.
      PubDate: 2018-01-19T04:40:28.552824-05:
      DOI: 10.1002/anie.201712081
       
  • A diazido mannose analog as a chemoenzymatic synthon for synthesizing
           di-N-acetyllegionaminic acid-containing glycosides
    • Authors: Abhishek Santra; An Xiao, Hai Yu, Wanqing Li, Yanhong Li, Linh Ngo, John B. McArthur, Xi Chen
      Abstract: A novel strategy is developed to expand the scope of chemoenzymatic synthetic products by designing a chemoenzymatic synthon. The synthon is enzymatically converted to carbohydrate analogs which are readily derivatized chemically to produce desired targets. The strategy is demonstrated for synthesizing glycosides containing 7,9-di-N-acetyllegionaminic acid (Leg5,7Ac2), a bacterial nonulosonic acid (NulO) analog of sialic acid. A versatile library of a2-3/6-linked Leg5,7Ac2- glycosides is built using chemically synthesized 2,4-diazido-2,4,6-trideoxy mannose as a chemoenzymatic synthon for highly efficient one-pot multienzyme (OPME) sialylation followed by a downstream chemical conversion of the azido group to an acetamido group. The overall yields of the syntheses are 34-52% in 10 steps from commercially available D-fucose, representing significant improvements over previous methods. Free Leg5,7Ac2 monosaccharide is also synthesized using a sialic acid aldolase-catalyzed reaction.
      PubDate: 2018-01-19T00:30:52.5659-05:00
      DOI: 10.1002/anie.201712022
       
  • Tuning High-Temperature Wetting Behavior of Metal toward Ultrafine
           Nanoparticles
    • Authors: Yubing Zhou; Bharath Natarajan, Yanchen Fan, Hua Xie, Chunpeng Yang, Shaomao Xu, Yonggang Yao, Feng Jiang, Qianfan Zhang, Jeffrey W. Gilman, Liangbing Hu
      Abstract: The interaction between the metal nanoparticles and their substrate plays a critical role in determining the particle morphology, distribution, and properties. Here we present the pronounced impact of a thin oxide coating to the dispersion of metal nanoparticles on a carbon matrix. We employ Al2O3-supported Pt nanoparticles in comparison with direct synthesis of Pt nanoparticles on bare carbon surfaces. Pt nanoparticles with an average size of ≈2 nm and a size distribution ranging between 0.5 nm and 4.0 nm are synthesized on the Al2O3 coated carbon nanofiber, significantly improved compared to those directly synthesized on bare carbon surface. First principles modeling verifies the stronger adsorption of Pt clusters on Al2O3 than on carbon, which attributes the formation of ultrafine Pt nanoparticles. Our strategy paves the way towards the rational design of nanoparticles with enhanced dispersion and controlled particle size, which are promising in energy storage and electrocatalysis.
      PubDate: 2018-01-18T15:25:30.026995-05:
      DOI: 10.1002/anie.201712202
       
  • Targeting a dark excited state of HIV-1 nucleocapsid by anti-retroviral
           thioesters revealed by NMR
    • Authors: Lalit Deshmukh; Vitali Tugarinov, Daniel H. Appella, G. Marius Clore
      Abstract: HIV-1 nucleocapsid (NCp7) is a two Cys2HisCys zinc knuckle (N-Zn and C-Zn) protein that plays a key role in viral replication. Here we characterize NCp7 conformational dynamics by NMR relaxation dispersion and chemical exchange saturation transfer measurements. While the N-Zn knuckle is conformationally stable, the C-Zn knuckle interconverts on the millisecond time scale between the major state, in which the zinc is coordinated by three cysteines and a histidine, and two folded minor species (with populations around 1%) in which one of the coordination bonds (Cys413-S---Zn or His421-N2---Zn) is hydrolysed. These findings explain why anti-retroviral thioesters specifically disrupt the C-Zn knuckle by initial acylation of Cys413, and show that transient, sparsely-populated ('dark'), excited states of proteins can present effective targets for rational drug design.
      PubDate: 2018-01-18T11:55:21.443696-05:
      DOI: 10.1002/anie.201713172
       
  • Elucidation of the Oxygen Reduction Volcano in Alkaline Media using a
           Copper-Platinum(111) Alloy
    • Authors: Kim Degn Jensen; Jakub Tymoczko, Jan Rossmeisl, Aliaksandr Bandarenka, Ib Chorkendorff, Maria Escudero-Escribano, Ifan Erfyl Lester Stephens
      Abstract: Herein we experimentally explore the relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, we tune the surface reactivity. We demonstrate that in both NaOH and KOH, the optimal catalyst should exhibit OH binding ~0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports. In 0.1 M KOH, the alloy catalyst at the peak of the volcano exhibits a maximum activity of 101±8 mA/cm2 at 0.9 V vs. a reversible hydrogen electrode (RHE). This activity constitutes a ~60-fold increase over Pt(111) in 0.1 M HClO4.
      PubDate: 2018-01-18T10:55:34.749082-05:
      DOI: 10.1002/anie.201711858
       
  • Oxidative mechanochemistry for direct, room-temperature, solvent-free
           conversion of palladium and gold metals into soluble salts and
           coordination complexes
    • Authors: Jean-Louis Do; Davin Tan, Tomislav Friscic
      Abstract: Noble metals are valued critical elements whose chemical activation or recycling is challenging, traditionally requiring high temperatures, strong acids or bases, or aggressive complexation agents. Using elementary palladium and gold, we demonstrate mechanochemistry for noble metal activation and recycling via mild, clean, solvent-free and room-temperature chemistry, leading to direct, efficient, one-pot conversion of the metals, including spent catalysts, to simple water-soluble salts, or to metal-organic catalysts.
      PubDate: 2018-01-18T09:55:24.72975-05:0
      DOI: 10.1002/anie.201712602
       
  • Stable and Highly Efficient Electrochemical Production of Formic Acid from
           Carbon Dioxide Using Diamond Electrodes
    • Authors: Keisuke Natsui; Hitomi Iwakawa, Norihito Ikemiya, Kazuya Nakata, Yasuaki Einaga
      Abstract: High faradaic efficiencies can be achieved in the production of formic acid (HCOOH) by metal electrodes, such as Sn or Pb, in the electrochemical reduction of carbon dioxide (CO2). However, the stability and environmental load in using them are problematic. Here, we investigated the electrochemical reduction of CO2 to HCOOH in a flow cell using boron-doped diamond (BDD) electrodes. BDD electrodes have superior electrochemical properties to metal electrodes, and, moreover, are highly durable. The faradaic efficiency for the production of HCOOH was as high as 94.7%. Furthermore, the selectivity for the production of HCOOH was more than 99%. The rate of the production was increased to 473 μmol m−2 s−1 at a current density of 15 mA cm−2 with a faradaic efficiency of 61%. The faradaic efficiency and the production rate are almost the same as or larger than those achieved using Sn and Pb electrodes. In addition, the stability of the BDD electrodes was confirmed by 24 hours operation.
      PubDate: 2018-01-18T09:25:28.085435-05:
      DOI: 10.1002/anie.201712271
       
  • MoP Nanoparticles Supported on In-doped Porous Carbon: Outstanding
           Catalysts for High-efficient CO2 Electroreduction
    • Authors: Xiaofu Sun; Lu Lu, qinggong Zhu, Congyi Wu, Dexin Yang, Chunjun Chen, Buxing Han
      Abstract: Electrochemical reduction of CO2 into value-added product is an interesting area. In this work, we synthesized MoP nanoparticles supported on porous carbon using metal-organic frameworks as the carbon precusor, and conducted the first work on CO2 electroreduction using MoP-based catalyst. It was discovered that MoP nanoparticles supported on In-doped porous carbon had outstanding performance for CO2 reduction to formic acid. The Faradaic efficiency and current density could reach 96.5 % and 43.8 mAcm-2, respectively, when using ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as the supporting electrolyte. The current density is higher than those reported up to date with very high Faradaic efficiency. The MoP nanoparticles and the doped In2O3 cooperated very well in catalyzing the CO2 electroreduction.
      PubDate: 2018-01-18T09:00:28.86406-05:0
      DOI: 10.1002/anie.201712221
       
  • Protection Group Effects During α,γ-Diol Lignin Stabilization Promote
           High-Selectivity Monomer Production
    • Authors: Wu Lan; Masoud Talebi Amiri, Christopher M. Hunston, Jeremy S. Luterbacher
      Abstract: Bountiful pickings. Selective hydrogenolysis of isolated lignin is achieved using tuned protection groups during mild acid-catalyzed lignin extraction, and an appropriate hydrogenolysis catalyst. In their Communication (
      DOI : 10.1002/anie.201710838), J. S. Luterbacher et al. report near-theoretical yields of monomers and, with wild-type hardwood, recovery of as few as two major products. A single major product is produced using high-syringyl transgenic hardwood as the source of lignin.
      PubDate: 2018-01-18T07:57:41.40581-05:0
       
  • Controlling the Polymer Microstructure in Anionic Polymerization by
           Compartmentalization
    • Authors: Elisabeth Rieger; Jan Blankenburg, Eduard Grune, Manfred Wagner, Katharina Landfester, Frederik R. Wurm
      Abstract: An ideal random anionic copolymerization is forced to produce gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO-in-cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real-time 1H NMR kinetics, proving a change of the reactivity ratios of the two monomers upon dilution of the continuous phase from ideal random to adjustable gradients by simple dilution.The selective solubility of two monomers in a DMSO/cyclohexane emulsion forces the production of controllable gradient copolymers.
      PubDate: 2018-01-18T07:57:38.854628-05:
      DOI: 10.1002/anie.201710417
       
  • Peripheral Templation-Modulated Interconversion between an A4L6
           Tetrahedral Anion Cage and A2L3 Triple Helicate with Guest Capture/Release
           
    • Authors: Xuemin Bai; Chuandong Jia, Yanxia Zhao, Dong Yang, Shi-Cheng Wang, Anyang Li, Yi-Tsu Chan, Yao-Yu Wang, Xiao-Juan Yang, Biao Wu
      Abstract: Peripheral templation was used to stabilize an unusual A4L6 tetrahedral cage (A=anion, L=ligand) as reported by C. Jia, B. Wu et al. in their Communication (
      DOI : 10.1002/anie.201712080). The A4L6 cage can be transformed into an A2L3 helicate in response to different stimuli (change template, concentration, or solvent), with accompanying guest capture and release. This process is illustrated in the picture by the famous Monkey King who has the power to change the shape and size of objects by blowing magic gas. Credits: Cartoon of the Monkey King from http://588ku.com/image/n-13858873.html.
      PubDate: 2018-01-18T07:57:31.691464-05:
       
  • Photoinduced Pedalo-Type Motion in an Azodicarboxamide-Based Molecular
           Switch
    • Authors: Saeed Amirjalayer; Alberto Martinez-Cuezva, Jose Berna, Sander Woutersen, Wybren Jan Buma
      Abstract: A new class of light-controlled molecular switches based on an azodicarboxamide chromophore is described by S. Amirjalayer, S. Woutersen, W. J. Buma et al. in their Communication (
      DOI : 10.1002/anie.201709666). These switches work like the crankshaft of a bicycle and, as switching requires a very small volume, will function even in rock-solid spatial constraints. The pedalo-like switching is observed in real time by using time-resolved vibrational spectroscopy to monitor the light-induced dynamics.
      PubDate: 2018-01-18T07:57:29.428059-05:
       
  • Reductive Amination by Photoredox Catalysis by Polarity-Matched Hydrogen
           Atom Transfer
    • Authors: Xingwei Guo; Oliver S. Wenger
      Abstract: The excitation of a RuII photosensitizer in the presence of ascorbic acid leads to the reduction of iminium ions to electron-rich α-aminoalkyl radical intermediates, which are rapidly converted into reductive amination products by thiol-mediated hydrogen atom transfer (HAT). As a result, the reductive amination of carbonyl compounds with amines by photoredox catalysis proceeds in good to excellent yields and with broad substrate scope and good functional group tolerance. The three key features of this work are 1) the rapid interception of electron-rich α-aminoalkyl radical intermediates by polarity-matched HAT in a photoredox reaction, 2) the method of reductive amination by photoredox catalysis itself, and 3) the application of this new method for temporally and spatially controlled reactions on a solid support, as demonstrated by the attachment of a fluorescent dye on an activated cellulose support by photoredox-catalyzed reductive amination.Light instead of hydride: A photoredox process for reductive amination is reported, alongside substrate scope studies and in-depth mechanistic investigations. With this new method, reductive amination reactions can be conducted in a temporally and spatially controlled fashion, for example, on solid supports.
      PubDate: 2018-01-18T07:57:26.771075-05:
      DOI: 10.1002/anie.201711467
       
  • Ion Specificity on Electric Energy Generated by Flowing Water Droplets
    • Authors: Junwoo Park; Suhwan Song, ChaeHo Shin, YoungJun Yang, Stefan A. L. Weber, Eunji Sim, Youn Sang Kim
      Abstract: The development of energy-conversion devices using water movement has actively progressed. Ionovoltaic devices, which are driven by ion dynamics, show ion specificity by which different ions with identical charges show different output performance. However, the ion specificity remains poorly understood because the influence of the ion species on generated electric signals is not elucidated. The ion specificity in electric signals induced by flowing water droplet was investigated in terms of its relationship with the potential profile across the solid–liquid interface.Origin of ion specificity: The ionovoltaic device driven by droplet flow showed ion specificity by which different ions with identical charges shows different output performance. The origin of ion specificity at solid–liquid interface is investigated.
      PubDate: 2018-01-18T07:57:19.311926-05:
      DOI: 10.1002/anie.201711505
       
  • Reversible Phase Transition of Robust Luminescent Hybrid Hydrogels
    • Authors: Zhiqiang Li; Guannan Wang, Yige Wang, Huanrong Li
      Abstract: We report herein on remote control over a reversible phase transition of robust luminescent hybrid hydrogels as enabled by the rational selection and incorporation of photoswitches. Azobenzene units functionalized with a guanidinium group were utilized as the photoswitches and incorporated through a host–guest inclusion method involving α-cyclodextrins functionalized with 2,6-pyridinedicarboxylic acid (PDA) groups. While the guanidinium functional groups bind to the negatively charged Laponite matrix surface to connect organic and inorganic components, the PDA groups enable simultaneous coordination with different lanthanide metal ions, thus rendering the hydrogel broadly luminescent. Owing to its conformation-dependent binding behavior with α-cyclodextrin, the isomerization of azobenzene induced association or dissociation of the inclusion complexes and thus lead to a reversible photocontrolled solgel phase transition of the luminescent hybrid hydrogels.Remote control over a reversible solgel phase transition of a robust luminescent hybrid hydrogel (see picture) was enabled by the incorporation of photoswitchable host–guest inclusion compounds into the hydrogel system. Guanidinium groups on the azobenzene guest units bind to a Laponite matrix, and pyridinedicarboxylic acid groups on the α-cyclodextrin host units coordinate to lanthanide ions, thus rendering the hydrogel broadly luminescent.
      PubDate: 2018-01-18T07:57:14.91489-05:0
      DOI: 10.1002/anie.201712670
       
  • Catalytic Asymmetric Synthesis of Trifluoromethylated γ-Amino Acids
           through the Umpolung Addition of Trifluoromethyl Imines to Carboxylic Acid
           Derivatives
    • Authors: Bin Hu; Li Deng
      Abstract: Novel cinchona alkaloid derived chiral phase-transfer catalysts enabled the highly chemo-, regio-, diastereo-, and enantioselective umpolung addition of trifluoromethyl imines to α,β-unsaturated N-acyl pyrroles. With a catalyst loading ranging from 0.2 to 5.0 mol %, this new catalytic asymmetric transformation provides facile and high-yielding access to highly enantiomerically enriched chiral trifluoromethylated γ-amino acids and γ-lactams.Can't teach an old dog' Try a new cat: Novel cinchona alkaloid derived phase-transfer catalysts enabled the highly chemo-, regio-, diastereo-, and enantioselective umpolung addition of trifluoromethyl imines to α,β-unsaturated N-acyl pyrroles (see scheme; PYR=6-chloro-2,5-diphenyl-4-pyrimidinyl). This transformation provides facile and high-yielding access to highly enantiomerically enriched trifluoromethylated γ-amino acids and γ-lactams.
      PubDate: 2018-01-18T07:57:03.629256-05:
      DOI: 10.1002/anie.201710915
       
  • Tandem Molecular Self-Assembly in Liver Cancer Cells
    • Authors: Jie Zhan; Yanbin Cai, Shuangshuang He, Ling Wang, Zhimou Yang
      Abstract: We herein describe the tandem molecular self-assembly of a peptide derivative (1) that is controlled by a combination of enzymatic and chemical reactions. In phosphate-buffered saline (PBS), compound 1 self-assembles first into nanoparticles by phosphatase and then into nanofibers by glutathione. Liver cancer cells exhibit higher concentrations of both phosphatase and GSH than normal cells. Therefore, the tandem self-assembly of 1 also occurs in the liver cancer cell lines HepG2 and QGY7703; compound 1 first forms nanoparticles around the cells and then forms nanofibers inside the cells. Owing to this self-assembly mechanism, compound 1 exhibits large ratios for cellular uptake and inhibition of cell viability between liver cancer cells and normal liver cells. We envision that using both extracellular and intracellular reactions to trigger tandem molecular self-assembly could lead to the development of supramolecular nanomaterials with improved performance in cancer diagnostics and therapy.Nanoparticles and nanofibers: Compound 1 self-assembles first into nanoparticles by phosphatase and then into nanofibers by glutathione, which works well in buffer solution and in liver cancer cells owing to the higher concentrations of both phosphatase and GSH in liver cancer cells. The cellular uptake and cell viability of this compound differ significantly between liver cancer cells and normal cells.
      PubDate: 2018-01-18T02:55:35.528432-05:
      DOI: 10.1002/anie.201710237
       
  • Norbert W. Mitzel
    • PubDate: 2018-01-18T02:45:48.747814-05:
      DOI: 10.1002/anie.201712874
       
  • Presence versus Proximity: The Role of Pendant Amines in the Catalytic
           Hydrolysis of a Nerve Agent Simulant
    • Authors: Timur Islamoglu; Manuel A. Ortuño, Emmanuel Proussaloglou, Ashlee J. Howarth, Nicolaas A. Vermeulen, Ahmet Atilgan, Abdullah M. Asiri, Christopher J. Cramer, Omar K. Farha
      Abstract: Amino-functionalized zirconium-based metal-organic frameworks (MOFs) have shown unprecedented catalytic activity compared to non-functionalized analogues for hydrolysis of organophosphonate-based toxic chemicals. Importantly, the effect of the amino group on the catalytic activity is significantly higher in the case of UiO-66-NH2, where the amino groups reside near the node, compared to UiO-67-m-NH2, where they are directed away from the node. Herein, we show that the proximity of the amino group is crucial for fast catalytic activity towards hydrolysis of organophosphonate-based nerve agents. The generality of the observed amine-proximity-dictated catalytic activity has been tested on two different MOF systems which have different topology. DFT calculations reveal that amino groups on all the MOFs studied are not acting as Brønsted bases; instead they control the microsolvation environment at the Zr6-node active site and therefore increase the overall catalytic rates.Proximity De-pendant: The role of amino groups on the hydrolysis of a nerve agent simulant, DMNP, has been explored. Experiments and theoretical calculations reveal that not only the presence but also the proximity of the amino group is important for effective chemical detoxification of DMNP. NU-1002-o-NH2, a Zr-based mesoporous metal–organic framework (MOF) with pendant amines demonstratest1/2 of 1.2 min with only 3 mol % catalyst loading.
      PubDate: 2018-01-18T02:40:58.448351-05:
      DOI: 10.1002/anie.201712645
       
  • Mechanofluorochromic Carbon Nanodots: Controllable Pressure-Triggered
           Blue- and Red-Shifted Photoluminescence
    • Authors: Cui Liu; Guanjun Xiao, Mengli Yang, Bo Zou, Zhi-Ling Zhang, Dai-Wen Pang
      Abstract: Mechanofluorochromic materials, which change their photoluminescence (PL) colors in responding to mechanical stimuli, can be used as mechanosensors, security papers, and photoelectronic devices. However, traditional mechanofluorochromic materials can only be adjusted to a monotone direction upon the external stimuli. Controllable pressure-triggered blue- and red-shifted PL is reported for C-dots. The origin of mechanofluorochromism (MFC) in C-dots is interpreted based on structure–property relationships. The carbonyl group and the π-conjugated system play key roles in the PL change of C-dots under high pressure. As the pressure increases, the enhanced π–π stacking of the π-conjugated system causes the red-shift of PL, while the conversion of carbonyl groups eventually induces a blue-shift. Together with their low toxicity, good hydrophilicity, and small size, the tunable MFC property would boost various potential applications of C-dots.Bidirectional mechanofluorochromic C-dots with a controllable blue-or red-shift of photoluminescence (PL) spectra was achieved under high pressure by adjusting their relative contents of carbonyl groups and a π-conjugated system. The origin of mechanofluorochromism in C-dots is interpreted using structure–property relationships.
      PubDate: 2018-01-18T02:40:49.418298-05:
      DOI: 10.1002/anie.201711409
       
  • The Molecular Structure of gauche-1,3-Butadiene: Experimental
           Establishment of Non-planarity
    • Authors: Joshua H. Baraban; Marie-Aline Martin-Drumel, P. Bryan Changala, Sandra Eibenberger, Matthew Nava, David Patterson, John F. Stanton, G. Barney Ellison, Michael C. McCarthy
      Abstract: The planarity of the second stable conformer of 1,3-butadiene, the archetypal diene for the Diels–Alder reaction in which a planar conjugated diene and a dienophile combine to form a ring, is not established. The most recent high level calculations predicted the species to adopt a twisted, gauche structure owing to steric interactions between the inner terminal hydrogens rather than a planar, cis structure favored by the conjugation of the double bonds. The structure cis-1,3-butadiene is unambiguously confirmed experimentally to indeed be gauche with a substantial dihedral angle of 34°, in excellent agreement with theory. Observation of two tunneling components indicates that the molecule undergoes facile interconversion between two equivalent enantiomeric forms. Comparison of experimentally determined structures for gauche- and trans-butadiene provides an opportunity to examine the effects of conjugation and steric interactions.Twist and shout: The structure of gauche-butadiene has been determined using a combination of sensitive microwave experiments, unambiguously proving its non-planarity with a twist angle of 34°. High-level theoretical calculations show that the cis structure is a transition state between the two gauche minima on the potential energy surface (see picture).
      PubDate: 2018-01-18T02:40:33.100248-05:
      DOI: 10.1002/anie.201709966
       
  • Total Synthesis and Conformational Study of The Anti-tubercular Cyclic
           Peptide Callyaerin A Bearing a Rare Rigidifying (Z)-2,3- Diaminoacrylamide
           Moiety
    • Authors: Margaret Anne Brimble; Shengping Zhang, Luis De Leon Rodriguez, Ivanhoe Leung, Greg Cook, Paul Harris
      Abstract: The first synthesis of the anti-TB cyclic peptide callyaerin A containing a rare (Z)-2,3-diaminoacrylamide bridging motif is reported. Fmoc-formylglycine-diethylacetal was used as a masked equivalent of formylglycine in the synthesis of the linear precursor of callyaerin A. Intramolecular cyclization between the formylglycine residue and the N-terminal amine in the linear peptide precursor afforded the macrocyclic natural product callyaerin A. Synthetic callyaerin A possessed potent anti-TB activity (MIC100 = 32 µM) while its all-amide congener was inactive. Variable temperature NMR studies of both the natural product and its all amide analogue revealed the extraordinary rigidity imposed by this diaminoacrylamide unit on peptide conformation. The work reported herein pinpoints the intrinsic role that the rare (Z)-2,3-diaminoacrylamide moiety confers on peptide bioactivity.
      PubDate: 2018-01-18T00:55:45.125924-05:
      DOI: 10.1002/anie.201712792
       
  • Electrocatalytic Activity of 2D Phosphorene Based Heteroelectrocatalyst
           for Photoelectrochemical Cells
    • Authors: Munkhbayar Batmunkh; Aabhash Shrestha, Munkhjargal Bat-Erdene, Md. Julker Nine, Cameron James Shearer, Christopher Gibson, Ashley Slattery, Sherif Tawfik, Michael Ford, Sheng Dai, Shizhang Qiao, Joseph George Shapter
      Abstract: Research into efficient synthesis, fundamental properties and potential applications of phosphorene is currently the subject of intense investigation. Herein, solution processed phosphorene or few-layer black phosphorus (FL-BP) sheets are prepared using microwave-exfoliation method and used in photoelectrochemical cells. Based on our experimental and theoretical (DFT) studies, we found that the FL-BP sheets can act as catalytically active sites and show excellent electrocatalytic activity for triiodide reduction in solar cells. Importantly, the device fabricated based on our newly designed cobalt sulfide (CoSx) decorated nitrogen, sulfur co-doped carbon nanotubes heteroelectrocatalyst coated with FL-BP (FL-BP@N, S-doped CNTs-CoSx) displayed an impressive photovoltaic efficiency of 8.31%, outperforming expensive platinum based cells. This work paves the way for advancing phosphorene research and using phosphorene based electrocatalysts for next-generation energy-storage systems.
      PubDate: 2018-01-17T22:00:57.669873-05:
      DOI: 10.1002/anie.201712280
       
