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  Subjects -> CHEMISTRY (Total: 849 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (598 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (42 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (598 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 32)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 226)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 14)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Hybrid Journal   (Followers: 13)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 159)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 210)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 282)
Biochemistry Insights     Open Access   (Followers: 5)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 108)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 93)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 67)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 173)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 147)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 250)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 11)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 57)
Dalton Transactions     Full-text available via subscription   (Followers: 19)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 9)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [159 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0044-8249 - ISSN (Online) 1521-3757
   Published by John Wiley and Sons Homepage  [1584 journals]
  • Unified Total Synthesis of Polyoxin J, L, and Their Fluorinated Analogues
           Based on Decarbonylative Radical Coupling Reactions
    • Authors: Masayuki Inoue; Haruka Fujino, Masanori Nagatomo, Atmika Paudel, Suresh Panthee, Hiroshi Hamamoto, Kazuhisa Sekimizu
      Abstract: Polyoxins J (1a) and L (1b) are important members of nucleoside antibiotics. The complex and densely functionalized dipeptide structures of 1a and 1b possess thymine and uracil nucleobases, respectively. Here we report the unified total synthesis of 1a, 1b, and their artificial analogues 1c and 1d, with trifluorothymine and fluorouracil structures. Decarbonylative radical coupling reactions between a-alkoxyacyl tellurides and a chiral glyoxylic oxime ether led to chemo- and stereoselective construction of the ribonucleoside a-amino acid structures of 1a-d without damaging the preinstalled nucleobases. The high applicability of the radical-based methodology was further demonstrated by preparation of the trihydroxynorvaline moiety of 1a-d. The two amino acid fragments were connected and elaborated into 1a-d (longest linear sequence: 11 steps). The thus-assembled 1a and 1b exhibited potent activities against true fungi, while only 1d was active against Gram-positive bacteria.
      PubDate: 2017-07-20T05:12:21.511477-05:
      DOI: 10.1002/ange.201706671
       
  • Fractal Crystals: Hunting the Hidden Dimension in Nanoporous Materials
    • Authors: Lei Wang; Shengcai Zhu, Meikun Shen, Haiwen Tian, Songhai Xie, Hongbin Zhang, Yahong Zhang, Yi Tang
      Abstract: Screw dislocation structure in crystal are origin of symmetry breaking in a wide range of dense phase crystals. Preparation of such analogous structure in framework phase crystals is of great importance in zeolites but still a challenge. On the basis of crystal structure-solving and model building, we found that the two specific intergrowths in MTW zeolite produce this complex fractal and spiral structure. With the structure determined parameters (spiral pitch h, screw angle θ and spatial angle ψ) of Burgers circuit, the screw dislocation structure can be constructed by two different dimensional intergrowth sections. Thus the reported complexity of various dimensions in diverse crystals can be unified.
      PubDate: 2017-07-20T05:11:59.970912-05:
      DOI: 10.1002/ange.201704499
       
  • Living and Conducting: Coating Individual Bacterial Cells with
           In Situ Formed Polypyrrole
    • Authors: Rong-Bin Song; YiChao Wu, Zong-Qiong Lin, Jian Xie, Chuan Hao Tan, Joachim Say Chye Loo, Bin Cao, Jian-Rong Zhang, Jun-Jie Zhu, Qichun Zhang
      Abstract: Die Beschichtung einzelner Bakterienzellen mit in situ gebildetem Polypyrrol wird von J. S. C. Loo, B. Cao, J. R. Zhang, J. J. Zhu et al. in ihrer Zuschrift (
      DOI : 10.1002/ange.201704729) beschrieben. Das Polypyrrol kann als leitfähiges Medium sowie als Schutzschicht fungieren. Ein erhöhter direkter kontaktbasierter extrazellulärer Elektronentransfer und eine bessere Lebensfähigkeit der Bakterienzellen werden beobachtet, wenn mit Polypyrrol beschichtete exoelektrogene Bakterien als Anode in mikrobiellen Brennstoffzellen eingesetzt werden.
      PubDate: 2017-07-20T04:47:15.573807-05:
       
  • Quantifying Hydrogen-Bond Populations in Dimethyl Sulfoxide/Water Mixtures
    • Authors: Kwang-Im Oh; Kavya Rajesh, John F. Stanton, Carlos R. Baiz
      Abstract: Wasser-Dimethylsulfoxid-Wechselwirkungen wurden mittels IR-Spektroskopie analysiert. In ihrer Zuschrift (
      DOI : 10.1002/ange.201704162 zeigen C. R. Baiz et al., dass die Wasserstoffbrückenpopulation in binären Mischungen direkt quantifiziert werden kann und die molekularen Ensemble mit makroskopischen Lösungseigenschaften korreliert werden können. Die Fische repräsentieren die in Gruppen aus dem Wasser springenden DMSO-Moleküle und stellen die starke Wechselwirkung zwischen den einzelnen DMSO-Molekülen dar.
      PubDate: 2017-07-20T04:47:13.488175-05:
       
  • Asymmetric Synthesis of Chiral Cyclopentanes Bearing an All-Carbon
           Quaternary Stereocenter via Zr-catalyzed Doubled Carboalumination
    • Authors: Shiqing Xu; Chuan Wang, Masato Komiyama, Yasuhiko Tomonari, Ei-ichi Negishi
      Abstract: Herein we report a Zr-catalyzed enantio- and diastereoselective inter-intramolecular doubled carboalumination of unactivated 2-substituted-1,5-dienes which provides an efficient and direct access to chiral cyclopentanes with generation of two stereocenters including an all-carbon quaternary stereocenter generally in excellent diastereomeric ratios and high enantiomeric excesses. This tandem carboalumination process creates two new C-C bonds as well as a C-Al bond which can be in-situ oxidized with O2 or hydrolyzed. Furthermore, the obtained chiral cyclopentanes can be readily functionalized to provide various chiral compounds.
      PubDate: 2017-07-20T00:34:22.40281-05:0
      DOI: 10.1002/ange.201706198
       
  • Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers
           by Nickel-Catalyzed Asymmetric Suzuki-Miyaura Coupling of Secondary Benzyl
           Bromides
    • Authors: Weichen Huang; Xiaolong Wan, Qilong Shen
      Abstract: A method for the construction of trifluoromethoxy-containing stereogenic centers with high enantiometric excess via nickel-catalyzed Suzuki-Miyaura coupling of easily available -bromobenzyl trifluoromethylethers 1a-g with a variety of aryl pinacol boronates was described. The reaction conditions were mild and a variety of common functional groups such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino and vinyl group were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without erosion of the enantioselectivity.
      PubDate: 2017-07-20T00:13:27.962044-05:
      DOI: 10.1002/ange.201706868
       
  • Colossal Stability of Gas Phase Tri-anions: The Concept of
           Super-pnictogens
    • Authors: Tianshan Zhao; Jian Zhou, Qian Wang, Puru Jena
      Abstract: Multiply charged negative ions are ubiquitous in nature. In crystals, they are stable due to charge compensating cations while in solutions, solvent molecules protect them; but they are rarely stable in the gas phase due to strong electrostatic repulsion between the extra electrons. Understanding their stability without the influence of the environment, therefore, has been of great interest to scientists for decades. While much of the past work has focused on the di-anions, work on triply charged negative ions is sparse and the search for the smallest stable tri-anion against spontaneous electron emission or fragmentation continues. We show here that BeB₁₁(X)₁₂³- (X=CN, SCN, BO) tri-anions are all stable in the gas phase, with BeB₁₁(CN)₁₂³- exhibiting colossal stability against electron emission by 2.65 eV and against its neutral by 15.85 eV! The unusual stability of these tri-anions opens the door to a new class of super-pnictogens with potential applications in Al-ion batteries.
      PubDate: 2017-07-20T00:10:21.893143-05:
      DOI: 10.1002/ange.201706764
       
  • Crystalline π-Stack Containing Five Stereoisomers: Insights into
           Conformational Isomorphism, Chirality Inversion and Disorder
    • Authors: Agnieszka Nowak-Krol; Merle Röhr, David Schmidt, Frank Würthner
      Abstract: An unprecedented crystal packing arrangement of a tetramethoxy-bay-substituted perylene bisimide (PBI) consists of three crystallographically independent molecules, i.e. an achiral (AC) PBI of saddle-shaped geometry along with two pairs of propeller-like twisted (P) and (M)enantiomeric PBI frameworks. All these five conformations are observed within a single π-stack revealing an intriguing packing sequence with an inversion of chirality from P to M via AC. Nudged elastic band calculations for the isolated molecule show that AC is a local minimum of the P to M interconversion path. In addition, two minor conformations were observed in the crystal, one of which resembles a transition state molecule. Theoretical studies of dimeric and trimeric stacks reveal that the coexistence of all these structures in the crystal lattice is facilitated by the strong dispersion interactions between PBI cores and perfectly interdigitated dodecyl chains which stabilize energetically higher conformations.
      PubDate: 2017-07-19T09:10:55.669406-05:
      DOI: 10.1002/ange.201705445
       
  • Controlling Reaction Selectivity through the Surface Termination of
           Perovskite Catalysts
    • Authors: Felipe Polo-Garzon; Shi-Ze Yang, Victor Fung, Guo Shiou Foo, Elizabeth E. Bickel, Matthew F. Chisholm, De-en Jiang, Zili Wu
      Abstract: Although perovskites have been widely used in catalysis, tuning of their surface termination to control reaction selectivity has not been well established. In this study, we employed multiple surface-sensitive techniques to characterize the surface termination (one aspect of surface reconstruction) of SrTiO3 (STO) after thermal pretreatment (Sr enrichment) and chemical etching (Ti enrichment). We show, by using the conversion of 2-propanol as a probe reaction, that the surface termination of STO can be controlled to greatly tune catalytic acid/base properties and consequently the reaction selectivity over a wide range, which is not possible with single-metal oxides, either SrO or TiO2. Density functional theory (DFT) calculations explain well the selectivity tuning and reaction mechanism on STO with different surface termination. Similar catalytic tunability was also observed on BaZrO3, thus highlighting the generality of the findings of this study.Es zählt, was an der Oberfläche ist: Durch gezielte Oberflächentermination von SrTiO3 – thermische Vorbehandlung (Sr-Anreicherung) und chemisches Ätzen (Ti-Anreicherung) – ließ sich die Selektivität in der Umwandlung von 2-Propanol steuern. Die Befunde haben große Bedeutung für die Katalyse durch gemischte Oxide, deren Oberflächen- und Bulkzusammensetzungen je nach Behandlung und Reaktionsbedingungen unterschiedlich sein können.
      PubDate: 2017-07-19T08:15:38.370706-05:
      DOI: 10.1002/ange.201704656
       
  • Phosphaborenes: Accessible Reagents for the Synthesis of
           C−C/P−B Isosteres
    • Authors: Amy N. Price; Gary S. Nichol, Michael J. Cowley
      Abstract: Formal exchange of C=C units with isoelectronic B=N or B=P units can provide access to molecules with unique electronic or chemical properties. Herein, we report the simple solution-phase generation of highly reactive phosphaborenes, RP=BR, and demonstrate their use for the introduction of P=B units into organic systems. Ring opening of a P−B-containing cyclobutene isostere provided access to unique 1,4-boraphosphabutadiene systems with conjugated main-group multiple bonds.Kurzlebige Phosphaborene, RP=BR, können in Lösung erzeugt und zur Einführung von PB-Einheiten als C=C-Isostere in organische Verbindungen genutzt werden (siehe Schema). Ein PB-haltiges Cyclobuten-Analog geht eine Ringöffnung zur Bildung von konjugierten Systemen mit Hautpgruppen-Mehrfachbindungen ein.
      PubDate: 2017-07-19T08:15:28.759635-05:
      DOI: 10.1002/ange.201705050
       
  • Fluorinative Rearrangements of Substituted Phenylallenes Mediated by
           (Difluoroiodo)toluene: Synthesis of a-(Difluoromethyl)styrenes
    • Authors: Zhensheng Zhao; Léanne Racicot, Graham K. Murphy
      Abstract: Phenylallenes undergo a fluorinative rearrangement by the action of (difluoroiodo)toluene, in the presence of 20 mol% BF3*OEt2, to yield a-difluoromethyl styrenes. This unprecedented reaction was entirely chemoselective for the internal allene pi-bond, and showed remarkable regioselectivity during the fluorination event. Substituted phenylallenes, phenylallenes possessing both phenyl- and a-allenyl substituents, and diphenylallenes were investigated, and good functional group compatibility was observed throughout. The ease with which allenes can be prepared on large scale, and the operational simplicity of this reaction have allowed us to rapidly access fluorine-containing building blocks that have not been accessed by conventional deoxyfluorination strategies.
      PubDate: 2017-07-19T08:07:11.220514-05:
      DOI: 10.1002/ange.201706798
       
  • Highly Ordered Self-Assembly of Native Proteins into 1D, 2D, and 3D
           Structures Modulated by the Tether Length of Assembly-Inducing Ligands
    • Authors: Guang Yang; Hong-ming Ding, Zdravko Kochovski, Rongting Hu, Yan Lu, Yu-qiang Ma, Guosong Chen, Ming Jiang
      Abstract: In der Natur bilden Proteine hochgeordnete selbstorganisierte Strukturen mit einer Vielzahl an Morphologien und Dimensionen. In ihrer Zuschrift (
      DOI : 10.1002/ange.201703052) berichten Y. Ma, G. Chen et al. über die Erzeugung von Proteinaggregaten mit dem nativen Protein LecA als Baustein, indem sie Zucker-Protein-Wechselwirkungen und die Rhodamindimerisierung nutzten. Die Morphologien und Dimensionen der Proteinaggregate lassen sich über die Länge der Verknüpfung von Zucker und Rhodamin einstellen.
      PubDate: 2017-07-19T07:50:43.654766-05:
       
  • A Membrane-Free Redox Flow Battery with Two Immiscible Redox Electrolytes
    • Authors: Paula Navalpotro; Jesus Palma, Marc Anderson, Rebeca Marcilla
      Abstract: Flexible and scalable energy storage solutions are necessary for mitigating fluctuations of renewable energy sources. The main advantage of redox flow batteries is their ability to decouple power and energy. However, they present some limitations including poor performance, short-lifetimes, and expensive ion-selective membranes as well as high price, toxicity, and scarcity of vanadium compounds. We report a membrane-free battery that relies on the immiscibility of redox electrolytes and where vanadium is replaced by organic molecules. We show that the biphasic system formed by one acidic solution and one ionic liquid, both containing quinoyl species, behaves as a reversible battery without any membrane. This proof-of-concept of a membrane-free battery has an open circuit voltage of 1.4 V with a high theoretical energy density of 22.5 Wh L−1, and is able to deliver 90 % of its theoretical capacity while showing excellent long-term performance (coulombic efficiency of 100 % and energy efficiency of 70 %).Ohne Membran: Die Verwendung nichtmischbarer Elektrolyte führte zu einem Batterieprototyp, der gänzlich ohne Membran auszkommt. Die üblicherweise in Redox-Flow-Batterien eingesetzten Metallpaare werden außerdem durch organische Moleküle ersetzt. Da in beiden Elektrolyten unterschiedliche Mechanismen ablaufen, konnte ein und das gleiche Molekül für ein symmetrisches Batteriedesign genutzt werden.
      PubDate: 2017-07-19T07:50:31.321925-05:
      DOI: 10.1002/ange.201704318
       
  • Reaktionen von Donor-Akzeptor-Cyclopropanen mit Naphthochinonen: eine
           Kombination aus Redox- und Lewis-Säure-Katalyse
    • Authors: Alexander Lücht; Lukas J. Patalag, André U. Augustin, Peter G. Jones, Daniel B. Werz
      Abstract: 2-Arylcyclopropandicarboxylate werden mit Naphthochinonen zur Reaktion gebracht. Der Schlüsselschritt besteht in der Verwendung von katalytischen Mengen an SnCl2, das sowohl als Elektronendonor als auch als Lewis-Säure fungiert. Mittels einer In-situ-Umpolung wird das vormals elektrophile Naphthochinon in ein Nukleophil überführt. Dieses löst die Ringöffnung des Dreirings aus, wobei eine neue C-C-Bindung geknüpft wird. Werden die so erhaltenen Produkte mit einer Base unter oxidativen Bindungen umgesetzt, führt dies – durch Abspaltung von Methylformiat – zu cyclopentanellierten Produkten mit einem komplett konjugierten π-System, welche eine intensive Absorption im sichtbaren Bereich aufweisen.Elektronen-Power: Elektrophile Naphthochinone werden mittels katalytischer Mengen an Zinn(II) in die entsprechenden nukleophilen Spezies umgewandelt, welche imstande sind, ein Donor-Akzeptor-Cyclopropan zu öffnen. Basische oxidative Bedingungen führen über eine [3+2]-Cyclopentanellierung zu einem vollständig konjugierten π-System.
      PubDate: 2017-07-19T07:45:35.929706-05:
      DOI: 10.1002/ange.201703732
       
  • Phosphorene Co-catalyst Advancing Highly Efficient Visible-Light
           Photocatalytic Hydrogen Production
    • Authors: Jingrun Ran; Bicheng Zhu, Shi-Zhang Qiao
      Abstract: Transitional metals are widely used as co-catalysts boosting photocatalytic H2 production. However, metal-based co-catalysts suffer from high cost, limited abundance and detrimental environment impact. To date, metal-free co-catalyst is rarely reported. Here we for the first time utilized density functional calculations to guide the application of phosphorene as a high-efficiency metal-free co-catalyst for CdS, Zn0.8Cd0.2S or ZnS. Particularly, phosphorene modified CdS shows a high apparent quantum yield of 34.7 % at 420 nm. This outstanding activity arises from the strong electronic coupling between phosphorene and CdS, as well as the favorable band structure, high charge mobility and massive active sites of phosphorene, supported by computations and advanced characterizations, for example, synchrotron-based X-ray absorption near edge spectroscopy. This work brings new opportunities to prepare highly-active, cheap and green photocatalysts.Dichtefunktionalrechnungen wurden verwendet, um die Entwicklung von Phosphoren als metallfreiem Cokatalysator für Metallsulfide in der photokatalytischen H2-Erzeugung zu steuern. Die verbesserte Leistung ist das Ergebnis der elektronischen Kopplung zwischen Metallsulfiden und Phosphoren sowie von dessen vorteilhafter Bandstruktur und exzellenter Ladungsträgerbeweglichkeit.
      PubDate: 2017-07-19T07:40:26.053191-05:
      DOI: 10.1002/ange.201703827
       