  • Optical structural analysis of individual α-synuclein oligomers
    • Authors: Juan Alberto Varela; Margarida Rodrigues, Suman De, Patrick Flagmeier, Sonia Gandhi, Christopher M. Dobson, David Klenerman, Steven Lee
      Abstract: Small aggregates of misfolded proteins play a key role in neurodegenerative disorders. Such species are difficult to study due to the lack of methods capable of resolving these heterogeneous aggregates, which are smaller than the optical diffraction limit. We demonstrate here an all-optical fluorescence microscopy method to characterise the structure of individual protein-aggregates based on the fluorescence anisotropy of dyes such as thioflavin-T, and show that this technology is capable of studying oligomers in human biofluids such as cerebrospinal fluid. We first investigated in vitro the structural changes in individual oligomers of recombinant α-synuclein. By studying the diffraction-limited aggregates we directly evaluated their structural conversion and correlated this with the potential of aggregates to disrupt lipid bilayers. We finally characterised the structural features of aggregates present in cerebrospinal fluid of Parkinson's disease patients and healthy controls.
      PubDate: 2018-01-17T14:25:25.528481-05:
      DOI: 10.1002/anie.201710779
       
  • Solvent-free enzyme activity: quick, high-yielding mechano-enzymatic
           hydrolysis of cellulose into glucose
    • Authors: Fabien Hammerer; Leigh Loots, Jean-Louis Do, J. P. Daniel Therien, Christopher W. Nickels, Tomislav Friscic, Karine Auclair
      Abstract: Mechanochemistry enables enzymatic cleavage of cellulose into glucose without bulk solvents, acids, other aggressive reagents or substrate pre-treatment. This clean mechano-enzymatic process is also directly applicable to biomass, avoids many limitations associated with the use of cellulases, and produces glucose concentrations>3 times the highest obtained by conventional methods.
      PubDate: 2018-01-17T12:55:23.896024-05:
      DOI: 10.1002/anie.201711643
       
  • Isotope substitution of promiscuous alcohol dehydrogenase reveals origin
           of substrate preference in transition state
    • Authors: Rudolf K Allemann; J Javier Ruiz-Pernia, Louis Luk, Inaki Tunon, Vicent Moliner, Enas Behiry
      Abstract: The origin of substrate preference in promiscuous enzymes was investigated by enzyme isotope labeling of the alcohol dehydrogenase from Geobacillus stearothermophilus (BsADH). At physiological temperature, protein dynamic coupling to the reaction coordinate was insignificant. However, the extent of dynamic coupling was highly substrate-dependent at lower temperatures. For benzyl alcohol, an enzyme isotope effect larger than unity was observed, whereas the enzyme isotope effect was close to unity for isopropanol. Frequency motion analysis on the transition states revealed that residues surrounding the active site undergo substantial displacement during catalysis for sterically bulky alcohols. BsADH prefers smaller substrates, which cause less protein friction along the reaction coordinate and reduced frequencies of dynamic recrossing. This hypothesis allows a prediction of the trend of enzyme isotope effects for a wide variety of substrates.
      PubDate: 2018-01-17T11:55:48.239607-05:
      DOI: 10.1002/anie.201712826
       
  • Organic Microcrystal Vibronic Lasers with Full-Spectrum Tunable Output
           beyond the Franck-Condon Principle
    • Authors: Yong Sheng Zhao; Haiyun Dong, Chunhuan Zhang, Yuan Liu, Yongli Yan, Fengqin Hu
      Abstract: The very broad emission bands of organic semiconductor materials are, in theory, suitable for achieving versatile solid state lasers; however, most of organic materials only lase at short wavelength corresponding to the 0−1 transition governed by the Franck-Condon (FC) principle. Here we develop a strategy to overcome the limit of FC principle for tailoring the output of microlasers over a wide range based on the controlled vibronic emission of organic materials at microcrystal state. For the first time, the output wavelength of organic lasers is tailored across all vibronic (0−1, 0−2, 0−3, and even 0−4) bands spanning the entire emission spectrum.
      PubDate: 2018-01-17T11:26:21.101072-05:
      DOI: 10.1002/anie.201712524
       
  • CO2-Triggered Switchable Hydrophilicity of Heterogeneous Conjugated
           Polymer Photocatalyst for Enhanced Catalytic Activity in Water
    • Authors: Jeehye Byun; Wei Huang, Di Wang, Run Li, Kai A. I. Zhang
      Abstract: Water-compatibility of heterogeneous photocatalysts has been pursued for energy and environmental applications. However, there exists a trade-off between hydrophilicity and recyclability of the photocatalyst. Herein, we report a conjugated polymer photocatalyst with tertiary amine terminals that reversibly binds CO2 in water, generating a switchable hydrophilicity. The CO2-assisted hydrophilicity boosted up the photocatalytic efficiency in aqueous medium with minimum dosage. When CO2 was desorbed, the photocatalyst could be simply regenerated from reaction media, facilitating the repeated use of photocatalyst. The hydrophilicity/hydrophobicity control of the polymer photocatalyst has successfully showcased through a variety of organic photo-redox reactions under visible light irradiation in water.
      PubDate: 2018-01-17T10:55:27.105835-05:
      DOI: 10.1002/anie.201711773
       
  • Tuning the adsorption energy of methanol molecules along Ni-N-doped carbon
           phase boundaries via the Mott-Schottky effect for highly efficient
           dehydrogenation of gas-phase methanol
    • Authors: Zhong-Hua Xue; Jing-Tan Han, Wei-Jie Feng, Qiu-Ying Yu, Xin-Hao Li, Markus Antonietti, Jie-Sheng Chen
      Abstract: Engineering the adsorption of molecules on active sites is an integral and challenging part for the design of highly efficient transition-metal-based catalysts for methanol dehydrogenation. Here we report a Mott-Schottky catalyst composed of Ni nanoparticles and tailorable nitrogen-doped carbon-foam (Ni/NCF) and thus tunable adsorption energy for highly efficient and selective dehydrogenation of gas-phase methanol to hydrogen and CO even under relatively high weight hourly space velocities (WHSV). Both theoretical and experimental results reveal the key role of the rectifying contact at the Ni/NCF boundaries in tailoring the electron density of Ni species and enhancing the absorption energies of methanol molecules, which leads to a remarkably high turnover frequency (TOF) value (356 mol methanol mol−1 Ni h−1 at 350 °C), 10-fold outpacing the bench-marked transition-metal catalysts in the literature.
      PubDate: 2018-01-17T10:25:54.654703-05:
      DOI: 10.1002/anie.201713429
       
  • A Stable Room-Temperature Luminescent Biphenylmethyl Radical
    • Authors: Xin Ai; Yingxin Chen, Yuting Feng, Feng Li
      Abstract: There is only one family of room-temperature luminescent radicals, the triphenylmethyl radicals, to date. Herein, we synthesize a new stable room-temperature luminescent radical, (N-carbazolyl)bis(2,4,6-tirchlorophenyl)methyl radical (CzBTM), which has improved properties compared to the triphenylmethyl radicals. X-ray crystallography, electron paramagnetic resonance spectroscopy, and magnetic susceptibility measurements confirmed the radical structure. CzBTM shows room-temperature deep-red to near-infrared emission in various solutions. Both thermal and photo stability were significantly enhanced by the replacement of trichlorobenzene by the carbazole moiety. The electroluminescence results of CzBTM verify its potential application to circumvent the problem of triplet harvesting in traditional fluorescent OLEDs. A new family of stable luminescent radicals based on CzBTM is anticipated.Radical enhancement: A stable room-temperature luminescent biphenylmethyl radical (CzBTM) was synthesized. Both thermal and photo stability were enhanced significantly by the replacement of a trichlorobenzene moiety by a carbazole moiety. The electroluminescence results of CzBTM support its potential application to circumvent the problem of triplet harvesting in traditional fluorescent OLEDs.
      PubDate: 2018-01-17T09:20:29.149034-05:
      DOI: 10.1002/anie.201713321
       
  • Control of Luminescence by Tuning of Crystal Symmetry and Local Structure
           in Mn4+-Activated Narrow Band Fluoride Phosphors
    • Authors: Mu-Huai Fang; Wei-Lun Wu, Ye Jin, Tadeusz Lesniewski, Sebastian Mahlik, Marek Grinberg, Mikhail G. Brik, Alok M. Srivastava, Chang-Yang Chiang, Wuzong Zhou, Donghyuk Jeong, Sun Hee Kim, Grzegorz Leniec, Slawomir M. Kaczmarek, Hwo-Shuenn Sheu, Ru-Shi Liu
      Abstract: Mn4+-doped fluoride phosphors have been widely used in wide-gamut backlighting devices because of their extremely narrow emission band. Solid solutions of Na2(SixGe1−x)F6:Mn4+ and Na2(GeyTi1−y)F6:Mn4+ were successfully synthesized to elucidate the behavior of the zero-phonon line (ZPL) in different structures. The ratio between ZPL and the highest emission intensity υ6 phonon sideband exhibits a strong relationship with luminescent decay rate. First-principles calculations are conducted to model the variation in the structural and electronic properties of the prepared solid solutions as a function of the composition. To compensate for the limitations of the Rietveld refinement, electron paramagnetic resonance and high-resolution steady-state emission spectra are used to confirm the diverse local environment for Mn4+ in the structure. Finally, the spectral luminous efficacy of radiation (LER) is used to reveal the important role of ZPL in practical applications.Solid solutions of Na2(SixGe1−x)F6:Mn4+ and Na2(GeyTi1−y)F6:Mn4+ were successfully synthesized by the co-precipitation method to elucidate the behavior of the zero-phonon line (ZPL) owing to its high sensitivity to the local coordinated environment. The control of the ZPL is examined from the view of structure, electronic, and optical properties. All show promise in the practical application of white-light diodes.
      PubDate: 2018-01-17T09:15:46.453218-05:
      DOI: 10.1002/anie.201708814
       
  • Lanthanide Complexes Supported by a Trizinc Crown Ether as Catalysts for
           Alternating Copolymerization of Epoxide and CO2: Telomerization Controlled
           by Carboxylate Anions
    • Authors: Haruki Nagae; Ryota Aoki, Shin-nosuke Akutagawa, Julian Kleemann, Risa Tagawa, Tobias Schindler, Gyeongshin Choi, Thomas P. Spaniol, Hayato Tsurugi, Jun Okuda, Kazushi Mashima
      Abstract: A new family of heterometallic catalysts based on trimetalated macrocyclic tris(salen) ligands and rare-earth metals was prepared and structurally characterized. The LaZn3 system containing anionic ligands such as acetate plays a critical role in catalyzing the alternating copolymerization of cyclohexene oxide (CHO) and CO2 with a high proportion of carbonate linkages. Among the lanthanide metals, the CeZn3 system exhibits high catalytic activity with a turnover frequency (TOF) of over 370 h−1. NMR analysis of the complex and end-group analysis of the polymer suggest that the acetate ligands are rapidly exchanged, not only among coordinated acetates, but also between coordinated acetates and added carboxylate anions. These unique properties make this the first example of telomerization for the copolymerization of CHO and CO2.Homogeneous heterometallic complexes based on the trizincated macrocycle trisaloph and a rare-earth metal showed high catalytic activity for the alternating copolymerization of cyclohexene oxide and CO2 with a high proportion of carbonate repeat units. The carboxylate anion of the ammonium salt initiates the telomerization, providing the polycarbonate with the corresponding carboxylate.
      PubDate: 2018-01-17T09:15:32.086854-05:
      DOI: 10.1002/anie.201709218
       
  • Total Synthesis of (±)-Phomoidride D
    • Authors: Joyce C. Leung; Aaron A. Bedermann, Jón T. Njardarson, David A. Spiegel, Graham K. Murphy, Naoto Hama, Barry M. Twenter, Ping Dong, Tatsuya Shirahata, Ivar M. McDonald, Munenori Inoue, Nobuaki Taniguchi, Travis C. McMahon, Christopher M. Schneider, Nancy Tao, Brian M. Stoltz, John L. Wood
      Abstract: Described herein is a synthetic strategy for the total synthesis of (±)-phomoidride D. This highly efficient and stereoselective approach provides rapid assembly of the carbocyclic core by way of a tandem phenolic oxidation/intramolecular Diels–Alder cycloaddition. A subsequent SmI2-mediated cyclization cascade delivers an isotwistane intermediate poised for a Wharton fragmentation that unveils the requisite bicyclo[4.3.1]decene skeleton and sets the stage for synthesis completion.Sets the stage: Described herein is a synthetic strategy for the total synthesis of (±)-phomoidride D. This highly efficient and stereoselective approach provides rapid assembly of the carbocyclic core by way of a tandem phenolic oxidation/intramolecular Diels–Alder cycloaddition. A subsequent SmI2-mediated cyclization cascade delivers an isotwistane intermediate poised for a Wharton fragmentation that unveils the requisite bicyclo[4.3.1]decene skeleton and sets the stage for synthesis completion.
      PubDate: 2018-01-17T09:11:01.488661-05:
      DOI: 10.1002/anie.201712369
       
  • Development of Antibody-Directed Therapies: Quo Vadis'
    • Authors: Tiago Rodrigues; Gonçalo J. L. Bernardes
      Abstract: Less is more: The efficacy of antibody–drug conjugates (ADCs) for cancer therapy is traditionally associated with cleavable linkers for payload release. Evidence now suggests that simpler constructs without cleavable moieties can afford more stable and effective ADCs.
      PubDate: 2018-01-17T09:10:49.412652-05:
      DOI: 10.1002/anie.201712185
       
  • Photocatalytic Aerobic Phosphatation of Alkenes
    • Authors: Christian Depken; Felix Krätzschmar, Rene Rieger, Katharina Rode, Alexander Breder
      Abstract: A catalytic regime for the direct phosphatation of simple, non-polarized alkenes has been devised that is based on using ordinary, non-activated phosphoric acid diesters as the phosphate source and O2 as the terminal oxidant. The title method enables the direct and highly economic construction of a diverse range of allylic phosphate esters. From a conceptual viewpoint, the aerobic phosphatation is entirely complementary to traditional methods for phosphate ester formation, which predominantly rely on the use of prefunctionalized or preactivated reactants, such as alcohols and phosphoryl halides. The title transformation is enabled by the interplay of a photoredox and a selenium π-acid catalyst and involves a sequence of single-electron-transfer processes.Once in a blue moon: The aerobic dehydrogenative coupling of simple hydrogen phosphates with non-activated alkenes generates a diverse range of allylic phosphates through the catalytic interplay of a photosensitizer (PS) and a chalcogen Lewis acid (Se). In addition to its operational simplicity and high chemoselectivity, the title reaction also enables the facile consecutive redox alkylation of olefins with organocuprates.
      PubDate: 2018-01-17T09:10:38.323103-05:
      DOI: 10.1002/anie.201711599
       
  • MoS2-on-MXene Heterostructures as Highly Reversible Anode Materials for
           Lithium-Ion Batteries
    • Authors: Chi Chen; Xiuqiang Xie, Babak Anasori, Asya Sarycheva, Taron Makaryan, Mengqiang Zhao, Patrick Urbankowski, Ling Miao, Jianjun Jiang, Yury Gogotsi
      Abstract: Two-dimensional (2D) heterostructured materials, combining the collective advantages of individual building blocks and synergistic properties, have spurred great interest as a new paradigm in materials science. The family of 2D transition-metal carbides and nitrides, MXenes, has emerged as an attractive platform to construct functional materials with enhanced performance for diverse applications. Here, we synthesized 2D MoS2-on-MXene heterostructures through in situ sulfidation of Mo2TiC2Tx MXene. The computational results show that MoS2-on-MXene heterostructures have metallic properties. Moreover, the presence of MXene leads to enhanced Li and Li2S adsorption during the intercalation and conversion reactions. These characteristics render the as-prepared MoS2-on-MXene heterostructures stable Li-ion storage performance. This work paves the way to use MXene to construct 2D heterostructures for energy storage applications.MoS2-on-MXene heterostructures were obtained by an in situ sulfidation of Mo2TiC2Tx MXene, which deliver improved Coulombic efficiency and cycling performance for the Li-ion battery. A computational study shows that the strong Li and Li2S adsorption on 2D heterostructures leads to a stable Li-ion storage performance.
      PubDate: 2018-01-17T09:10:29.053519-05:
      DOI: 10.1002/anie.201710616
       
  • IR Spectrum and Structure of Protonated Monosilanol: Dative Bonding
           between Water and the Silylium Ion**
    • Authors: Martin Andreas Robert George; Nguyen Xuan Truong, Marco Savoca, Otto Dopfer
      Abstract: We report the spectroscopic characterization of protonated monosilanol (SiH3OH2+) isolated in the gas phase, thus providing the first experimental determination of the structure and bonding of a member of the elusive silanole family. The SiH3OH2+ ion is generated in a silane/water plasma expansion, and its structure is derived from the IR photodissociation (IRPD) spectrum of its Ar cluster measured in a tandem mass spectrometer. The chemical bonding in SiH3OH2+ is analyzed by density functional theory (DFT) calculations, providing detailed insight into the nature of the dative H3Si+-OH2 bond. Comparison with protonated methanol illustrates the differences in bonding between carbon and silicon, which is mainly related to their different electronegativity and the different energy of the vacant valence pz orbital of SiH3+ and CH3+.
      PubDate: 2018-01-17T08:56:07.023278-05:
      DOI: 10.1002/anie.201712999
       
  • Halogen Bonding in Solution: From Anion Recognition through Templated
           Self-Assembly to Organo-catalysis
    • Authors: Ulrich S. Schubert; Ronny Tepper
      Abstract: The halogen bond is a supramolecular interaction between a Lewis-acidic region of a covalently bound halogen and a Lewis base. It has been studied widely in silico and experimentally in the solid state; however, solution phase applications have attracted enormous interest in the last years. This Minireview highlights selected recent developments of halogen bond interactions in solution with focus on the use of halogen bond receptors in anion recognition and sensing, anion templated self-assembly as well as in organo-catalysis.
      PubDate: 2018-01-17T07:55:32.037013-05:
      DOI: 10.1002/anie.201707986
       
  • Reconstitution of a Type II Polyketide Synthase that Catalyzes Polyene
           Formation
    • Authors: Danyao Du; Yohei Katsuyama, Kazuo Shin-ya, Yasuo Ohnishi
      Abstract: While type II polyketide synthases (PKSs) are known for producing aromatic compounds, a phylogenetically new subfamily of type II PKSs have been recently proposed to synthesize polyene structures. Here we report in vitro analysis of such a type II PKS, IgaPKS for ishigamide biosynthesis. The ketoreductase (Iga13) and dehydratase (Iga16) were shown to catalyze the reduction of a β-keto group and dehydration of a β-hydroxy group, respectively, to form a trans double bond. Incubation of the acyl carrier protein (Iga10), the ketosynthase/chain length factor complex (Iga11–Iga12), Iga13 and Iga16 with malonyl and hexanoyl-CoAs and NADPH followed by KOH hydrolysis resulted in the formation of four unsaturated carboxylic acids (C8, C10, C12, and C14), indicating that IgaPKS catalyzes tetraene formation by repeating the cycle of condensation, keto-reduction and dehydration with strict stereo-specificity. We propose “highly reducing type II PKS subfamily” for the polyene-producing type II PKSs.Round round get around: While type II polyketide synthases (PKSs) are known for producing aromatic compounds, in vitro analysis of the type II PKS for ishigamide biosynthesis demonstrated that it catalyzes tetraene formation through a repeating cycle of condensation, ketoreduction, and dehydration with strict stereospecificity. This establishes a subfamily of type II PKS, namely highly reducing type II PKSs, which synthesize polyenes.
      PubDate: 2018-01-17T04:12:00.097186-05:
      DOI: 10.1002/anie.201709636
       
  • Thermoregulated Phase-Transition Synthesis of Two-Dimensional Carbon
           Nanoplates Rich in sp2 Carbon and Unimodal Ultramicropores for Kinetic Gas
           Separation
    • Authors: Lu-Hua Zhang; Wen-Cui Li, Hong Liu, Quan-Gao Wang, Lei Tang, Qing-Tao Hu, Wen-Jing Xu, Wei-Hong Qiao, Zhong-Yuan Lu, An-Hui Lu
      Abstract: The development of highly selective, chemically stable and moisture-resistant adsorbents is a key milestone for gas separation. Porous carbons featured with random orientation and cross-linking of turbostratic nanodomains usually have a wide distribution of micropores. Here we have developed a thermoregulated phase-transition-assisted synthesis of carbon nanoplates with more than 80 % sp2 carbon, unimodal ultramicropore and a controllable thickness. The thin structure allows oriented growth of carbon crystallites, and stacking of crystallites in nearly parallel orientation are responsible for the single size of the micropores. When used for gas separation from CH4, carbon nanoplates exhibit high uptakes (5.2, 5.3 and 5.1 mmol g−1) and selectivities (7, 71 and 386) for CO2, C2H6 and C3H8 under ambient conditions. The dynamic adsorption capacities are close to equilibrium uptakes of single components, further demonstrating superiority of carbon nanoplates in terms of selectivity and sorption kinetics.A selective adsorbent: Two-dimensional carbon nanoplates with single-sized accessible ultramicropores and precisely controlled thickness have been prepared using the thermoregulated phase-transition method. The nanoplates show an excellent kinetic gas separation property.
      PubDate: 2018-01-17T01:55:41.430176-05:
      DOI: 10.1002/anie.201712913
       
  • Pd-Catalyzed Atom Transfer Radical Cyclization at Remote Unactivated
           C(sp3)-H Sites Enabled by Hydrogen Atom Transfer of Hybrid Vinyl
           Pd-Radical Intermediates
    • Authors: Vladimir Gevorgyan; Maxim Ratushnyy, Marvin Parasram, Yang Wang
      Abstract: A novel mild, visible light-induced Pd-catalyzed hydrogen atom translocation/atom transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5-HAT process of previously unknown hybrid vinyl Pd-radical intermediates leading to iodomethyl carbo- and heterocyclic structures.
      PubDate: 2018-01-16T21:55:38.710178-05:
      DOI: 10.1002/anie.201712775
       
  • DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K+
           Channels
    • Authors: Tatsuki Kurokawa; Shigeki Kiyonaka, Eiji Nakata, Masayuki Endo, Shohei Koyama, Emiko Mori, Nam Ha Tran, Huyen Dinh, Yuki Suzuki, Kumi Hidaka, Masaaki Kawata, Chikara Sato, Hiroshi Sugiyama, Takashi Morii, Yasuo Mori
      Abstract: In native systems, scaffolding proteins play important roles in assembling proteins into complexes to transduce signals. This concept is yet to be incorporated in assembling functional transmembrane protein complexes in artificial systems. To address this issue, DNA origami has potentiality to serve as scaffolds that arrange proteins at specific positions in complexes. Here, we report that Kir3 K+ channel proteins are assembled through zinc-finger protein (ZFP)-adaptors at specific locations on DNA origami scaffolds. Specific binding of the ZFP-fused Kir3 channels and ZFP-based adaptors on DNA origami were confirmed by atomic force microscopy and gel electrophoretic analyses. Furthermore, the DNA origami with ZFP binding sites nearly tripled the K+ channel current activity elicited by heterotetrameric Kir3 channels in HEK293T cells. Thus, our method provides a useful template to artificially control the oligomerization states of membrane protein complexes in vitro and in living cells.
      PubDate: 2018-01-16T21:55:32.775878-05:
      DOI: 10.1002/anie.201709982
       
  • Fused-Ring Formation via an Intramolecular "Cut-and-Sew" Reaction between
           Cyclobutanones and Alkynes
    • Authors: Lin Deng; Likun Jin, Guangbin Dong
      Abstract: Herein, we describe the development of a catalytic intramolecular "cut-and-sew" transformation between cyclobutanones and alkynes to construct cyclohexenone-fused rings. The challenge arises from the need for selective coupling at the more sterically hindered proximal position, which can be addressed using an electron-rich but less bulky phosphine ligand. The control experiment and 13C-labelling study suggest that the reaction may start with cleavage of the less hindered distal C-C bond of cyclobutanones, followed by decarbonylation and CO reinsertion to enable Rh insertion at the more hindered proximal position.
      PubDate: 2018-01-16T10:50:30.314166-05:
      DOI: 10.1002/anie.201712487
       
  • Gram-Scale Synthesis and Highly Regioselective Bromination of
           1,1,9,9-Tetramethyl[9](2,11)teropyrenophane
    • Authors: Kiran Sagar Unikela; Tracey L. Roemmele, Václav Houska, Kaitlin E. McGrath, David M. Tobin, Louise N. Dawe, René T. Boeré, Graham J. Bodwell
      Abstract: An improved synthetic pathway to the nanobelt-like 1,1,9,9-tetramethyl[9](2,11)teropyrenophane has been developed, and enables the synthesis of gram quantities of material. Key innovations are the development of a sequential chlorination/Friedel–Crafts alkylation reaction, a sequential iodination/Wurtz coupling reaction, and a room-temperature teropyrene-forming reaction. The teropyrenophane was found to form a very stable radical cation and undergo a completely regioselective fourfold bromination reaction.Go big or stay home! The title compound can now be synthesized on a gram scale by an improved synthetic pathway. The EPR spectroscopy of its radical cation provides a rationale for the completely regioselective fourfold bromination of the severely bent teropyrene system.
      PubDate: 2018-01-16T10:16:28.219662-05:
      DOI: 10.1002/anie.201713067
       
  • Artificial Cysteine S-Glycosylation Induced by Per-O-Acetylated Unnatural
           Monosaccharides during Metabolic Glycan Labeling
    • Authors: Wei Qin; Ke Qin, Xinqi Fan, Linghang Peng, Weiyao Hong, Yuntao Zhu, Pinou Lv, Yifei Du, Rongbing Huang, Mengting Han, Bo Cheng, Yuan Liu, Wen Zhou, Chu Wang, Xing Chen
      Abstract: Peracetylated unnatural sugars—the “arrows” used by glycoscientists for decades to label cellular glycans—can induce artificial cysteine glycosylation on various proteins, as reported in the Communication (
      DOI : 10.1002/anie.201711710) by C. Wang, X. Chen et al. This “off-targeting” of the per-O-acetylated sugar reporters can be likened to Cao Cao shooting arrows at scarecrows and straw boats in the fictitious story “Romance of the Three Kingdoms”, and calls for caution in the use of peracetylated sugars and the development of better versions.
      PubDate: 2018-01-16T10:16:16.235973-05:
       
  • Enzymatic Electrosynthesis of Alkanes by Bioelectrocatalytic
           Decarbonylation of Fatty Aldehydes
    • Authors: Sofiene Abdellaoui; Florika C. Macazo, Rong Cai, Antonio L. De Lacey, Marcos Pita, Shelley D. Minteer
      Abstract: An enzymatic electrosynthesis system was created by combining an aldehyde deformylating oxygenase (ADO) from cyanobacteria that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface. This system is able to produce a range of alkanes (octane to propane) from aldehydes and alcohols. The combination of this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell (EFC) able to simultaneously generate electrical energy with a maximum current density of 25 μA cm−2 at 0.6 V and produce hexane with a faradaic efficiency of 24 %.The combination of an aldehyde deformylating oxygenase that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface yields an enzymatic electrosynthesis system that produces various alkanes from aldehydes and alcohols. Combining this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell that generates electrical energy while producing hexane.
      PubDate: 2018-01-16T10:16:02.122251-05:
      DOI: 10.1002/anie.201712890
       
  • Stereoselective Construction of Halogenated Quaternary Carbon Centers by
           Brønsted Base Catalyzed [4+2] Cycloaddition of α-Haloaldehydes
    • Authors: Qiang Li; Liang Zhou, Xu-Dong Shen, Kai-Chuan Yang, Xiang Zhang, Qing-Song Dai, Hai-Jun Leng, Qing-Zhu Li, Jun-Long Li
      Abstract: Asymmetric construction of halogenated quaternary carbon centers under mild reaction conditions remains challenging. Reported here is an unprecedented and highly stereoselective Brønsted base catalyzed [4+2] cycloaddition between either α-chloro- or α-bromoaldehydes and cyclic enones. The key intermediate, an α-halogenated enolate, is susceptible to dehalogenation and can be stabilized and stereochemically controlled using bifunctional tertiary amines. This method provides facile access to a collection of optically pure bicyclic dihydropyrans having three contiguous stereocenters, including a halogen-bearing quaternary carbon center. Of note, the product can be transformed in situ into densely functionalized spirocyclopropanes in a highly efficient and stereoselective manner.Hello Halo! An unprecedented highly enantioselective, Brønsted base catalyzed [4+2] cycloaddition of α-haloaldehydes and electron-deficient cyclic enones has been developed. A series of fused bicyclic dihydropyrans featuring a halogenated quaternary stereocenter was synthesized in excellent yields with up to>99 % ee under mild reaction conditions. These products were further transformed into spirocyclopropanes having two vicinal all-carbon quaternary centers.
      PubDate: 2018-01-16T10:15:56.781194-05:
      DOI: 10.1002/anie.201711813
       
  • Synthesis and Structure Revision of Dichrocephones A and B
    • Authors: Volker M. Schmiedel; Young J. Hong, Dieter Lentz, Dean J. Tantillo, Mathias Christmann
      Abstract: Herein, we report the first enantioselective synthesis of dichrocephones A and B, which are cytotoxic triquinane sesquiterpenes with a dense array of stereogenic centers within a strained polycyclic environment. Key features include the application of a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Double reductive ring cleavage yielded the proposed structure of dichrocephone A. Mismatched spectroscopic data for our synthetic material compared to the natural isolate led us to revise the previously proposed configuration based on biosynthetic considerations and NMR calculations. Implementation of these findings culminated in the synthesis of dichrocephones A and B.Cyclize and revise: Total synthesis of the densely functionalized dichrocephones A and B is described. Key features include a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Mismatched spectroscopic data for the initial synthetic product compared to the natural isolate led to a revision of the previously proposed configuration.
      PubDate: 2018-01-16T10:15:46.532135-05:
      DOI: 10.1002/anie.201711766
       
  • Palladium-Catalyzed Enantioselective Desymmetrizing Aza-Wacker Reaction:
           Development and Application to the Total Synthesis of (−)-Mesembrane and
           (+)-Crinane
    • Authors: Xu Bao; Qian Wang, Jieping Zhu
      Abstract: Reported is an unprecedented catalytic enantioselective desymmetrizing aza-Wacker reaction. In the presence of a catalytic amount of a newly developed Pd(CPA)2(MeCN)2 catalyst (CPA=chiral phosphoric acid), a pyrox ligand, and molecular oxygen, cyclization of properly functionalized prochiral 3,3-disubstituted cyclohexa-1,4-dienes afforded enantioenriched cis-3a-substituted tetrahydroindoles in good yields with excellent enantioselectivities. A cooperative effect between the phosphoric acid and the pyrox ligand ensured efficient transformation. This reaction was tailor-made for Amaryllidaceae and Sceletium alkaloids as illustrated by its application in the development of the concise and divergent total synthesis of (−)-mesembrane and (+)-crinane.Let's cooperate: In the catalytic enantioselective cyclization of 1 to 2, the pyrox ligand L* determined the sense of enantioselectivity, while the matched chiral phosphoric acid increased both the ee value and the yield of the product. Concise and divergent total syntheses of (−)-mesembrane and (+)-crinane were subsequently developed.
      PubDate: 2018-01-16T10:15:26.282544-05:
      DOI: 10.1002/anie.201712521
       
  • Directed Evolution of an Artificial Imine Reductase
    • Authors: Martina Hestericová; Tillman Heinisch, Lur Alonso-Cotchico, Jean-Didier Maréchal, Pietro Vidossich, Thomas R. Ward
      Abstract: Artificial metalloenzymes, resulting from incorporation of a metal cofactor within a host protein, have received increasing attention in the last decade. The directed evolution is presented of an artificial transfer hydrogenase (ATHase) based on the biotin-streptavidin technology using a straightforward procedure allowing screening in cell-free extracts. Two streptavidin isoforms were yielded with improved catalytic activity and selectivity for the reduction of cyclic imines. The evolved ATHases were stable under biphasic catalytic conditions. The X-ray structure analysis reveals that introducing bulky residues within the active site results in flexibility changes of the cofactor, thus increasing exposure of the metal to the protein surface and leading to a reversal of enantioselectivity. This hypothesis was confirmed by a multiscale approach based mostly on molecular dynamics and protein–ligand dockings.Skipping steps: An artificial imine reductase is generated by incorporation of a biotinylated iridium piano-stool complex within streptavidin. A streamlined process allows a faster screening in cell-free extracts. With this system, both enantiomers of the product can be obtained in high ee after only a few rounds of saturation mutagenesis.
      PubDate: 2018-01-16T10:02:30.622786-05:
      DOI: 10.1002/anie.201711016
       
  • Synthesis of α-Chiral Ketones and Chiral Alkanes Using Radical Polar
           Crossover Reactions of Vinyl Boron Ate Complexes
    • Authors: Carolin Gerleve; Marvin Kischkewitz, Armido Studer
      Abstract: Vinyl boron ate complexes of enantioenriched secondary alkyl pinacolboronic esters undergo stereospecific radical-induced 1,2-migration in radical polar crossover reactions. In this three-component process various commercially available alkyl iodides act as radical precursors and light is used for chain initiation. Subsequent oxidation and protodeborylation leads to valuable α-chiral ketones and chiral alkanes, respectively, with excellent enantiopurity.Radical and polar! Various chiral vinyl boron ate complexes, readily generated from the corresponding pinacolboronic esters and vinyllithium, react in a radical polar crossover cascade to produce secondary alkyl boronic esters that are either oxidized to valuable α-chiral ketones or protodeborylated to the corresponding alkanes. Products are isolated in good overall yields and excellent stereospecificity. Pin=pinacolate.
      PubDate: 2018-01-16T10:02:12.403432-05:
      DOI: 10.1002/anie.201711390
       
  • All-in-One Cellulose Nanocrystals for 3D Printing of Nanocomposite
           Hydrogels
    • Authors: Jieping Wang; Annalisa Chiappone, Ignazio Roppolo, Feng Shao, Erika Fantino, Massimo Lorusso, Daniel Rentsch, Kurt Dietliker, Candido Fabrizio Pirri, Hansjörg Grützmacher
      Abstract: Cellulose nanocrystals (CNCs) with>2000 photoactive groups on each can act as highly efficient initiators for radical polymerizations, cross-linkers, as well as covalently embedded nanofillers for nanocomposite hydrogels. This is achieved by a simple and reliable method for surface modification of CNCs with a photoactive bis(acyl)phosphane oxide derivative. Shape-persistent and free-standing 3D structured objects were printed with a mono-functional methacrylate, showing a superior swelling capacity and improved mechanical properties.Allrounder: Multifunctional cellulose nanocrystals were achieved by facile surface immobilization of photoactive groups. They serve as highly efficient visible light photoinitiators, cross-linkers and covalently embedded nanofillers for 3D printing of nanocomposite hydrogels, using a mono-functional methacrylate as monomer without any conventional cross-linkers.
      PubDate: 2018-01-16T10:02:02.879944-05:
      DOI: 10.1002/anie.201710951
       
  • A 3D Nanostructured Hydrogel Framework-Derived High-Performance Composite
           Polymer Lithium-Ion Electrolyte
    • Authors: Jiwoong Bae; Yutao Li, Jun Zhang, Xingyi Zhou, Fei Zhao, Ye Shi, John B. Goodenough, Guihua Yu
      Abstract: Solid-state electrolytes have emerged as a promising alternative to existing liquid electrolytes for next generation Li-ion batteries for better safety and stability. Of various types of solid electrolytes, composite polymer electrolytes exhibit acceptable Li-ion conductivity due to the interaction between nanofillers and polymer. Nevertheless, the agglomeration of nanofillers at high concentration has been a major obstacle for improving Li-ion conductivity. In this study, we designed a three-dimensional (3D) nanostructured hydrogel-derived Li0.35La0.55TiO3 (LLTO) framework, which was used as a 3D nanofiller for high-performance composite polymer Li-ion electrolyte. The systematic percolation study revealed that the pre-percolating structure of LLTO framework improved Li-ion conductivity to 8.8×10−5 S cm−1 at room temperature.Path finder: The percolation effect on the conductivity of composite polymer electrolytes has been investigated. Typical nanoparticle fillers agglomerate at high concentrations resulting in discontinuous lithium-ion conducting pathways. A nanostructured hydrogel-framework electrolyte exhibits much higher conductivity through a continuous interphase formed by a pre-percolated network.
      PubDate: 2018-01-16T10:01:50.632395-05:
      DOI: 10.1002/anie.201710841
       
  • Photocontrolled Release of Chemicals from Nano- and Microparticle
           Containers
    • Authors: Christoph Englert; Ivo Nischang, Cornelia Bader, Philipp Borchers, Julien Alex, Michael Pröhl, Martin Hentschel, Matthias Hartlieb, Anja Traeger, Georg Pohnert, Stephanie Schubert, Michael Gottschaldt, Ulrich S. Schubert
      Abstract: A benzoin-derived diol linker was synthesized and used to generate biocompatible polyesters that can be fully decomposed on demand upon UV irradiation. Extensive structural optimization of the linker unit was performed to enable the defined encapsulation of diverse organic compounds in the polymeric structures and allow for a well-controllable polymer cleavage process. Selective tracking of the release kinetics of encapsulated model compounds from the polymeric nano- and microparticle containers was performed by confocal laser scanning microscopy in a proof-of-principle study. The physicochemical properties of the incorporated and released model compounds ranged from fully hydrophilic to fully hydrophobic. The demonstrated biocompatibility of the utilized polyesters and degradation products enables their use in advanced applications, for example, for the smart packaging of UV-sensitive pharmaceuticals, nutritional components, or even in the area of spatially selective self-healing processes.Chemicals on demand: Biocompatible polyesters were synthesized that can be fully decomposed by UV irradiation. The formation of nano- and microparticles allows for the defined encapsulation of structurally diverse organic compounds and a controllable cleavage process. These particles can be used for the smart packaging of UV-sensitive pharmaceuticals or for spatially selective self-healing processes.
      PubDate: 2018-01-16T10:01:18.067479-05:
      DOI: 10.1002/anie.201710756
       
  • Divergent Pathways Involving 1,3-Dipolar Addition and N−N Bond Splitting
           of an Organic Azide across a Zirconium Methylidene
    • Authors: Takashi Kurogi; Manoj V. Mane, Shuai Zheng, Patrick J. Carroll, Mu-Hyun Baik, Daniel J. Mindiola
      Abstract: The zirconium methylidene (PNP)Zr=CH2(OAr) (1) reacts with N3Ad to give two products (PNP)Zr=NAd(OAr) (2) and (PNP)Zr(η2-N=NAd)(N=CH2)(OAr) (3), both resulting from a common cycloaddition intermediate (PNP)Zr(CH2N3Ad)(OAr) (A). Using a series of control experiments in combination with DFT calculations, it was found that 2 results from a nitrene by a carbene metathesis reaction in which N2 acts as a delivery vehicle and forms N2CH2 as a side product. In the case of 3, N−N bond splitting of the azide at the α-position allowed the isolation of a rare example of a parent ketimide complex of zirconium. Isotopic labeling studies and solid-state X-ray analysis are presented for 2 and 3, in addition to an independent synthesis for the former.The zirconium methylidene (PNP)Zr=CH2(OAr) reacts with N3Ad to give two products (PNP)Zr=NAd(OAr) and (PNP)Zr(η2-N=NAd)(N=CH2)(OAr), both resulting from a common cycloaddition intermediate, (PNP)Zr(CH2N3Ad)(OAr). A series of control experiments in combination with DFT calculations reveal how the two different products are formed.
      PubDate: 2018-01-16T10:01:04.670195-05:
      DOI: 10.1002/anie.201711587
       
  • A Highly Stable Copper-Based Catalyst for Clarifying the Catalytic Roles
           of Cu0 and Cu+ Species in Methanol Dehydrogenation
    • Authors: Huanhuan Yang; Yanyan Chen, Xiaojing Cui, Guofu Wang, Youliang Cen, Tiansheng Deng, Wenjun Yan, Jie Gao, Shanhui Zhu, Unni Olsbye, Jianguo Wang, Weibin Fan
      Abstract: Identification of the active copper species, and further illustration of the catalytic mechanism of Cu-based catalysts is still a challenge because of the mobility and evolution of Cu0 and Cu+ species in the reaction process. Thus, an unprecedentedly stable Cu-based catalyst was prepared by uniformly embedding Cu nanoparticles in a mesoporous silica shell allowing clarification of the catalytic roles of Cu0 and Cu+ in the dehydrogenation of methanol to methyl formate by combining isotope-labeling experiment, in situ spectroscopy, and DFT calculations. It is shown that Cu0 sites promote the cleavage of the O−H bond in methanol and of the C−H bond in the reaction intermediates CH3O and H2COOCH3 which is formed from CH3O and HCHO, whereas Cu+ sites cause rapid decomposition of formaldehyde generated on the Cu0 sites into CO and H2.A couple of coppers: A stable Cu-based catalyst prepared by embedding Cu nanoparticles in a mesoporous silica shell enables clarification of the roles of Cu0 and Cu+ sites in the dehydrogenation of methanol to methyl formate. Cu0 catalyzes the cleavage of O−H and C−H bonds to give HCHO, and the reaction of HCHO with CH3O to form HCOOCH3. Cu+ converts HCHO into CO and H2.
      PubDate: 2018-01-16T09:46:02.7955-05:00
      DOI: 10.1002/anie.201710605
       
  • Insights into the Desaturation of Cyclopeptin and its C3 Epimer Catalyzed
           by a non-Heme Iron Enzyme: Structural Characterization and Mechanism
           Elucidation
    • Authors: Hsuan-Jen Liao; Jikun Li, Jhih-Liang Huang, Madison Davidson, Igor Kurnikov, Te-Sheng Lin, Justin L. Lee, Maria Kurnikova, Yisong Guo, Nei-Li Chan, Wei-chen Chang
      Abstract: AsqJ, an iron(II)- and 2-oxoglutarate-dependent enzyme found in viridicatin-type alkaloid biosynthetic pathways, catalyzes sequential desaturation and epoxidation to produce cyclopenins. Crystal structures of AsqJ bound to cyclopeptin and its C3 epimer are reported. Meanwhile, a detailed mechanistic study was carried out to decipher the desaturation mechanism. These findings suggest that a pathway involving hydrogen atom abstraction at the C10 position of the substrate by a short-lived FeIV-oxo species and the subsequent formation of a carbocation or a hydroxylated intermediate is preferred during AsqJ-catalyzed desaturation.Make it a double: The mechanism of the desaturation catalyzed by AsqJ, a non-heme iron enzyme, was elucidated using a complementary approach including probe design, X-ray crystallography, molecular dynamics simulations, and spectroscopic characterizations. Subsequent to primary C−H bond activation, a carbocation or a hydroxylated intermediate is likely to be involved in the desaturation.
      PubDate: 2018-01-16T09:45:53.912075-05:
      DOI: 10.1002/anie.201710567
       
  • Solventless and Metal-Free Synthesis of High-Molecular-Mass
           Polyaminoboranes from Diisopropylaminoborane and Primary Amines
    • Authors: Carlos Antonio De Albuquerque Pinheiro; Claire Roiland, Philippe Jehan, Gilles Alcaraz
      Abstract: The solventless reaction of diisopropylaminoborane with n-butylamine, at room temperature, leads to a mixture of B(sp2)H-, B(sp3)H2-, and B(sp3)H3-containing species. At low temperature, the reaction outcome is completely modified, thus leading selectively to the formation of high-mass polybutylaminoborane. When extended to a variety of primary amines, under solventless conditions and at low temperature, this reaction provides a new, efficient, and direct metal-free access to high-molecular-mass polyaminoboranes in good to high yields under mild reaction conditions.Critical mass: Diisopropylaminoborane undergoes a BH2-transfer reaction with primary amines, at low temperature, thus leading selectively to the formation of high-molecular-mass polyaminoboranes. This reaction provides a new, efficient, and direct metal-free access to polyaminoboranes in good to high yields under mild reaction conditions.
      PubDate: 2018-01-16T09:45:44.240763-05:
      DOI: 10.1002/anie.201710293
       
  • “Dumbbell”- and “Clackers”-Shaped Dimeric Derivatives of
           Monocarba-closo-dodecaborate
    • Authors: Yu Kitazawa; Mamoru Watanabe, Yui Masumoto, Mai Otsuka, Kazunori Miyamoto, Atsuya Muranaka, Daisuke Hashizume, Ryo Takita, Masanobu Uchiyama
      Abstract: We designed, synthesized, and characterized two types of dimeric forms of monocarba-closo-dodecaborate, namely, a “dumbbell”-shaped dianion having a C−C bond and a “clackers”-shaped monoanion having an iodonium linker. The unique architectures of these anionic molecules were established by X-ray analysis. Spectroscopic analysis, DFT calculations, and reactivity experiments revealed high anionic and chemical stability of both anions, which are crucial properties for weakly coordinating anions.Weakest link: Coupling of monocarba-closo-dodecaborate resulted in “dumbbell”- and “clackers”-shaped dimeric derivatives (see picture; purple sphere=iodine). X-ray analysis established the unique architectures of these anionic molecules. Combined spectroscopic analysis, DFT calculations, and experimental studies revealed their distinctive properties as weakly coordinating anions (WCAs).
      PubDate: 2018-01-16T09:45:35.45114-05:0
      DOI: 10.1002/anie.201710122
       
  • Frontispiece: Photoinduced Rearrangement of Dienones and Santonin Rerouted
           by Amines
    • Authors: Zhipeng Zhang; Maxim Ratnikov, Glen Spraggon, Phil B. Alper
      Abstract: Photochemistry P. B. Alper et al. report in their Communication on page 904 ff. that the photoinduced rearrangement pathways of simple 2,5-dienones and the natural product santonin are effectively rerouted by amines.
      PubDate: 2018-01-16T09:14:18.752873-05:
      DOI: 10.1002/anie.201880461
       
  • Seeded Polymerization through the Interplay of Folding and Aggregation of
           an Amino-Acid-based Diamide
    • Authors: Soichiro Ogi; Kentarou Matsumoto, Shigehiro Yamaguchi
      Abstract: Amino-acid-based diamides are widely used as a substructure in supramolecular polymers, and also represent key components of polypeptides that help to understand protein folding. Herein, we report that the interplay of folding and aggregation of a diamide can be used to achieve seed-initiated supramolecular polymerization. For that purpose, a pyrene-substituted diamide was synthesized, in which pyrene is used as a tracer to monitor the supramolecular polymerization. Thermodynamic and time-dependent studies revealed that the folding of the diamide moiety, via the formation of intramolecular hydrogen bonds, effectively prevents a spontaneous nucleation that leads to supramolecular polymerization. Under such out-of-equilibrium conditions, the addition of seeds successfully initiates the supramolecular polymerization. These results demonstrate the utility of such amino-acid-based diamides in programmable supramolecular polymerizations.
      PubDate: 2018-01-16T06:32:01.69515-05:0
      DOI: 10.1002/anie.201712119
       
  • Palladium-Catalyzed Asymmetric Aminohydroxylation of 1,3-Dienes
    • Authors: Liuzhu Gong; Hong-Cheng Shen, Yu-Feng Wu, Ying Zhang, Lian-Feng Fan, Zhi-Yong Han
      Abstract: A Pd(II)-catalyzed asymmetric aminohydroxylation of 1,3-dienes with N-tosyl-2-aminophenols has been developed with a chiral pyridinebis(oxazoline) ligand. The highly regioselective reaction provides a direct and efficient approach to access chiral 3,4-dihydro-2H-1,4-benzoxazines in high levels of yield and enantioselectivity (up to 96:4 e.r.). The reaction employs readily available N-tosyl-2-aminophenols as a unique aminohydroxylation reagent complementary to known asymmetric aminohydroxylation methods.
      PubDate: 2018-01-16T05:50:50.698864-05:
      DOI: 10.1002/anie.201712350
       
  • Direct Annulation between Aryl Iodides and Epoxides through
           Palladium/Norbornene Cooperative Catalysis
    • Authors: Renhe Li; Guangbin Dong
      Abstract: Herein we report a direct annulation between aryl iodides and epoxides through palladium/norbornene (Pd/NBE) cooperative catalysis. An iso-propyl ester substituted NBE was found to be most efficient to suppress the formation of multiple-NBE-insertion byproducts and affords the desired 2,3-dihydrobenzofuran derivatives in 44–99 % yields. The reaction is scalable and tolerates a range of functional groups. Asymmetric synthesis is realized using an enantiopure epoxide. Application of this method into a concise synthesis of insecticide fufenozide is demonstrated.We go together: A simple and direct annulation between readily available aryl iodides and epoxides is enabled by palladium/norbornene (Pd/NBE) cooperative catalysis. This approach offers a practical synthesis of various 2,3-dihydrobenzofuran derivatives.
      PubDate: 2018-01-16T05:40:49.588352-05:
      DOI: 10.1002/anie.201712393
       
  • Near-Infrared Triggered Decomposition of Nanocapsules with High Tumor
           Accumulation and Stimuli Responsive Fast Elimination
    • Authors: Dongyuan Zhao; Tiancong Zhao, Peiyuan Wang, Qin Li, Areej Abdulkareem Al-Khalaf, Wael N. Hozzein, Fan Zhang, Xiaomin Li
      Abstract: Nanoparticle based diagnosis-therapy integrative systems represent an emerging approach to cancer treatment. However, a series of size-dependent biological barriers impede nanomedicine from clinical implementation, especially the contradiction on optimum sizes for long blood circulation and quick metabolization. Herein, we demonstrate a novel NIR induced decomposable nanocapsule. The nanocapsules are fabricated based on layer-by-layer assembly of azobenzene functionalized polymers and up/downconversion nanoparticles (U/DCNPs). When the nanocapsules are exposed to NIR light, UV/vis photons emitted by the U/DCNPs can trigger the photo-isomerization of azobenzene groups. The nanocapsules could decompose from large nanocapsule to small U/DCNPs. Due to their optimized size, the nanocapsules can provide a long blood circulation and achieve four-fold tumor accumulation. It can fast eliminate from tumor within one hour and release the loaded drugs for therapy after NIR-induced dissociation.
      PubDate: 2018-01-16T05:20:52.95995-05:0
      DOI: 10.1002/anie.201711354
       
  • Stabilization of the Pentazolate Anion in a Zeolitic Architecture with
           Na20N60 and Na24N60 Nanocages
    • Authors: Qinghua Zhang; Wenquan Zhang, Kangcai Wang, Juecheng Li, Zhien Lin, Siwei Song, Shiliang Huang, Yu Liu, Fude Nie
      Abstract: The experimental detection and synthesis of pentazole (HN5) and its anion (cyclo-N5-) have been actively pursued for the past hundred years in worldwide laboratories. In this study, we describe the synthesis of an aesthetical three-dimensional metal-pentazolate framework (denoted as MPF-1) consisting of sodium ions and cyclo-N5- anions, in which the isolated cyclo-N5- anions are preternaturally stabilized in this inorganic open-framework featuring two types of nanocages (Na20N60 and Na24N60) through strong metal coordination bonds. The compound MPF-1 is indefinitely stable at room temperature and exhibits relatively high thermal stability than the reported cyclo-N5- salts. This finding offers a new approach to create metal-pentazolate frameworks (MPFs) and enables the future exploration of interesting pentazole chemistry and also related functional materials.
      PubDate: 2018-01-16T04:50:25.134509-05:
      DOI: 10.1002/anie.201710602
       