  • Unique Spectral Overlap and Resonant Energy Transfer between Europium(II)
           and Ytterbium(III) Cations: No Quantum Cutting
    • Authors: Lei Zhou; Peter A. Tanner, Weijie Zhou, Yeye Ai, Lixin Ning, Mingmei M. Wu, Hongbin Liang
      Abstract: Samples of the Ca3Sc2Si3O12 (CSS) host singly doped with Eu2+ or Yb3+, doubly doped with Eu2+ and Yb3+, and triply doped with Ce3+, Eu2+ and Yb3+ were synthesized by a sol–gel combustion process under reducing conditions. Unlike previous reports of Eu2+Yb3+ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb3+ is further enhanced by co-doping with Ce3+ in addition to Eu2+. The quantum efficiencies of the doped materials range between 9 % and 93 %.Gewinnung von Sonnenenergie: Einfach mit Eu2+ oder Yb3+, doppelt mit Eu2+ und Yb3+ und dreifach mit Ce3+, Eu2+ und Yb3+ dotierte Ca3Sc2Si3O12(CSS)-Wirtgitter wurden in einem Sol-Gel-Verbrennungsprozess synthetisiert. Das dreifach dotierte System wandelt Sonnenenergie in eine Nahinfrarot-Emission des Yb3+-Ions um (dd=Dipol-Dipol-, dq=Dipol-Quadrupol-Wechselwirkungen; ET=Elektronentransfer).
      PubDate: 2017-07-19T07:35:26.473953-05:
      DOI: 10.1002/ange.201703331
       
  • Efficient Access to All-Carbon Quaternary and Tertiary α-Functionalized
           Homoallyl Aldehydes from Ketones
    • Authors: VITTORIO PACE; Laura Castoldi, Eugenia Mazzeo, Marta Rui, Thierry Langer, Wolfgang Holzer
      Abstract: Widely substituted all-carbon quaternary and tertiary α-homoallyl aldehydes are rapidly assembled through a unique synthetic operation from ketones consisting in: 1) C1-homologation; 2) epoxide-aldehyde Lewis acid mediated isomerization and, 3) electrophilic trapping. The synthetic equivalence between a vinyl oxirane and a β,γ-unsaturated aldehyde is the key concept for introducing such a previously undisclosed tactic. Mechanistic studies and labeled experiments suggest the intervention of an aldehyde enolate as the crucial intermediate. Significantly, the homologating carbenoid formation event (carbenoid precursor and organolithium) plays a critical role in determining the chemoselectivity.
      PubDate: 2017-07-19T07:13:02.526095-05:
      DOI: 10.1002/ange.201706236
       
  • Iridium-Catalyzed Enantioselective Synthesis of Pyrrole-Annulated
           Medium-Sized-Ring Compounds
    • Authors: Lin Huang; Yue Cai, Chao Zheng, Li-Xin Dai, Shu-Li You
      Abstract: Enantioselective synthesis of pyrrole-annulated medium-sized-ring compounds by an iridium-catalyzed allylic dearomatization/retro-Mannich/hydrolysis sequence is presented. Various substituted pyrrole-annulated seven- and eight-membered-ring products were obtained under mild reaction conditions with moderate to good yields and excellent enantioselectivity. Additionally, these products contain a scaffold widely distributed in natural products and biologically active compounds. The current method provides a convenient way for accessing such pyrrole-anuulated medium-sized-ring compounds.Die enantioselektive Synthese von Pyrrol-anellierten mittelgroßen Ringen gelingt durch eine Sequenz aus Iridium-katalysierter allylischer Dearomatisierung, Retro-Mannich-Reaktion und Hydrolyse. Vielfältig substituierte Pyrrol-anellierte sieben- und achtgliedrige Ringe wurden unter milden Bedingungen mit mäßigen bis guten Ausbeuten und exzellenten Enantioselektivitäten erhalten.
      PubDate: 2017-07-19T06:21:48.435304-05:
      DOI: 10.1002/ange.201705068
       
  • Bromination of Cycloparaphenylenes: Strain-Induced Site-Selective
           Bis-Addition and its Application for Late-Stage Functionalization
    • Authors: Eiichi Kayahara; Rui Qu, Shigeru Yamago
      Abstract: Bromination of [n]cycloparaphenylenes (CPPs) is herein reported. Small [n]CPPs (n
      PubDate: 2017-07-19T06:21:36.030523-05:
      DOI: 10.1002/ange.201704982
       
  • Pancake Bond Orders of a Series of π-Stacked Triangulene Radicals
    • Authors: Zhongyu Mou; Miklos Kertesz
      Abstract: Conjugated radicals are capable of forming π-stacking “pancake-bonded” dimers. Members of the family of triangulene hydrocarbons, non-Kekulé neutral multiradicals, can utilize more than one singly occupied molecular orbital (SOMO) to form multiple pancake-bonded dimers with formal bond orders of up to five. The resulting dimer binding energies can be quite high and the intermolecular contacts rather small compared to the respective van der Waals values. The preferred configurations are driven by the large stabilization energy of overlapping SOMOs.Grundzustände mit hohem Spin ermöglichen kurze und starke Pancake-Bindungen zwischen dreieckförmigen Graphenflocken mit multipler π-Stapelung durch den Raum.
      PubDate: 2017-07-19T06:21:30.377822-05:
      DOI: 10.1002/ange.201704941
       
  • A Porphyrin Complex as a Self-Conditioned Electrode Material for
           High-Performance Energy Storage
    • Authors: Ping Gao; Zhi Chen, Zhirong Zhao-Karger, Jonathan E. Mueller, Christoph Jung, Svetlana Klyatskaya, Thomas Diemant, Olaf Fuhr, Timo Jacob, R. Jürgen Behm, Mario Ruben, Maximilian Fichtner
      Abstract: The novel functionalized porphyrin [5,15-bis(ethynyl)-10,20-diphenylporphinato]copper(II) (CuDEPP) was used as electrodes for rechargeable energy-storage systems with an extraordinary combination of storage capacity, rate capability, and cycling stability. The ability of CuDEPP to serve as an electron donor or acceptor supports various energy-storage applications. Combined with a lithium negative electrode, the CuDEPP electrode exhibited a long cycle life of several thousand cycles and fast charge–discharge rates up to 53 C and a specific energy density of 345 Wh kg−1 at a specific power density of 29 kW kg−1. Coupled with a graphite cathode, the CuDEPP anode delivered a specific power density of 14 kW kg−1. Whereas the capacity is in the range of that of ordinary lithium-ion batteries, the CuDEPP electrode has a power density in the range of that of supercapacitors, thus opening a pathway toward new organic electrodes with excellent rate capability and cyclic stability.Geben und nehmen: Auf einem Kupferporphyrin basierende Elektroden zeigen einen exzellenten Kapazitätsbehalt über mehrere Tausend Zyklen und sehr schnelle Lade/Entlade-Raten, was den Weg zu organischen Elektrodenmaterialien mit der Kapazität einer Lithiumionenbatterie und der Ratenkapazität eines guten Superkondensators ebnet. Die Fähigkeit des Porphyrinkomplexes, als Elektronendonor oder -akzeptor zu fungieren, bietet hier den Vorteil, verschiedene Energiespeicheranwendungen zu realisieren (siehe Bild).
      PubDate: 2017-07-19T06:21:18.877039-05:
      DOI: 10.1002/ange.201702805
       
  • Size Dependence of Doping by a Vacancy Formation Reaction in Copper
           Sulfide Nanocrystals
    • Authors: Orian Elimelech; Jing Liu, Anna M. Plonka, Anatoly I. Frenkel, Uri Banin
      Abstract: Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sized NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.Die Bildung von Gitterlücken und die Plasmonenreaktion wurden in I2-behandelten Cu2S-Halbleiter-Nanokristallen (NCs) analysiert. Die Redoxreaktion von Cu2S mit I2 erzeugt Gitterlücken in der Cu2S-Phase, deren Zahl mit der NC-Größe steigt. Die Plasmonenreaktion kann durch die NC-Größe oder den Löcherdotierungsgrad, der vom I/Cu-Verhältnis abhängt, gesteuert werden.
      PubDate: 2017-07-19T06:21:04.269503-05:
      DOI: 10.1002/ange.201702673
       
  • From a Molecular 2Fe-2Se Precursor to a Highly Efficient Iron Diselenide
           Electrocatalyst for Overall Water Splitting
    • Authors: Chakadola Panda; Prashanth W. Menezes, Carsten Walter, Shenglai Yao, Matthias E. Miehlich, Vitaly Gutkin, Karsten Meyer, Matthias Driess
      Abstract: A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.Doppelfunktion: Ein hoch aktiver Eisendiselenid-Elektrokatalysator wurde aus einem bioinspirierten 2Fe-2Se-Molekülkomplex hergestellt (Dep=Diethylphenyl) und für bifunktionelle Sauerstoff- und Wasserstoffentwicklungsreaktionen sowie die Gesamtwasserspaltung eingesetzt. Die Natur der aktiven Zentren und Struktur-Aktivitäts-Beziehungen des Elektrokatalysators wurden ermittelt.
      PubDate: 2017-07-19T06:11:22.265957-05:
      DOI: 10.1002/ange.201706196
       
  • Controlling Regioselectivity in the Enantioselective N-Alkylation of
           Indole Analogues Catalyzed by Dinuclear Zinc-ProPhenol
    • Authors: Barry M. Trost; Elumalai Gnanamani, Chao-I (Joey) Hung
      Abstract: The enantioselective N-alkylation of indole and its derivatives with aldimines is efficiently catalyzed by a zinc-ProPhenol dinuclear complex under mild conditions to afford N-alkylated indole derivatives in good yield (up to 86 %) and excellent enantiomeric ratio (up to 99.5:0.5 e.r.). This method tolerates a wide array of indoles, as well as pyrrole and carbazole, to afford the corresponding N-alkylation products. The reaction can be run on a gram scale with reduced catalyst loading without impacting the efficiency. The chiral aminals were further elaborated into various chiral polyheterocyclic derivatives. The surprising stability of the chiral N-alkylation products will open new windows for asymmetric catalysis and medicinal chemistry.Die enantioselektive N-Alkylierung von Indol und seinen Derivaten mit Aldiminen wird von einem Zink-ProPhenol-Zweikernkomplex unter milden Bedingungen effizient katalysiert. Die Produkte werden in guten Ausbeuten (bis 86 %) und mit hervorragenden Enantiomerenverhältnissen (bis 99.5:0.5 e.r.) erhalten. Die Methode eignet sich für zahlreiche Indole und liefert auch mit Pyrrol und Carbazol die entsprechenden N-Alkylierungsprodukte.
      PubDate: 2017-07-19T06:11:15.079739-05:
      DOI: 10.1002/ange.201705315
       
  • Sol–Gel-Derived Biohybrid Materials Incorporating Long-Chain DNA
           Aptamers
    • Authors: Carmen Carrasquilla; Emily Kapteyn, Yingfu Li, John D. Brennan
      Abstract: Funktionelle DNA-Biohybride makroporöser Silicamaterialien, die Megadalton-Amplikons von Tandem-Repeat-DNA-Aptameren enthalten, sid im Bild gezeigt. In ihrer Zuschrift (
      DOI : 10.1002/ange.201702859) berichten Y. Li, J. D. Brennan et al., dass diese Materialien als Durchflussbiosensoren zum Multiplexnachweis einer großen Vielfalt an Analyten verwendet werden können, was den Anwendungsbereich von Sol-Gel-Biohybridmaterialien stark erweitert.
      PubDate: 2017-07-19T06:05:25.165425-05:
       
  • Isothermal Chirality Switching with Non-Polarized Light
    • Authors: Mohamed Alaasar; Silvio Poppe, Qingshu Dong, Feng Liu, Carsten Tschierske
      Abstract: Spontaneous mirror symmetry breaking is a fundamental process for development of chirality in natural and in artificial self-assembled systems. Here we report a new series of triple chain azobenzene based rod-like compounds, which for the first time show mirror symmetry breaking in an isotropic liquid occurring adjacent to a lamellar LC phase. The transition between the lamellar phase and the symmetry broken liquid is affected by trans-cis photoisomerization which allows a fast and reversible photoinduced switching between chiral and achiral states with non-polarized light.
      PubDate: 2017-07-19T05:10:56.40222-05:0
      DOI: 10.1002/ange.201705559
       
  • RadH a Versatile Halogenase for Integration into Synthetic Pathways.
    • Authors: Binuraj Menon; Eileen Brandenburger, Humera Sharif, Ulrike Klemstein, Sarah Shepherd, Michael Greaney, Jason Micklefield
      Abstract: Flavin-dependent halogenases are useful enzymes providing halogenated molecules with improved biological activity or intermediates for synthetic derivatization. Here we demonstrate how the fungal halogenase RadH can be used to regioselectively halogenate a range of bioactive aromatic scaffolds. Site-directed mutagenesis of RadH was used to identify catalytic residues and provide insights into the mechanism of fungal halogenases. A high throughput fluorescence screen was also developed enabling a RadH mutant to be evolved with improved properties. Finally we demonstrate how biosynthetic genes from fungi, bacteria and plants can be combined, to encode a new pathway generating a novel chlorinated coumarin 'non-natural' product in E. coli.
      PubDate: 2017-07-19T05:10:36.623113-05:
      DOI: 10.1002/ange.201706342
       
  • Enantioselective Synthesis of Acyclic α-Quaternary Carboxylic Acid
           Derivatives via Iridium-Catalyzed Allylic Alkylation
    • Authors: Samantha Shockley; John Caleb Hethcox, Brian Stoltz
      Abstract: : The first highly enantioselective iridium-catalyzed allylic alkylation providing access to products bearing an allylic all-carbon quaternary stereogenic center has been developed. The reaction utilizes a masked acyl cyanide (MAC) reagent, which enables the one-pot preparation of α-quaternary carboxylic acids, esters, and amides with a high degree of enantioselectivity. The utility of these products is further explored via a series of diverse product transformations.
      PubDate: 2017-07-19T04:16:29.419076-05:
      DOI: 10.1002/ange.201707015
       
  • Understanding the Role of Additive Leads to an Improved Synthetic Protocol
           Obviating Additive: Organocatalytic Synthesis of Chiral Diarylmethyl
           Alkynes
    • Authors: Min Chen; Jianwei Sun
      Abstract: The use of additives for organic synthesis has become a common tactic to improve organic reaction outcomes. In this report, using an organocatalytic process for the synthesis of chiral diarylmethyl alkynes as a platform, we describe how an additive is involved in the improvement of the process. The evolution of an excellent synthetic protocol has been achieved via three stages, from (1) initially no catalyst turnover to (2) good conversion and enantioselectivity with a superior additive, and eventually (3) even better efficiency and selectivity without using additive. It is an important and rare demonstration that understanding the role of additive can be so beneficial as to obviate using the additive.
      PubDate: 2017-07-19T04:16:09.590586-05:
      DOI: 10.1002/ange.201706579
       
  • Anti-Markovnikov Hydrofunctionalization of Alkenes - Use of a Benzyl Group
           as a Traceless Redox-active Hydrogen Donor
    • Authors: Geoffroy Hervé Lonca; Derek Yiren Ong, Thi Mai Huong Tran, Ciputra Tejo, Shunsuke Chiba, Fabien Gagosz
      Abstract: A protocol for the anti-Markovnikov hydrofunctionalization of alkenes, that utilizes a benzyl group as a traceless redox-active hydrogen donor, has been developed. Under copper catalysis and in the presence of CF3- or N3-containing hypervalent iodine reagents, a series of homoallylic alcohol derivatives could be regioselectivity hydrofunctionalized. A similar principle was also applied to the hydrofunctionalization of alkenols.
      PubDate: 2017-07-19T04:10:42.449553-05:
      DOI: 10.1002/ange.201705368
       
  • Control of Redox Events by Dye Encapsulation Applied to Light-driven
           Splitting of Hydrogen Sulfide
    • Authors: Xu Jing; Yang Yang, Cheng He, Zhiduo Chang, Joost N. H. Reek, Chunying Duan
      Abstract: Inspired by the pocket feature of enzymes, a synthetic platform to combine photocatalytic hydrogen evolution with sulfide oxidation in a one-pot process via control over the location of electron transfer steps is reported in this paper. The redox-active coordination vessel Ni-TFT, which exhibits an octahedral pocket, encapsulates an organic dye to pre-organize for photocatalytic proton reduction via an oxidative quenching pathway using the nickel corners as catalysts, generating molecular hydrogen and the oxidized dye. The oxidized dye is displaced by a neutral dye and oxidizes sulfide once outside the pocket to give element sulfur. The overall reaction constitutes hydrogen sulfide splitting, forming molecular hydrogen and elemental sulfur, which is analogous to the water-splitting reaction. The high efficiency, simple separation of hydrogen gas and sulfur solid from the reaction mixture, represent major advantages for potential applications.
      PubDate: 2017-07-19T04:10:22.211727-05:
      DOI: 10.1002/ange.201704327
       
  • Suppression of Oligomer Formation and Formation of Non-Toxic Fibrils upon
           Addition of Mirror-Image Aβ42 to the Natural l-Enantiomer
    • Authors: Subrata Dutta; Alejandro R. Foley, Christopher J. A. Warner, Xiaolin Zhang, Marco Rolandi, Benjamin Abrams, Jevgenij A. Raskatov
      Abstract: Racemates often have lower solubility than enantiopure compounds, and the mixing of enantiomers can enhance the aggregation propensity of peptides. Amyloid beta (Aβ) 42 is an aggregation-prone peptide that is believed to play a key role in Alzheimer's disease. Soluble Aβ42 aggregation intermediates (oligomers) have emerged as being particularly neurotoxic. We hypothesized that the addition of mirror-image d-Aβ42 should reduce the concentration of toxic oligomers formed from natural l-Aβ42. We synthesized l- and D-Aβ42 and found their equimolar mixing to lead to accelerated fibril formation. Confocal microscopy with fluorescently labeled analogues of the enantiomers showed their colocalization in racemic fibrils. Owing to the enhanced fibril formation propensity, racemic Aβ42 was less prone to form soluble oligomers. This resulted in the protection of cells from the toxicity of l-Aβ42 at concentrations up to 50 μm. The mixing of Aβ42 enantiomers thus accelerates the formation of non-toxic fibrils.Das Mischen der zwei Enantiomere von Aβ42 führt zu einer signifikanten Beschleunigung der Fibrillisierung. Mit fluoreszenzmarkierten Analoga wird gezeigt, dass die Enantiomer-Colokalisierung in den racemischen Fibrillen hoch ist. Aufgrund der geringeren Neigung des Racemats, oligomere Aggregationsintermediate auszubilden, wird die Toxizität des natürlichen l-Aβ42-Enantiomers im Racemat unterdrückt.
      PubDate: 2017-07-19T03:05:35.952109-05:
      DOI: 10.1002/ange.201706279
       
  • Unusual Internal Electron Transfer in Conjugated Radical Polymers
    • Authors: Fei Li; Danielle N Gore, Shaoyang Wang, Jodie L Lutkenhaus
      Abstract: Nitroxide-containing organic radical polymers (ORPs) have captured attention for their high power and fast redox kinetics. Yet a major challenge is the polymer's aliphatic backbone, resulting in a low electronic conductivity. Recent attempts that replace the aliphatic backbone with a conjugated one have not met with success. The reason for this is not understood until now. We examine a family of polythiophenes bearing nitroxide radical groups, showing that while both species are electrochemically active, there exists an internal electron transfer mechanism that interferes with stabilization of the polymer's fully oxidized form. This finding directs the future design of conjugated radical polymers in energy storage and electronics, where careful attention to the redox potential of the backbone relative to the organic radical species is needed.Konjugierte radikalische Polymere: Der interne Transfer eines Elektrons von einer Nitroxid-Gruppe auf das Polythiophen-Rückgrat wurde beobachtet. Dieser Prozess erklärt die Leitfähigkeit und Redoxaktivität von Polythiophenen mit radikalischen Nitroxid-Seitengruppen.
      PubDate: 2017-07-19T03:01:21.435312-05:
      DOI: 10.1002/ange.201705204
       
  • Frontispiz: Water Transport with Ultralow Friction through Partially
           Exfoliated g-C3N4 Nanosheet Membranes with Self-Supporting Spacers
    • Authors: Yanjie Wang; Libo Li, Yanying Wei, Jian Xue, Huang Chen, Li Ding, Jürgen Caro, Haihui Wang
      Abstract: Reibungsarme Membranen In der Zuschrift auf S. 9102 ff. berichten J. Caro et al. über eine Wasseraufbereitungsmembran aus Nanoschichten von graphitischem Kohlenstoffnitrid. Freitragende Abstandhalter sowie intrisische und künstliche Nanoporen bewirken einen reibungsarmen Wassertransport.
      PubDate: 2017-07-19T02:33:39.207809-05:
      DOI: 10.1002/ange.201783161
       
  • Stereospecific 1,3-Aminobromination of Donor-Acceptor Cyclopropanes
    • Authors: Saikat Das; Constantin Gabriel Daniliuc, Armido Studer
      Abstract: Sn(OTf)2-catalyzed 1,3-aminobromination of donor-acceptor cyclopropanes with various sulfonyl amides or electron poor anilines and N-bromosuccinimide is reported. Reactions which are experimentally easy to conduct, occur with complete regio- and stereospecificity (for anilines) resulting in γ-aminated α-brominated malonic diesters which are obtained in good to excellent yields (up to 98%). These compounds are valuable substrates for follow-up chemistry to provide substituted azetidines and γ-lactams in high yields.
      PubDate: 2017-07-19T02:30:42.296467-05:
      DOI: 10.1002/ange.201704092
       
  • Metal-Free Nitrile Diboration through Activation by an Electron-Rich
           Diborane
    • Authors: Markus Frick; Elisabeth Kaifer, Hans-Jörg Himmel
      Abstract: Diboration of unsaturated organic compounds is an extremely useful reaction in synthetic chemistry. Herein we report the first diboration of a nitrile by an electron-rich diborane, mediated by an electrophilic borane. The reaction is metal-free, and all reagents are readily available.
      PubDate: 2017-07-19T02:30:22.321348-05:
      DOI: 10.1002/ange.201706001
       
  • Mineralized State of the Avian Influenza Virus in the Environment
    • Authors: Hangyu Zhou; Guangchuan Wang, Xiaoyu Wang, Zhiyong Song, Ruikang Tang
      Abstract: Although the circulation of avian influenza in humans is limited, they can be transmitted from Aves to humans, representing a great challenge. Herein, we suggest that influenza viruses from Aves might exist in a mineralized state due to the high calcium concentrations in the avian intestine. Using two typical influenza viruses as examples, we demonstrate these viruses can self-mineralize in simulated avian intestinal fluid, resulting in egg-like virus-mineral structured composites. The mineralized viruses are more robust, with enhanced infectivity and thermostability. More importantly, the mineral exterior of mineralized viruses can alter their cell internalization, expanding the possible tropisms. The discovery of a mineralized state of influenza highlights the integration of nanomaterials and viruses in the environment, which provides a new understanding of avian influenza infection and its control.
      PubDate: 2017-07-18T23:30:23.063794-05:
      DOI: 10.1002/ange.201705769
       
  • Branched Aramid Nanofibers
    • Authors: Jian Zhu; Ming Yang, Ahmet Emre, Joong Hwan Bahng, Lizhi Xu, Jihyeon Yeom, Bongjun Yeom, Yoonseob Kim, Kyle Johnson, Peter Green, Nicholas Alexander Kotov
      Abstract: Interconnectivity of molecular or nanoscale components in three-dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network relies on weak short-range intermolecular interactions. The intrinsic stiffness and rod-like geometry of known nanofibers limits the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Here, we show that branched aramid nanofibers (BANFs) readily produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible with the number of branches controlled by the base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro- and aerogel monoliths with an order of magnitude less solid content than rod-like nanocomponents. Branching of the nanofibers also leads to improved mechanics of gels and nanocomposites
      PubDate: 2017-07-18T21:35:41.227939-05:
      DOI: 10.1002/ange.201703766
       
  • Rare Earth- and Uranium-Mesoionic Carbenes: A New Class of f-Block Carbene
           Complex Derived from an N-Heterocyclic Olefin
    • Authors: Stephen Liddle; John Seed, Matthew Gregson, Floriana Tuna, Nicholas Chilton, Ashley Wooles, Eric McInnes
      Abstract: Neutral mesoionic carbenes (MICs) have emerged as an important class of carbene, however they are found only in the free form or ligated to a few d-block ions. Here, we report unprecedented f-block MIC complexes [M(N'')3{CN(Me)C(Me)N(Me)CH}] (M = U, Y, La, Nd; N'' = N(SiMe3)2). These complexes were prepared by a formal 1,4-proton migration reaction when the metal-triamides [M(N'')3] were treated with the N-heterocyclic olefin H2C=C(NMeCH)2, which constitutes a new, general way to prepare MIC complexes. Quantum chemical calculations on the 5f3 uranium(III) complex suggest the presence of a U=C donor-acceptor bond, composed of a MICU σ-component and a U(5f)MIC(2p) π-back-bond, but for the d0f0 Y and La and 4f3 Nd congeners only MICM σ-bonding is found. Considering the generally negligible π-acidity of MICs, this is surprising and highlights that greater consideration should possibly be given to recognising MICs as potential π-acid ligands when coordinated to reducing metals.
      PubDate: 2017-07-18T11:30:33.746514-05:
      DOI: 10.1002/ange.201706546
       
  • Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10
           Two-dimensional Multilayered Perovskite Ferroelectric for High Performance
           Photodetectors
    • Authors: Junhua Luo; Lina Li, Zhihua Sun, Peng Wang, Weida Hu, Sasa Wang, Chengmin Ji, Maochun Hong
      Abstract: Two-dimensional (2D) layered hybrid perovskites have shown great potentials in optoelectronics. However, although great efforts have been made, 2D hybrid perovskite ferroelectrics remain rare. Here, we constructed the first ferroelectric with 2D multilayered perovskite framework, (C4H9NH3)2(CH3NH3)2Pb3Br10 (1), by tailored alloying mixed-organic-cations into the prototype of CH3NH3PbBr3. For the first time, concrete ferroelectricity was created by molecular reorientation and synergic ordering of organic cations, which is unprecedented for the known 2D hybrid perovskites. Besides, single-crystal photodetectors of 1 show fascinating behaviors, such as extremely low dark current (10-12 A), large on/off current ratio (2.5×103) and highly-fast response rate (150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH3NH3PbI3. This work paves a pathway to design new hybrid ferroelectrics for high-performance optoelectronic devices.
      PubDate: 2017-07-18T08:31:11.039567-05:
      DOI: 10.1002/ange.201705836
       
  • Development of new supramolecular lyotropic liquid crystals and their
           application as alignment media for organic compounds
    • Authors: Martin Leyendecker; Nils-Christopher Meyer, Christina Thiele
      Abstract: Most alignment media for the residual dipolar coupling (RDC) based molecular structure determination of small organic compounds consist of rod-like polymers dissolved in organic solvents or of swollen cross-linked polymer gels. So far the synthesis of polymer based alignment media is a challenging process which is often followed by a time consuming sample preparation. We propose the use of non-polymeric alignment media based on benzene-tricarboxamides (BTA) which self-assemble into rod-like supramolecules. Our newly found supramolecular lyotropic liquid crystals (LLC) are characterized for LLC properties and their suitability as alignment medium in NMR spectroscopy. Scalable enantiodifferentiating properties are introduced through a sergeant-and-soldier principle by blending achiral with chiral substituted BTAs.
      PubDate: 2017-07-18T08:31:07.749363-05:
      DOI: 10.1002/ange.201705642
       
  • New Insight into Magnetic Interaction in Monodisperse Gd12Fe14 Metal
           Cluster
    • Authors: Xiu-Ying Zheng; Hui Zhang, Zhenxing Wang, Pengxin Liu, Ming-Hao Du, Ying-Zi Han, Rong-Jia Wei, Zhongwen Ouyang, Xiang-Jian Kong, Gui-Lin Zhuang, La-Sheng Long, Lan-Sun Zheng
      Abstract: Largest Ln-Fe metal cluster of [Gd12Fe14(μ3-OH)12(μ4-OH)6(μ4-O)12(TEOA)6(CH3COO)16(H2O)8]*(CH3COO)2(CH3CN)2* (H2O)20 (1) and core-shell monodisperse metal cluster of 1a@SiO2 (1a = [Gd12Fe14(μ3-OH)12(μ4-OH)6(μ4-O)12(TEOA)6(CH3COO)16 (H2O)8]2+) were prepared. Experimental and theoretical studies on the magnetic properties of 1 and 1a@SiO2 reveal that encapsulation of one cluster into one silica nanosphere not only effectively decreases intermolecular magnetic interaction but also significantly increases the zero-field splitting effect of the outer layer Fe3+ ions.
      PubDate: 2017-07-18T08:30:58.395659-05:
      DOI: 10.1002/ange.201705697
       
  • Cesium's Off-the-Map Valence Orbital
    • Authors: Maarten G. Goesten; Martin Rahm, F. Matthias Bickelhaupt, Emiel J. M. Hensen
      Abstract: The Td-symmetric [CsO4]+ ion, featuring Cs in an oxidation state of 9, is computed to be a minimum. Cs uses outer core 5s and 5p orbitals to bind the oxygen atoms. The valence Cs 6s orbital lies too high to be involved in bonding, and contributes to Rydberg levels only. From a molecular orbital perspective, the bonding scheme is reminiscent of XeO4: an octet of electrons to bind electronegative ligands, and no low-lying acceptor orbitals on the central atom. In this sense, Cs+ resembles hypervalent Xe.Caesium mobilisiert die Reserven: Das Td-symmetrische [CsO4]+-Ion mit Caesium in der Oxidationsstufe IX erwies sich in Rechnungen als Energieminimum. Cs nutzt in diesem Ion 5s- und 5p-Rumpforbitale zur Bindung der Sauerstoffatome. Das 6s-Valenzorbital ist zu energiereich, um an der Bindung teilzunehmen, und trägt lediglich zu Rydberg-Niveaus bei.
      PubDate: 2017-07-18T06:55:34.147746-05:
      DOI: 10.1002/ange.201704118
       
  • SN2 Reactions at Tertiary Carbon Centers in Epoxides
    • Authors: Yong-Qiang Zhang; Christina Poppel, Anastasia Panfilova, Fabian Bohle, Stefan Grimme, Andreas Gansäuer
      Abstract: Described herein is a novel concept for SN2 reactions at tertiary carbon centers in epoxides without activation of the leaving group. Quantum chemical calculations show why SN2 reactions at tertiary carbon centers are proceeding in these systems. The reaction allows flexible synthesis of 1,3-diol building blocks for natural product synthesis with excellent control of the relative and absolute configurations.Im Angriffmodus: SN2-Reaktionen an tertiären Kohlenstoffzentren in Epoxiden sind möglich, wenn der Winkel des rückseitigen Angriffs gesteuert wird. Diese Steuerung wird durch Bindung des Reagens und dessen Aktivierung für den Hydridtransfer durch Fluorid erreicht. Die Reaktion verläuft mit exzellenter Regioselektivität und ermöglicht die Synthese von Acetat- und Propionat-abgeleiteten 1,3-Dioleinheiten, die für die Naturstoffsynthese relevant sind.
      PubDate: 2017-07-18T05:06:21.721482-05:
      DOI: 10.1002/ange.201702882
       
  • Unconventional Route to Uniform Hollow Semiconducting Nanoparticles with
           Tailorable Dimensions, Compositions, Surface Chemistry and Near-Infrared
           Absorption
    • Authors: Yanjie He; Xinchang Pang, Beibei Jiang, Chaowei Feng, Yeu Wei Harn, Yihuang Chen, Young Jun Yoon, Shuang Pan, Cheng-Hsin Lu, Yajing Chang, Mona Zebarjadi, Zhitao Kang, Naresh Thadhani, Juan Peng, Zhiqun Lin
      Abstract: Despite recent impressive advances in synthesizing lead chalcogenide solid nanoparticles, there are no demonstrations of lead chalcogenide hollow nanoparticles (HNPs) with controlled hollow diameter and shell thickness as current synthetic approaches for HNPs have inherent limitations associated with inability to precisely control the dimensions and restriction of applicable materials in scope. Herein, we report on an unconventional strategy for crafting uniform PbS and PbTe HNPs with tailorable size, surface chemistry, and near-IR absorption. Amphiphilic star-like PS-b-PAA-b-PS and PS-b-PAA-b-PEDOT triblock copolymers are rationally synthesized and exploited as nanoreactors to create uniform PbS and PbTe HNPs. Compared to solid NPs, the near-IR absorption of HNPs exhibits a blue-shift due to the presence of hollow interior. The star-like block copolymer nanoreactor strategy can be readily extended to create other types of intriguing low bandgap HNPs for diverse applications.
      PubDate: 2017-07-18T03:15:42.149111-05:
      DOI: 10.1002/ange.201706182
       
  • High-Field NMR Spectroscopy Reveals Aromaticity-Modulated Hydrogen Bonding
           in Heterocycles
    • Authors: Tayeb Kakeshpour; John P. Bailey, Madison R. Jenner, Darya E. Howell, Richard J. Staples, Daniel Holmes, Judy I. Wu, James E. Jackson
      Abstract: From DNA base pairs to drug–receptor binding, hydrogen (H-)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored. H-bond strength modulation due to enhancement or disruption of aromaticity of heterocycles is experimentally revealed by comparing homodimer H-bond energies of aromatic heterocycles with analogs that have the same H-bonding moieties but lack cyclic π-conjugation. NMR studies of dimerization in C6D6 find aromaticity-modulated H-bonding (AMHB) energy effects of approximately ±30 %, depending on whether they enhance or weaken aromatic delocalization. The attendant ring current perturbations expected from such modulation are confirmed by chemical shift changes in both observed ring C−H and calculated nucleus-independent sites. In silico modeling confirms that AMHB effects outweigh those of hybridization or dipole–dipole interaction.Abgestimmte H-Brücken: Hochfeld-NMR-Messungen zeigen, dass die Wasserstoffbrückenstärke von Heterocyclen durch Perturbationen ihrer Aromatizität bei H-Brücken-Bildung in Lösung wirksam moduliert wird. Laut quantenchemischer Studien sind die Aromatizitätsperturbationen dominant und übertreffen Hybridisierungs- oder Dipoleffekte.
      PubDate: 2017-07-18T02:42:27.296384-05:
      DOI: 10.1002/ange.201705023
       
  • Arthur C. Cope Scholar Awards
    • PubDate: 2017-07-18T02:42:19.830832-05:
      DOI: 10.1002/ange.201706659
       
  • Stabilizing Otherwise Unstable Anions with Halogen Bonding
    • Authors: Xinxing Zhang; Gaoxiang Liu, Sandra Ciborowski, Kit Bowen
      Abstract: Both hydrogen bonding (HB) and halogen bonding (XB) are essentially electrostatic interactions, but whereas hydrogen bonding has a well-documented record of stabilizing unstable anions, little is known about halogen bonding's ability to do so. Herein, we present a combined anion photoelectron spectroscopic and density functional theory study of the halogen bond-stabilization of the pyrazine (Pz) anion, an unstable anion in isolation due to its neutral counterpart having a negative electron affinity (EA). The halogen bond formed between the σ-hole on bromobenzene (BrPh) and the lone pair(s) of Pz significantly lowers the energies of the Pz(BrPh)1− and Pz(BrPh)2− anions relative to the neutral molecule, resulting in the emergence of a positive EA for the neutral complexes. As seen through its charge distribution and electrostatic potential analyses, the negative charge on Pz− is diluted due to the XB. Thermodynamics reveals that the low temperature of the supersonic expansion plays a key role in forming these complexes.Wie Brüderchen und Schwesterchen: Im Unterschied zu Wasserstoffbrücken (HB) wurden Halogenbrücken (XB) noch nicht genutzt, um instabile Anion zu stabilisieren. Nun wurden mithilfe von XB ansonsten instabile Pyrazin-Anionen stabilisiert.
      PubDate: 2017-07-18T02:42:16.944201-05:
      DOI: 10.1002/ange.201705738
       