  • Fe2Si5N8 - Access to Open-Shell Transition Metal Nitridosilicates
    • Authors: Philipp Bielec; Oliver Janka, Theresa Block, Rainer Pöttgen, Wolfgang Schnick
      Abstract: Highly condensed nitridosilicates doped with Eu2+ or Ce3+ play an important role in saving energy by converting the blue light of (In,Ga)N-LEDs. Although nitridosilicates are known for great structural variety based on covalent anionic Si-N networks, elemental variety is restricted. Presenting a significant extension of the latter, this work describes a general access to open-shell transition metal nitridosilicates. As proof of principle the first iron nitridosilicate, namely Fe2Si5N8 was prepared by exchanging Ca2+ in α Ca2Si5N8 applying a FeCl2 melt (salt metathesis). The title compound was analyzed by powder X ray diffraction, EDX, ICP-OES, combustion analysis, TG/DSC, Mössbauer spectroscopy and magnetic susceptibility measurements. Furthermore, the structure of α Ca2Si5N8 was determined at 1073 and 1173 K confirming the α [Si5N8]4−-network providing possible migration pathways for the ion exchange reaction.
      PubDate: 2018-01-16T04:23:02.335168-05:
      DOI: 10.1002/anie.201713006
       
  • Rhodium-Catalyzed Enantioposition-Selective Hydroarylation of
           Divinylphosphine Oxides with Aryl Boroxines
    • Authors: Zhe Wang; Tamio Hayashi
      Abstract: The rhodium-catalyzed hydroarylation of divinylphosphine oxides (RP(O)(CH=CH2)2) with aryl boroxines ((ArBO)3) gives the corresponding monoarylation products (RP(O)(CH=CHAr)CH2CH3) in high yields. One of the two vinyl groups in the phosphine oxide undergoes oxidative arylation while the other one is reduced to an ethyl moiety. These reactions proceed with high selectivity in terms of the enantiotopic vinyl groups in the presence of (R)-DTBM-segphos/Rh to give the P-stereogenic monoarylation products with high enantioselectivity.Oxidation and reduction: The rhodium-catalyzed hydroarylation of divinylphosphine oxides with aryl boroxines results in the corresponding monoarylation products by oxidative arylation of one of the two vinyl groups and reduction of the second one to an ethyl moiety. These reactions proceed with high enantioselectivity in the presence of (R)-DTBM-segphos/Rh.
      PubDate: 2018-01-16T04:11:17.434374-05:
      DOI: 10.1002/anie.201712572
       
  • Regulation of Coordination Number over Single Co Sites: Triggering the
           Efficient Electroreduction of CO2
    • Authors: Xiaoqian Wang; Zhao Chen, Xuyan Zhao, Tao Yao, Wenxing Chen, Rui You, Changming Zhao, Geng Wu, Jing Wang, Weixin Huang, Jinlong Yang, Xun Hong, Shiqiang Wei, Yuen Wu, Yadong Li
      Abstract: The design of active, selective, and stable CO2 reduction electrocatalysts is still challenging. A series of atomically dispersed Co catalysts with different nitrogen coordination numbers were prepared and their CO2 electroreduction catalytic performance was explored. The best catalyst, atomically dispersed Co with two-coordinate nitrogen atoms, achieves both high selectivity and superior activity with 94 % CO formation Faradaic efficiency and a current density of 18.1 mA cm−2 at an overpotential of 520 mV. The CO formation turnover frequency reaches a record value of 18 200 h−1, surpassing most reported metal-based catalysts under comparable conditions. Our experimental and theoretical results demonstrate that lower a coordination number facilitates activation of CO2 to the CO2.− intermediate and hence enhances CO2 electroreduction activity.A remarkable carbon dioxide electroreduction catalytic performance with superior activity and high selectivity was achieved on atomically dispersed Co sites through coordination environment regulating. First step in picture: C–N fragments, 1000 °C; second step: NH3 treatment.
      PubDate: 2018-01-16T04:10:57.05891-05:0
      DOI: 10.1002/anie.201712451
       
  • Cationic Metallo-Polyelectrolytes for Robust Alkaline Anion-Exchange
           Membranes
    • Authors: Tianyu Zhu; Shichao Xu, Anisur Rahman, Emir Dogdibegovic, Peng Yang, Parasmani Pageni, Mohammad Pabel Kabir, Xiao-dong Zhou, Chuanbing Tang
      Abstract: Chemically inert, mechanically tough, cationic metallo-polyelectrolytes were conceptualized and designed as durable anion-exchange membranes (AEMs). Ring-opening metathesis polymerization (ROMP) of cobaltocenium-containing cyclooctene with triazole as the only linker group, followed by backbone hydrogenation, led to a new class of AEMs with a polyethylene-like framework and alkaline-stable cobaltocenium cation for ion transport. These AEMs exhibited excellent thermal, chemical and mechanical stability, as well as high ion conductivity.Ring-opening metathesis polymerization of cobaltocenium-containing cyclooctene with triazole as the only linker group, followed by backbone hydrogenation, has led to a new class of anion-exchange membranes (AEMs) with a polyethylene-like framework and alkaline-stable cobaltocenium cations for the ion transport. The AEMs show excellent thermal, chemical and mechanical stability, as well as high ion conductivity.
      PubDate: 2018-01-16T04:10:34.292473-05:
      DOI: 10.1002/anie.201712387
       
  • A Terminal Fluoride Ligand Generates Axial Magnetic Anisotropy in
           Dysprosium Complexes
    • Authors: Lucie Norel; Lucy E. Darago, Boris Le Guennic, Khetpakorn Chakarawet, Miguel I. Gonzalez, Jacob H. Olshansky, Stéphane Rigaut, Jeffrey R. Long
      Abstract: The first dysprosium complexes with a terminal fluoride ligand are obtained as air-stable compounds. The strong, highly electrostatic dysprosium–fluoride bond generates a large axial crystal-field splitting of the J=15/2 ground state, as evidenced by high-resolution luminescence spectroscopy and correlated with the single-molecule magnet behavior through experimental magnetic susceptibility data and ab initio calculations.A strong donor terminal fluoride ligand generates large crystal-field splittings within dysprosium(III) complexes and gives rise to new air-stable single molecule magnets with large barriers to magnetic relaxation. High-resolution luminescence spectroscopy data are presented and correlated with the single-molecule magnet behavior through experimental magnetic susceptibility data and ab initio calculations.
      PubDate: 2018-01-16T04:00:56.712645-05:
      DOI: 10.1002/anie.201712139
       
  • A Keggin Polyoxometalate Shows Water Oxidation Activity at Neutral pH:
           POM@ZIF-8, an Efficient and Robust Electrocatalyst
    • Authors: Subhabrata Mukhopadhyay; Joyashish Debgupta, Chandani Singh, Aranya Kar, Samar K. Das
      Abstract: Keggin-type polyoxometalate anions [XM12O40]n− are versatile, as their applications in interdisciplinary areas show. The Keggin anion [CoW12O40]6− turns into an efficient and robust electrocatalyst upon its confinement in the well-defined void space of ZIF-8, a metal–organic framework (MOF). [H6CoW12O40]@ZIF-8 is so stable to water oxidation that it retains its initial activity even after 1000 catalytic cycles. The catalyst has a turnover frequency (TOF) of 10.8 mol O2(mol Co)−1 s−1, one of the highest TOFs for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoOx in this electrocatalyic water oxidation.Active upon encapsulation: An efficient (turnover frequency ca. 11 s−1) and robust electrochemical water oxidation catalyst was designed and synthesized by exploring host–guest chemistry between two catalytically inactive components, zeolitic imidazolate framework-8 and a Keggin polyoxometalate anion. The encapsulated unsubstituted Keggin anion shows water oxidation activity at neutral pH.
      PubDate: 2018-01-16T04:00:47.423401-05:
      DOI: 10.1002/anie.201711920
       
  • A Photoinduced Reversible Phase Transition in a Dipeptide Supramolecular
           Assembly
    • Authors: Xianbao Li; Jinbo Fei, Youqian Xu, Dongxiang Li, Tingting Yuan, Guangle Li, Chenlei Wang, Junbai Li
      Abstract: Tunable supramolecular assembly has found various applications in biomedicine, molecular catalysis, optoelectronics, and nanofabrication. Unlike traditional covalent conjugation, non-covalent introduction of a photoswitchable moiety enables reversible photomodulation of non-photosensitive dipeptide supramolecular assembly. Under light illumination, a long-lived photoacid generator releases a proton and mediates the dissociation of dipeptide-based organogel, thereby resulting in sol formation. Under darkness, the photoswitchable moiety entraps a proton, resulting in gel regeneration. Furthermore, accompanying the isothermal recycled gel–sol transition in a spatially controlled manner, renewable patterns are spontaneously fabricated. This new concept of light-controlled phase transition of amino acid-based supramolecular assemblies will open up the possibility of wide applications.Introducing a long-lived photoacid generator non-covalently enables reversible photomodulation of phase transition in dipeptide supramolecular assembly. Accompanying the isothermal recycled gel–sol transition in a spatially controlled manner, renewable patterns are spontaneously fabricated.
      PubDate: 2018-01-16T03:56:36.407086-05:
      DOI: 10.1002/anie.201711547
       
  • An Aluminum–Sulfur Battery with a Fast Kinetic Response
    • Authors: Huicong Yang; Lichang Yin, Ji Liang, Zhenhua Sun, Yuzuo Wang, Hucheng Li, Kuang He, Lipo Ma, Zhangquan Peng, Siyao Qiu, Chenghua Sun, Hui-Ming Cheng, Feng Li
      Abstract: The electrochemical performance of the aluminum-sulfur (Al-S) battery has very poor reversibility and a low charge/discharge current density owing to slow kinetic processes determined by an inevitable dissociation reaction from Al2Cl7− to free Al3+. Al2Cl6Br− was used instead of Al2Cl7− as the dissociation reaction reagent. A 15-fold faster reaction rate of Al2Cl6Br− dissociation than that of Al2Cl7− was confirmed by density function theory calculations and the Arrhenius equation. This accelerated dissociation reaction was experimentally verified by the increase of exchange current density during Al electro-deposition. Using Al2Cl6Br− instead of Al2Cl7−, a kinetically accelerated Al-S battery has a sulfur utilization of more than 80 %, with at least four times the sulfur content and five times the current density than that of previous work.A major hindrance of Al-S batteries is slow kinetics, leading to a low charge/discharge current density and low sulfur content. The relationship between the electrochemical kinetics and the electrolyte was explored, focusing on accelerating the rate-determining step (dissociation of Al2X7− anions in ionic-liquid electrolyte). Using Al2Cl6Br− instead of Al2Cl7− led to faster dissociation and an improvement of electrochemical performance.
      PubDate: 2018-01-16T03:56:11.500252-05:
      DOI: 10.1002/anie.201711328
       
  • A BN Aromatic Ring Strategy for Tunable Hydroxy Content in Polystyrene
    • Authors: Heidi L. van de Wouw; Jae Young Lee, Elorm C. Awuyah, Rebekka S. Klausen
      Abstract: BN 2-vinylnaphthalene, a BN aromatic vinyl monomer, is copolymerized with styrene under free radical conditions. Oxidation yields styrene–vinyl alcohol (SVA) statistical copolymers with tunable hydroxy group content. Comprehensive spectroscopic investigation provides proof of structure. Physical properties that vary systematically with hydroxy content include solubility and glass transition temperature. BN aromatic polymers represent a platform for the preparation of diverse functional polymeric architectures via the remarkable reaction chemistry of C−B bonds.A versatile strategy for functional polymer synthesis is described. An aromatic cage around a vinyl boron compound lends it styrene-like reactivity, while postpolymerization oxidation reveals a hydroxy functional group.
      PubDate: 2018-01-16T03:50:36.378109-05:
      DOI: 10.1002/anie.201711650
       
  • Formation and Isolation of a Four-Electron-Reduced Porphyrin Derivative by
           Reduction of a Stable 20π Isophlorin
    • Authors: Wataru Suzuki; Hiroaki Kotani, Tomoya Ishizuka, Yoshihito Shiota, Kazunari Yoshizawa, Takahiko Kojima
      Abstract: The two-electron reduction of a diprotonated dodecaphenylporphyrin derivative by Na2S2O4 gave a corresponding isophlorin (Iph) selectively. Formation of Iph was confirmed by spectroscopic measurements and the isolation of tetramethylated Iph. Further reduction of Iph proceeded to form an unprecedented four-electron-reduced porphyrin (IphH2), which was fully characterized by spectroscopic and X-ray crystallographic analysis. IphH2, with a unique conformation, could be oxidized to reproduce the starting porphyrin, resulting in a proton-coupled four-electron reversible redox system.A four-electron-reduced porphyrin was fully characterized by X-ray crystallography and was found to have a unique conformation. Additionally, this reduced porphyrin could be oxidized to afford the starting porphyrin, resulting in a proton-coupled four-electron reversible redox system.
      PubDate: 2018-01-16T03:46:30.48687-05:0
      DOI: 10.1002/anie.201711058
       
  • Temperature-Selective Dual Radical Generation from Alkyl Diiodide:
           Applications to Synthesis of Asymmetric CABC Multi-Block Copolymers and
           Their Unique Assembly Structures
    • Authors: Jie Zheng; Chen-Gang Wang, Yu Yamaguchi, Michihiko Miyamoto, Atsushi Goto
      Abstract: Temperature-selective radical generation from a newly designed alkyl diiodide (I−R2−R1−I) was studied. R1−I and I−R2 had different reactivities for generating alkyl radicals in the presence of a tetraoctylammonium iodide (ONI) catalyst. Taking advantage of the temperature selectivity, we used the alkyl diiodide as a dual initiator in ONI-catalyzed living radical polymerization to uniquely synthesize CABC non-symmetric multi-block copolymers. Because of their non-symmetric structure, CABC multi-block copolymers form unique assemblies, that is, Janus-type particles with hetero-segment coronas and flower-like particles with hetero-segment petals.An alkyl diiodide (I−R2−R1−I) served as a temperature-selective dual initiator in organocatalyzed living radical polymerization to synthesize CABC non-symmetric multi-block copolymers. Taking advantage of the non-symmetric structure, a Janus-type particle with hetero-segment coronas and a flower-like particle with hetero-segment petals were synthesized as new types of nanoparticles.
      PubDate: 2018-01-16T03:45:48.862155-05:
      DOI: 10.1002/anie.201710964
       
  • Potassium Amide-Catalyzed Benzylic C−H Bond Addition of
           Alkylpyridines to Styrenes
    • Authors: Dan-Dan Zhai; Xiang-Yu Zhang, Yu-Feng Liu, Lei Zheng, Bing-Tao Guan
      Abstract: The benzylic functionalization of alkylpyridines is an important pathway for pyridine derivatives synthesis. The reaction partners, however, were mostly limited to highly reactive polar electrophiles. Herein, we report a potassium amide-catalyzed selective benzylic C−H bond addition of alkylpyridines to styrenes. Potassium bis(trimethylsilyl)amide (KHMDS), a readily available Brønsted base, showed excellent catalytic activity and chemoselectivity. A series of alkylpyridine derivatives, including benzylic quaternary carbon substituted pyridines, were obtained in good to high yield. Preliminary mechanistic studies revealed that the deprotonation equilibrium is probably responsible for the excellent selectivity.The simpler the better: A potassium amide-catalyzed selective benzylic C−H bond addition of alkylpyridines to styrenes was achieved for the first time. Potassium bis(trimethylsilyl)amide (KHMDS), a simple and readily available Brønsted base catalyst, displayed excellent activity and selectivity for the alkylation of alkylpyridines.
      PubDate: 2018-01-16T03:45:40.493378-05:
      DOI: 10.1002/anie.201710128
       
  • Fourier Transform Surface Plasmon Resonance (FTSPR) with Gyromagnetic
           Plasmonic Nanorods
    • Authors: Insub Jung; Haneul Yoo, Hee-Jeong Jang, Sanghyun Cho, Kyungeun Lee, Seunghun Hong, Sungho Park
      Abstract: An unprecedented active and dynamic sensing platform based on a LSPR configuration that is modulated by using an external magnetic field is reported. Electrochemically synthesized Au/Fe/Au nanorods exhibited plasmonically active behavior through plasmonic coupling, and the middle ferromagnetic Fe block responded to a magnetic impetus, allowing the nanorods to be modulated. The shear force variation induced by the specific binding events between antigens and antibodies on the nanorod surface is used to enhance the sensitivity of detection of antigens in the plasmonics-based sensor application. As a proof-of-concept, influenza A virus (HA1) was used as a target protein. The limit of detection was enhanced by two orders of magnitude compared to that of traditional LSPR sensing.FTSPR: Simple LSPR-based biosensing combined with magnetic rotation by introducing a ferromagnetic Fe segment into plasmonic Au blocks by an electrochemical method is demonstrated. By introducing specific binding events, a dynamically perturbed system was realized, resulting in the frequency lag of nanorods above a critical driving frequency that was analyzed by Fourier transformation.
      PubDate: 2018-01-16T03:45:27.520409-05:
      DOI: 10.1002/anie.201710619
       
  • Reversible CO2 Addition to Si=O Bond and Synthesis of a Persistent
           SiO2-CO2-Cycloadduct Stabilized by a Lewis Donor-Acceptor Ligand
    • Authors: Tsuyoshi Kato; Ricardo Rodriguez, Isabel Alvarado-Beltran, Jérémy Saouli, Antoine Baceiredo, Nathalie Saffon-Merceron, Vicenç Branchadell
      Abstract: The donor-stabilized sila--lactone reacts with CO2 via a [2+2]-cycloaddition to form the spiro-cyclic silicon carbonate derivative. Of particular interest, this process is reversible at room temperature. Furthermore, the photolysis of resulting CO2 adduct affords the first persistent SiO2-CO2 mixed dimer (SiCO4), presenting a Si2O4-like structure, which is stabilized by a Lewis donor-acceptor type ligand. As predicted by theoretical calculations, in marked contrast to Si2O4, the mixed dimer SiCO4 is labile and readily releases CO2.
      PubDate: 2018-01-15T21:51:24.130319-05:
      DOI: 10.1002/anie.201709787
       
  • Ag(I)-catalyzed widely applicable aerobic 1,2-diol oxidative cleavage
    • Authors: Zhong-zhen Zhou; Mingxin Liu, Leiyang Lv, Chao-Jun Li
      Abstract: The oxidative cleavage of 1,2-diol is one of the fundamental organic transformations. Up to now, stoichiometric oxidants such as H5IO6, Pb(OAc)4, or KMnO4 are still predominantly employed to carry out such oxidative cleavage, which generate stoichiometric hazardous waste. Herein, we have developed a widely applicable and highly selective Ag(I)-catalyzed oxidative cleavage of 1,2-diol that consume atmospheric oxygen as the sole oxidant, serving as a potentially greener alternative for the classical fundamental transformations.
      PubDate: 2018-01-15T21:51:11.288686-05:
      DOI: 10.1002/anie.201711531
       
  • A non-heme iron photocatalyst for light driven aerobic oxidation of
           methanol
    • Authors: Wesley Richard Browne; Juan Chen, Apparao Draksharapu, Maja Gruden, Stepan Stepanovic
      Abstract: The non-heme (L)FeIII and (L)FeIII-O-FeIII(L) complexes (L = 1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)ethan-1-amine) undergoes reduction under irradiation to the FeII state with concomitant oxidation of methanol to methanal, without the need for a secondary photosensitizer. Spectroscopic and Density Functional Theory (DFT) studies support a mechanism in which irradiation results in charge transfer excitation of a FeIII--O-FeIII complex to generate [(L)FeIV=O]2+ (observed transiently during irradiation in acetonitrile), and an equivalent of LFeII. Under aerobic conditions, irradiation accelerates reoxidation from the FeII to FeIII state with O2 closing the cycle of methanol oxidation to methanal.
      PubDate: 2018-01-15T15:50:33.165169-05:
      DOI: 10.1002/anie.201712678
       
  • Mechanochemical Activation of Iron Cyano Complexes: A Prebiotic Impact
           Scenario for the Synthesis of α-Amino Acid Derivatives
    • Authors: Carsten Bolm; Rita Mocci, Christian Schumacher, Mathias Turberg, Francesco Puccetti, José G. Hernández
      Abstract: Mechanochemical activation of iron cyano complexes by ball milling results in the formation of HCN, which can be trapped and incorporated into α-aminonitriles. This prebiotic impact scenario can be extended by mechanochemically transforming the resulting α-aminonitriles into α-amino amides using a chemical route related to early Earth conditions.
      PubDate: 2018-01-15T11:20:25.713615-05:
      DOI: 10.1002/anie.201713109
       
  • In vivo EPR characterization of semi-synthetic [FeFe] hydrogenases
    • Authors: Livia S. Meszaros; Brigitta Nemeth, Charlene Esmieu, Pierre Ceccaldi, Gustav Berggren
      Abstract: EPR spectroscopy reveals the formation of two different semi-synthetic hydrogenases in vivo. [FeFe] hydrogenases are metalloenzymes that catalyse the interconversion of molecular hydrogen and protons. The reaction is catalyzed by the H-cluster, consisting of a canonical iron-sulfur cluster and an organometallic [2Fe] subsite. It was recently shown how the enzyme can be reconstituted with synthetic cofactors mimicking the composition of the [2Fe] subsite, resulting in semi-synthetic hydrogenases. Here we employ EPR spectroscopy to monitor the formation of two such semi-synthetic enzymes in whole cells. The study provides the first spectroscopic characterization of semi-synthetic hydrogenases in vivo, and the observation of two different oxidized states of the H-cluster under intracellular conditions. Moreover, these findings underscore how synthetic chemistry can be a powerful tool for manipulation and examination of the hydrogenase enzyme under in vivo conditions.
      PubDate: 2018-01-15T10:53:21.63955-05:0
      DOI: 10.1002/anie.201710740
       
  • Cross-Linking/Mass Spectrometry for Studying Protein Structures and
           Protein-Protein Interactions: Where Are We Now and Where Should We Go From
           Here'
    • Authors: Andrea Sinz
      Abstract: Structural mass spectrometry (MS) is gaining increasing importance in deriving valuable three-dimensional structural information on proteins and protein complexes and complements existing techniques, such as NMR spectroscopy and X-ray crystallography. Structural MS unites different MS-based techniques, i.e, hydrogen-deuterium exchange, native MS, ion-mobility MS, protein footprinting, and chemical cross-linking/MS, and allows fundamental questions in structural biology to be addressed. In this article, I will focus on the cross-linking/MS strategy. This method not only delivers tertiary structural information on proteins, but also is increasingly being used to decipher protein interaction networks - both in-vitro and in-vivo. Cross-linking/MS is currently one of the most promising MS-based approaches to derive structural information on very large and transient protein assemblies and intrinsically disordered proteins.
      PubDate: 2018-01-15T07:50:46.101173-05:
      DOI: 10.1002/anie.201709559
       
  • Ultrathin FeOOH Nanolayers with Rich Oxygen Vacancies on BiVO4 Photoanodes
           for Efficient Water Oxidation
    • Authors: Yingpu Bi; Beibei Zhang, Lei Wang, Yajun Zhang, Yong Ding
      Abstract: Photoelectrochemical (PEC) water splitting is a promising method for storing solar energy in the form of hydrogen fuel, but greatly hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Herein, a facile solution impregnation method is developed for growing highly crystalline β-FeOOH nanolayers with ultrathin thickness (2 nm) and abundant oxygen vacancies on BiVO4 photoanodes, which exhibited a remarkable photocurrent density of 4.3 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode (RHE), AM 1.5 G), approximately 2-fold higher than that of amorphous FeOOH fabricated by electrodepositions. Systematic studies reveal that the excellent PEC activity should be attributed to their ultrathin crystalline structure and abundant oxygen vacancies, which could effectively facilitate the hole transport/trapping and provide more active sites for water oxidation.
      PubDate: 2018-01-14T23:20:24.623017-05:
      DOI: 10.1002/anie.201712499
       
  • Catalytic and Atom Economic Csp3 - Csp3 Bond Formation α-to Nitrogen.
           Alkyl Tantalum Ureates for Hydroaminoalkylation
    • Authors: Rebecca C. DiPucchio; Sorin-Claudiu Rosca, Laurel Schafer
      Abstract: Atom-economic and regioselective Csp3-Csp3 bond formation has been achieved by rapid C-H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH2SiMe3)3Cl2, and a ureate N,O-chelating ligand salt gives an in situ prepared catalytic system that can realize high yields of β-alkylated aniline derivatives using either terminal or internal alkene substrates. These new catalyst systems realize C-H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration.
      PubDate: 2018-01-13T00:26:17.503599-05:
      DOI: 10.1002/anie.201712668
       