  • TMSCF3 as a Convenient Source of CF2=CF2 for Pentafluoroethylation,
           (Aryloxy)tetrafluoroethylation, and Tetrafluoroethylation
    • Authors: Lingchun Li; Chuanfa Ni, Qiqiang Xie, Mingyou Hu, Fei Wang, Jinbo Hu
      Abstract: A new method for the on-site preparation of tetrafluoroethylene (TFE) and a procedure for its efficient use in pentafluoroethylation by fluoride addition were developed by using a simple two-chamber system. The on-site preparation of TFE was accomplished by dimerization of difluorocarbene derived from (trifluoromethyl)trimethylsilane (TMSCF3) under mild conditions. Other fluoroalkylation reactions, such as (aryloxy)tetrafluoroethylation and tetrafluoroethylation processes, were also achieved using a similar approach. This work not only demonstrates a convenient and safe approach for the generation and use of TFE in academic laboratories, but also provides a new strategy for pentafluoroethylation.Im eigenen Labor: CF2=CF2 wurde unter Verwendung eines Zweikammersystems unter milden Bedingungen aus TMSCF3 generiert und für Per/Polyfluoralkylierungen verwendet. Eine praktische Methode für die Verwendung von CF2=CF2 in gewöhnlichen Laboratorien sowie ein neuer Ansatz für Pentafluorethylierungen werden beschrieben.
      PubDate: 2017-07-18T02:42:13.387329-05:
      DOI: 10.1002/ange.201705734
       
  • Unsupported Pt-Ni Aerogels with Enhanced High Current Performance and
           Durability in Fuel Cell Cathodes
    • Authors: Sebastian Henning; Hiroshi Ishikawa, Laura Kühn, Juan Herranz, Elisabeth Müller, Alexander Eychmüller, Thomas J. Schmidt
      Abstract: Highly active and durable oxygen reduction catalysts are needed to reduce the costs and enhance the service life of polymer electrolyte fuel cells (PEFCs). This can be accomplished by alloying Pt with a transition metal (for example Ni) and by eliminating the corrodible, carbon-based catalyst support. However, materials combining both approaches have seldom been implemented in PEFC cathodes. In this work, an unsupported Pt-Ni alloy nanochain ensemble (aerogel) demonstrates high current PEFC performance commensurate with that of a carbon-supported benchmark (Pt/C) following optimization of the aerogel's catalyst layer (CL) structure. The latter is accomplished using a soluble filler to shift the CL's pore size distribution towards larger pores which improves reactant and product transport. Chiefly, the optimized PEFC aerogel cathodes display a circa 2.5-fold larger surface-specific ORR activity than Pt/C and maintain 90 % of the initial activity after an accelerated stress test (vs. 40 % for Pt/C).Ein trägerfreier Dimetallkatalysator für die Sauerstoffreduktion (ORR) wurde in einer Polymerelektrolyt-Brennstoffzelle eingesetzt, wo er in beschleunigten Belastungstests eine hohe Stromleistung erbrachte und eine überlegene Haltbarkeit bewies.
      PubDate: 2017-07-18T02:42:07.259536-05:
      DOI: 10.1002/ange.201704253
       
  • Microfluidic Formation of Monodisperse Coacervate Organelles in Liposomes
    • Authors: Nan-Nan Deng; Wilhelm T. S. Huck
      Abstract: Coacervates have been widely studied as model compartments in protocell research. Complex coacervates composed of disordered proteins and RNA have also been shown to play an important role in cellular processes. Herein, we report on a microfluidic strategy for constructing monodisperse coacervate droplets encapsulated within uniform unilamellar liposomes. These structures represent a bottom-up approach to hierarchically structured protocells, as demonstrated by storage and release of DNA from the encapsulated coacervates as well as localized transcription.Künstliche Organellen: Monodisperse Liposome mit monodispersen dynamischen funktionellen Kompartimenten wurden nach einem Mikrofluidikverfahren hergestellt und als (Proto)Zellmodelle für die intrazelluläre Kompartimentalisierung durch membranlose Organellen getestet.
      PubDate: 2017-07-18T02:41:10.071847-05:
      DOI: 10.1002/ange.201703145
       
  • One-Compound-Based Highly Efficient Deep-Red to Near-Infrared Thermally
           Activated Delayed Fluorescence Organic Solid Films and Electroluminescent
           Devices
    • Authors: Yue Wang; Chenglong Li, Ruihong Duan, Baoyan Liang, Guangchao Han, Shipan Wang, Kaiqi Ye, Yu Liu, Yuanping Yi
      Abstract: The design and synthesis of highly efficient deep red (DR) and near-infrared (NIR) organic emitting materials with characteristic of thermally activated delayed fluorescence (TADF) still remains a great challenge. In this contribution, we developed a strategy to construct TADF organic solid films with strong DR or NIR emission feature. The triphenylamine (TPA) and quinoxaline-6,7-dicarbonitrile (QCN) were respectively employed as electron donor (D) and acceptor (A) to synthesize a TADF compound, TPA-QCN. The TPA-QCN molecule with orange-red emission in solution was employed as a dopant to prepare DR and NIR luminescent solid thin films. The high doped concentration and neat films exhibited efficient DR and NIR emissions, respectively. The highly efficient DR and NIR organic light-emitting devices (OLEDs) were fabricated by regulating TPA-QCN dopant concentration in the emitting layers.
      PubDate: 2017-07-17T22:16:31.776188-05:
      DOI: 10.1002/ange.201706464
       
  • A Boron Alkylidene-Alkene Cycloaddition Reaction: Application to the
           Synthesis of Aphanamal
    • Authors: James Patrick Morken; Xun Liu, Timothy Maxwell Deaton, Fredrik Haeffner
      Abstract: We describe an unusual net 2+2 cycloaddition reaction between boron alkylidenes and unactivated alkenes. This reaction provides a new method for construction of carbocyclic ring systems bearing versatile organoboronic esters. In addition to surveying the scope of this reaction, we provide details about the mechanistic underpinnings of this process, and examine application to the synthesis of the natural product aphanamal.
      PubDate: 2017-07-17T22:16:05.721514-05:
      DOI: 10.1002/ange.201705720
       
  • Properties of water confined in periodic mesoporous organosilicas -
           nanoimprinting the local structure
    • Authors: Michael Fröba; J. Benedikt Mietner, Felix J. Brieler, Young Joo Lee
      Abstract: The properties of materials confined in porous media are important in scientific and technological aspects. Topology, size and surface polarity of the pores play a critical role in the confinement effects, however, knowledge regarding the guest-pore interface structure is still lacking. Here, we show that the molecular mobility of water confined in periodic mesoporous organosilicas (PMOs) is influenced by the polarity of the organic moiety. Multidimensional solid state NMR directly probes the spatial arrangement of water inside the pores, demonstrating that water interacts either with only the silicate layer or with both silicate and organic layers depending on the alternating surface polarity. A modulated and a uniform pore filling mode are proposed for different types of PMOs. Our study gives a molecular-level picture of the adsorbate-surface interaction, which helps understanding confinement effects and provides a new design concept of the pore structures with the desired properties
      PubDate: 2017-07-17T13:15:24.498367-05:
      DOI: 10.1002/ange.201705707
       
  • Ionophore-based anion-selective optode printed on cellulose paper
    • Authors: Xuewei Wang; Qi Zhang, Changwoo Nam, Michael Hickner, Mollie Mahoney, Mark Meyerhoff
      Abstract: We report a general anion sensing platform based on a portable and cost-effective ion-selective optode and a smartphone detector equipped with a color analysis app. In contrast to traditional anion-selective optodes using a hydrophobic polymer and/or plasticizer to dissolve hydrophobic sensing elements, the new optode relies on hydrophilic cellulose paper. The anion ionophore and a lipophilic pH indicator are inkjet-printed and adsorbed on paper and form a "dry" hydrophobic sensing layer. Porous cellulose sheets also allow the sensing site to be modified with dried buffer that prevents any sample pH dependence of the observed color change. A highly selective fluoride optode using an Al(III)-porphyrin ionophore is examined as an initial example of this new anion sensing platform for measurements of fluoride levels in drinking water samples. In addition to Lewis acid-base recognition, hydrogen bonding recognition is also shown to be compatible with this sensing platform.
      PubDate: 2017-07-17T12:15:43.321428-05:
      DOI: 10.1002/ange.201706147
       
  • Cyclodextrin cavity-induced mechanistic switch in copper-catalyzed
           hydroboration
    • Authors: Pinglu Zhang; Jorge Meijide Suarez, Thomas Driant, Etienne Derat, Yongmin Zhang, Mickaël Ménand, Sylvain Roland, Matthieu Sollogoub
      Abstract: NHC-capped cyclodextrin (ICyD) ligands, α-ICyD and β-ICyD derived from α- and β-cyclodextrin respectively give opposite regioselectivities in a copper-catalyzed hydroboration. The site-selectivity results from two different mechanisms: the conventional "parallel" one and a new "orthogonal" mechanism. The shape of the cavity was shown not only to induce a regioselectivity switch but also a mechanistic switch. The scope of interest of the encapsulation of a reactive center is therefore broadened by this study.
      PubDate: 2017-07-17T08:19:35.520376-05:
      DOI: 10.1002/ange.201705303
       
  • A Convergent Synthesis of Functionalized Alkenyl Halides through
           Cobalt(III)-Catalyzed Three-Component C−H Bond Addition
    • Authors: Jeffrey A. Boerth; Jonathan A. Ellman
      Abstract: A CoIII-catalyzed three-component coupling of C(sp2)−H bonds, alkynes, and halogenating agents to give alkenyl halides is reported. This transformation proceeds with high regio- and diastereoselectivity, and is effective for a broad range of aryl and alkyl terminal alkynes. Diverse C−H bond partners also exhibit good reactivity for a range of heteroaryl and aryl systems as well as synthetically useful secondary and tertiary amide, urea, and pyrazole directing groups. This multicomponent transformation is also compatible with allenes in place of alkynes to furnish tetrasubstituted alkenyl halides, showcasing the first halo-arylation of allenes.Der konvergente Aufbau funktionalisierter Alkenylhalogenide gelingt durch eine CoIII-katalysierte Dreikomponentenkupplung unter C-H-Aktivierung in Gegenwart von Halogenierungsmitteln. Der Prozess verläuft hoch regio- und diastereoselektiv mit vielfältigen Alkinen und C-H-Substraten. Ausgehend von Allenen sind auch tetrasubstituierte Alkenylhalogenide zugänglich.
      PubDate: 2017-07-17T08:19:28.567154-05:
      DOI: 10.1002/ange.201705817
       
  • The Covalent Functionalization of Layered Black Phosphorus by Nucleophilic
           Reagents
    • Authors: Zdeněk Sofer; Jan Luxa, Daniel Bouša, David Sedmidubský, Petr Lazar, Tomáš Hartman, Hilde Hardtdegen, Martin Pumera
      Abstract: Layered black phosphorus has been attracting great attention due to its interesting material properties which lead to a plethora of proposed applications. Several approaches are demonstrated here for covalent chemical modifications of layered black phosphorus in order to form P−C and P-O-C bonds. Nucleophilic reagents are highly effective for chemical modification of black phosphorus. Further derivatization approaches investigated were based on radical reactions. These reagents are not as effective as nucleophilic reagents for the surface covalent modification of black phosphorus. The influence of covalent modification on the electronic structure of black phosphorus was investigated using ab initio calculations. Covalent modification exerts a strong effect on the electronic structure including the change of band-gap width and spin polarization.Phosphor plus: Schichten von schwarzem Phosphor können durch nukleophile Substitution mithilfe von Halogen- und Hydroxyspezies unter Bildung kovalenter P-C- und P-O-C-Bindungen an der Oberfläche modifiziert werden.
      PubDate: 2017-07-17T08:19:24.020837-05:
      DOI: 10.1002/ange.201705722
       
  • Nickel-Catalyzed Intermolecular Carbosulfonylation of Alkynes via Sulfonyl
           Radicals
    • Authors: Andrés García-Domínguez; Simona Müller, Cristina Nevado
      Abstract: β,β-Disubstituted vinyl sulfones were obtained with complete regio- and stereocontrol in a multicomponent reaction involving alkynes, organoboronic acids, and sulfonyl chlorides in the presence of a nickel catalyst. The reaction proceeds via sulfonyl radicals generated in situ under mild reaction conditions.Leicht verfügbare Alkine, Boronsäuren und Sulfonylchloride reagieren in Gegenwart eines Nickelkatalysators zu β,β-disubstituierten Vinylsulfonen mit vollständiger Regio- und Stereokontrolle. Die Reaktion verläuft über Sulfonylradikale, die in situ unter milden Bedingungen und mit hoher Toleranz gegenüber funktionellen Gruppen erzeugt werden.
      PubDate: 2017-07-17T08:19:18.513563-05:
      DOI: 10.1002/ange.201704862
       
  • Mechanistic Insight into Nanoparticle Surface Adsorption by Solution NMR
           Spectroscopy in an Aqueous Gel
    • Authors: Timothy K. Egner; Pranjali Naik, Nicholas C. Nelson, Igor I. Slowing, Vincenzo Venditti
      Abstract: Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found that the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. We believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.Kinetik und Thermodynamik der Adsorption kleiner Moleküle an Nanopartikeloberflächen wurden durch NMR-Spektroskopie in einem wässrigen Gel untersucht (siehe Bild), das die Nanopartikelsedimentation über längere Zeiträume verhindert. Ein mehrstufiger Bindungsmechanismus wird identifiziert, bei dem ein schwach assoziierter Begegnungskomplex in ein fest gebundenes Molekül-Nanopartikel-Addukt übergeht.
      PubDate: 2017-07-17T08:19:09.871854-05:
      DOI: 10.1002/ange.201704471
       
  • Eine sich selbst opfernde N-Methyltransferase ist die Vorstufe des
           pilzlichen Sekundärmetaboliten Omphalotin
    • Authors: Sascha Ramm; Bartlomiej Krawczyk, Agnes Mühlenweg, Annette Poch, Eva Mösker, Roderich D. Süssmuth
      Abstract: Die Forschung an ribosomal synthetisierten und posttranslational modifizierten Peptiden (RiPPs) hat das Verständnis von Biosynthesemechanismen zum Aufbau dieser Peptide weit vorangetrieben. Während die meisten Beispiele für RiPPs von Bakterien stammen, gibt es außer den Amanitinen und Phalloidinen nur wenig bekannte Vertreter, die von Pilzen produziert werden. Das pilzliche Cyclopeptid Omphalotin A trägt mehrere N-Methylierungen des Peptidrückgrats, eine Modifikation die so bisher nur für nicht-ribosomal synthetisierte Peptide beschrieben wurde. Bei Untersuchungen des Genoms eines Omphalotin-produzierenden Pilzes konnten zwei Gene identifiziert werden, die an der Biosynthese beteiligt sind. Ein Gen kodiert für die Methyltransferase OphMA, die eine Selbstmethylierung am eigenen C-Terminus durchführt und anschließend durch eine von einem zweiten Gen kodierte Prolyl-Oligopeptidase (OphP) erkannt, abgespalten und cyclisiert wird. Diese Arbeit zeigt einen neuen Biosynthesemechanismus für RiPPs auf, bei dem das Vorstufenpeptid Bestandteil des posttranslational modifizierenden Enzyms ist.Das pilzliche Cyclopeptid Omphalotin A trägt mehrere N-Methylierungen des Peptidrückgrats. Bei Untersuchungen des Genoms eines Produzenten wurden zwei Gene identifiziert. Eines kodiert für die Methyltransferase OphMA, die eine Selbstmethylierung am eigenen C-Terminus durchführt und dann durch eine von einem zweiten Gen kodierte Prolyl-Oligopeptidase OphP erkannt, abgespalten und cyclisiert wird. Bei diesem neuen Biosynthesemechanismus ist das Vorstufenpeptid Bestandteil des posttranslational modifizierenden Enzyms.
      PubDate: 2017-07-17T08:18:57.748263-05:
      DOI: 10.1002/ange.201703488
       
  • Identification of a Stable ZnII–Oxyl Species Produced in an MFI Zeolite
           and Its Reversible Reactivity with O2 at Room Temperature
    • Authors: Akira Oda; Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda
      Abstract: Although a terminal oxyl species bound to certain metal ions is believed to be the intermediate for various oxidation reactions, such as O−O bond generation in photosystem II (PSII), such systems have not been characterized. Herein, we report a stable ZnII–oxyl species induced by an MFI-type zeolite lattice and its reversible reactivity with O2 at room temperature. Its intriguing characteristics were confirmed by in situ spectroscopic studies in combination with quantum-chemical calculations, namely analyses of the vibronic Franck–Condon progressions and the ESR signal features of both ZnII–oxyl and ZnII–ozonide species formed during this reversible process. Molecular orbital analyses revealed that the reversible reaction between a ZnII–oxyl species and an O2 molecule proceeds via a radical O–O coupling–decoupling mechanism; the unpaired electron of the oxyl species plays a pivotal role in the O−O bond generation process.Reversible Radikalbildung: Eine ZnII-Oxyl-Spezies wurde unter Verwendung eines ZnII-basierten MFI-Zeoliths als subnanometergroßes Reaktionsgefäß gebildet. Der Oxyl-Komplex reagiert bei Raumtemperatur mit O2, und sein ungepaartes Elektron spielt eine wichtige Rolle bei dieser reversiblen Reaktion.
      PubDate: 2017-07-17T08:18:44.629734-05:
      DOI: 10.1002/ange.201702570
       
  • Das Distortion/Interaction-Activation-Strain-Modell zur Analyse von
           Reaktionsgeschwindigkeiten
    • Authors: F. Matthias Bickelhaupt; Kendall N. Houk
      Abstract: Das Activation-Strain- oder Distortion/Interaction-Modell ist ein Instrument zur Analyse von Aktivierungsbarrieren und damit von Reaktionsgeschwindigkeiten. Für eine bimolekulare Reaktion ergibt sich die Aktivierungsenergie aus der Summe der Energien, die für die Deformation der Grundzustandsgeometrie der Reaktanten benötigt wird, um die Geometrie des Übergangszustands anzunehmen, plus der Wechselwirkungsenergie zwischen diesen deformierten Reaktanten. Die mit der Deformation assoziierte Energie wird “activation strain” (Aktivierungsspannung) oder “distortion energy” (Deformationsenergie) genannt. Diese Energie bildet den Hauptbeitrag zur Aktivierungsbarriere. Der Übergangszustand wird erreicht, wenn die stabilisierende Wechselwirkung die Aktivierungsspannung überwindet. Die Verlaufsanalyse dieser Energien gibt Einblicke in die reaktivitätsbestimmenden physikalischen Faktoren. Anwendungsbeispiele für das Modell sind die Analyse von Substitutions- und Eliminierungsreaktionen sowie Cycloadditionen.Die Kernbegriffe eines Modells, das Reaktionsprofile und das Ausmaß von Reaktionsbarrieren anhand der Eigenschaften der Reaktanten erklärt, werden vorgestellt. Insbesondere betrifft dies die mit der Deformation der Reaktanten verbundene Spannungsenergie und die Wechselwirkung zwischen den deformierten Reaktanten (siehe Abbildung). Dieses Modell ist als Activation-Strain- oder Distortion/Interaction-Modell bekannt.
      PubDate: 2017-07-17T08:18:32.885959-05:
      DOI: 10.1002/ange.201701486
       
  • Nuclear Spin Isomers: Engineering a Et4N[DyPc2] Spin Qudit
    • Authors: Eufemio Moreno-Pineda; Marko Damjanović, Olaf Fuhr, Wolfgang Wernsdorfer, Mario Ruben
      Abstract: Two dysprosium isotopic isomers were synthesized: Et4N[163DyPc2] (1) with I=5/2 and Et4N[164DyPc2] (2) with I=0 (where Pc=phthalocyaninato). Both isotopologues are single-molecule magnets (SMMs); however, their relaxation times as well as their magnetic hystereses differ considerably. Quantum tunneling of the magnetization (QTM) at the energy level crossings is found for both systems via ac-susceptibility and μ-SQUID measurements. μ-SQUID studies of 1(I=5/2) reveal several nuclear-spin-driven QTM events; hence determination of the hyperfine coupling and the nuclear quadrupole splitting is possible. Compound 2(I=0) shows only strongly reduced QTM at zero magnetic field. 1(I=5/2) could be used as a multilevel nuclear spin qubit, namely qudit (d=6), for quantum information processing (QIP) schemes and provides an example of novel coordination-chemistry-discriminating nuclear spin isotopes. Our results show that the nuclear spin of the lanthanide must be included in the design principles of molecular qubits and SMMs.Auf dem Weg zum Quantencomputer: Isotopologe Lanthanoid-Doppeldeckerkomplexe Et4N[163DyPc2] und Et4N[164DyPc2] (Pc=Phthalocyaninato) zeigen ein Quantentunneln der Magnetisierung. Aufgrund seiner Quantenmerkmale kann Et4N[163DyPc2] als plausibler Kandidat für Kernspin-Qudits (mit d=6) für neuartige Datensuchalgorithmen angesehen werden.
      PubDate: 2017-07-17T08:10:28.928795-05:
      DOI: 10.1002/ange.201706181
       
  • Colorimetric Recognition of Aldehydes and Ketones
    • Authors: Zheng Li; Ming Fang, Maria K. LaGasse, Jon R. Askim, Kenneth S. Suslick
      Abstract: A colorimetric sensor array has been designed for the identification of and discrimination among aldehydes and ketones in vapor phase. Due to rapid chemical reactions between the solid-state sensor elements and gaseous analytes, distinct color difference patterns were produced and digitally imaged for chemometric analysis. The sensor array was developed from classical spot tests using aniline and phenylhydrazine dyes that enable molecular recognition of a wide variety of aliphatic or aromatic aldehydes and ketones, as demonstrated by hierarchical cluster, principal component, and support vector machine analyses. The aldehyde/ketone-specific sensors were further employed for differentiation among and identification of ten liquor samples (whiskies, brandy, vodka) and ethanol controls, showing its potential applications in the beverage industry.One Bourbon, One Scotch, One Brandy: Eine Anordnung colorimetrischer Sensoren für die Dampfphasenidentifizierung einer breiten Palette von Aldehyden und Ketonen unter Verwendung von Mustererkennungstechniken (z. B. durch hierarchische Clusteranalysen und Stützvektorverfahren) wurde entworfen. Die Aldehyd/Keton-spezifischen Sensoren wurden zur Unterscheidung von zehn Spirituosen (Whiskies, Weinbrand, Wodka) und Ethanol-Vergleichsproben eingesetzt, um ihr Potenzial für die Getränkeindustrie aufzuzeigen.
      PubDate: 2017-07-17T07:06:04.852969-05:
      DOI: 10.1002/ange.201705264
       
  • Structure of Human Tyrosinase Related Protein 1 Reveals a Binuclear Zinc
           Active Site Important for Melanogenesis
    • Authors: Xuelei Lai; Harry J. Wichers, Montserrat Soler-Lopez, Bauke W. Dijkstra
      Abstract: Tyrosinase-related protein 1 (TYRP1) is one of three tyrosinase-like glycoenzymes in human melanocytes that are key to the production of melanin, the compound responsible for the pigmentation of skin, eye, and hair. Difficulties with producing these enzymes in pure form have hampered the understanding of their activity and the effect of mutations that cause albinism and pigmentation disorders. Herein we show that the typical tyrosinase-like subdomain of TYRP1 contains two zinc ions in the active site instead of copper ions as found in tyrosinases, which explains why TYRP1 does not exhibit tyrosinase redox activity. In addition, the structures reveal for the first time that the Cys-rich subdomain, which is unique to vertebrate melanogenic proteins, has an epidermal growth factor-like fold and is tightly associated with the tyrosinase subdomain. Our structures suggest that most albinism-related mutations of TYRP1 affect its stability or activity.„Gezinktes” Enzym: Die erste Kristallstruktur eines an der Melanin-Biosynthese beteiligten Säugerenzyms offenbart die strukturelle Grundlage von mit OCA3-Albinismus assoziierten Mutationen. Die Tyrosinase-artige Subdomäne von TYRP1 enthält im aktiven Zentrum zwei Zinkionen anstelle von Kupferionen (wie bei den Tyrosinasen der Fall), was erklärt, weshalb TYRP1 nicht die Redoxaktivität der Tyrosinasen aufweist.
      PubDate: 2017-07-17T07:05:59.303694-05:
      DOI: 10.1002/ange.201704616
       
  • Fusing Dicarbollide Ions with N-Heterocyclic Carbenes
    • Authors: Jess Estrada; Vincent Lavallo
      Abstract: Discovered by Hawthorne in 1965, dicarbollide ions are an intriguing class of nido-carboranes that mimic the behavior of the cyclopentadienyl anion. Herein, we show that it is possible to directly link the dicarbollide ion to an N-heterocyclic carbene (NHC) to form an isolable N-dicarbollide-substituted NHC dianion. This molecule can be accessed by the sequential double deprotonation of a mono-nido-carboranyl imidazolium zwitterion. As revealed by a single-crystal X-ray diffraction study, the first deprotonation leads to a monoanionic dicarbollide ion that adopts a bis(dicarbollide) structure in the solid state. Subsequent deprotonation of this monoanion leads to the first N-dicarbollide NHC, which was fully characterized by multinuclear NMR spectroscopy as well as single-crystal X-ray diffraction.Eine glückliche Verbindung: Mehr als 50 Jahre nach Hawthornes bahnbrechender Entdeckung des Dicarbollid-Ions wird gezeigt, dass dieses klassische Analogon des Cyclopentadienyl-Anions direkt mit stabilen Carbenen verknüpft werden kann. Die Verschmelzung dieser zwei ungewöhnlichen Klassen an kohlenstoffhaltigen Verbindungen etabliert einen neuartigen Ansatz für die Entwicklung von NHC-Liganden.
      PubDate: 2017-07-17T07:02:05.899687-05:
      DOI: 10.1002/ange.201705857
       
  • Heterocorrole Conformations: Little Saddling, Much Ruffling
    • Authors: Jörn Rösner; Birte Cordes, Stefanie Bahnmüller, Gabor Homolya, Dimitri Sakow, Peter Schweyen, Richard Wicht, Martin Bröring
      Abstract: 10-Heterocorrole complexes with oxygen, sulfur, and selenium at position 10 of the macrocycle and with the divalent ions of nickel, copper, and palladium were prepared and investigated. The focus was set on the size adaptation and matching mechanisms of cavity size versus ionic radius in corrole-type macrocycles. A full set of single-crystal X-ray analytical data revealed that in all but one case the N4 binding site of the ring-contracted tetrapyrrole was larger than necessary to bind the metal ion without deformation. In-plane size adaptation through M−N bond-length elongation by 2.5–3.2 % was effective, as well as pronounced out-of-plane ruffling of the macrocycle for those compounds with a more severe size mismatch. Such ruffling had been excluded for corroles previously, but is apparently the most efficient mechanism to adapt to small central ions.Und sie können es doch! Trotz der Gegenwart einer direkten Pyrrol-Pyrrol-Verknüpfung nehmen 10-Heterocorrole bei Bindung an Zentralionen mit kleinen Radien sehr effiziente Ruffling-Konformationen ein (siehe Bild). Ruffling wird als die hauptsächliche Geometrieverzerrung aus der Ebene zur Anpassung an die Größe des Ligandenhohlraums in Koordinationsverbindungen beobachtet. Dieser Befund widerlegt die Hypothese, dass „Corrole kein Ruffling können”.
      PubDate: 2017-07-17T07:01:57.202921-05:
      DOI: 10.1002/ange.201705551
       
  • Copper-Catalyzed Enantio-, Diastereo-, and Regioselective
           [2,3]-Rearrangements of Iodonium Ylides
    • Authors: Bin Xu; Uttam K. Tambar
      Abstract: The first highly enantioselective, diastereoselective, and regioselective [2,3]-rearrangement of iodonium ylides has been developed as a general solution to catalytic onium ylide rearrangements. In the presence of a chiral copper catalyst, substituted allylic iodides couple with α-diazoesters to generate metal-coordinated iodonium ylides, which undergo [2,3]-rearrangements with high selectivities (up to>95:5 r.r., up to>95:5 d.r., and up to 97 % ee). The enantioenriched iodoester products can be converted stereospecifically into a variety of onium ylide rearrangement products, as well as compounds that are not accessible by classical onium ylide rearrangements.Geschickt arrangiert: Die Titelreaktion bietet eine allgemeine Lösung für katalytische Onium-Ylid-Umlagerungen. In Gegenwart eines chiralen Kupferkatalysators kuppeln substituierte Allyliodide mit α-Diazoestern zu metallkoordinierten Iodonium-Yliden, die hoch selektive [2,3]-Umlagerungen eingehen.
      PubDate: 2017-07-17T07:01:40.939978-05:
      DOI: 10.1002/ange.201705317
       
  • LiTMP Trans-Metal-Trapping of Fluorinated Aromatic Molecules: A
           Comparative Study of Aluminum and Gallium Carbanion Traps
    • Authors: Ross McLellan; Marina Uzelac, Alan R. Kennedy, Eva Hevia, Robert E. Mulvey
      Abstract: Fluoroaromatic scaffolds pose a challenge to lithiation due to low stability of lithiated intermediates. Here we apply trans-metal-trapping (TMT) to a series of key fluorinated aromatics. In TMT, LiTMP performs the metalation, while an organometallic trap intercepts the emergent carbanion. This study contrasts the trapping abilities of iBu2AlTMP and Ga(CH2SiMe3)3, structurally mapping their TMT reactions and probing relative stabilities of metalated fluoroaromatic intermediates by NMR studies. Results show the installed Al−C(aryl) bonds are more prone to decomposition by benzyne formation and Li-F liberation, than the Ga−C(aryl) species. The latter are thus better for onward reactivity as demonstrated in cross-coupling reactions with benzoyl chloride that produce ketones.Gekonnter Umgang mit Fluor: Hoch empfindliche lithiierte Fluorarene lassen sich für weitere Umwandlungen stabilisieren, wenn Ga(CH2SiMe3)3 als Carbanionenfalle verwendet wird. Die entsprechende Aluminiumverbindung iBu2AlTMP ist weniger wirksam.
      PubDate: 2017-07-17T06:50:49.092455-05:
      DOI: 10.1002/ange.201706064
       
  • Biokatalyse mit nicht-natürlichen Aminosäuren: Enzymologie
           trifft Xenobiologie
    • Authors: Federica Agostini; Jan-Stefan Völler, Beate Koksch, Carlos G. Acevedo-Rocha, Vladimir Kubyshkin, Nediljko Budisa
      Abstract: Das Ziel der Xenobiologie ist das Design von biologischen Systemen, die mit nicht-natürlichen biochemischen Funktionen ausgestattet sind, während die Enzymologie sich mit dem Verständnis von Enzymen auseinandersetzt, den Routinewerkzeugen der Biokatalyse. In der Biokatalyse werden Enzyme und Organismen dazu verwendet, um nützliche und leistungsfähige Biotransformationen in der synthetischen Chemie und Biotechnologie durchzuführen. In den vergangenen Jahren sind die Auswirkungen des Einbaus von nicht-kanonischen Aminosäuren (nkAAs) in Enzyme, welche potentiell interessante Anwendung für die Biokatalyse aufweisen, mit gesteigerter Aufmerksamkeit untersucht worden. Mit diesem Aufsatz wollen wir einen Überblick über die Effekte und Auswirkungen neuer chemischer Funktionalitäten geben, mit denen Proteine ausgestattet wurden, um eine Vielzahl von Aspekten der enzymatischen Biokatalyse zu verbessern. Ein weiteres Hauptaugenmerk liegt auf zukünftigen Forschungsperspektiven, welche die nicht-natürliche Mutagenese durch die Möglichkeiten des herkömmlichen Protein-Engineerings ergänzen werden, um neue und vielseitige Biokatalysatoren mit Anwendungen in der synthetischen organischen Chemie und Biotechnologie zu generieren.Die Xenobiologie zielt darauf ab, biologische Systeme zu entwerfen, die mit ungewöhnlichen biochemischen Einheiten ausgestattet sind. Zum Beispiel gewinnt man durch die Erweiterung des genetischen Codes mit nicht-natürlichen Aminosäuren oder durch die Einführung künstlicher Kofaktoren Enzyme mit einzigartigen Eigenschaften, die als nützliche Biokatalysatoren verwendet werden können.
      PubDate: 2017-07-17T06:40:53.110802-05:
      DOI: 10.1002/ange.201610129
       
  • A Carbene Catalysis Strategy for the Synthesis of Protoilludane Natural
           Products
    • Authors: M. Todd Hovey; Daniel T. Cohen, Daniel M. Walden, Paul H.-Y. Cheong, Karl A. Scheidt
      Abstract: The Armillaria and Lactarius genera of fungi produce the antimicrobial and cytotoxic mellolide, protoilludane, and marasmane sesquiterpenoids. We report a unified synthetic strategy to access the protoilludane, mellolide, and marasmane families of natural products. The key features of these syntheses are 1) the organocatalytic, enantioselective construction of key chiral intermediates from a simple achiral precursor, 2) the utility of a key 1,2-cyclobutanediol intermediate to serve as a precursor to each natural product class, and 3) a direct chemical conversion of a protoilludane to a marasmane through serendipitous ring contraction, which provides experimental support for their proposed biosynthetic relationships.Proto-Typ: Die ersten Totalsynthesen der Protoilludane Armillaridin und Echinochidin B und D werden vorgestellt. Schlüsselschritte sind: 1) eine enantioselektive NHC-katalysierte Anellierung zum Aufbau des cis-Cyclopentan-Kerns, 2) eine späte VII/ZnII-vermittelte reduktive Pinakolkupplung zur Bildung einer cis-Cyclobutandiol-Zwischenstufe und 3) eine potenziell biomimetische Ringverengung des Protoilludan-Grundgerüsts zum Marasman-Kern.
      PubDate: 2017-07-17T06:36:48.55246-05:0
      DOI: 10.1002/ange.201705308
       
  • Material-Efficient Microfluidic Platform for Exploratory Studies of
           Visible-Light Photoredox Catalysis
    • Authors: Connor W. Coley; Milad Abolhasani, Hongkun Lin, Klavs F. Jensen
      Abstract: We present an automated microfluidic platform for in-flow studies of visible-light photoredox catalysis in liquid or gas–liquid reactions at the 15 μL scale. An oscillatory flow strategy enables a flexible residence time while preserving the mixing and heat transfer advantages of flow systems. The adjustable photon flux made possible with the platform is characterized using actinometry. Case studies of oxidative hydroxylation of phenylboronic acids and dimerization of thiophenol demonstrate the capabilities and advantages of the system. Reaction conditions identified through droplet screening translate directly to continuous synthesis with minor platform modifications.Durchleuchtet: Ein automatisiertes photochemisches System als Umgebung eines Wechselfluss-Mikrofluidikreaktors ermöglicht effiziente Untersuchungen photokatalysierter Reaktionen in Flüssig- und Gas/Flüssig-Phasen für einzelne 15-μL-Tröpfchen. Die durch Screening identifizierten Bedingungen wurden direkt auf kontinuierliche Flusssynthesen übertragen.
      PubDate: 2017-07-17T06:36:37.566803-05:
      DOI: 10.1002/ange.201705148
       