  • Stereodivergent Synthesis of Tetrahydrofuroindoles via Pd-Catalyzed
           Asymmetric Dearomative Formal [3+2] Cycloaddition Reactions
    • Authors: Shuli You; Qiang Cheng, Fang Zhang, Yue Cai, Yin-Long Guo
      Abstract: Stereodivergent synthesis of tetrahydrofuroindoles via palladium-catalyzed asymmetric dearomative formal [3+2] cycloaddition of nitroindoles with epoxybutenes was developed. Polarity of solvent was found to play as the key role on the switch of diastereoselectivity. In toluene, good to excellent yields (70-99%), diastereo- (87/13->95/5 dr) and enantioselectivity (85/15-94/6 er) were obtained regardless of the properties of substituents on nitroindoles. In acetonitrile, tetrahydrofuroindoles of another diastereoisomer were produced with good to excellent yields (75-98%) and stereoselectivity (78/22-93/7 dr, 93/7-99/1 er). Mechanistic studies were conducted to illustrate the origin of the diastereodivergency. The kinetic experiments indicate that the rate-determining step of this reaction has been altered in different solvents. The ESI-MS experiments also support the existence of the key palladium-complex intermediates and the catalytic cycle of the reaction.
      PubDate: 2018-01-13T00:26:06.926782-05:
      DOI: 10.1002/anie.201711873
       
  • Organometallic Mediated Radical Polymerization of Vinylidene Fluoride
    • Authors: Bruno Michel Ameduri; Rinaldo Poli, Vincent Ladmiral, Sanjib Banerjee, Antoine Debuigne, Christophe Detrembleur
      Abstract: An unprecedented level of control for the radical polymerization of vinylidene fluoride (VDF), yielding well-defined PVDF (at least up to 14,500 g/mol) with low dispersity (≤1.32), was achieved using organometallic mediated radical polymerization (OMRP) with an organocobalt compound as initiator. The high chain-end fidelity was demonstrated by the synthesis of PVDF- and PVAc-containing di-and tri-block copolymers. DFT calculations rationalize the equally efficient reactivation of the dormant species with both head and tail chain ends.
      PubDate: 2018-01-12T13:50:21.932503-05:
      DOI: 10.1002/anie.201712347
       
  • C=O***Isothiouronium Interaction Dictates Enantiodiscrimination in
           Acylative Kinetic Resolution of Tertiary Heterocyclic Alcohols
    • Authors: Mark Greenhalgh; Samuel Smith, Daniel Walden, James Taylor, Zamira Brice, Emily Robinson, Charlene Fallan, David Cordes, Alexandra Slawin, Hannah Camille Richardson, Markas Grove, Paul Cheong, Andrew David Smith
      Abstract: A combination of experimental and computational studies have identified a C=O***isothiouronium interaction as key to efficient enantiodiscrimination in the kinetic resolution of tertiary heterocyclic alcohols bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. This discrimination was exploited in the isothiourea-catalyzed acylative kinetic resolution of tertiary heterocyclic alcohols (38 examples, s up to> 200). The reaction proceeds at low catalyst loadings (generally 1 mol%) using either isobutyric or acetic anhydride as the acylating agent under mild conditions.
      PubDate: 2018-01-12T12:20:42.184485-05:
      DOI: 10.1002/anie.201712456
       
  • An Exceptionally Close, Non-Bonded Hydrogen-Hydrogen Contact with Strong
           Through-Space Spin-Spin Coupling
    • Authors: Yonglong Xiao; Joel T. Mague, Robert A. Pascal
      Abstract: Condensation of 1,8,13-tris(mercaptomethyl)triptycene and tris(bromomethyl)methane yields an in,in-cyclophane with two inwardly directed methine groups. Based on X-ray analysis and DFT and MP2 calculations, the hydrogen-hydrogen non-bonded contact distance is estimated to be 1.50-1.53 Å. In addition, the two in-hydrogen atoms show obvious spin-spin coupling with J = 2.0 Hz.
      PubDate: 2018-01-12T10:50:27.564058-05:
      DOI: 10.1002/anie.201712304
       
  • Benzonorcorrole Ni(II) Complexes: Enhancement of Paratropic Ring Current
           and Singlet Diradical Character by Benzo-Fusion
    • Authors: Takuya Yoshida; Kohtaro Takahashi, Yuki Ide, Ryohei Kishi, Jun-ya Fujiyoshi, Sangsu Lee, Yuya Hiraoka, Dongho Kim, Masayoshi Nakano, Takahisa Ikeue, Hiroko Yamada, Hiroshi Shinokubo
      Abstract: Fused benzene rings to antiaromatic compounds generally improve their stability but attenuate their antiaromaticity. Here we report the opposite case. We have synthesized Ni(II) benzonorcorroles and elucidated the effect of benzo-fusion on the antiaromaticity. The benzo-fusion resulted in significant decrease of the HOMO-LUMO gaps and enhancement of the paratropic ring current effect. Furthermore, the introduction of the benzo groups induced singlet diradical character in the antiaromaric porphyrinoid.
      PubDate: 2018-01-12T06:50:54.517777-05:
      DOI: 10.1002/anie.201712961
       
  • Tetrablock Metallopolymer Electrochromes
    • Authors: Didier Astruc; Haibin Gu, Roberto Ciganda, Patricia Castel, Sergio Moya, Ricardo Hernandez, Jaime Ruiz
      Abstract: Multi-block polymers are highly desirable for their addressable functions that are both unique and complementary among the blocks. With metal-containing polymers, the goal is even more challenging insofar as the metal properties may considerably extend the materials functions to sensing, catalysis, interaction withmetal nanoparticles and electro- or photochrome switching. Ring-opening-metathesis polymerization (ROMP) has become available for the formation of living polymers using highly efficient initiators such as the 3rd-generation Grubbs catalyst [RuCl2(NHC)(=CHPh)(3-Br-C5H4N)2], 1. Among the 24 possibilities to introduce 4 blocks of metallopolymers into a tetrablock metallocopolymer by ROMP using the catalyst 1, we have disclosed two viable pathways. The synthesis, characterization, electrochemistry, electron-transferchemistry and remarkable electrochromic properties of these new nanomaterials are presented herein.
      PubDate: 2018-01-12T05:20:36.591584-05:
      DOI: 10.1002/anie.201712945
       
  • Configurational Isomerism in Polyoxovanadates
    • Authors: Lisa Mahnke; Aleksandar Kondinski, Ulrike Warzok, Christian Näther, Jan van Leusen, Christoph Schalley, Kirill Yu. Monakhov, Paul Kögerler, Wolfgang Bensch
      Abstract: A water-soluble derivative of the polyoxovanadate {V15E6O42} (E = semimetal) archetype enables the study of cluster shell rearrangements driven by supramolecular interactions. A reaction unique to E = Sb, induced exclusively by ligand metathesis in peripheral [NiII(ethylenediamine)] counterions, results in the nearly quantitative formation of the metastable α1* conformational isomer of the {V14Sb8O42} cluster type. Contrary to all other polyoxovanadate shell architectures, this isomer comprises an inward-oriented vanadyl group and is ca. 50 and 12 kJ mol-1 higher in energy than the previously isolated α and isomers, respectively. We discuss this unexpected reaction in light of supramolecular Sb-O···V and Sb-O···Sb contacts manifested in {V14Sb8O42}2 dimers observed in the solid state. ESI MS experiments confirm the stability of these dimers also in solution and in the gas phase. DFT calculations indicate that other, as of yet elusive isomers might be accessible as well.
      PubDate: 2018-01-12T04:50:52.136875-05:
      DOI: 10.1002/anie.201712417
       
  • Catalytic Asymmetric Dearomatization of Indolyl Dihydropyridines via
           Enamine Isomerization/Spirocyclization/Transfer Hydrogenation Sequence
    • Authors: Shuli You; Zi-Lei Xia, Chao Zheng, Shou-Guo Wang
      Abstract: A highly efficient synthesis of enantioenriched spiroindolines by catalytic asymmetric dearomatization of indolyl dihydropyridines via chiral phosphoric acid catalyzed enamine isomerization/spirocyclization/transfer hydrogenation sequence has been developed. This reaction proceeds under mild reaction conditions to afford novel spiroindolines in good yields (up to 88%) with excellent enantioselectivity (up to 97% ee). DFT calculations provide insights into the reaction mechanism as well as the origin of stereochemistry.
      PubDate: 2018-01-11T21:57:58.797023-05:
      DOI: 10.1002/anie.201712435
       
  • From Intramolecular (Circular) in an Isolated Molecule to Intermolecular
           Hole Delocalization in a Two-Dimensional Solid-State Assembly: The Case of
           Pillarene
    • Authors: Maxim Ivanov; Denan Wang, Tushar Navale, Sergey Lindeman, Rajendra Rathore
      Abstract: To achieve long-range charge transport/separation and, in turn, bolster the efficiency of modern photovoltaic devices, new molecular scaffolds are needed that can self-assemble in two-dimensional (2D) arrays while maintaining both intra- and inter-molecular electronic coupling. In an isolated molecule of pillarene, a single hole delocalizes intramolecularly via hopping amongst the circularly arrayed hydroquinone ether rings. The crystallization of pillarene cation radical produces a 2D self-assembly with three intermolecular dimeric (sandwich-like) contacts. Surprisingly, each pillarene in the crystal lattice bears a fractional formal charge of +1.5. This unusual stoichiometry of oxidized pillarene in crystals arises from effective charge distribution within the 2D array via an interplay of intra- and inter-molecular electronic couplings. This important finding is expected to help advance the rational design of efficient solid-state materials for long-range charge transfer.
      PubDate: 2018-01-11T21:57:33.480754-05:
      DOI: 10.1002/anie.201712159
       
  • Reductive Carbocyclization of Homoallylic Alcohols to syn- Cyclobutanes
           via Boron-Catalyzed Dual Ring-Closing Pathway
    • Authors: Chinmoy Kumar Hazra; Jinhoon Jeong, Hyunjoong Kim, Mu-Hyun Baik, Sehoon Park, Sukbok Chang
      Abstract: Organoborane-catalyzed reductive carbocyclization of homoallylic alcohols has been developed by using hydrosilanes as a reducing reagent to provide a range of 1,2-disubstituted arylcyclobutanes. It proceeds in a cis-selective manner with high efficiency under mild conditions. Mechanistic studies including deuterium scrambling and Hammett studies, and DFT calculations allowed to propose a dual ring-closing pathway.
      PubDate: 2018-01-11T21:56:24.623602-05:
      DOI: 10.1002/anie.201713285
       
  • Active Intracellular Delivery of Cas9-sgRNA Complex Using
           Ultrasound-Propelled Nanomotors
    • Authors: Malthe Hansen-Bruhn; Berta Esteban-Fernandez de Avila, Mara Beltrán-Gastélum, Jing Zhao, Doris E. Ramírez-Herrera, Pavimol Angsantikul, Kurt Vesterager Gothelf, Liangfang Zhang, Joseph Wang
      Abstract: Direct and rapid intracellular delivery of functional Cas9-sgRNA complex using ultrasound-powered nanomotors is reported. The Cas9-sgRNA complex is loaded onto the nanomotors surface through a reversible disulfide linkage. A 5-min ultrasound treatment enables the Cas9-sgRNA-loaded nanomotors to directly penetrate through the plasma membrane of GFP-expressing B16F10 cells. The carried Cas9-sgRNA is released inside the cells achieving highly effective GFP-gene knockout. The acoustic Cas9-sgRNA-loaded nanomotors display more than 80% GFP-knockout within 2 h of cell incubation compared to 30% knockout using static nanowires. More impressively, the nanomotors enable high-efficient knockout with just 0.6 nM of the Cas9-sgRNA complex. This nanomotor-based intracellular delivery method thus offers an attractive route to overcome physiological barriers for intracellular delivery of functional proteins and RNAs, indicating considerable promise for highly efficient therapeutic applications.
      PubDate: 2018-01-11T13:50:32.450096-05:
      DOI: 10.1002/anie.201713082
       
  • Copper-Catalyzed Enantioselective Arylative Desymmetrization of Prochiral
           Cyclopentenes with Diaryliodonium Salts
    • Authors: Hua Wu; Qian Wang, Jieping Zhu
      Abstract: A copper-catalyzed enantioselective arylative desymmetrization of prochiral cyclopentenes with diaryliodonium salts was developed. In the presence of a catalytic amount of the in situ generated chiral copper-bisoxazoline complex, reaction of 4-substituted or 4,4-disubstituted cyclopent-1-enes with the diaryliodonium hexafluoroarsenate afforded the chiral arylated products in good yields with excellent enantioselectivities. Use of the cyclohexyl-containing Box ligand was essential for the high enantioselectivity. Transformation of the enantioenriched adducts to other chiral building blocks was also documented.
      PubDate: 2018-01-11T09:51:13.553825-05:
      DOI: 10.1002/anie.201713329
       
  • Solvation-induced changes of the mechanism of alcohol oxidation at aqueous
           versus gas phase Au/TiO₂ nanocatalysts
    • Authors: Daniel Muñoz-Santiburcio; Matteo Farnesi Camellone, Dominik Marx
      Abstract: Gold/titania catalysts are widely used for key reactions, notably including the selective oxidation of alcohols in the liquid phase. Our large-scale ab initio simulations disclose that the liquid-phase reaction mechanism is distinctly different from that in the gas phase due to active participation of water molecules. While concerted charge transfers related to O₂ splitting and abstraction of both, protonic and hydridic hydrogens are enforced under dry conditions, stepwise charge transfer is preferred in the condensed phase. Dissociation of reactive water molecules and subsequent Grotthuss migration of protonic defects, H+(aq), allows for such a decoupling of the oxidation process, both in time and space. It is expected that these observations are paradigmatic for heterogeneous catalysis in aqueous phases.
      PubDate: 2018-01-11T05:36:41.165672-05:
      DOI: 10.1002/anie.201710791
       
  • Light-Driven Shape Memory Porous Films with Precisely Controlled
           Dimensions
    • Authors: Wei Wang; Dingfeng Shen, Xiao Li, Yuan Yao, Jiaping Lin, Aurelia Wang, Jiwoo Yu, Zhonglin Wang, Suck Won Hong, Shaoliang Lin, Zhiqun Lin
      Abstract: Here we report an unconventional strategy for crafting light-driven shape memory porous films (SMPFs) by judiciously constructing highly ordered porous films via a facile "breath figure" approach, followed by sequential vapor crosslinking and nondestructive directional light manipulation. The latter can conveniently and precisely transform round micropores into other shapes including round-rectangle, round-rhombus and size-reduced micropores at room temperature. Importantly, the transformed micropores can be perfectly reverted to original shapes by either thermal annealing or UV irradiation. As such, this strategy expands the rich diversity of SMPs accessible, particularly SMPFs of different shapes, compositions and functionalities, and has promising potential to underpin future advances in electronics, photonics, robust membrane for efficient separation and purification, functional biomaterials for the regenerative therapy, among other areas.
      PubDate: 2018-01-11T05:32:03.79529-05:0
      DOI: 10.1002/anie.201712100
       
  • Dicationic E4 chains (E = P, As, Sb, Bi) embedded in the coordination
           sphere of transition metals
    • Authors: Manfred Scheer; Luis Dütsch, Martin Fleischmann, Stefan Welsch, Gabor Balaszs, Werner Kremer
      Abstract: A comparison of the oxidation chemistry of the complexes [{CpMo(CO)2}2(µ,η2:η2-E2)] (E = P (A), As (B), Sb (C), Bi (D)) is presented. The oxidation of A-D with [Thia]+ (= [C12H8S2]+) results in the selective formation of the dicationic E4 complexes [{CpMo(CO)2}4(µ4,η2:η2:η2:η2-E4)]2+ (E = P (1), As (2), Sb (3), Bi (4)) stabilized by four [CpMo(CO)2] fragments. The formation of the corresponding monocations [A]+, [C]+ and [D]+ could not be detected by cyclovoltammetry, EPR or NMR spectroscopy. This suggests a fast dimerization and no dissociation in solution, which is also predicted by DFT calculations. However, EPR measurements of 2 prove small amounts of the radical cation [B]+ in solution. Single crystal X-ray diffraction reveals that the products 1 and 2 show a zigzag E4 chain in the solid state, while 3 and 4 bear a central E4 cage exhibiting a distorted "butterfly-like" geometry. Additionally, 1 can be easily reversibly converted into a symmetric and an asymmetric form.
      PubDate: 2018-01-11T05:31:56.324805-05:
      DOI: 10.1002/anie.201712884
       
  • Catalytic Desymmetrizing Dehydrogenation of 4-Substituted Cyclohexanones
           through Enamine Oxidation
    • Authors: Lihui Zhu; Long Zhang, Sanzhong Luo
      Abstract: A chiral primary amine catalyzed desymmetric dehydrogenation process is herein described. The reaction proceeds via ketone enamine oxidation by IBX and enables highly enantioselective desymmetrization of 4-substituted cyclohexanones, generating chiral 4-substituted cyclohexanones bearing remote γ-stereocenter.
      PubDate: 2018-01-11T05:31:44.207919-05:
      DOI: 10.1002/anie.201713327
       
  • Interconversion of Molybdenum Imido and Amido Complexes by Proton Coupled
           Electron Transfer
    • Authors: Paul James Chirik; Mate Bezdek
      Abstract: Interconversion of the molybdenum amido [(PhTpy)(PPh2Me)2Mo(NHtBuAr)][BArF24] [PhTpy = 4'-Ph-2,2',6',2"-terpyridine; tBuAr = 4-tert-butyl-C6H4; ArF24 = (C6H3-3,5-(CF3)2)4)] and imido [(PhTpy)(PPh2Me)2Mo(NtBuAr)][BArF24] complexes has been accomplished by proton coupled electron transfer (PCET). Tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(PhTpy)(PPh2Me)2Mo(NH3)][BArF24] as the reductant. The amido N-H BDFE formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal/mol, in agreement with a DFT-computed value of 48 kcal/mol. The N-H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N-H bond forming sequence and favor initial electron transfer or concerted pathways.
      PubDate: 2018-01-10T08:55:29.285249-05:
      DOI: 10.1002/anie.201708406
       
  • Novel Active Molybdenum-Based Anode for Dehydrogenative Coupling Reactions
    • Authors: Siegfried R Waldvogel; Sebastian B Beil, Timo Müller, Sydney Sillart, Peter Franzmann, Alexander Bomm, Michael Holtkamp, Uwe Karst, Wolfgang Schade
      Abstract: A new and powerful active anode system that can be operated in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) was found. The molybdenum anode forms in HFIP a compact, conductive, and electroactive layer of higher-valent molybdenum species. This system can be used to replace powerful but stoichiometrically required Mo(V) reagents for dehydrogenative coupling of aryls. The performance of this electrolytic protocol is more sustainable and allows the conversion of a broad scope of activated arenes.
      PubDate: 2018-01-10T04:56:35.479913-05:
      DOI: 10.1002/anie.201712718
       
  • Enantioselective Desymmetrization of Cyclobutanones Enabled by Synergistic
           Pd/Enamine Catalysis
    • Authors: Meng Wang; Jun Chen, Zongjia Chen, Changxu Zhong, Ping Lu
      Abstract: The enantioselective intramolecular -arylation of cyclobutanone has been established by combining palladium and enamine catalyst system. Two different enantioselective control strategies have been developed for substrates bearing O- or N- tethered aryl bromides and cyclobutanones respectively. Further synthetic applications are also reported.
      PubDate: 2018-01-09T22:56:26.437281-05:
      DOI: 10.1002/anie.201711845
       
  • Molecular Firefighting - How Modern Phosphorus Chemistry Can Help Solve
           the Flame Retardancy Task
    • Authors: Maria M Velencoso; Alexander Battig, Jens C Markwart, Bernhard Schartel, Frederik Roman Wurm
      Abstract: The ubiquity of polymeric materials in daily life comes at an increased fire risk, and enduring research into efficient flame retardants is the key to ensuring the safety of the populace and material goods from accidental fires. Phosphorus, a versatile and effective element for use in flame retardants, has the potential to supersede halogenated variants still widely used today: current formulations employ a variety of modes of action and methods of implementation, as additives or as reactants, to solve the task of flame retarding polymeric materials. Phosphorus flame retardants can act in both the gas and condensed phase during a fire. This review investigates how current phosphorus chemistry helps in reducing flammability of polymers, and addresses the future of sustainable, efficient and safe phosphorus-based flame retardant chemistry from renewable sources.
      PubDate: 2018-01-09T21:57:23.366602-05:
      DOI: 10.1002/anie.201711735
       
  • Total Synthesis of Aurofusarin: Studies of the Atropisomeric Stability of
           Bis-Naphthoquinones
    • Authors: John Porco; Chao Qi, Wenyu Wang, Kyle Reichl, James McNeely
      Abstract: An efficient annulation involving pyrone addition to a quinone and Dieckmann condensation has been developed for rapid assembly of a γ-naphthopyrone monomeric precursor to the bis-naphthoquinone natural product aurofusarin. Dimerization was achieved through Pd(II)-catalyzed dehydrogenative coupling. Further studies employing asymmetric nucleophilic epoxidation indicate that the atropisomers of aurofusarin and derivatives are not configurationally stable at ambient temperature.
      PubDate: 2018-01-09T21:56:02.795177-05:
      DOI: 10.1002/anie.201711535
       
  • From Designing the Molecules of Life to Designing Life: Future
           Applications Derived from Advances in DNA Technologies
    • Authors: Richie E Kohman; Aditya M Kunjapur, Eriona Hysolli, Yu Wang, George M. Church
      Abstract: Since the elucidation of its structure, DNA has been at the forefront of biological research. In the past half century, an explosion of DNA-based technology development has occurred with the most rapid advances being made for DNA sequencing. In parallel, dramatic improvements have also been made in the synthesis and editing of DNA from the oligonucleotide to the genome scale. In this Review, we will summarize four different subfields relating to DNA technologies following this trajectory of smaller to larger scale. We begin by talking about building materials out of DNA which in turn can act as delivery vehicles in vivo. We then discus how altering microbial genomes can lead to novel methods of production for industrial biologics. Next, we talk about the future of writing whole genomes as a method of studying evolution. Lastly, we highlight the ways in which barcoding biological systems will allow for their three dimensional analysis in a highly multiplexed fashion.
      PubDate: 2018-01-09T14:20:51.545584-05:
      DOI: 10.1002/anie.201707976
       
  • Spectroscopic Characterization of a [C-F-C]+ Fluoronium Ion in Solution
    • Authors: Cody Ross Pitts; Maxwell Gargiulo Holl, Thomas Lectka
      Abstract: We report the first spectroscopic evidence for a [C-F-C]+ fluoronium ion in solution. Extensive NMR studies (19F, 1H, 13C) characterize a symmetrical cage-like species in which fluorine exhibits substantial covalent bonding to each of the two carbon atoms involved in the three-center interaction. Experimental NMR data comport well with calculated values to lend credence to the structural assignment. As the culminating experiment, the Saunders isotopic perturbation test definitively confirms a symmetrical structure. Congruent with the trend in other types of onium ions, the calculated charge at fluorine moves in a more positive (less negative) direction from the neutral. It is this important trend that explains in part the extraordinary historical difficulty in making theoretical predictions of fluoronium ions come true in solution, and why it takes fluorine captured in a cage to produce, finally, a stable ion and complete the historical arc of the organic halonium ion story.
      PubDate: 2018-01-09T10:20:30.163708-05:
      DOI: 10.1002/anie.201712021
       
  • Cobalt Bridged with Ionic Liquid Polymer on Carbon Nanotube for Enhanced
           Oxygen Evolution Reaction Activity
    • Authors: Yuxiao Ding; Alexander Klyushin, Xing Huang, Travis Jones, Detre Teschner, Frank Girgsdies, Tania Rodenas, Robert Schlögl, Saskia Heumann
      Abstract: By taking inspiration from the catalytic properties of single-site catalysts and the enhancement of performance through ionic liquids on metal catalysts, we exploited a scalable way to deliberately place single cobalt ions on carbon nanotube surface bridged by polymerized ionic liquid. Single dispersed cobalt ions coordinated by ionic liquid are used as heterogeneous catalysts for the oxygen evolution reaction (OER). Performance data reveals high activity and stable operation without chemical instability.
      PubDate: 2018-01-09T06:50:53.904179-05:
      DOI: 10.1002/anie.201711688
       
  • Dual Ligand-Enabled Non-Directed C-H Olefination of Arenes
    • Authors: Hao Chen; Philipp Wedi, Tim Meyer, Ghazal Tavakoli, Manuel van Gemmeren
      Abstract: The applicability of the Pd-catalyzed oxidative C-H olefination of arenes, also known as the Fujiwara-Moritani reaction, has traditionally been limited by the requirement for directing groups on the substrate or the need to use the arene in large excess, typically as (co)solvent. Herein we report the development of a catalytic system that, through the combined action of two complimentary ligands, enables the use of directing group free arenes as limiting reagents for the first time. The reactions proceed under a combination of both steric and electronic control and enable the application of this powerful reaction to valuable arenes, which cannot be utilized in excess.
      PubDate: 2018-01-09T03:50:26.198877-05:
      DOI: 10.1002/anie.201712235
       
  • A sulfoxide-based isobaric labelling reagent for accurate quantitative
           mass spectrometry
    • Authors: Michael Stadlmeier; Jana Bogena, Miriam Wallner, Thomas Carell
      Abstract: Modern proteomics requires reagents for exact quantification of peptides in complex mixtures. Peptide labelling is most typically achieved with isobaric tags that consist of a balancer and a reporter part that separate in the gas phase. An ingenious distribution of stable isotopes provides multiple reagents with identical molecular weight but a different mass of the reporter groups, allowing relative quantification of multiple samples in one measurement. Current generation reagents require a high fragmentation energy for cleavage, leading to incomplete fragmentation and hence loss of signal intensity. Here we report a new isobaric labelling reagent, where the balancer and the reporter are linked by a sulfoxide group, which, based on the sulfoxide pyrolysis, leads to easy and asymmetric cleavage at low fragmentation energy. The fragmentation of our new design is significantly improved, yielding more intense complementary ion signals, allowing complementary ion cluster analysis as well.
      PubDate: 2018-01-08T12:20:38.672077-05:
      DOI: 10.1002/anie.201708867
       