  • Antimonene Quantum Dots: Synthesis and Application as Near-Infrared
           Photothermal Agents for Effective Cancer Therapy
    • Authors: Wei Tao; Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid C. Farokhzad
      Abstract: Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium. The PEG-coated AMQDs showed a PTCE of 45.5 %, which is higher than many other NMs-based PTAs such as graphene, Au, MoS2, and black phosphorus (BP). The AMQDs-based PTAs also exhibited a unique feature of NIR-induced rapid degradability. Through both in vitro and in vivo studies, the PEG-coated AMQDs demonstrated notable NIR-induced tumor ablation ability. This work is expected to expand the utility of 2D antimonene (AM) to biomedical applications through the development of an entirely novel PTA platform.Antimonen-Quantenpunkte (AMQDs) wurden nach einer Abblätterungsmethode synthetisiert. Die Polyethylenglykol-beschichteten AMQDs weisen einen hohen photothermischen Wirkungsgrad (45.5 %) auf. Durch ihre Nahinfrarot-induzierte Abbaubarkeit und Biokompatibilität eignen sie sich als neue Wirkstoffe für die photothermische Krebstherapie.
      PubDate: 2017-07-17T06:36:30.703744-05:
      DOI: 10.1002/ange.201703657
       
  • Ein allgemeiner Mechanismus der Photokonvertierung von grün-zu-rot
           fluoreszierenden Proteinen unter blauem und infrarotem Licht reduziert
           Phototoxität in der Einzelmolekülmikroskopie von lebenden Zellen
    • Authors: Bartosz Turkowyd; Alexander Balinovic, David Virant, Haruko G. Gölz Carnero, Fabienne Caldana, Marc Endesfelder, Dominique Bourgeois, Ulrike Endesfelder
      Abstract: Photokonversion von fluoreszierenden Proteinen mithilfe von blauem und komplementärem nah-infraroten Licht, genannt “Primed Conversion” (PC), ist ein kürzlich für Dendra2 entdeckter Mechanismus. Die Kontrolle über die Konformation von Arginin an Position 66 und Threonin an Position 69 fluoreszierender Proteine aus Anthozoa (Proteinfamilien Dendra2, mMaple, Eos, mKikGR, pcDronpa) ermöglicht in allgemeiner Weise PC. Mutationen von Alanin 159 oder Serin 173, die dafür bekannt sind, die Chromophorflexibilität zu beeinflussen und reversibles Photoschalten zu ermöglichen, verhindern PC. Eine verbesserte Photokonversion wurde für pcDronpa-Varianten mit Asparagin 116 beobachtet. Die reduzierte Phototoxizität bei der Anwendung von PC in der Einzelmolekül-Mikroskopie von lebenden Zellen wird demonstriert, und es werden Trajektorien der RNA-Polymerase-Dynamiken in Escherichia-coli-Zellen aufgezeichnet.Photokonversion mit blauem und komplementärem Nah-IR-Licht bietet eine Alternative zur UV-vermittelten Photokonversion von Proteinen, deren Fluoreszenz von Grün zu Rot photokonvertierbar ist. Dieser Photokonversionsweg fluoreszierender Proteine aus Anthozoa mit Threonin an Position 69 zeigt eine effiziente Photokonversion und verringerte Phototoxizität gegenüber UV-Photokonversion bei der Verfolgung einzelner Moleküle in lebenden Escherichia-coli-Zellen.
      PubDate: 2017-07-17T06:36:19.050531-05:
      DOI: 10.1002/ange.201702870
       
  • Two-Dimensional Metal–Organic Framework Nanosheets for
           Membrane-Based Gas Separation
    • Authors: Yuan Peng; Yanshuo Li, Yujie Ban, Weishen Yang
      Abstract: Metal–organic framework (MOF) nanosheets could serve as ideal building blocks of molecular sieve membranes owing to their structural diversity and minimized mass-transfer barrier. To date, discovery of appropriate MOF nanosheets and facile fabrication of high performance MOF nanosheet-based membranes remain as great challenges. A modified soft-physical exfoliation method was used to disintegrate a lamellar amphiprotic MOF into nanosheets with a high aspect ratio. Consequently sub-10 nm-thick ultrathin membranes were successfully prepared, and these demonstrated a remarkable H2/CO2 separation performance, with a separation factor of up to 166 and H2 permeance of up to 8×10−7 mol m−2 s−1 Pa−1 at elevated testing temperatures owing to a well-defined size-exclusion effect. This nanosheet-based membrane holds great promise as the next generation of ultrapermeable gas separation membrane.MOF-Nanomembranen: Aus schichtförmigen Zn2(Benzimidazol)3(OH)(H2O)-Vorstufen wurden Nanoplättchen abgeblättert. Durch anschließende Abscheidung auf anisotropen α-Al2O3-Substraten entstehen leistungsstarke Molekularsiebmembranen mit hoher H2/CO2-Selektivität und ausgezeichneter Durchlässigkeit für H2. Zn grün, N orange, C grau, O rot.
      PubDate: 2017-07-17T06:36:02.478993-05:
      DOI: 10.1002/ange.201703959
       
  • Effect of Selective CF3 Substitution on the Physical and Chemical
           Properties of Gold Corroles
    • Authors: Kolanu Sudhakar; Amir Mizrahi, Monica Kosa, Natalia Fridman, Boris Tumanskii, Magal Saphier, Zeev Gross
      Abstract: Gold corroles are not readily accessible and they display no interesting physical or chemical properties. A facile methodology has now been developed for obtaining selectively CF3-substituted gold(III) corroles and the introduction of these groups has been found to have an immense effect on the structures of the complexes, their photophysical and redox properties, and on their ability to participate in catalytic processes.Einschneidende Veränderungen hinsichtlich der Struktur sowie der optischen und elektrochemischen Eigenschaften ergeben sich aus der Trifluormethylierung inerter Goldcorrole. Dies belegt eine Kombination aus analytischen Methoden. Der vierfach CF3-substituierte Goldkomplex vermittelt die elektrokatalytische Reduktion von Protonen unter Bildung von Wasserstoffgas.
      PubDate: 2017-07-17T06:35:31.823798-05:
      DOI: 10.1002/ange.201705007
       
  • Colloidal Rings by Site-Selective Growth on Patchy Colloidal Disc
           Templates
    • Authors: Yuanyuan Wu; Zhang Luo, Bing Liu, Zhenzhong Yang
      Abstract: Anisotropic colloidal building blocks are quite attractive as they enable the self-assembly towards new materials with designated hierarchical structures. Although many advances have been achieved in colloidal synthetic methodology, synthesis of colloidal rings with low polydispersity and on a large scale remains a challenge. To address this issue we introduce a new site-selective growth strategy, which relies on using patchy particles. For example, by using patchy discs as templates, silica can selectively be grown on only side surfaces, resulting in formation of silica rings. We demonstrate that shape parameters are tunable and find that these silica rings can be used as secondary template to synthesize other types of rings. This method for synthesizing ring-like colloids provides possibilities for studying their self-assembly and associated phase transitions, and this patchy particles template strategy paves a new route for fabricating other new colloidal particles.Monodisperse ringförmige Kolloide wurden durch selektives Anwachsen von SiO2 an den Seitenflächen der scheibenförmigen Kolloidplättchen synthetisiert. Der Durchmesser und das Aspektverhältnis können gezielt eingestellt werden, und die Methode ermöglicht die Herstellung im großen Maßstab. Die SiO2-Ringe haben Janus-Charakter und können als Template zur Synthese andere Ringe verwendet werden.
      PubDate: 2017-07-17T06:31:24.798051-05:
      DOI: 10.1002/ange.201704541
       
  • Structure of Amorphous Selenium by 2D 77Se NMR Spectroscopy: An End to the
           Dilemma of Chain versus Ring
    • Authors: Maxwell Marple; Jackson Badger, Ivan Hung, Zhehong Gan, Kirill Kovnir, Sabyasachi Sen
      Abstract: Amorphous selenium, owing to its tremendous technological importance and perhaps to its chemical simplicity, has been studied for nearly a century and yet an unequivocal structural description of this material remains lacking to date. The primary controversy regarding the structure of amorphous Se relates to the relative fraction of Se atoms residing in ∞1Se chains versus in Se8 rings. Herein we present the results of a two-dimensional solid-state 77Se nuclear magnetic resonance (NMR) spectroscopic study of the chain and ring crystalline allotropes of Se as well as of amorphous Se to unequivocally demonstrate that 1) the Se8 rings and the ∞1Se chains are characterized by their unique 77Se NMR signatures and 2) the structure of amorphous Se consists exclusively of ∞1Se chains.Amorphes Selen wurde fast hundert Jahre lang untersucht, ohne dass eine eindeutige Strukturbeschreibung gelang. Der wichtigste Streitpunkt betraf das Verhältnis zwischen Se-Atomen in ∞1Se-Ketten und in Se8-Ringen. 77Se-MATPASS/CPMG-NMR-Spektroskopie kann zwischen den beiden Umgebungen unterscheiden und räumt diesbezügliche Zweifel nun aus: Amorphes Selen enthält ausschließlich ∞1Se-Ketten.
      PubDate: 2017-07-17T06:31:16.530186-05:
      DOI: 10.1002/ange.201704323
       
  • Associating and Dissociating Nanodimer Analysis for Quantifying Ultrasmall
           Amounts of DNA
    • Authors: Keunsuk Kim; Jeong-Wook Oh, Young Kwang Lee, Jiwoong Son, Jwa-Min Nam
      Abstract: The amplification- and enzyme-free quantification of DNA at ultralow concentrations, on the order of 10–1000 targets, is highly beneficial but extremely challenging. To address this challenge, true detection signals must be reliably discriminated from false or noise signals. Herein, we describe the development of associating and dissociating nanodimer analysis (ADNA) as a method that enables a maximum number of detection signals to be collected from true target-binding events while keeping nonspecific signals at a minimum level. In the ADNA assay for ultralow target concentrations, Au nanoprobes on a lipid micropattern were monitored and analyzed in situ, and newly defined dissociating dimers, which are eventually decoupled into monomers again, were incorporated into the detection results. Tens to thousands of DNA copies can be reliably quantified with excellent single-base-mismatch differentiation capability by this non-enzymatic, amplification-free ADNA method.Wie weit kannst du gehen' Eine neue Methode für die DNA-Quantifizierung (ADNA für associating and dissociating nanodimer analysis) nutzt die DNA-Erkennung durch plasmonische Nanosonden auf einem Lipid-Mikromuster. Der Nachweis und die Quantifizierung von Dimeren, die assoziieren und wieder dissoziieren, sowie von gebundenen Dimeren ermöglichen die verlässliche Quantifizierung ultrakleiner Mengen an Biomolekülen (nur 47 DNA-Kopien) ohne Amplifizierungsschritte.
      PubDate: 2017-07-17T06:31:12.186008-05:
      DOI: 10.1002/ange.201705330
       
  • Vom Boran zum Borylen ohne Reduktion: Ambiphiles Verhalten einer
           monovalenten Silylisonitril-Borverbindung
    • Authors: Merle Arrowsmith; Dominic Auerhammer, Rüdiger Bertermann, Holger Braunschweig, Mehmet Ali Celik, Julian Erdmannsdörfer, Ivo Krummenacher, Thomas Kupfer
      Abstract: Die Deprotonierung von [(cAAC)BH2(CN)] ermöglicht den Zugang zum stabilen Borylanion, [(cAAC)BH(CN)]−. Während die Addition weicher Elektrophile am nukleophilen Boratom stattfindet, addieren härtere Silylelektrophile am härteren terminalen Stickstoff der Cyanogruppe. Die daraus entstandene Verbindung, [(cAAC)BH(CNSiPh3)], reagiert sowohl als ein Silyliumboryl-Nukleophil wie auch als ein neutrales Silylisonitril-Borylen.Findet die Addition weicher Elektrophile mit [(cAAC)B(CN)H]− am nukleophilen Borkern statt, so addieren vergleichsweise härtere Silylelektrophile am härteren Cyano-Endstickstoff. Die jeweiligen [(cAAC)BH(CNSiR3)]-Verbindungen verhalten sich sowohl wie zwitterionische Silyliumboryle als auch wie neutrale Silylisonitrilborylene: BI-Verbindungen, die durch einfache Deprotonierung und Salzmetathese zugänglich sind. cAAC=cyclische Alkylaminocarbene.
      PubDate: 2017-07-17T06:30:29.531693-05:
      DOI: 10.1002/ange.201705561
       
  • Annulated 1,3,4-azadiphospholides: Heterocycles with widely tunable
           optical properties
    • Authors: Hansjörg Grützmacher; Riccardo Suter, Zoltán Benkö, Mark Bispinghoff
      Abstract: Phosphorus heterocycles find applications in the synthesis of π-conjugated compounds and as precursors for optoelectronic materials such as organic light emitting diodes (OLEDs), electronic switches, and transistors. We report a high yield, one pot synthesis of anionic annulated 1,3,4-azadiphospholides from Na(OCP) and 2-chloro pyridines. The synthesis proceeds without the use of transition metals and tolerates a wide range of substrates. Cyano-substituted compounds are especially deeply colored and have absorption maxima which range from λmax = 525 to 596 nm. The optical properties are dominated by the spatial separation of an electron acceptor and donor unit within one molecule (push-pull chromophore). The anionic 1,3,4-azadiphospholides are silylated to neutral siloxy compounds with a strong blue-shifted absorption. This reaction can be reversed by addition of fluoride ions, which allows to detect optically fluoride in low concentrations.
      PubDate: 2017-07-17T06:16:02.134284-05:
      DOI: 10.1002/ange.201705473
       
  • Manganese-Catalyzed C−H Functionalizations: Hydroarylations and
           Alkenylations Involving an Unexpected Heteroaryl Shift
    • Authors: Chengming Wang; Ai Wang, Magnus Rueping
      Abstract: A manganese-catalyzed regio- and stereoselective hydroarylation of allenes is reported. The C−H functionalization method provides access to various alkenylated indoles in excellent yields. Moreover, a hydroarylation/cyclization cascade involving an unexpected C−N bond cleavage and aryl shift has been developed, which provides a new synthetic approach to substituted pyrroloindolones.Zwei Möglichkeiten: Eine effiziente, skalierbare, regio- und stereoselektive Mangan-katalysierte C-H-Arylierung von Allenen wird beschrieben. Mit trisubstituierten Allenen liefert eine Reaktionskaskade aus C-H-Funktionalisierung, C-N-Bindungsbruch und Cyclisierung Pyrroloindolone. Mechanistische Studien deuten darauf hin, dass ein Manganacyclus am Katalysezyklus beteiligt ist.
      PubDate: 2017-07-17T04:10:47.511296-05:
      DOI: 10.1002/ange.201704682
       
  • Polyladderane Constructed from Gemini Monomer via Photoreaction
    • Authors: Zhihan Wang; Benjamin Miller, Jonathan Butz, Katelyn Randazzo, Zijun D. Wang, Qianli Rick Chu
      Abstract: Polyladderane, the first polymer to contain the ladderane functional group, was successfully synthesized from gemini monomer through photoreaction in the solid state. The modular design of the gemini monomers used to create polyladderane allowed specific structural modification, resulting in the formation of two distinct polymer products. Monomers were synthesized by connecting two photoreactive units, either sorbic acids (monomer I) or 2-furanacrylic acids (monomer II), with a 1,4-butanediol linker. Single crystal X-ray diffraction analysis of the monomers confirmed that they packed in the desired head-to-tail orientation and within a viable distance for photoreaction by electronically-complementary interaction. Pre-organized gemini monomers were irradiated with UV light and monitored by FT-IR. Two polyladderanes with cis,anti,cis-[3]-ladderane as a characteristic functional group were constructed stereospecifically in 24-36 hours.
      PubDate: 2017-07-17T03:15:58.769263-05:
      DOI: 10.1002/ange.201705937
       
  • Pd(II)-Catalyzed Site-Selective C(sp3)-H Alkynylation of Oligopeptides: A
           Linchpin Approach for Oligopeptide-Drug Conjugation
    • Authors: Tao Liu; Jennifer X Qiao, Michael A Poss, Jin-Quan Yu
      Abstract: The palladium(II)-catalyzed C(sp3)-H alkynylation of oligopeptides was developed with tetrabutylammonium acetate as a key additive. Through molecular design, the acetylene motif serves as a linchpin to introduce a broad range of carbonyl-containing pharmacophores onto oligopeptides, thus providing a chemical tool for the synthesis and modification of novel oligopeptide-pharmacophore conjugates via C-H functionalization. Dipeptide conjugates with coprostanol and estradiol has been synthesized using this method for potential application in targeted drug delivery to tumor cells with overexpressed nuclear hormone receptors.
      PubDate: 2017-07-17T03:15:33.325225-05:
      DOI: 10.1002/ange.201706367
       
  • Intermediate product regulation in tandem solid catalysts with multimodal
           porosity for high-yield synthetic fuel production
    • Authors: Nicolas Duyckaerts; Mathias Bartsch, Ioan-Teodor Trotus, Norbert Pfänder, Axel Lorke, Ferdi Schüth, Gonzalo Prieto
      Abstract: Tandem catalysis is an attractive strategy to intensify chemical processes but simultaneous control over the individual and concerted catalyst performances poses a challenge. We show that enhanced pore transport within a Co/Al2O3 Fischer-Tropsch (FT) catalyst with a hierarchical porosity enables its tandem integration with a Pt/ZSM-5 zeolitic hydrotreating catalyst in a spatially distant fashion ‒ permitting a catalyst-specific temperature adjustment ‒ albeit resembling a close active site proximity ‒ by mitigating secondary reactions of primary FT α-olefin products. This approach enables the conciliation of in situ de-waxing with a minimum production of gases (18 wt%) and an up to two-fold higher (50 wt%) selectivity to middle-distillates compared to benchmark mesoporous FT catalysts. An overall 80% selectivity to liquid hydrocarbons from syngas is attained in one step, attesting for the potential of this strategy to increase the efficiency in intensified gas-to-liquid technologies.
      PubDate: 2017-07-16T21:22:39.849327-05:
      DOI: 10.1002/ange.201705714
       
  • Bioinspired, size-tunable self-assembly of polymer-lipid bilayer nanodiscs
    • Authors: Thirupathi Ravula; Sudheer Ramadugu, Giacomo Di Mauro, Ayyalusamy Ramamoorthy
      Abstract: Polymer-based nanodiscs are valuable tools in biomedical research that can offer a detergent-free solubilization of membrane proteins maintaining their native lipid environment. Here, we introduce a novel ~1.6 kDa SMA-based polymer with styrene:maleic acid moieties that can form nanodiscs containing a planar lipid bilayer which are useful to reconstitute membrane proteins for structural and functional studies. The physicochemical properties and the mechanism of formation of polymer-based nanodiscs are characterized by light scattering, NMR, FT-IR, and TEM imaging experiments. A remarkable feature is that nanodiscs of different sizes, from nanometer to sub micrometer diameter, can be produced only by varying the lipid-to-polymer ratio. As demonstrated, the small size nanodiscs (up to ~30 nm diameter) can be used for solution NMR studies whereas the magnetic-alignment of macro-nanodiscs (diameter of>~40 nm) can be exploited for solid-state NMR studies on membrane proteins.
      PubDate: 2017-07-16T21:22:30.300447-05:
      DOI: 10.1002/ange.201705569
       
  • Carbonitride Aerogels for the Photoredox Conversion of Water
    • Authors: Honghui Ou; Pengju Yang, Lihua Lin, Masakazu Anpo, Xinchen Wang
      Abstract: Aerogel structures have attracted increasing research interest in energy storage and conversion owing to their unique structural features, and a variety of matters has been engineered into aerogels, including carbons, metal oxides, linear polymers and even metal chalcogenides. However, manufacturing of aerogels from nitride-based materials, particularly the emerging light-weight carbonitride (CN) is rarely reported. Here, we develop a facile method based on self-assembly chemistry to produce self-supported CN aerogels, without using any cross-linking agents. The combination of the large surface area, the incorporated functional group and the 3D network structure, endow the resulting freestanding aerogels with high photoreactiveity for hydrogen evolution and H2O2 production under visible light irradiation. This work presents a simple colloid chemistry strategy to construct 3D CN aerogel network that shows great potentials for solar to chemical conversion by artificial photosynthesis.
      PubDate: 2017-07-15T04:25:24.131498-05:
      DOI: 10.1002/ange.201705926
       
  • Enhanced carbon dioxide electroreduction to carbon monoxide over defect
           rich plasma-activated silver catalysts
    • Authors: Hemma Mistry; Yong-Wook Choi, Alexander Bagger, Fabian Scholten, Cecile Bonifacio, Ilya Sinev, Nuria J. Divins, Ioannis Zegkinoglou, Hyo Sang Jeon, Kim Kisslinger, Eric A. Stach, Judith C. Yang, Jan Rossmeisl, Beatriz Roldán Cuenya
      Abstract: Efficient, stable catalysts with high selectivity for a single product are essential to making the electroreduction of CO2 a viable route to the synthesis of industrial feedstocks and fuels. We reveal how a plasma oxidation pre-treatment can lead to an enhanced content of low-coordinated active sites which dramatically lower the overpotential and increase the activity of CO2 electroreduction to CO. At -0.6 V vs. RHE, more than 90% Faradaic efficiency towards CO could be achieved on a pre-oxidized silver foil. While transmission electron microscopy and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulk of the catalyst during the reaction, in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. DFT calculations show how the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields results in a drastic decrease in the overpotential for the electroreduction of CO2.
      PubDate: 2017-07-14T23:30:37.781428-05:
      DOI: 10.1002/ange.201704613
       
  • Rational Control on the Selectivity of Ru Catalyst for Hydrogenation of
           4-Nitrostyrene via Strain Regulation
    • Authors: Yadong Li; Junjie Mao, Wenxing Chen, Wenming Sun, Zheng Chen, Jiajing Pei, Dongsheng He, Chunlin Lv, Dingsheng Wang
      Abstract: Tuning the selectivity of metal catalysts is of paramount importance, yet a great challenge. Here, a new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is reported. In this approach, we introduce a certain amount of Co atoms into Ru catalysts to compress the Ru lattice, as confirmed by aberration corrected high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS) measurements. We discover that, the lattice strain of Ru catalysts can greatly affect their selectivity and Ru with 3% lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene compared to pristine Ru (99% Vs. 66%). The theoretical studies prove that the optimized lateral compressive strain facilitates hydrogenation of nitro-group but impedes the hydrogenation of vinyl-group. This study provides a new guideline for designing metal catalysts with high selectivity.
      PubDate: 2017-07-14T23:30:28.743489-05:
      DOI: 10.1002/ange.201706645
       
  • Total Syntheses of the Reported Structures of Curcusone I and J via Tandem
           Gold Catalysis
    • Authors: Yong Li; Mingji Dai
      Abstract: Total syntheses of the reported structures of the rhamnofolane diterpene natural products curcusone I and J in racemic forms have been achieved. The synthetic strategy features a novel tandem gold-catalyzed furan formation and furan-allene [4+3] cycloaddition to build the 5,7-fused ring system with an oxa-bridge in one step and a stereoselective exo-Diels-Alder reaction to form the 6-membered ring. The newly developed tandem gold catalysis is quite general and can be scaled up. Our syntheses suggested that structural revisions of curcusone I and J are needed.
      PubDate: 2017-07-14T10:26:26.092188-05:
      DOI: 10.1002/ange.201706845
       
  • Pd-Catalyzed Spirocyclization via C-H Activation and Regioselective Alkyne
           Insertion
    • Authors: Hyung Yoon; Martin Rolz, Felicitas Landau, Mark Lautens
      Abstract: A Pd-catalyzed spirocyclization involving a sequential carbopalladation, intramolecular C-H activation and a highly regioselective alkyne insertion to afford spirooxindoles and spirodihydrobenzofurans has been achieved. The spirocyclic products were generated in good to excellent yields with complete regiocontrol in a readily scalable procedure.
      PubDate: 2017-07-14T09:25:35.630362-05:
      DOI: 10.1002/ange.201706325
       
  • Palladium Catalyzed Suzuki-Miyaura Cross-Coupling of Secondary
           α-(Trifluoromethyl)benzyl Tosylates
    • Authors: Marta Brambilla; Matthew Tredwell
      Abstract: A palladium catalyzed C(sp3)-C(sp2) Suzuki-Miyaura cross-coupling of aryl boronic acids and α-(trifluoromethyl)benzyl tosylates is reported. The reaction uses a readily available, air-stable palladium catalyst to access a wide range of functionalized 1,1-diaryl-2,2,2-trifluoroethanes. Enantioenriched α-(trifluoromethyl)benzyl tosylates were found to undergo cross-coupling to give the corresponding enantioenriched cross-coupled products with an overall inversion in configuration. The crucial role of the CF3 group in promoting this transformation is demonstrated by comparison with non-fluorinated derivatives.
      PubDate: 2017-07-14T08:25:33.99457-05:0
      DOI: 10.1002/ange.201706631
       
  • Catalytic Nitrene Transfer To Alkynes: A Novel and Versatile Route for the
           Synthesis of Sulfinamides and iso-Thiazoles
    • Authors: Pedro J. Pérez; M. Mar Diaz-Requejo, Manuel R. Rodríguez, Álvaro Beltrán, Eleuterio Alvarez, Angel Mudarra, Feliu Maseras
      Abstract: A novel transformation is reported for the reaction of terminal or internal alkynes with the nitrene precursor PhI=NTs (Ts = p-toluenesulfonyl) in the presence of catalytic amounts of TpBr3Cu(NCMe) (TpBr3 = hydrotris(3,4,5-tribromo-pyrazolylborate). Two products containing an imine functionality have been isolated from the reaction mixtures, identified as sulfinamides and iso-thiazoles. The former correspond to the formal reduction of the sulfone group into sulfoxide, whereas the latter involves the insertion of an alkyne carbon atom into the aromatic ring of the N-tosyl moiety.
      PubDate: 2017-07-14T07:25:29.767752-05:
      DOI: 10.1002/ange.201705664
       
  • Catalytic Regio- and Enantioselective [4+2] Annulation Reactions of
           Non-activated Allenes by a Chiral Cationic Indium Complex
    • Authors: Le Wang; Jian Lv, Long Zhang, Sanzhong Luo
      Abstract: Regio- and enantioselective [4+2] annulation between ,γ-unsaturated -keto esters and non-activated allenes has been achieved by a chiral cationic indium(III)/phosphate catalyst. The reaction affords the corresponding C3-selective dihydropyrans in good yields and with high enantioselectivities (up to 99% ee).
      PubDate: 2017-07-14T05:26:09.647372-05:
      DOI: 10.1002/ange.201704020
       
  • Supramolecular Nanotubules as Catalytic Regulator for Pd Cation and Their
           Application in Selective Catalysis
    • Authors: Zhegang Huang; Shanshan Wu, Yongguang Li, Siying Xie, Cong Ma, Joonwon Lim, Jiong Zhao, Dae Seok Kim, Minyong Yang, Doong Ki Yoon, Myongsoo Lee, Sang Ouk Kim
      Abstract: Despite recent development of highly efficient and stable metal catalysts, conferral of regulatory characteristic to the catalytic reaction in heterogeneous system remains a challenge. Herein, novel supramolecular nanotubules were prepared by alternative stacking from trimeric macrocycles, which was found to be able to coordinate with Pd cations. The Pd complexes exhibited a high catalytic performance for C-C coupling reaction. Notably, the tubular catalyst was observed to be controlled by supramolecular reversible assembly and showed superior heterogeneous catalytic activity maintained for a number of recycles or reuse under aerobic environment. Furthermore, the supramolecular catalyst showed unprecedented selectivity for the multi-functional coupling reaction and was able to serve as a new construction of asymmetrical compounds.
      PubDate: 2017-07-14T04:25:24.852229-05:
      DOI: 10.1002/ange.201706373
       
  • Selective Pd(II)-Catalyzed Carbonylation of Methylene beta-C-H Bonds in
           Aliphatic Amines
    • Authors: Matthew James Gaunt; Jaime Cabrera-Pardo, Aaron Trowbridge, Manuel Nappi, Kyohei Ozaki
      Abstract: Pd(II)-catalyzed C-H carbonylation of methylene C-H bonds in secondary aliphatic amines leads to the formation trans-disubstituted beta-lactams in excellent yields and selectivities. The generality of the C-H carbonylation process is aided by the action of xantphos-based ligands and is important in securing good yields of the beta-lactam products.
      PubDate: 2017-07-14T03:25:42.327791-05:
      DOI: 10.1002/ange.201706303
       
  • Facile Synthesis of Azetidine Nitrones and Diastereoselective Conversion
           to Densely-Substituted Azetidines
    • Authors: Tyler W Reidl; Jongwoo Son, Donald J Wink, Laura L Anderson
      Abstract: Discovery of an electrocyclization route to azetidine nitrones from N-alkenylnitrones has been shown to provide facile access to these unsaturated strained heterocycles. Reactivity studies have shown that these compounds undergo a variety of reduction, cycloaddition, and nucleophilic addition reactions to form highly-substituted azetidines with excellent diastereoselectivity. Taken together, these transformations provide a fundamentally different approach to azetidine synthesis than traditional cyclization by nucleophilic displacement and provide novel access to a variety of underexplored, strained heterocyclic compounds.
      PubDate: 2017-07-14T00:42:42.882041-05:
      DOI: 10.1002/ange.201705681
       
  • Colloidal Synthesis of Silicon@Carbon Composite Materials for Lithium-Ion
           Batteries
    • Authors: Haiping Su; Alejandro A Barragan, Linxiao Geng, Donghui Long, Licheng Ling, Krassimir N Bozhilov, Lorenzo Mangolini, Juchen Guo
      Abstract: We report colloidal routes to synthesize silicon@carbon composites for the first time. Surface-functionalized Si nanoparticles (SiNPs) dissolved in styrene and hexadecane are used as the dispersed phase in oil-in-water emulsions, from which yolk-shell and dual-shell hollow SiNPs@C composites are produced via polymerization and subsequent carbonization. As anode materials for Li-ion batteries, the SiNPs@C composites demonstrate excellent cycling stability and rate performance, which is ascribed to the uniform distribution of SiNPs within the carbon hosts. The Li-ion anodes composed of 46 wt.% of dual-shell SiNPs@C, 46 wt.% of graphite, 5 wt.% of acetylene black, and 3 wt.% of carboxymethyl cellulose with> 3 mg cm-2 areal loading achieve an overall specific capacity of> 600 mAh g-1, which is>100% improvement from the pure graphite anode. These new colloidal routes present a promising general method to produce viable Si-C composites for Li-ion batteries.
      PubDate: 2017-07-14T00:42:30.593381-05:
      DOI: 10.1002/ange.201705200
       
  • Synthesis and Reactivity of Fluoroalkyl Copper Complexes by the
           Oxycupration of Tetrafluoroethylene
    • Authors: Masato Ohashi; Takuya Adachi, Naoyoshi Ishida, Kotaro Kikushima, Sensuke Ogoshi
      Abstract: The copper(I)-mediated generation of -OCF2CF2- moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2-aryloxy-1,1,2,2-tetrafluoroethyl and 2-alkoxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE, and their structures in solution and in the solid state were unambiguously determined by multinuclear NMR spectroscopy and X-ray diffraction analysis. These copper complexes subsequently reacted with aryl iodides (ArI) to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.Die Oxycuprierung von Tetrafluorethylen (TFE) liefert -OCF2CF2-Einheiten. Die entscheidenden Zwischenstufen – 2-Aryloxy- und 2-Alkyloxy-1,1,2,2-tetrafluorethyl-Kupferkomplexe – entstehen durch die Reaktion der Aryloxy- bzw. Alkoxy-Kupferkomplexe mit TFE. Anschließend führt die Umsetzung mit Aryliodiden in hohen Ausbeuten zu ROCF2CF2Ar (R=Aryl oder Alkyl).
      PubDate: 2017-07-14T00:36:09.985483-05:
      DOI: 10.1002/ange.201703923
       
  • Fine Tuning of MOF-505 Analogues to Reduce Low Pressure Methane Uptake and
           Enhance Methane Working Capacity
    • Authors: Junfeng Bai; Mingxing Zhang, Wei Zhou, Tony Pham, Katherine A Forrest, Wenlong Liu, Yabing He, Hui Wu, Taner Yildirim, banglin chen, Brian Space, Yi Pan, Michael J Zaworotko
      Abstract: We present a crystal engineering strategy to fine tune the pore chemistry and CH4 storage performance of a family of isomorphous MOFs based upon PCN-14. These MOFs exhibit similar pore size, pore surface and surface area (around 3000 m2 g-1) and were prepared with the goal to enhance CH4 working capacity. [Cu2(L2)(H2O)2]n (NJU-Bai 41: NJU-Bai for Nanjing University Bai's group), [Cu2(L3)(H2O)2]n (NJU-Bai 42) and [Cu2(L4)(DMF)2]n (NJU-Bai 43) were prepared and we observed that the CH4 volumetric working capacity and volumetric uptake values are impacted by subtle changes in structure and chemistry. In particular, the CH4 working capacity of NJU-Bai 43 reaches 198 cm3 (STP: 273.15 K, 1 atm) cm-3 at 298 K and 65 bar, which is amongst the highest reported for MOFs under these conditions and is much higher than the corresponding value for PCN-14 (157 cm3 (STP) cm-3).
      PubDate: 2017-07-13T22:25:25.240547-05:
      DOI: 10.1002/ange.201704974
       
  • Rhodium-Catalyzed Enantioselective Reductive Arylation: Convenient Access
           to 3,3-Disubstituted Oxindoles
    • Authors: Mark Lautens; Young Jin Jang, Egor Mikhailovich Larin
      Abstract: A rhodium-Josiphos(L*) catalyzed enantioselective intramolecular hydroarylation reaction is described. The reductive cyclization of o-bromoaniline-derived acrylamides provides convenient access to 3,3-disubstituted oxindoles in good yields and with excellent enantioselectivity across a range of substrates. We propose that the key cyclization proceeds via a rhodium(III) intermediate. Overall, this method represents an unusual mode of reactivity for rhodium catalysis and is complementary to palladium(0)-catalyzed α-arylation protocols.
      PubDate: 2017-07-13T13:25:56.694209-05:
      DOI: 10.1002/ange.201704922
       
  • Unveiling the target promiscuity of pharmacologically active compounds in
           silico
    • Authors: Petra Schneider; Gisbert Schneider
      Abstract: Drug discovery is governed by the desire to find ligands with defined modes of action. It has been realized that even designated selective drugs may have more macromolecular targets than is commonly thought. Consequently, it will be mandatory to consider multi-target activity for the design of future medicines. Computational models assist medicinal chemists in this effort by helping to eliminate unsuitable lead structures and spot undesired drug effects early in the discovery process. Here, we present a straightforward computational method to find previously unknown targets of pharmacologically active compounds. Validation experiments revealed hitherto unknown targets of the natural product resveratrol and the nonsteroidal anti-inflammatory drug celecoxib. The obtained results advocate machine-learning for polypharmacology-based molecular design, drug re-purposing, and the "de-orphaning" of phenotypic drug effects.
      PubDate: 2017-07-13T11:25:44.757784-05:
      DOI: 10.1002/ange.201706376
       
  • A Bulky m-Terphenyl Cyclopentadienyl Ligand and its Alkali Metal Complexes
           (Li, Na, K, Rb, and Cs)
    • Authors: Alex J. Veinot; Angela D.K. Todd, Jason Masuda
      Abstract: The synthesis of the new m-terphenyl substituted cyclopentadienyl ligand precursor 1-cyclopentadiene-2,6-bis(2,4,6-trimethylphenyl)benzene (TerMesCpH) is described. Synthesis proceeds through the reaction of TerMesLi with cobaltocenium iodide, followed by oxidation of the intermediate cobalt(I) species to give the corresponding cyclopentadiene as a mixture of isomers. The preparation and spectroscopic properties of the alkali metal salts (Li-Cs) is described, as well as structural information obtained by X-ray diffraction studies for the lithium, potassium, and caesium analogues. Crystallographic data demonstrates the utility of these new ligands to act as monoanionic chelates by forming metal complexes with Cp-M-Ar bonding environments.
      PubDate: 2017-07-13T08:25:36.71273-05:0
      DOI: 10.1002/ange.201706398
       