  • Modifying the Sterics In the Second Coordination Sphere Of Designed
           Peptides Leads to Enhancement of Nitrite Reductase Activity
    • Authors: Karl Koebke; Fangting Yu, Elvin Salerno, Casey Van Stappen, Alison Tebo, James Penner-Hahn, Vincent Louis Pecoraro
      Abstract: Protein design is a useful strategy to interrogate the protein structure-function relationship. We demonstrate using a highly modular 3-stranded Coiled Coil (TRI-peptide system) that a functional type 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and water. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75-fold compared to previously reported systems. We find also that steric bulk can be used to enforce a three-coordinate Cu(I) in a site, which tends toward two-coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metal center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.
      PubDate: 2018-01-08T11:20:24.822771-05:
      DOI: 10.1002/anie.201712757
       
  • Cation-Tuned Synthesis of Fluorooxoborates: Approaching the Optimal
           Deep-Ultraviolet Nonlinear Optical Materials
    • Authors: Ying Wang; Bingbing Zhang, Zhihua Yang, Shilie Pan
      Abstract: Developing new nonlinear optical (NLO) materials for deep-ultraviolet (DUV) applications is in great demand. However, it is still a serious material discovery challenge to synthesize an ideal DUV NLO crystal. Here, three new alkali metal fluorooxoborates in a family, AB4O6F (A = K, Rb, and Cs, and mixed cation between two of them), were successfully synthesized by cation regulation. It is found that all reported compounds exhibit short UV absorption edges (
      PubDate: 2018-01-08T07:20:36.888922-05:
      DOI: 10.1002/anie.201712168
       
  • Selective production of renewable para-xylene via tungsten
           carbide-catalyzed atom-economic cascade reactions
    • Authors: Changzhi Li; Tao Dai, Lin Li, Zongbao Kent Zhao, Bo Zhang, Yu Cong, Aiqin Wang
      Abstract: Tungsten carbide was employed as a catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA), the product of Diels-Alder reaction between two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization-hydrodeoxygenation cascade pathway via intramolecular hydrogen transfer without involving any external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W2C surface. Notably, the new process is readily applicable to the synthesis of various (multi)methylated benzenes from bio-based building blocks, thus providing a potentially petroleum-independent solution to valuable aromatics.
      PubDate: 2018-01-08T04:21:06.05582-05:0
      DOI: 10.1002/anie.201710074
       
  • Molecular Barrier Enhanced Aromatic Fluorophores in Co-Crystals with Unity
           Quantum Efficiency
    • Authors: Qichun Zhang; Huanqing ye, Guangfeng Liu, Sheng Liu, David Casanova Casanova, Xin Ye, Xutang Tao, Qihua Xiong
      Abstract: Singlet-triplet conversion in organic light-emitting materials introduces non-emissive (dark) and long-lived triplet states, which represents a significant challenge in constraining the optical properties. There have been considerable attempts in separating singlets and triplets in polymers, scavenging or quenching triplets by heavy metals. Such triplet-induced loss cannot be fully eliminated. Herein, we report a new strategy of crafting periodic molecular barrier into the π-conjugated matrices of organic aromatic fluorophores. The molecular barriers effectively block the singlet-to-triplet pathway, resulting in nearly unity photoluminescence quantum efficiency of the organic fluorophores. The transient optical spectroscopy measurements confirm the absence of the triplet absorption. Our studies provide a general approach to preventing the formation of dark triplet states in organic semiconductors and bring new opportunities for the development of advanced organic optics and photonics.
      PubDate: 2018-01-06T00:30:53.079966-05:
      DOI: 10.1002/anie.201712104
       
  • Electrochemical C-H/N-H Activation by Water-Tolerant Cobalt-Catalysis at
           Room Temperature
    • Authors: Cong Tian; Leonardo Massignan, Tjark H. Meyer, Lutz Ackermann
      Abstract: Electrochemistry enabled C-H/N-H functionalizations at room temperature by external oxidant-free cobalt catalysis. Thus, the sustainable cobalt electrocatalysis manifold occurred with excellent levels of chemo and positional selectivity with ample scope, allowing for electrochemical C-H activation under exceedingly mild reaction conditions at room temperature in water.
      PubDate: 2018-01-05T14:25:32.575478-05:
      DOI: 10.1002/anie.201712647
       
  • SuFEx Chemistry of Thionyl Tetrafluoride (SOF4) with Organolithium
           Nucleophiles: Synthesis of Sulfonimidoyl Fluorides, Sulfoximines,
           Sulfonimidamides and Sulfonimidates
    • Authors: K. Barry Sharpless; BING GAO, Suhua Li, Peng Wu, John E Moses
      Abstract: Thionyl tetrafluoride (SOF4) is a valuable connective gas for sulfur fluoride exchange (SuFEx) click chemistry, that enables multidimensional linkages to be created via sulfur-oxygen (S-O) and sulfur-nitrogen (S-N) bonds. In this report, we expand the available SuFEx chemistry of SOF4 to include organolithium nucleophiles, and demonstrate, for the first time, the controlled projection of sulfur-carbon links at the sulfur center of SOF4-derived iminosulfur oxydifluorides (R1-N=SOF2). This protocol enables rapid and modular access to sulfonimidoyl fluorides [R1-N=SOFR2], another array of versatile SuFEx connectors with readily tunable reactivity of the S-F handle. Divergent connections derived from these valuable sulfonimidoyl fluoride units are also demonstrated, including the synthesis of sulfoximines, sulfonimidamides, and sulfonimidates.
      PubDate: 2018-01-04T11:56:08.848547-05:
      DOI: 10.1002/anie.201712145
       
  • Cover Picture: Building Organic/Inorganic Hybrid Interphases for Fast
           Interfacial Transport in Rechargeable Metal Batteries (Angew. Chem. Int.
           Ed. 4/2018)
    • Authors: Qing Zhao; Zhengyuan Tu, Shuya Wei, Kaihang Zhang, Snehashis Choudhury, Xiaotun Liu, Lynden A. Archer
      Pages: 853 - 853
      Abstract: The solid electrolyte interphase (SEI) on metallic electrodes must be elastic and able to reversibly flex and expand to accommodate changes in electrode volume. In their Communication on page 992 ff., L. A. Archer et al. describe the use of SiCl4 as an interfacial cross-linking agent in liquid electrolytes to create hybrid SEIs on Li metal anodes. The hybrid SEIs are composed of Si-interlinked OOCOR molecules and host LiCl salt. These systems exhibit good charge-transfer kinetics and high exchange current densities.
      PubDate: 2018-01-05T04:01:58.022351-05:
      DOI: 10.1002/anie.201712924
       
  • Inside Cover: Confined Carbon Mediating Dehydroaromatization of Methane
           over Mo/ZSM-5 (Angew. Chem. Int. Ed. 4/2018)
    • Authors: Nikolay Kosinov; Alexandra S. G. Wijpkema, Evgeny Uslamin, Roderigh Rohling, Ferdy J. A. G. Coumans, Brahim Mezari, Alexander Parastaev, Artem S. Poryvaev, Matvey V. Fedin, Evgeny A. Pidko, Emiel J. M. Hensen
      Pages: 854 - 854
      Abstract: Confined carbon species play a dual role in the non-oxidative dehydroaromatization of methane over single-atom Mo/ZSM-5 catalysts. In their Communication on page 1016 ff., N. Kosinov, E. J. M. Hensen et al. applied operando spectroscopy, microscopy, and isotope labeling of methane to establish that polyaromatic hydrocarbons, formed in the micropores of the zeolite catalyst, are necessary intermediates for benzene formation. These species lead to catalyst deactivation by agglomeration in heavy deposits that block access to the pores.
      PubDate: 2018-01-04T06:06:38.465118-05:
      DOI: 10.1002/anie.201713047
       
  • Graphical Abstract: Angew. Chem. Int. Ed. 4/2018
    • Pages: 857 - 870
      PubDate: 2018-01-16T09:14:16.129073-05:
      DOI: 10.1002/anie.201880411
       
  • Corrigendum: Interband Absorption Enhanced Optical Activity in Discrete
           Au@Ag Core–Shell Nanocuboids: Probing Extended Helical Conformation of
           Chemisorbed Cysteine Molecules
    • Authors: Zhi Yong Bao; Wei Zhang, Yong-Liang Zhang, Jijun He, Jiyan Dai, Chi-Tung Yeung, Ga-Lai Law, Dang Yuan Lei
      Pages: 870 - 870
      PubDate: 2018-01-16T09:14:21.976707-05:
      DOI: 10.1002/anie.201712503
       
  • Corrigendum: Nanoscale Control of Homoepitaxial Growth on a
           Two-Dimensional Zeolite
    • Authors: Meera Shete; Manjesh Kumar, Donghun Kim, Neel Rangnekar, Dandan Xu, Berna Topuz, Kumar Varoon Agrawal, Evguenia Karapetrova, Benjamin Stottrup, Shaeel Al-Thabaiti, Sulaiman Basahel, Katabathini Narasimharao, Jeffrey D. Rimer, Michael Tsapatsis
      Pages: 870 - 870
      PubDate: 2018-01-16T09:14:17.172306-05:
      DOI: 10.1002/anie.201712681
       
  • Spotlights on our sister journals: Angew. Chem. Int. Ed. 4/2018
    • Pages: 872 - 875
      PubDate: 2018-01-16T09:14:17.241196-05:
      DOI: 10.1002/anie.201880413
       
  • Sinter-Resistant Platinum Catalyst Supported by Metal–Organic
           Framework
    • Authors: In Soo Kim; Zhanyong Li, Jian Zheng, Ana E. Platero-Prats, Andreas Mavrandonakis, Steven Pellizzeri, Magali Ferrandon, Aleksei Vjunov, Leighanne C. Gallington, Thomas E. Webber, Nicolaas A. Vermeulen, R. Lee Penn, Rachel B. Getman, Christopher J. Cramer, Karena W. Chapman, Donald M. Camaioni, John L. Fulton, Johannes A. Lercher, Omar K. Farha, Joseph T. Hupp, Alex B. F. Martinson
      Pages: 909 - 913
      Abstract: Single atoms and few-atom clusters of platinum are uniformly installed on the zirconia nodes of a metal-organic framework (MOF) NU-1000 via targeted vapor-phase synthesis. The catalytic Pt clusters, site-isolated by organic linkers, are shown to exhibit high catalytic activity for ethylene hydrogenation while exhibiting resistance to sintering up to 200 °C. In situ IR spectroscopy reveals the presence of both single atoms and few-atom clusters that depend upon synthesis conditions. Operando X-ray absorption spectroscopy and X-ray pair distribution analyses reveal unique changes in chemical bonding environment and cluster size stability while on stream. Density functional theory calculations elucidate a favorable reaction pathway for ethylene hydrogenation with the novel catalyst. These results provide evidence that atomic layer deposition (ALD) in MOFs is a versatile approach to the rational synthesis of size-selected clusters, including noble metals, on a high surface area support.Resistance is useful: Platinum nanoclusters installed on metal–organic frameworks (MOFs) via targeted vapor-phase synthesis exhibit sinter-resistance upon ethylene hydrogenation up to 200 °C. Operando EXAFS analysis reveals a coordination environment which remains unchanged under the strongly exothermic hydrogenation reaction of ethylene, ALD=atomic layer deposition.
      PubDate: 2018-01-02T08:41:08.916487-05:
      DOI: 10.1002/anie.201708092
       
  • A Breathing Atom-Transfer Radical Polymerization: Fully Oxygen-Tolerant
           Polymerization Inspired by Aerobic Respiration of Cells
    • Authors: Alan E. Enciso; Liye Fu, Alan J. Russell, Krzysztof Matyjaszewski
      Pages: 933 - 936
      Abstract: The first well-controlled aqueous atom-transfer radical polymerization (ATRP) conducted in the open air is reported. This air-tolerant ATRP was enabled by the continuous conversion of oxygen to carbon dioxide catalyzed by glucose oxidase (GOx), in the presence of glucose and sodium pyruvate as sequential sacrificial substrates. Controlled polymerization using initiators for continuous activator regeneration (ICAR) ATRP of oligo(ethylene oxide) methyl ether methacrylate (OEOMA, Mn=500) yielded polymers with low dispersity (1.09≤Đ≤1.29) and molecular weights (MWs) close to theoretical values in the presence of pyruvate. Without added pyruvates, lower MWs were observed due to generation of new chains by H2O2 formed by reaction of O2 with GOx. Successful chain extension of POEOMA500 macroinitiator with OEOMA300 (Đ≤1.3) and Bovine Serum Albumin bioconjugates (Đ≤1.22) confirmed a well-controlled polymerization. The reactions in the open air in larger scale (25 mL) were also successful.Oxygen-tolerant: Well-controlled aqueous atom-transfer radical polymerization (ATRP) conducted in the open air was made possible by continuous conversion of oxygen to carbon dioxide catalyzed by glucose oxidase (GOx), in the presence of glucose and sodium pyruvate as sequential sacrificial substrates. Without pyruvate lower molecular weights were observed due to the generation of new chains by H2O2 formed by reaction of O2 with GOx.
      PubDate: 2018-01-02T04:00:31.593426-05:
      DOI: 10.1002/anie.201711105
       
  • Modulating Cell-Surface Receptor Signaling and Ion Channel Functions by
           In Situ Glycan Editing
    • Authors: Hao Jiang; Aimé López-Aguilar, Lu Meng, Zhongwei Gao, Yani Liu, Xiao Tian, Guangli Yu, Ben Ovryn, Kelley W. Moremen, Peng Wu
      Pages: 967 - 971
      Abstract: Glycans anchored on cell-surface receptors are active modulators of receptor signaling. A strategy is presented that enforces transient changes to cell-surface glycosylation patterns to tune receptor signaling. This approach, termed in situ glycan editing, exploits recombinant glycosyltransferases to incorporate monosaccharides with linkage specificity onto receptors in situ. α2,3-linked sialic acid or α1,3-linked fucose added in situ suppresses signaling through epidermal growth factor receptor and fibroblast growth factor receptor. We also applied the same strategy to regulate the electrical signaling of a potassium ion channel–human ether-à-go-go-related gene channel. Compared to gene editing, no long-term perturbations are introduced to the treated cells. In situ glycan editing therefore offers a promising approach for studying the dynamic role of specific glycans in membrane receptor signaling and ion channel functions.Fucose a go-go: Monosaccharides added in situ actively tune cell-surface receptor signaling and ion channel properties. α2,3-linked sialic acid or α1,3-linked fucose suppress signaling through the epidermal and fibroblast growth factor receptor. In situ glycan editing offers a promising approach for studying the dynamic role of specific glycans in membrane receptor signaling and ion channel functions.
      PubDate: 2018-01-02T05:55:51.502557-05:
      DOI: 10.1002/anie.201706535
       
  • Generating Hydrated Electrons for Chemical Syntheses by Using a Green
           Light-Emitting Diode (LED)
    • Authors: Robert Naumann; Florian Lehmann, Martin Goez
      Pages: 1078 - 1081
      Abstract: We present the first working system for accessing and utilizing laboratory-scale concentrations of hydrated electrons by photoredox catalysis with a green light-emitting diode (LED). Decisive are micellar compartmentalization and photon pooling in an intermediate that decays with second-order kinetics. The only consumable is the nontoxic and bioavailable vitamin C. A turnover number of 1380 shows the LED method to be on par with electron generation by high-power pulsed lasers, but at a fraction of the cost. The extreme reducing power of the electron and its long unquenched life as a ground-state species are synergistic. We demonstrate the applicability to the dechlorination, defluorination, and hydrogenation of compounds that are inert towards all other visible-light photoredox catalysts known to date. A comprehensive mechanistic investigation from microseconds to hours yields results of general validity for photoredox catalysis with photon pooling, allowing optimization and upscaling.Asc the Cat: A micellized catalyst (Cat) turns ascorbate (Asc2−) into a “caged” hydrated electron (eaq•-), which is liberated by a green LED with a high turnover number (TON) and efficiently converts quasi-inert substrates S. SDS=sodium dodecyl sulfate.
      PubDate: 2018-01-04T02:41:37.737543-05:
      DOI: 10.1002/anie.201711692
       
  • ortho-Directing Chromium Arene Complexes as Efficient Mediators for
           Enantiospecific C(sp2)–C(sp3) Cross-Coupling Reactions
    • Authors: Raphael Bigler; Varinder K. Aggarwal
      Pages: 1082 - 1086
      Abstract: A new strategy for the coupling of a broad scope of electronically diverse aromatics to boronic esters is reported. The coupling sequence, which relies on the directed ortho-lithiation of chromium arene complexes followed by boronate formation and oxidation, occurs with complete ortho-selectivity and enantiospecificity to give the coupling products in excellent yields and with high functional group tolerance. An intermediate chromium arene boronate complex was characterized by X-ray, NMR, and IR experiments to elucidate the reaction mechanism.The C(sp2)–C(sp3) coupling of chromium arene complexes with boronic esters is reported. After ortho-selective lithiation of the aromatic and boronate formation, oxidation at the electron-rich chromium center with I2 triggers the 1,2-migration and Bpin elimination to directly afford the decomplexed ortho-coupled products in high yield and with complete enantiospecificity.
      PubDate: 2018-01-03T07:21:48.798956-05:
      DOI: 10.1002/anie.201711816
       
  • Triplet Tellurophene-Based Acceptors for Organic Solar Cells
    • Authors: Lei Yang; Wenxing Gu, Lei Lv, Yusheng Chen, Yufei Yang, Pan Ye, Jianfei Wu, Ling Hong, Aidong Peng, Hui Huang
      Pages: 1096 - 1102
      Abstract: Triplet materials have been employed to achieve high-performing organic solar cells (OSCs) by extending the exciton lifetime and diffusion distances, while the triplet non-fullerene acceptor materials have never been reported for bulk heterojunction OSCs. Herein, for the first time, three triplet molecular acceptors based on tellurophene with different degrees of ring fusing were designed and synthesized for OSCs. Significantly, these molecules have long exciton lifetime and diffusion lengths, leading to efficient power conversion efficiency (7.52 %), which is the highest value for tellurophene-based OSCs. The influence of the extent of ring fusing on molecular geometry and OSCs performance was investigated to show the power conversion efficiencies (PCEs) continuously increased along with increasing the extent of ring fusing.Solar fusion: Three triplet molecular acceptors based on tellurophene with different degrees of ring fusing were prepared for organic solar cells (OSCs). These molecules have long exciton lifetimes and diffusion lengths, leading to increasing power conversion efficiencies (PCE) up to 7.52 %, which is the highest value for tellurophene-based OSCs, as the degree of ring-fusion increases.
      PubDate: 2018-01-04T08:00:35.411138-05:
      DOI: 10.1002/anie.201712011
       
  • Deuterated Molecular Ruby with Record Luminescence Quantum Yield
    • Authors: Cui Wang; Sven Otto, Matthias Dorn, Elisabeth Kreidt, Jakob Lebon, Laura Sršan, Patrick Di Martino-Fumo, Markus Gerhards, Ute Resch-Genger, Michael Seitz, Katja Heinze
      Pages: 1112 - 1116
      Abstract: The recently reported luminescent chromium(III) complex 13+ ([Cr(ddpd)2]3+; ddpd=N,N′-dimethyl-N,N′-dipyridine-2-yl-pyridine-2,6-diamine) shows exceptionally strong near-IR emission at 775 nm in water under ambient conditions (Φ=11 %) with a microsecond lifetime as the ligand design in 13+ effectively eliminates non-radiative decay pathways, such as photosubstitution, back-intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and the ddpd ligands probes the efficiency of these oscillators in the excited state deactivation. Addressing these energy-transfer pathways in the first and second coordination sphere furnishes a record 30 % quantum yield and a 2.3 millisecond lifetime for a metal complex with an earth-abundant metal ion in solution at room temperature.Record ruby: Deuteration of the solvent and especially the ligand boosts the photoluminescence quantum yield of the chromium(III) complex with strong-field ddpd ligands (molecular ruby) from 11 % to a record value of 30 % in solution at room temperature. At the same time, the luminescence lifetime more than doubles to over two milliseconds. The α-CH group of the ddpd ligand provides the most decisive oscillator.
      PubDate: 2018-01-02T08:40:49.064304-05:
      DOI: 10.1002/anie.201711350
       
  • Back Cover: Integration of Plasmonic Effects and Schottky Junctions into
           Metal–Organic Framework Composites: Steering Charge Flow for Enhanced
           Visible-Light Photocatalysis (Angew. Chem. Int. Ed. 4/2018)
    • Authors: Juan-Ding Xiao; Lili Han, Jun Luo, Shu-Hong Yu, Hai-Long Jiang
      Pages: 1118 - 1118
      Abstract: Based on a semiconductor-like metal–organic framework (MOF), the Pt@MOF/Au catalyst integrates the surface plasmon resonance excitation of Au nanorods with a Pt-MOF Schottky junction, which extends the light absorption of the MOF from the UV to the visible region and greatly accelerates charge transfer. H.-L. Jiang et al. show in their Communication on page 1103 ff. that the spatial separation of Pt and Au particles by the MOF further steers the formation of charge flow and expedites electron migration, leading to a very high photocatalytic H2 production rate.
      PubDate: 2018-01-08T03:28:58.851458-05:
      DOI: 10.1002/anie.201713194
       
  • Richard J. Payne
    • Pages: 876 - 876
      Abstract: “My favorite food is the humble burrito. My worst nightmare is missing an international flight ...” This and more about Richard J. Payne can be found on page 876.
      PubDate: 2017-10-04T02:30:08.773995-05:
      DOI: 10.1002/anie.201709516
       
  • The Chemical Record Lectureship: M. Grätzel / Baizer Award: F. Maran /
           Werner Prize and Hans G. A. Hellmann Prize: S. Luber / Max Bergmann
           Medal: J. Buchner
    • Pages: 877 - 877
      PubDate: 2017-12-12T08:58:59.001638-05:
      DOI: 10.1002/anie.201712406
       
  • A Step Closer to Metal-Free Dinitrogen Activation: A New Chapter in the
           Chemistry of Frustrated Lewis Pairs
    • Authors: Rebecca L. Melen
      Pages: 880 - 882
      Abstract: The end of the metal age: Recent developments in small-molecule activation and chemical transformations of main-group species pose the question as to whether metal catalysts could be avoided altogether in the activation of dinitrogen. A ground-breaking study by Stephan and co-workers clearly implies that the metal-free activation of N2 with frustrated Lewis pairs may be achievable in the not-too-distant future.
      PubDate: 2017-12-08T05:23:43.871741-05:
      DOI: 10.1002/anie.201711945
       
  • Validation of Molecular Simulation: An Overview of Issues
    • Authors: Wilfred F. van Gunsteren; Xavier Daura, Niels Hansen, Alan E. Mark, Chris Oostenbrink, Sereina Riniker, Lorna J. Smith
      Pages: 884 - 902
      Abstract: Computer simulation of molecular systems enables structure–energy–function relationships of molecular processes to be described at the sub-atomic, atomic, supra-atomic, or supra-molecular level. To interpret results of such simulations appropriately, the quality of the calculated properties must be evaluated. This depends on the way the simulations are performed and on the way they are validated by comparison to values Qexp of experimentally observable quantities Q. One must consider 1) the accuracy of Qexp, 2) the accuracy of the function Q(rN) used to calculate a Q-value based on a molecular configuration rN of N particles, 3) the sensitivity of the function Q(rN) to the configuration rN, 4) the relative time scales of the simulation and experiment, 5) the degree to which the calculated and experimental properties are equivalent, and 6) the degree to which the system simulated matches the experimental conditions. Experimental data is limited in scope and generally corresponds to averages over both time and space. A critical analysis of the various factors influencing the apparent degree of (dis)agreement between simulations and experiment is presented and illustrated using examples from the literature. What can be done to enhance the validation of molecular simulation is also discussed.Assumptions, approximations, and pitfalls: Validation of the results of molecular simulations is a process beset with theoretical and practical problems. The effects of the various assumptions and approximations involved in the formulation of a molecular model and its simulation and the pitfalls of comparing simulated with experimental data are discussed. Ways to enhance validation of molecular simulation are suggested.
      PubDate: 2017-12-27T10:18:56.478228-05:
      DOI: 10.1002/anie.201702945
       
  • Photoinduced Rearrangement of Dienones and Santonin Rerouted by Amines
    • Authors: Zhipeng Zhang; Maxim Ratnikov, Glen Spraggon, Phil B. Alper
      Pages: 904 - 908
      Abstract: The photoinduced rearrangement pathways of simple 2,5-dienones and the natural product santonin were found to be effectively rerouted by amines, giving rise to unprecedented products. Either cis olefins or cyclobutenes were obtained from 4,4-disubstituted 2,5-dienone upon irradiation (365 nm) in the presence of various amines depending on the solvent. Previously undescribed [4.4.0] and [5.3.0] fused-ring-containing products were obtained when santonin was irradiated (365 nm) in the presence of methylamine. The amines present in these reactions were incorporated into the products by means of amide-group formation.Small perturbation, big difference: Photoinduced rearrangement pathways of simple 2,5-dienones and the natural product santonin were effectively rerouted by amines, giving rise to unprecedented cis olefins or cyclobutenes from 2,5-dienone and novel [4.4.0] and [5.3.0] fused-ring-containing structures from santonin. DME=dimethoxyethane.
      PubDate: 2017-12-20T09:50:56.350975-05:
      DOI: 10.1002/anie.201710463
       
  • Heterotelechelic Polymers by Ring-Opening Metathesis and Regioselective
           Chain Transfer
    • Authors: Peng Liu; Mohammad Yasir, Albert Ruggi, Andreas F. M. Kilbinger
      Pages: 914 - 917
      Abstract: Heterotelechelic polymers were synthesized by a kinetic telechelic ring-opening metathesis polymerization method relying on the regioselective cross-metathesis of the propagating Grubbs’ first-generation catalyst with cinnamyl alcohol derivatives. This procedure allowed the synthesis of hetero-bis-end-functional polymers in a one-pot setup. The molecular weight of the polymers could be controlled by varying the ratio between cinnamyl alcohol derivatives and monomer. The end functional groups can be changed using different aromatically substituted cinnamyl alcohol derivatives. Different monomers were investigated and the presence of the functional groups was shown by NMR spectroscopy and MALDI-ToF mass spectrometry. Labeling experiments with dyes were conducted to demonstrate the orthogonal addressability of both chain ends of the heterotelechelic polymers obtained.Heterotelechelic polymers were synthesized by a kinetic telechelic ring-opening metathesis polymerization method relying on the regioselective cross-metathesis of the propagating Grubbs’ first-generation (G1) catalyst with cinnamyl alcohol derivatives. The molecular weight of the polymers could be controlled by varying the ratio between cinnamyl alcohol derivatives and monomer.
      PubDate: 2017-12-27T10:18:49.519318-05:
      DOI: 10.1002/anie.201708733
       
  • Mimicking Class I b Mn2-Ribonucleotide Reductase: A MnII2 Complex and
           Its Reaction with Superoxide
    • Authors: Adriana M. Magherusan; Ang Zhou, Erik R. Farquhar, Max García-Melchor, Brendan Twamley, Lawrence Que, Aidan R. McDonald
      Pages: 918 - 922
      Abstract: A fascinating discovery in the chemistry of ribonucleotide reductases (RNRs) has been the identification of a dimanganese (Mn2) active site in class I b RNRs that requires superoxide anion (O2.−), rather than dioxygen (O2), to access a high-valent Mn2 oxidant. Complex 1 ([Mn2(O2CCH3)(N-Et-HPTB)](ClO4)2, N-Et-HPTB=N,N,N′,N′-tetrakis(2-(1-ethylbenzimidazolyl))-2-hydroxy-1,3-diaminopropane) was synthesised in high yield (90 %). 1 was reacted with O2.− at −40 °C resulting in the formation of a metastable species (2). 2 displayed electronic absorption features (λmax=460, 610 nm) typical of a Mn-peroxide species and a 29-line EPR signal typical of a MnIIMnIII entity. Mn K-edge X-ray absorption near-edge spectroscopy (XANES) suggested a formal oxidation state change of MnII2 in 1 to MnIIMnIII for 2. Electrospray ionisation mass spectrometry (ESI-MS) suggested 2 to be a MnIIMnIII-peroxide complex. 2 was capable of oxidizing ferrocene and weak O−H bonds upon activation with proton donors. Our findings provide support for the postulated mechanism of O2.− activation at class I b Mn2 RNRs.Superoxide activation: The chemistry of class I b Mn2-ribonucleotide reductases was mimicked by probing the reaction between a synthetic MnII2 complex and superoxide, which yielded a MnIIMnIII-peroxide species. Proton donors activated the MnIIMnIII-peroxide core, facilitating electron transfer and hydrogen atom transfer reactivity.
      PubDate: 2017-12-27T10:18:26.631923-05:
      DOI: 10.1002/anie.201709806
       
  • Dichotomy of Manganese Catalysis via Organometallic or Radical Mechanism:
           Stereodivergent Hydrosilylation of Alkynes
    • Authors: Xiaoxu Yang; Congyang Wang
      Pages: 923 - 928
      Abstract: Herein, we disclose the first manganese-catalyzed hydrosilylation of alkynes featuring diverse selectivities. The highly selective formation of E-products was achieved by using mononuclear MnBr(CO)5 with the arsenic ligand, AsPh3. Whereas using the dinuclear catalyst Mn2(CO)10 and LPO (dilauroyl peroxide) enabled the reversed generation of Z-products in good to excellent stereo- and regioselectivity. Such a way of controlling the reaction stereoselectivity is unprecedented. Mechanistic experiments revealed the dichotomy of manganese catalysis via organometallic and radical pathways operating in the E- and Z-selective routes, respectively.Dichotomy of Man(ganese): In the manganese-catalyzed hydrosilylation of alkynes, a highly selective formation of E-products was achieved by using mononuclear MnBr(CO)5 with AsPh3. However, with the dinuclear catalyst Mn2(CO)10 and LPO (dilauroyl peroxide) the Z-products were obtained. Mechanistic experiments revealed catalysis via organometallic and radical pathways.
      PubDate: 2017-12-27T10:22:09.70777-05:0
      DOI: 10.1002/anie.201710206
       
  • Site-Selective Linear Alkylation of Anilides by Cooperative
           Nickel/Aluminum Catalysis
    • Authors: Shogo Okumura; Takuya Komine, Erika Shigeki, Kazuhiko Semba, Yoshiaki Nakao
      Pages: 929 - 932
      Abstract: We report meta- and para-selective linear alkylation reactions of anilides with alkenes by nickel/N-heterocyclic carbene (NHC) and aluminum catalysis. With a less bulky NHC, the alkylation reaction of N-methyl-N-phenylcyclohexanecarboxamides proceeded mainly at the meta position. In contrast, a bulky NHC ligand led to the para-selective alkylation of N-sec-alkyl anilides.Hit the right site: Cooperative nickel/ N-heterocyclic carbene (NHC) and aluminum catalysis enabled both the meta- and para-selective linear alkylation of anilides with alkenes. With a less bulky NHC ligand, the alkylation of N-methyl-N-phenylcyclohexanecarboxamides proceeded mainly at the meta position. In contrast, a bulky NHC ligand resulted in the para-selective alkylation of N-sec-alkyl anilides.
      PubDate: 2017-12-18T04:11:51.195724-05:
      DOI: 10.1002/anie.201710520
       
  • Stereoselective Total Synthesis of Hetisine-type C20-Diterpenoid
           Alkaloids: Spirasine IV and XI
    • Authors: Quanzheng Zhang; Zhongshan Zhang, Zhong Huang, Changhui Zhang, Song Xi, Min Zhang
      Pages: 937 - 941
      Abstract: The first total synthesis of the architecturally complex hetisine-type heptacyclic C20-diterpenoid alkaloids (±)-spirasine IV and XI is reported. The A/F/G/C tetracyclic skeleton with the challenging N−C6 and C14−C20 linkages was efficiently constructed by an intramolecular azomethine-ylide-based 1,3-dipolar cycloaddition with unusual regioselectivity. SmI2-mediated free-radical addition to the arene moiety without prior dearomatization and a stereoselective intramolecular aldol reaction further enabled rapid access to the hetisine core, providing a bicyclo[2.2.2]octane ring with a new oxygen substitution pattern.Seven-ring wonders: In the total synthesis of the title hetisine-type heptacyclic C20-diterpenoid alkaloids, the A/F/G/C tetracyclic skeleton was constructed by an intramolecular 1,3-dipolar cycloaddition with unusual regioselectivity (see scheme). SmI2-mediated free-radical addition to the arene moiety without prior dearomatization and an aldol reaction further enabled rapid access to the hetisine core.
      PubDate: 2017-12-27T10:20:41.140781-05:
      DOI: 10.1002/anie.201711414
       
  • Total Synthesis of Bryostatin 8 Using an Organosilane-Based Strategy
    • Authors: Yuebao Zhang; Qianyou Guo, Xianwei Sun, Ji Lu, Yanjun Cao, Qiang Pu, Zhiwen Chu, Lu Gao, Zhenlei Song
      Pages: 942 - 946
      Abstract: Convergent total synthesis of bryostatin 8 has been accomplished by an organosilane-based strategy. The C ring is constructed stereoselectively through a geminal bis(silane)-based [1,5]-Brook rearrangement, and the B ring through geminal bis(silane)-based Prins cyclization, thus efficiently joining the northern and southern parts of the molecule.The eight ball: Convergent total synthesis of bryostatin 8 has been accomplished using an organosilane-based strategy. The C ring is constructed stereoselectively through a geminal bis(silane)-based [1,5]-Brook rearrangement, and the B ring through a geminal bis(silane)-based Prins cyclization, thus efficiently joining the northern and southern parts of the molecule.
      PubDate: 2017-12-20T09:51:12.465965-05:
      DOI: 10.1002/anie.201711452
       
  • Divergent Total Syntheses of (−)-Daphnilongeranin B and
           (−)-Daphenylline
    • Authors: Xiaoming Chen; Hai-Jun Zhang, Xinkan Yang, Houqiang Lv, Xiaoru Shao, Cheng Tao, Huifei Wang, Bin Cheng, Yun Li, Jingjing Guo, Jing Zhang, Hongbin Zhai
      Pages: 947 - 951
      Abstract: (−)-Daphnilongeranin B and (−)-daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (−)-daphnilongeranin B and a bioinspired synthesis of (−)-daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late-stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.Two of a kind: The hexacyclic Daphniphyllum alkaloids (−)-daphnilongeranin B and (−)-daphenylline were synthesized from a common pentacyclic intermediate (see scheme). The key features of the syntheses included an intermolecular [3+2] cyclization, a late-stage aldol cyclization to install the cyclopentenone ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.
      PubDate: 2017-12-05T09:12:29.924395-05:
      DOI: 10.1002/anie.201709762
       
  • Total Syntheses of Daphenylline, Daphnipaxianine A, and
           Himalenine D
    • Authors: Yu Chen; Wenhao Zhang, Lu Ren, Jian Li, Ang Li
      Pages: 952 - 956
      Abstract: We report the total syntheses of daphenylline (1), daphnipaxianine A (5), and himalenine D (6), three Daphniphyllum alkaloids from the calyciphylline A subfamily. A pentacyclic triketone was prepared by using atom-transfer radical cyclization and the Lu [3+2] cycloaddition as key steps. Inspired by the proposed biosynthetic relationship between 1 and another calyciphylline A type alkaloid, we developed a ring-expansion/aromatization/aldol cascade to construct the tetrasubstituted benzene moiety of 1. The versatile triketone intermediate was also elaborated into 5 and 6 through a C=C bond migration/aldol cyclization approach.Hat trick: Total syntheses of three Daphniphyllum alkaloids of the calyciphylline A subfamily were inspired by the proposed biosynthetic relationship between 1 and another calyciphylline A type alkaloid. Thus, the tetrasubstituted benzene moiety of 1 was constructed by a ring-expansion/aromatization/aldol cascade, and the versatile triketone intermediate was also elaborated into 2 and 3 through C=C bond migration and aldol cyclization.
      PubDate: 2017-12-21T07:36:23.986468-05:
      DOI: 10.1002/anie.201711482
       
  • Visible-Light Emulsion Photopolymerization of Styrene
    • Authors: Frédéric Le Quéméner; Daniel Subervie, Fabrice Morlet-Savary, Jacques Lalevée, Muriel Lansalot, Elodie Bourgeat-Lami, Emmanuel Lacôte
      Pages: 957 - 961
      Abstract: The photopolymerization of styrene in emulsion is achieved in a conventional double-wall reactor equipped with a LED ribbon coiled around the external glass wall. Styrene mixed to acridine orange is added to the water phase containing sodium dodecyl sulfate, a water-soluble N-heterocyclic carbene–borane and disulfide, and irradiated. Highly stable latexes are obtained, with particles up to a diameter of 300 nm. The ability to reach such large particle sizes via a photochemical process in a dispersed medium is due to the use of visible light: the photons in the visible range are less scattered by larger objects and thus penetrate and initiate better the polymerizations. They are also greener and cheaper to produce via LEDs, and much safer than UVs. The method presented does not require any specific glassware; it works at lower temperature and delivers larger particles compared to thermal processes at similar solids contents and surfactant concentrations.Seeing the light: Styrene can be photopolymerized in emulsion using visible light. By using a water-soluble N-heterocyclic carbene–borane as initiator, stable latexes were obtained. The nanoparticles can have diameters up to 300 nm, the largest particle size ever reached by a photochemical process in a dispersed medium.
      PubDate: 2017-12-27T10:21:52.334321-05:
      DOI: 10.1002/anie.201710488
       
  • Living Ab Initio Emulsion Polymerization of Methyl Methacrylate in Water
           Using a Water-Soluble Organotellurium Chain Transfer Agent under Thermal
           and Photochemical Conditions
    • Authors: Weijia Fan; Masatoshi Tosaka, Shigeru Yamago, Michael F. Cunningham
      Pages: 962 - 966
      Abstract: Ab initio emulsion polymerization of methyl methacrylate (MMA) using a water-soluble organotellurium chain transfer agent in the presence of the surfactant Brij 98 in water is reported. Polymerization proceeded under both thermal and visible light-irradiation conditions, giving poly(methyl methacrylate) (PMMA) with controlled molecular weight and low dispersity (Đ
      PubDate: 2017-11-30T04:10:41.918905-05:
      DOI: 10.1002/anie.201710754
       
  • In Situ Spatial Complementation of Aptamer-Mediated Recognition Enables
           Live-Cell Imaging of Native RNA Transcripts in Real Time
    • Authors: Zejun Wang; Yao Luo, Xiaodong Xie, Xingjie Hu, Haiyun Song, Yun Zhao, Jiye Shi, Lihua Wang, Gennadi Glinsky, Nan Chen, Ratnesh Lal, Chunhai Fan
      Pages: 972 - 976
      Abstract: Direct cellular imaging of the localization and dynamics of biomolecules helps to understand their function and reveals novel mechanisms at the single-cell resolution. In contrast to routine fluorescent-protein-based protein imaging, technology for RNA imaging remains less well explored because of the lack of enabling technology. Herein, we report the development of an aptamer-initiated fluorescence complementation (AiFC) method for RNA imaging by engineering a green fluorescence protein (GFP)-mimicking turn-on RNA aptamer, Broccoli, into two split fragments that could tandemly bind to target mRNA. When genetically encoded in cells, endogenous mRNA molecules recruited Split-Broccoli and brought the two fragments into spatial proximity, which formed a fluorophore-binding site in situ and turned on fluorescence. Significantly, we demonstrated the use of AiFC for high-contrast and real-time imaging of endogenous RNA molecules in living mammalian cells. We envision wide application and practical utility of this enabling technology to in vivo single-cell visualization and mechanistic analysis of macromolecular interactions.Let's split! An aptamer-initiated fluorescence complementation (AiFC) method was developed for RNA imaging by engineering a green fluorescence protein (GFP)-mimicking turn-on RNA aptamer into two split fragments that could tandemly bind to target mRNA. The use of AiFC enables the non-invasive, high-contrast real-time imaging of endogenous RNA molecules in living mammalian cells.
      PubDate: 2017-12-15T05:51:18.851006-05:
      DOI: 10.1002/anie.201707795
       
  • Toblerols: Cyclopropanol-Containing Polyketide Modulators of Antibiosis in
           Methylobacteria
    • Authors: Reiko Ueoka; Miriam Bortfeld-Miller, Brandon I. Morinaka, Julia A. Vorholt, Jörn Piel
      Pages: 977 - 981
      Abstract: Trans-AT polyketide synthases (PKSs) are a family of biosynthetically versatile modular type I PKSs that generate bioactive polyketides of impressive structural diversity. In this study, we detected, in the genome of several bacteria a cryptic, architecturally unusual trans-AT PKS gene cluster which eluded automated PKS prediction. Genomic mining of one of these strains, the model methylotroph Methylobacterium extorquens AM1, revealed unique epoxide- and cyclopropanol-containing polyketides named toblerols. Relative and absolute stereochemistry were determined by NMR experiments, chemical derivatization, and the comparison of CD data between the derivatized natural product and a synthesized model compound. Biosynthetic data suggest that the cyclopropanol moiety is generated by carbon–carbon shortening of a more extended precursor. Surprisingly, a knock-out strain impaired in polyketide production showed strong inhibitory activity against other methylobacteria in contrast to the wild-type producer. The activity was inhibited by complementation with toblerols, thus suggesting that these compounds modulate an as-yet unknown methylobacterial antibiotic.Anti-antibiotics: The structurally and functionally unusual toblerols were identified as products of a cryptic polyketide synthase gene cluster from the methylotrophic model bacterium Methylobacterium extorquens AM1. Biosynthetic studies suggest that the cyclopropanol moiety is generated by carbon–carbon bond cleavage of an extended precursor.
      PubDate: 2017-12-18T08:56:53.608565-05:
      DOI: 10.1002/anie.201709056
       
  • Quantitative Prediction of Rate Constants for Aqueous Racemization To
           Avoid Pointless Stereoselective Syntheses
    • Authors: Andrew Ballard; Hiwa O. Ahmad, Stefania Narduolo, Lucy Rosa, Nikki Chand, David A. Cosgrove, Peter Varkonyi, Nabil Asaad, Simone Tomasi, Niklaas J. Buurma, Andrew G. Leach
      Pages: 982 - 985
      Abstract: Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and 1H NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second-order rate constants for general-base-catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.The racemization potential of complex organic molecules has been predicted using simple quantum mechanical calculations and a group additivity scheme. Organic chemists can first check whether a given synthetic target will be configurationally stable before embarking on a potentially lengthy and expensive chiral synthesis.
      PubDate: 2017-11-15T05:41:02.351555-05:
      DOI: 10.1002/anie.201709163
       
  • Platelet-Facilitated Photothermal Therapy of Head and Neck Squamous Cell
           Carcinoma
    • Authors: Lang Rao; Lin-Lin Bu, Liang Ma, Wenbiao Wang, Huiqin Liu, Da Wan, Jian-Feng Liu, Andrew Li, Shi-Shang Guo, Lu Zhang, Wen-Feng Zhang, Xing-Zhong Zhao, Zhi-Jun Sun, Wei Liu
      Pages: 986 - 991
      Abstract: Here, we present a platelet-facilitated photothermal tumor therapy (PLT-PTT) strategy, in which PLTs act as carriers for targeted delivery of photothermal agents to tumor tissues and enhance the PTT effect. Gold nanorods (AuNRs) were first loaded into PLTs by electroporation and the resulting AuNR-loaded PLTs (PLT-AuNRs) inherited long blood circulation and cancer targeting characteristics from PLTs and good photothermal property from AuNRs. Using a gene-knockout mouse model, we demonstrate that the administration of PLT-AuNRs and localizing laser irradiation could effectively inhibit the growth of head and neck squamous cell carcinoma (HNSCC). In addition, we found that the PTT treatment augmented PLT-AuNRs targeting to the tumor sites and in turn, improved the PTT effects in a feedback manner, demonstrating the unique self-reinforcing characteristic of PLT-PTT in cancer therapy.Platelets (PLTs) are circulating sentinels that can accumulate in injured tissues to trigger the repair processes. Photothermal therapy (PTT) uses heat generated from light to ablate tumor tissues. Inspired by both observations, gold nanorods were loaded into PLTs for enhanced PTT of head and neck squamous cell carcinoma.
      PubDate: 2017-12-20T09:50:43.70349-05:0
      DOI: 10.1002/anie.201709457
       
  • Building Organic/Inorganic Hybrid Interphases for Fast Interfacial
           Transport in Rechargeable Metal Batteries
    • Authors: Qing Zhao; Zhengyuan Tu, Shuya Wei, Kaihang Zhang, Snehashis Choudhury, Xiaotun Liu, Lynden A. Archer
      Pages: 992 - 996
      Abstract: We report a facile in situ synthesis that utilizes readily accessible SiCl4 cross-linking chemistry to create durable hybrid solid–electrolyte interphases (SEIs) on metal anodes. Such hybrid SEIs composed of Si-interlinked OOCOR molecules that host LiCl salt exhibit fast charge-transfer kinetics and as much as five-times higher exchange current densities, in comparison to their spontaneously formed analogues. Electrochemical analysis and direct optical visualization of Li and Na deposition in symmetric Li/Li and Na/Na cells show that the hybrid SEI provides excellent morphological control at high current densities (3–5 mA cm−2) for Li and even for notoriously unstable Na metal anodes. The fast interfacial transport attributes of the SEI are also found to be beneficial for Li-S cells and stable electrochemical cycling was achieved in galvanostatic studies at rates as high as 2 C. Our work therefore provides a promising approach towards rational design of multifunctional, elastic SEIs that overcome the most serious limitations of spontaneously formed interphases on high-capacity metal anodes.A facile chemical route is reported for synthesizing elastic solid–electrolyte interphases (SEIs) on reactive metal anodes. Composed of interlinked organic molecules that host inorganic salts, this hybrid SEI can flex to accommodate volume changes at the anode and also enables fast interfacial ion transport. Li-Li, Li-S, Li-Li4Ti5O12, and Na-Na cells based on this SEI concept display exceptional chemical and physical stability.
      PubDate: 2017-12-21T10:46:46.5529-05:00
      DOI: 10.1002/anie.201711598
       
  • A Simply Synthesized, Tough Polyarylene with Transient Mechanochromic
           Response
    • Authors: Fabian Kempe; Oliver Brügner, Hannah Buchheit, Sarah N. Momm, Felix Riehle, Sophie Hameury, Michael Walter, Michael Sommer
      Pages: 997 - 1000
      Abstract: A simple and high-yielding route to tough polyarylenes of the type poly(meta,meta,para-phenylene) (PmmpP) is developed. PmmpP is tough even in its as-synthesized state which has an intermediate molar mass of Mw≈60 kg mol−1 and exhibits outstanding mechanical properties at further optimized molecular weight of Mw=96 kg mol−1, E=0.9 GPa, ϵ=300 %. Statistical copolymers with para,para-spiropyran (SP) are mechanochromic, and the toughness allows mechanochromism to be investigated. Strained samples instantaneously lose color upon force release. DFT calculations show this phenomenon to be caused by the PmmpP matrix that allows build-up of sufficiently large forces to be transduced to SP, and the relatively unstable corresponding merocyanine (MC) form arising from the aromatic co-monomer. MC units covalently incorporated into PmmpP show a drastically reduced half life time of 3.1 s compared to 4.5 h obtained for SP derivatives with common 6-nitro substitution.Pimp my polymer: A simple and high-yielding synthesis gives high molecular weight, tough poly(meta,meta,para-phenylene) (PmmpP). Statistical copolymers of PmmpP with para,para-spiropyran are mechanochromic under positive uniaxial strain, but lose color instantaneously after force release.
      PubDate: 2017-11-24T05:01:08.266824-05:
      DOI: 10.1002/anie.201709142
       
  • Exploring Tetrathiafulvalene–Carbon Nanodot Conjugates in Charge
           Transfer Reactions
    • Authors: Andrés Ferrer-Ruiz; Tobias Scharl, Philipp Haines, Laura Rodríguez-Pérez, Alejandro Cadranel, M. Ángeles Herranz, Dirk M. Guldi, Nazario Martín
      Pages: 1001 - 1005
      Abstract: Carbon nanodots (CNDs) were synthesized using low-cost and biocompatible starting materials such as citric acid/urea, under microwave irradiation, and constant pressure conditions. The obtained pressure-synthesized CNDs (pCNDs) were covalently modified with photo- and electroactive π-extended tetrathiafulvalene (exTTF) by means of a two-step esterification reaction, affording pCND-exTTF. The electronic interactions between the pCNDs and exTTF were investigated in the ground and excited states. Ultrafast pump–probe experiments assisted in corroborating that charge separation governs the deactivation of photoexcited pCND-exTTF. These size-regular structures, as revealed by AFM, are stable electron donor–acceptor conjugates of interest for a better understanding of basic processes such as artificial photosynthesis, catalysis, and photovoltaics, involving readily available fluorescent nanodots.Carbon nanodots (CNDs) were functionalized with π-extended tetrathiafulvalene (exTTF) units by using a covalent synthetic approach. Upon photoexcitation, a charge-separated state with a lifetime in the range of picoseconds evolves from electron donor–acceptor interactions between the carbon nanodots and the electron-donating exTTF.
      PubDate: 2017-12-29T03:50:37.534287-05:
      DOI: 10.1002/anie.201709561
       
  • One-Pot Synthesis of Contracted and Expanded Porphyrins with meso-CF3
           Groups
    • Authors: Qiu-Cheng Chen; Matan Soll, Amir Mizrahi, Irena Saltsman, Natalia Fridman, Magal Saphier, Zeev Gross
      Pages: 1006 - 1010
      Abstract: Corrole and sapphyrin with the smallest meso-substituents reported so far were prepared in a one-pot synthesis that relies on a non-aldehydic precursor for introducing CF3 groups. The substantial amounts of products obtained by this facile pathway allowed for the full characterization of 5,10,15-tris(trifluoromethyl)corrole, the access to a variety of stable chelates thereof and investigations that disclose the unique structural and chemical properties induced by the CF3 substituents. The novel 5,10,15,20-tetra(trifluoromethyl)sapphyrin undergoes only single protonation, which according to its crystal structure is stabilized by favorable non-bonding F/H interaction between the meso-CF3 and the inverted pyrrolic NH.A galaxy of porphyrins: meso-Trifluoromethylated corroles and sapphyrin display features not shared with any other analogues reported so far. They were prepared in a one-pot synthesis that relies on a non-aldehydic precursor for introducing CF3 groups. The cheaper and much less volatile 2-bromo-2-chloro-1,1,1-trifluoroethane was employed in the synthesis instead of trifluoroacetaldehyde.
      PubDate: 2017-12-29T04:31:36.691743-05:
      DOI: 10.1002/anie.201710106
       
  • A 30 nm Nanopore Electrode: Facile Fabrication and Direct Insights into
           the Intrinsic Feature of Single Nanoparticle Collisions
    • Authors: Rui Gao; Yi-Lun Ying, Yuan-Jie Li, Yong-Xu Hu, Ru-Jia Yu, Yao Lin, Yi-Tao Long
      Pages: 1011 - 1015
      Abstract: Clarifying the hidden but intrinsic feature of single nanoparticles by nanoelectrochemistry could help understand its potential for diverse applications. The uncontrolled interface and bandwidth limitation in the electrochemical measurement put the obstacle in single particle collision. Here, we demonstrate a well-defined 30 nm nanopore electrode with a rapid chemical-electrochemical fabrication method which provides a high reproducibility in both size and performance. A capacitance-based detection mechanism is demonstrated to achieve a high current resolution of 0.6 pA ±0.1 pA (RMS) and a high the temporal resolution of 0.01 ms. By utilizing this electrode, the dynamic interactions of every single particle in the mixture could be directly read during the collision process. The collision frequency is two orders of magnitude higher than previous reports, which helps reveal the hidden features of nanoparticles during the complex and multidimensional interaction processes.Probing for nanoparticles: A 30 nm confined nanopore electrode (CNE) was fabricated to directly recognize intrinsic collision information of single nanoparticles of different sizes. The rapid method and controlled nanopore dimensions enable a high reproducibility. A new detection mechanism enables 0.01 ms ultrasensitive collision detection with high current resolution and collision frequency.
      PubDate: 2017-12-21T10:46:55.864998-05:
      DOI: 10.1002/anie.201710201
       
  • Confined Carbon Mediating Dehydroaromatization of Methane over Mo/ZSM-5
    • Authors: Nikolay Kosinov; Alexandra S. G. Wijpkema, Evgeny Uslamin, Roderigh Rohling, Ferdy J. A. G. Coumans, Brahim Mezari, Alexander Parastaev, Artem S. Poryvaev, Matvey V. Fedin, Evgeny A. Pidko, Emiel J. M. Hensen
      Pages: 1016 - 1020
      Abstract: Non-oxidative dehydroaromatization of methane (MDA) is a promising catalytic process for direct valorization of natural gas to liquid hydrocarbons. The application of this reaction in practical technology is hindered by a lack of understanding about the mechanism and nature of the active sites in benchmark zeolite-based Mo/ZSM-5 catalysts, which precludes the solution of problems such as rapid catalyst deactivation. By applying spectroscopy and microscopy, it is shown that the active centers in Mo/ZSM-5 are partially reduced single-atom Mo sites stabilized by the zeolite framework. By combining a pulse reaction technique with isotope labeling of methane, MDA is shown to be governed by a hydrocarbon pool mechanism in which benzene is derived from secondary reactions of confined polyaromatic carbon species with the initial products of methane activation.Combined pulse reaction experiments, spectroscopy, microscopy, and isotopic labeling were carried out on zeolite Mo/ZSM-5. It was shown that a hydrocarbon pool of polyaromatics confined in the zeolite pores is involved in the aromatization of methane over single-site Mo/ZSM-5 catalysts.
      PubDate: 2017-12-27T10:21:07.403793-05:
      DOI: 10.1002/anie.201711098
       
  • A Zero-Dimensional Organic Seesaw-Shaped Tin Bromide with Highly Efficient
           Strongly Stokes-Shifted Deep-Red Emission
    • Authors: Chenkun Zhou; Haoran Lin, Hongliang Shi, Yu Tian, Chongin Pak, Michael Shatruk, Yan Zhou, Peter Djurovich, Mao-Hua Du, Biwu Ma
      Pages: 1021 - 1024
      Abstract: The synthesis and characterization is reported of (C9NH20)2SnBr4, a novel organic metal halide hybrid with a zero-dimensional (0D) structure, in which individual seesaw-shaped tin (II) bromide anions (SnBr42−) are co-crystallized with 1-butyl-1-methylpyrrolidinium cations (C9NH20+). Upon photoexcitation, the bulk crystals exhibit a highly efficient broadband deep-red emission peaked at 695 nm, with a large Stokes shift of 332 nm and a high quantum efficiency of around 46 %. The unique photophysical properties of this hybrid material are attributed to two major factors: 1) the 0D structure allowing the bulk crystals to exhibit the intrinsic properties of individual SnBr42− species, and 2) the seesaw structure enabling a pronounced excited state structural deformation as confirmed by density functional theory (DFT) calculations.Little red seesaw: A zero-dimensional organic–inorganic hybrid containing a seesaw-shaped tin bromide species is reported. It exhibits a highly efficient strongly Stokes-shifted broadband deep-red emission, which is a result of excited-state structural deformation from a seesaw to a flattened tetrahedron structure.
      PubDate: 2017-12-21T10:46:32.671925-05:
      DOI: 10.1002/anie.201710383
       
  • Nanoscale Chemical Imaging of Reversible Photoisomerization of an
           Azobenzene-Thiol Self-Assembled Monolayer by Tip-Enhanced Raman
           Spectroscopy
    • Authors: Li-Qing Zheng; Xing Wang, Feng Shao, Martin Hegner, Renato Zenobi
      Pages: 1025 - 1029
      Abstract: An understanding of the photoisomerization mechanism of molecules bound to a metal surface at the molecular scale is required for designing photoswitches at surfaces. It has remained a challenge to correlate the surface structure and isomerization of photoswitches at ambient conditions. Herein, the photoisomerization of a self-assembled monolayer of azobenzene-thiol molecules on a Au surface was investigated using scanning tunneling microscopy and tip-enhanced Raman spectroscopy. The unique signature of the cis isomer at 1525 cm−1 observed in tip-enhanced Raman spectra was clearly distinct from the trans isomer. Furthermore, tip-enhanced Raman images of azobenzene thiols after ultraviolet and blue light irradiation are shown with nanoscale spatial resolution, demonstrating a reversible conformational change. Interestingly, the cis isomers of azobenzene-thiol molecules were preferentially observed at Au grain edges, which is confirmed by density functional theory.Switchin’ on the edge: The reversible photoisomerization of an azobenzene thiol (ABT) self-assembled monolayer was demonstrated by tip-enhanced Raman spectroscopy. The cis isomers of ABT were preferentially observed at Au grain edges.
      PubDate: 2017-12-27T10:22:03.419021-05:
      DOI: 10.1002/anie.201710443
       
  • Temperature-Responsive Luminescent Solar Concentrators: Tuning Energy
           Transfer in a Liquid Crystalline Matrix
    • Authors: Jeroen A. H. P. Sol; Volker Dehm, Reinhard Hecht, Frank Würthner, Albertus P. H. J. Schenning, Michael G. Debije
      Pages: 1030 - 1033
      Abstract: Temperature-responsive luminescent solar concentrators (LSCs) have been fabricated in which the Förster resonance energy transfer (FRET) between a donor–acceptor pair in a liquid crystalline solvent can be tuned. At room temperatures, the perylene bisimide (PBI) acceptor is aggregated and FRET is inactive; while after heating to a temperature above the isotropic phase of the liquid crystal solvent, the acceptor PBI completely dissolves and FRET is activated. This unusual temperature control over FRET was used to design a color-tunable LSC. The device has been shown to be highly stable towards consecutive heating and cooling cycles, making it an appealing device for harvesting otherwise unused solar energy.FRET-hot solar energy collection: A novel fluorescent dye was placed in a liquid-crystal-based luminescent solar concentrator to create a supramolecular FRET pair showing an inverse thermal response. At low temperature, no energy transfer is detected and the device is green; after heating, the acceptor becomes active and a red emission is visible.
      PubDate: 2017-12-20T11:11:17.8167-05:00
      DOI: 10.1002/anie.201710487
       
  • A Molecular Pillar Approach To Grow Vertical Covalent Organic Framework
           Nanosheets on Graphene: Hybrid Materials for Energy Storage
    • Authors: Jinhua Sun; Alexey Klechikov, Calin Moise, Mariana Prodana, Marius Enachescu, Alexandr V. Talyzin
      Pages: 1034 - 1038
      Abstract: Hybrid 2D–2D materials composed of perpendicularly oriented covalent organic frameworks (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF-1 nanosheets (v-COF-GO). The hybrid material has a forest of COF-1 nanosheets with a thickness of 3 to 15 nm in edge-on orientation relative to GO. The reaction performed without molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into a conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as a high-performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D-2D materials with control of their relative orientation.COF to GO: Hybrid 2D–2D materials composed of covalent organic framework (COF) nanosheets oriented perpendicularly to the surface of graphene oxide (GO) were prepared using diboronic acid molecules covalently attached to the surface of GO in an edge-on orientation as a vertical-growth directing agent. The standing COF nanosheets, which were converted into boron-doped carbon materials, act as an electrode material for supercapacitors.
      PubDate: 2017-12-20T11:37:15.473103-05:
      DOI: 10.1002/anie.201710502
       
  • Asymmetric Synthesis of 2H-Azirines with a Tetrasubstituted Stereocenter
           by Enantioselective Ring Contraction of Isoxazoles
    • Authors: Kazuhiro Okamoto; Atsushi Nanya, Akira Eguchi, Kouichi Ohe
      Pages: 1039 - 1043
      Abstract: Highly strained 2H-azirines with a tetrasubstituted stereocenter were synthesized by the enantioselective isomerization of isoxazoles with a chiral diene–rhodium catalyst system. The effect of ligands and the coordination behavior support the proposed catalytic cycle in which the coordination site is fixed in favor of efficient enantiodiscrimination by a bulky substituent of the ligand. In silico studies also support the existence of a rhodium–imido complex as a key intermediate for enantiodiscrimination.Coping well under the strain: Highly strained 2H-azirines with tetrasubstituted stereocenters were synthesized with high enantioselectivity by the N−O bond-cleaving isomerization of isoxazoles in the presence of a chiral diene–rhodium catalyst (see scheme). This asymmetric ring contraction of isoxazoles proceeded under mild reaction conditions to give 2-alkoxycarbonyl 2H-azirines with various substituents, including halogen groups.
      PubDate: 2017-12-12T08:52:14.513502-05:
      DOI: 10.1002/anie.201710920
       
  • Identification and Characterization of a Single High-Affinity Fatty Acid
           Binding Site in Human Serum Albumin
    • Authors: Lea Wenskowsky; Herman Schreuder, Volker Derdau, Hans Matter, Julia Volkmar, Marc Nazaré, Till Opatz, Stefan Petry
      Pages: 1044 - 1048
      Abstract: A single high-affinity fatty acid binding site in the important human transport protein serum albumin (HSA) is identified and characterized using an NBD (7-nitrobenz-2-oxa-1,3-diazol-4-yl)-C12 fatty acid. This ligand exhibits a 1:1 binding stoichiometry in its HSA complex with high site-specificity. The complex dissociation constant is determined by titration experiments as well as radioactive equilibrium dialysis. Competition experiments with the known HSA-binding drugs warfarin and ibuprofen confirm the new binding site to be different from Sudlow-sites I and II. These binding studies are extended to other albumin binders and fatty acid derivatives. Furthermore an X-ray crystal structure allows locating the binding site in HSA subdomain IIA. The knowledge about this novel HSA site will be important for drug depot development and for understanding drug-protein interaction, which are important prerequisites for modulation of drug pharmacokinetics.It's not a hydrophobic sponge: The identification and characterization of a single high-affinity fatty acid binding site in human serum albumin has been achieved using a labeled fatty acid with highly specific binding. An X-ray crystal structure locates the binding site in subdomain IIA. The identified binding site helps in the understanding of drug protein binding, modulation of pharmacokinetic profiles, and drug depot development.
      PubDate: 2017-12-27T10:22:53.273112-05:
      DOI: 10.1002/anie.201710437
       
  • A Scandium-Stabilized Diisophosphaethynolate Ligand: [OCPPCO]4−
    • Authors: Lauren N. Grant; Balazs Pinter, Brian C. Manor, Hansjörg Grützmacher, Daniel J. Mindiola
      Pages: 1049 - 1052
      Abstract: The first example of the OCPPCO ligand, diisophosphaethynolate, is reported via reductive coupling of a Sc−OCP precursor. Upon reduction with KC8, isolation of the dinuclear complex, namely [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4−, stabilized by two scandium centers. Detailed NMR spectra of all complexes as well as IR and single crystal X-ray studies were obtained to fully elucidate the nature of these complexes in solution as well as in the solid state. Theory is combined to probe the electronic structure and orbitals responsible for the bonding interactions in the Sc−OCPPCO−Sc skeleton but also to compare to the linear mode observed in the precursor.The OCPPCO ligand, diisophosphaethynolate, formed by reductive coupling of a Sc−OCP precursor, is reported. Upon reduction with KC8, isolation of the dinuclear complex, [K(OEt2)]2[(nacnac)Sc(OAr)]2(OCPPCO), is observed, leading to a unique motif [OCPPCO]4− stabilized by two scandium centers. NMR, IR, and X-ray diffraction were used to study these complexes in solution as well as in the solid state.
      PubDate: 2017-12-21T07:36:17.177446-05:
      DOI: 10.1002/anie.201710757
       
  • Synthesis of Low-Dimensional Polyion Complex Nanomaterials via
           Polymerization-Induced Electrostatic Self-Assembly
    • Authors: Yi Ding; Meng Cai, Zhigang Cui, Leilei Huang, Lei Wang, Xinhua Lu, Yuanli Cai
      Pages: 1053 - 1056
      Abstract: Nanostructured polyion complexes (PICs) are appealing in biomaterials applications. Yet, conventional assembly suffers from the weakness in scale-up and reproducibility. Only a few low-dimensional PICs are available to date. Herein we report an efficient and scalable strategy to prepare libraries of low-dimensional PICs. It involves a visible-light-mediated RAFT polymerization of ionic monomer in the presence of a polyion of the opposite charge at 5–50 % w/w total solids concentration in water at 25 °C, namely, polymerization-induced electrostatic self-assembly (PIESA). A Vesicle, multi-compartmental vesicle, and large-area unilamellar nanofilm can be achieved in water. A long nanowire and porous nanofilm can be prepared in methanol/water. An unusual unimolecular polyion complex (uPIC)-sphere-branch/network-film transition is reported. This green chemistry offers a general platform to prepare various low-dimensional PICs with high reproducibility on a commercially viable scale under eco-friendly conditions.Shape up: An efficient and scalable strategy allows the preparation of libraries of low-dimensional polyion complexes. It proceeds via in situ polyion complexation in a visible-light-mediated polymerization-induced electrostatic self-assembly in water at 25 °C. A nanosphere, nanowire, large-area nanofilm, porous nanofilm, vesicle, and multi-compartmental vesicle can be prepared.
      PubDate: 2017-12-20T09:50:32.712535-05:
      DOI: 10.1002/anie.201710811
       
  • Artificial β-Double Helices from Achiral γ-Peptides
    • Authors: Rajkumar Misra; Sanjit Dey, Rahi M. Reja, Hosahudya N. Gopi
      Pages: 1057 - 1061
      Abstract: Double helices are not common in polypeptides and proteins except in the peptide antibiotic gramicidin A and analogous l,d-peptides. In contrast to natural polypeptides, remarkable β-double-helical structures from achiral γ-peptides built from α,β-unsaturated γ-amino acids have been observed. The crystal structures suggest that they adopted parallel β-double helical structures and these structures are stabilized by the interstrand backbone amide H-bonds. Furthermore, both NMR spectroscopy and fluorescence studies support the existence of double-helical conformations in solution. Although a variety of folded architectures featuring distinct H-bonds have been discovered from the β- and γ-peptide foldamers, this is the first report to show that achiral γ-peptides can spontaneously intertwine into β-double helical structures.The double helix is a common structural feature in nucleic acids and polysaccharides. However, double helix structures are not common in polypeptides except in the peptide antibiotic gramicidin A. A new class of achiral γ-peptides, which spontaneously intertwine into parallel β-double helices, is reported.
      PubDate: 2017-12-27T10:20:55.110144-05:
      DOI: 10.1002/anie.201711124
       
  • Reversing Conventional Reactivity of Mixed Oxo/Alkyl Rare-Earth Complexes:
           Non-Redox Oxygen Atom Transfer
    • Authors: Jianquan Hong; Haiwen Tian, Lixin Zhang, Xigeng Zhou, Iker del Rosal, Linhong Weng, Laurent Maron
      Pages: 1062 - 1067
      Abstract: The preferential substitution of oxo ligands over alkyl ones of rare-earth complexes is commonly considered as “impossible” due to the high oxophilicity of metal centers. Now, it has been shown that simply assembling mixed methyl/oxo rare-earth complexes to a rigid trinuclear cluster framework cannot only enhance the activity of the Ln-oxo bond, but also protect the highly reactive Ln-alkyl bond, thus providing a previously unrecognized opportunity to selectively manipulate the oxo ligand in the presence of numerous reactive functionalities. Such trimetallic cluster has proved to be a suitable platform for developing the unprecedented non-redox rare-earth-mediated oxygen atom transfer from ketones to CS2 and PhNCS. Controlled experiments and computational studies shed light on the driving force for these reactions, emphasizing the importance of the sterical accessibility and multimetallic effect of the cluster framework in promoting reversal of reactivity of rare-earth oxo complexes.The preferential substitution and functionalization of oxo ligands over alkyl ones is commonly referred to as “impossible” in lanthanide chemistry due to the high oxophilicity of the metal center. Now, it has been shown that the reactivity of mixed methyl/oxo lanthanide complexes can be switched and controlled.
      PubDate: 2017-12-28T07:31:44.72472-05:0
      DOI: 10.1002/anie.201711305
       
  • Enantioselective Photochemical Organocascade Catalysis
    • Authors: Łukasz Woźniak; Giandomenico Magagnano, Paolo Melchiorre
      Pages: 1068 - 1072
      Abstract: Reported herein is a photochemical cascade process that combines the excited-state and ground-state reactivity of chiral organocatalytic intermediates. This strategy directly converts racemic cyclopropanols and α,β-unsaturated aldehydes into stereochemically dense cyclopentanols with exquisite stereoselectivity. Mechanistic investigations have enabled elucidating the origin of the stereoconvergence, which is governed by a kinetic resolution process.Light it up: A photochemical radical/polar cascade process that combines the excited-state and ground-state reactivity of chiral organocatalytic intermediates is reported. This strategy directly converts racemic cyclopropanols and α,β-unsaturated aldehydes into stereochemically dense cyclopentanols with exquisite stereoselectivity.
      PubDate: 2017-12-20T11:11:28.929173-05:
      DOI: 10.1002/anie.201711397
       
  • Cleavage of Unstrained C−C Bonds in Acenes by Boron and Light:
           Transformation of Naphthalene into Benzoborepin
    • Authors: Suning Wang; Kang Yuan, Ming-Feng Hu, Xiang Wang, Tai Peng, Nan Wang, Quan-Song Li
      Pages: 1073 - 1077
      Abstract: Naphthalene and acenaphthene with peri 2-py and BMes2 (py=pyridyl, Mes=mesityl) substituents have been found to undergo facile phototransformation, cleavage of a C−C bond of naphthalene, and formation of 2-py-bound benzoborepins as the major products. Mechanistic pathways of this photoreaction have been established by examination of both excited and ground states by using CASSCF and CASPT2 methods in DFT and time-dependent DFT calculations. The mesityl to py-naphthyl charge-transfer transition and the mesityl migration from the boron atom to the naphthyl moiety drive this unprecedented C−C bond cleavage and boron-insertion reaction.Cleavage of unstrained arene C−C bonds has been established in boron-functionalized naphthalene and its derivatives. The method provides a new and convenient approach for the synthesis of borepin molecules. Mes=Mesityl.
      PubDate: 2017-12-20T09:51:47.08153-05:0
      DOI: 10.1002/anie.201711658
       
  • Emissive Synthetic Cofactors: Enzymatic Interconversions of tzA Analogues
           of ATP, NAD+, NADH, NADP+, and NADPH
    • Authors: François Hallé; Andrea Fin, Alexander R. Rovira, Yitzhak Tor
      Pages: 1087 - 1090
      Abstract: A series of enzymatic transformations, which generate visibly emissive isofunctional cofactors based on an isothiazolo[4,3-d]pyrimidine analogue of adenosine (tzA), was developed. Nicotinamide adenylyl transferase condenses nicotinamide mononucleotide and tzATP to yield NtzAD+, which can be enzymatically phosphorylated by NAD+ kinase and ATP or tzATP to the corresponding NtzADP+. The latter can be engaged in NADP-specific coupled enzymatic transformations involving conversion to NtzADPH by glucose-6-phosphate dehydrogenase and reoxidation to NtzADP+ by glutathione reductase. The NtzADP+/NtzADPH cycle can be monitored in real time by fluorescence spectroscopy.Relatives in the spotlight: A series of enzymatic transformations generate visibly emissive isofunctional cofactors based on an isothiazolo[4,3-d]pyrimidine analogue of adenosine (tzA, see figure). These synthetic cofactors may find utility as tools for monitoring redox reactions in vitro or potentially in living systems.
      PubDate: 2017-12-21T10:45:48.573328-05:
      DOI: 10.1002/anie.201711935
       
  • Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using
           Diffusion-Limited Atomic Layer Deposition
    • Authors: Shufang Zhang; Bin Zhang, Haojie Liang, Yequn Liu, Yan Qiao, Yong Qin
      Pages: 1091 - 1095
      Abstract: The heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion-limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub-nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA-15, SBA-16, and MCM-41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD-assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.Fitting the plug: Metal complexes have been successfully encapsulated in mesoporous materials by atomic layer deposition of metal oxides at/near the pore entrance. A hollow plug is thereby formed by controlling the diffusion time of the precursors.
      PubDate: 2017-12-27T10:20:11.916254-05:
      DOI: 10.1002/anie.201712010
       
  • Integration of Plasmonic Effects and Schottky Junctions into
           Metal–Organic Framework Composites: Steering Charge Flow for Enhanced
           Visible-Light Photocatalysis
    • Authors: Juan-Ding Xiao; Lili Han, Jun Luo, Shu-Hong Yu, Hai-Long Jiang
      Pages: 1103 - 1107
      Abstract: A wide range of light absorption and rapid electron–hole separation are desired for efficient photocatalysis. Herein, on the basis of a semiconductor-like metal–organic framework (MOF), a Pt@MOF/Au catalyst with two types of metal–MOF interfaces integrates the surface plasmon resonance excitation of Au nanorods with a Pt-MOF Schottky junction, which not only extends the light absorption of the MOF from the UV to the visible region but also greatly accelerates charge transfer. The spatial separation of Pt and Au particles by the MOF further steers the formation of charge flow and expedites the charge migration. As a result, the Pt@MOF/Au presents an exceptionally high photocatalytic H2 production rate by water splitting under visible light irradiation, far superior to Pt/MOF/Au, MOF/Au and other counterparts with similar Pt or Au contents, highlighting the important role of each component and the Pt location in the catalyst.Up the junction: A wide-band-gap semiconductor-like metal–organic framework (MOF), MIL-125, with Pt nanoparticles in its crystal structure and Au nanorods on its outer surface gives Pt@MIL-125/Au, a catalyst with two metal–MOF interfaces. The integration of surface plasmon resonance (SPR) Au excitation with the Pt–MOF Schottky junction results in high photocatalytic H2 production activity.
      PubDate: 2017-12-21T10:46:23.006896-05:
      DOI: 10.1002/anie.201711725
       
  • Cobalt-Catalyzed Electrophilic Amination of Aryl- and Heteroarylzinc
           Pivalates with N-Hydroxylamine Benzoates
    • Authors: Yi-Hung Chen; Simon Graßl, Paul Knochel
      Pages: 1108 - 1111
      Abstract: Aryl- and heteroarylzinc pivalates can be aminated with O-benzoylhydroxylamines at 25 °C within 2–4 h in the presence of 2.5–5.0 % CoCl2⋅2 LiCl to furnish the corresponding tertiary arylated or heteroarylated amines in good yields. This electrophilic amination also provides access to diarylamines and aryl(heteroaryl)amines. A new tuberculosis drug candidate (Q203) was prepared in six steps and 56 % overall yield by using this cobalt-catalyzed amination as the key step.Animating aminations: A range of aryl- and heteroarylzinc pivalates underwent cobalt-catalyzed electrophilic aminations with O-benzoylhydroxylamines in good yields under mild conditions. This reaction can be applied to prepare arylamines and diarylamines. A new tuberculosis drug candidate was prepared in six steps and 56 % overall yield by using the cobalt-catalyzed amination as the key step.
      PubDate: 2017-12-28T08:36:14.217299-05:
      DOI: 10.1002/anie.201710931
       
  • Inside Back Cover: Asymmetric Synthesis of 2H-Azirines with a
           Tetrasubstituted Stereocenter by Enantioselective Ring Contraction of
           Isoxazoles (Angew. Chem. Int. Ed. 4/2018)
    • Authors: Kazuhiro Okamoto; Atsushi Nanya, Akira Eguchi, Kouichi Ohe
      Pages: 1117 - 1117
      Abstract: 2H-Azirines are highly strained three-membered N-heterocycles, and their enantioselective synthesis is challenging. In their Communication on page 1039 ff., K. Okamoto, K. Ohe et al. report a novel enantioselective synthesis of 2H-azirines that is based on the transition-metal-catalyzed ring contraction of planar isoxazoles. The reaction is proposed to proceed through N−O bond cleavage of the isoxazoles followed by the formation of alkenylimide–rhodium intermediates to afford chiral 2-alkoxycarbonyl-2H-azirines with various substituents.
      PubDate: 2017-12-29T05:10:51.73883-05:0
      DOI: 10.1002/anie.201713148
       
 
 
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