  • Selenium-Doped Carbon Quantum Dots for Free Radical Scavenging
    • Authors: Feng Li; Tianyu Li, Chenxing Sun, Jiahao Xia, Yang Jiao, Huaping Xu
      Abstract: Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium-doped carbon dots have rarely been reported, even though selenium has unique chemical properties such as redox-responsive properties owing to its special electronegativity. Herein, a facile and high-output strategy to fabricate selenium-doped carbon quantum dots (Se-CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions. Selenium heteroatoms endow the Se-CQDs with redox-dependent reversible fluorescence. Furthermore, free radicals such as .OH can be effectively scavenged by the Se-CQDs. Once Se-CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are decreased. This property makes the Se-CQDs capable of protecting biosystems from oxidative stress.Durch Hydrothermalbehandlung von Selenocystin wurden Selen-dotierte Kohlenstoff-Quantenpunkte (Se-CQDs) mit redoxabhängiger Fluoreszenz und der Fähigkeit zum Abfangen von Radikalen hergestellt. Nach der Internalisierung durch Zellen senken die Se-CQDs hohe Konzentrationen an schädlichen reaktiven Sauerstoffspezies (ROS) und schützen so vor oxidativem Stress.
      PubDate: 2017-07-13T07:42:28.546785-05:
      DOI: 10.1002/ange.201705989
       
  • Ni3FeN-Supported Fe3Pt Intermetallic Nanoalloy as a High-Performance
           Bifunctional Catalyst for Metal–Air Battery
    • Authors: Zhiming Cui; Gengtao Fu, Yutao Li, John B. Goodenough
      Abstract: Electrocatalysts for both the oxygen reduction and evolution reactions (ORR and OER) are vital for the performances of rechargeable metal–air batteries. Herein, we report an advanced bifunctional oxygen electrocatalyst consisting of porous metallic nickel-iron nitride (Ni3FeN) supporting ordered Fe3Pt intermetallic nanoalloy. In this hybrid catalyst, the bimetallic nitride Ni3FeN mainly contributes to the high activity for the OER while the ordered Fe3Pt nanoalloy contributes to the excellent activity for the ORR. Robust Ni3FeN-supported Fe3Pt catalysts show superior catalytic performance to the state-of-the-art ORR catalyst (Pt/C) and OER catalyst (Ir/C). The Fe3Pt/Ni3FeN bifunctional catalyst enables Zn–air batteries to achieve a long-term cycling performance of over 480 h at 10 mA cm−2 with high efficiency. The extraordinarily high performance of the Fe3Pt/Ni3FeN bifunctional catalyst makes it a very promising air cathode in alkaline electrolyte.OER und ORR: Eine Fe3Pt-Nanolegierung auf Ni3FeN-Träger ist ein aktiver und stabiler Elektrokatalysator für die Sauerstoffentwicklung und -reduktion (OER und ORR) unter alkalischen Bedingungen. Der Fe3Pt/Ni3FeN-Katalysator ergab eine Zink-Luft-Batterie, die über 480 h zyklenstabil war, und übertraf Pt/C+Ir/C-Mischkatalysatoren deutlich.
      PubDate: 2017-07-13T07:42:20.076707-05:
      DOI: 10.1002/ange.201705778
       
  • Janusarene: A Homoditopic Molecular Host
    • Authors: Tao Li; Luoyi Fan, Hao Gong, Zeming Xia, Yanpeng Zhu, Nianqiang Jiang, Long Jiang, Gaofeng Liu, Yang Li, Jiaobing Wang
      Abstract: A homoditopic molecular host, janusarene, is presented that has two back-to-back compactly arranged nanocavities for guest complexation. The unique two-face structural feature of janusarene allows it to bind and align various guest compounds concurrently, which include spherical pristine fullerene C60 and planar polycyclic aromatic hydrocarbons (PAHs), such as pyrene, perylene, and 9,10-dimethylanthracene. The host–guest interactions were characterized by single-crystal X-ray diffraction. A pairwise encapsulation of the PAH guests by janusarene enables PAH dimers to be obtained that deliver spectroscopic properties distinct from those of PAHs dissolved in solution, or in the bulk state. A monotopic control host was also synthesized and used to characterize the host–guest complexing behavior in solution.Rücken an Rücken sind zwei Bindestellen in der homoditopen Wirtverbindung „Janus-Aren” angeordnet. Dieses beispiellose Strukturmotiv ermöglicht die Bindung und Ausrichtung von Gastspezies mit breit variierenden Größen und Formen, von sphärischem Fulleren bis zu planaren polycyclischen aromatischen Kohlenwasserstoffen.
      PubDate: 2017-07-13T07:42:05.946184-05:
      DOI: 10.1002/ange.201705451
       
  • A Dysprosium Metallocene Single-Molecule Magnet Functioning at the Axial
           Limit
    • Authors: Fu-Sheng Guo; Benjamin M. Day, Yan-Cong Chen, Ming-Liang Tong, Akseli Mansikkamäki, Richard A. Layfield
      Abstract: ion of a chloride ligand from the dysprosium metallocene [(Cpttt)2DyCl] (1Dy Cpttt=1,2,4-tri(tert-butyl)cyclopentadienide) by the triethylsilylium cation produces the first base-free rare-earth metallocenium cation [(Cpttt)2Dy]+ (2Dy) as a salt of the non-coordinating [B(C6F5)4]− anion. Magnetic measurements reveal that [2Dy][B(C6F5)4] is an SMM with a record anisotropy barrier up to 1277 cm−1 (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low-lying Kramers doublets correspond to a well-defined MJ value, with no significant mixing even in the higher doublets.Rekordhalter: Ein Dysprosium(III)-Metalloceniumkation ist ein Einzelmolekülmagnet mit einer Rekord-Anisotropiebarriere von 1277 cm−1 und -Blockierungstemperatur bis 60 K, einschließlich einer Hysterese mit Koerzivität.
      PubDate: 2017-07-13T07:41:46.878719-05:
      DOI: 10.1002/ange.201705426
       
  • Palladium-Catalyzed Fluoroarylation of gem-Difluoroalkenes
    • Authors: Hai-Jun Tang; Ling-Zhi Lin, Chao Feng, Teck-Peng Loh
      Abstract: A Pd-catalyzed fluoroarylation of gem-difluoroalkenes with aryl halides is reported. By taking advantage of the in situ generated α-CF3-benzylsilver intermediates derived from the nucleophilic addition of silver fluoride to gem-difluoroalkenes, this strategy bypasses the use of a strong base, thus enabling a mild and general synthetic method for ready access to non-symmetric α,α-disubstituted trifluoroethane derivatives.Es ist von Vorteil, eine α-(Trifluormethyl)benzylsilber-Zwischenstufe in situ zu erzeugen, um einen allgemeinen Syntheseweg für 1,1,1-Trifluor-2-arylalkan-Derivate im Sinne der Titelreaktion zu erschließen. So lassen sich α-trifluormethylierte Alkylmotive über eine Zwei-Elektronen-Transmetallierung einführen.
      PubDate: 2017-07-13T07:41:33.936512-05:
      DOI: 10.1002/ange.201705321
       
  • Phosphonium Salts as Pseudohalides: Regioselective Nickel-Catalyzed
           Cross-Coupling of Complex Pyridines and Diazines
    • Authors: Xuan Zhang; Andrew McNally
      Abstract: Heterobiaryls are important pharmacophores that are challenging to prepare by traditional cross-coupling methods. An alternative approach is presented where pyridines and diazines are converted into heteroaryl phosphonium salts and coupled with aryl boronic acids. Nickel catalysts are unique for selective heteroaryl transfer, and the reaction has a broad substrate scope that includes complex pharmaceuticals. Phosphonium ions also display orthogonal reactivity in cross-couplings compared to halides, enabling chemoselective palladium- and nickel-catalyzed coupling sequences.Pyridine und Diazine können selektiv in heterocyclische Phosphoniumsalze überführt werden, die als generische Alternativen zu Heteroarylhalogeniden in Nickel-katalysierten Suzuki-Miyaura-Kupplungen eingesetzt werden können. Komplexe Pyridine, wirkstoffartige Fragmente und Wirkstoffe können so in zwei Stufen aryliert werden.
      PubDate: 2017-07-13T07:41:14.036841-05:
      DOI: 10.1002/ange.201704948
       
  • A Second-coordination-sphere Strategy to Modulate Nickel- and
           Palladium-catalyzed Olefin Polymerization and Copolymerization
    • Authors: Min Li; Xingbao Wang, Yi Luo, Changle Chen
      Abstract: Transition-metal-catalyzed copolymerizations of olefins with polar functionalized comonomers are highly important and also highly challenging. We introduce a second-coordination-sphere strategy to address some of the difficulties encountered in these copolymerization reactions. A series of α-diimine ligands bearing nitrogen-containing second coordination spheres were prepared and characterized. The properties of the corresponding nickel and palladium catalysts in ethylene polymerizations and copolymerizations were investigated. In the nickel system, significant reduction in polymer branching density was observed, while lower polymer branching densities as well as wider range of polar monomer substrates were achieved in the palladium system. Control experiments and computational results reveal the critical role of the metal-nitrogen interaction in these polymerization and copolymerization reactions.
      PubDate: 2017-07-13T05:37:20.114572-05:
      DOI: 10.1002/ange.201706249
       
  • Building Morphan Derivatives by Nitroso-Ene Cyclization: Mechanistic
           Insights and Total Synthesis of (±)-Kopsone
    • Authors: Ran Hong; Li Zhai, Xuechao Tian, Chao Wang, Wenhua Li, Zhi-Xiang Yu, Sha-Hua Huang, Qi Cui
      Abstract: A type II nitroso-ene cyclization was developed for the construction of morphan derivatives with a good functional group tolerance. DFT calculations revealed the nitroso-ene reaction is stepwise involving diradical or zwitterionic intermediates. The rate-determining step is the C-N bond formation, following by a rapid hydrogen transfer step with a chair-conformation transition state. The current approach was also successfully applied in the first total synthesis of (±)-kopsone, a highly strained yet simple morphan-type alkaloid isolated from Kopsia macrophylla.
      PubDate: 2017-07-13T05:36:33.45931-05:0
      DOI: 10.1002/ange.201706018
       
  • B(C6F5)3: Stoichiometric and Catalytic C-C and C-H Bond Formation via
           Cationic Intermediates
    • Authors: Yashar Soltani; Lewis Charles Wilkins, Rebecca Melen
      Abstract: This work showcases a new method of catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C-H or C-C bond formation. Activation of alkyne containing substrates using B(C6F5)3 allows catalytic intramolecular cyclizations of carboxylic acid substrates to be achieved for the first time using this Lewis acid. In addition, intramolecular cyclizations of esters enables C-C bond formation in which catalytic B(C6F5)3 is used to effect formal 1,5-alkyl migrations from ester functionalities to unsaturated carbon-carbon frameworks. Using this new methodology, the catalytic formation of complex dihydropyrones and coumarins in extremely good yields under relatively mild conditions with excellent atom efficiency can be achieved in a metal-free manner.
      PubDate: 2017-07-13T05:25:50.436117-05:
      DOI: 10.1002/ange.201704789
       
  • Discovery of Small Molecules that Induce Degradation of Huntingtin
    • Authors: Shusuke Tomoshige; Sayaka Nomura, Kenji Ohgane, Yuichi Hashimoto, Minoru Ishikawa
      Abstract: Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by aggregation of mutant huntingtin (mHtt), and removal of toxic mHtt is expected to be an effective therapeutic approach. We designed two small hybrid molecules 1 and 2, by linking a ligand for ubiquitin ligase (cellular inhibitor of apoptosis protein 1; cIAP1) with probes for mHtt aggregates, anticipating that these compounds would recruit cIAP1 to mHtt and induce selective degradation via the ubiquitin-proteasome system. The synthesized compounds reduced mHtt levels in HD patients' fibroblasts, and appear to be promising candidates for treatment of HD.
      PubDate: 2017-07-13T04:25:42.535287-05:
      DOI: 10.1002/ange.201706529
       
  • Two-Dimensional Seeded Self-Assembly of a Complex Hierarchical
           Heterostructure
    • Authors: Yin Liu; Cheng Peng, Wei Xiong, Yifan Zhang, Yanjun Gong, Yanke Che, Jincai Zhao
      Abstract: In this work, a complex two-dimensional (2D) hierarchical heterostructure was fabricated via a sequential two-dimensional seeded self-assembly, which consisted of laterally grown nanotubes from 1 and terminally elongated nanocoils from 2 on microribbon seed from 3. Because monomers 1 and 2 can form kinetically trapped off-pathway aggregates to prevent self-nucleation and have similar molecular organizations to different facets of the seeds from 3, monomers 1 and 2 preferentially nucleated and grew on the seed sides and terminal ends, respectively, to form a complex 2D hierarchical heterostructure. The strategy used in this work can be extended to fabricate other complex nanoarchitectures from small molecules, which remains a great challenge.
      PubDate: 2017-07-13T00:40:23.538107-05:
      DOI: 10.1002/ange.201704015
       
  • Fluorescent Probes with Multiple Binding Sites to Distinguish Cys, Hcy and
           GSH
    • Authors: Cai-Xia Yin; Kang-Ming Xiong, Fang-Jun Huo, James C. Salamanca, Robert Michael Strongin
      Abstract: Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play crucial roles in maintaining redox homeostasis in biological systems. This Mini Review summarizes the most significant current challenges in the field of thiol-reactive probes for biomedical research and diagnostics, emphasizing needs and opportunities that have been under-investigated by chemists in the selective probe and sensor field. Progress on multiple binding site probes to distinguish Cys, Hcy and GSH is highlighted as a creative new direction in the field that can enable simultaneous, accurate ratiometric monitoring. New probe design strategies and researcher priorities can better help address current challenges, including the monitoring of disease states such as autism and chronic diseases involving oxidative stress that are characterized by divergent levels of GSH, Cys and Hcy.
      PubDate: 2017-07-12T20:46:10.31816-05:0
      DOI: 10.1002/ange.201704084
       
  • Diastereo- and Enantioselective Synthesis of β-Aminoboronate Esters by
           Copper(I)-Catalyzed 1,2-Addition of 1,1-Bis[(pinacolato)boryl]alkanes to
           Imines
    • Authors: Jeongho Kim; Kwangwook Ko, Seung Hwan Cho
      Abstract: We report an efficient Cu(I)-catalytic system for the diastereo- and enantioselective 1,2-addition of 1,1-bis[(pinacolato)boryl]alkanes to protected imines to afford synthetically valuable enantioenriched ß-aminoboron compounds bearing contiguous stereogenic centers. The reaction exhibits a broad scope with respect to protected imines and 1,1-bis[(pinacolato)boryl]alkanes, providing ß-aminoboronate esters with excellent diastereo- and enantioselectivity. The synthetic utility of the obtained ß-aminoboronate ester was also demonstrated.
      PubDate: 2017-07-12T12:40:25.978309-05:
      DOI: 10.1002/ange.201705829
       
  • A Novel Esterase-sensitive Prodrug Approach for Controllable Delivery of
           Persulfide Species
    • Authors: Yueqin Zheng; Bingchen Yu, Zhen Li, Zhengnan Yuan, David J. Lefer, Binghe Wang, Siming Wang, Chelsea L. Organ, Rishi K. Trivedi
      Abstract: A new strategy to deliver a well-defined persulfide species in a biological medium is described herein. Under near physiological conditions, the persulfide prodrug can be activated by an esterase to generate a "hydroxyl methyl persulfide" intermediate, which rapidly collapses to form a defined persulfide. Such persulfide prodrugs can be used either as chemical tools to study persulfide chemistry and biology or for future development as H2S-based therapeutic reagents. Using the persulfide prodrugs developed in this study, the reactivity between S-methyl methanethiosulfonate (MMTS) with persulfide was unambiguously demonstrated. In addition, a representative prodrug exhibited potent cardioprotective effects in a murine model of myocardial ischemia-reperfusion (MI/R) injury with a bell shape therapeutic profile.
      PubDate: 2017-07-12T11:40:50.113983-05:
      DOI: 10.1002/ange.201704117
       
  • Crystallization of a Two-Dimensional Hydrogen-Bonded Molecular Assembly:
           Evolution of the Local Structure Resolved by Atomic Force Microscopy
    • Authors: Laerte L. Patera; Xunshan Liu, Nico Mosso, Silvio Decurtins, Shi-Xia Liu, Jascha Repp
      Abstract: Surface-assisted self-assembly structures of the aromatic N-heterocyclic hexaazatriphenylene (HAT) molecular synthon were determined with sub-Å resolution by means of noncontact Atomic Force Microscopy (nc-AFM), both in the kinetically trapped amorphous state and in the thermodynamically stable crystalline phase. These results reveal how, for non-flexible molecular species, the crystallization governs the length-scale of the network order, without affecting the local bonding schemes. The capability of nc-AFM to accurately resolve structural relaxations will be highly relevant for the characterization of vitreous structure of 2-dimensional supramolecular materials.
      PubDate: 2017-07-12T10:40:28.183369-05:
      DOI: 10.1002/ange.201705338
       
  • Copper-alkyne complexation is responsible for the Nucleolar Localisation
           of Quadruplex Nucleic Acid Drugs Labelled by Click Chemistry
    • Authors: Marie-Paule Teulade-Fichou; Joël Lefebvre, Corinne Guetta, florent Poyer, florence Mahuteau-Betzer
      Abstract: G-quadruplex(es) (G4) are non-canonical nucleic acid structures found in guanine-rich sequences. They can be targeted with small molecules (G4-ligands) acting as reporters, for tracking both in vitro and in cells. We explored the cellular localisation of PhenDC3, one of the most powerful G4 ligands, by synthesising two clickable azide and alkyne derivatives (PhenDC3-alk, PhenDC3-az) and labelling them in situ with the corresponding Cy5 click partners. A careful comparison of the results obtained for the copper-based CuAAC and copper-free SPAAC methodologies in fixed cells implicated Cu(I) /alkyne intermediates in the non-specific localisation of ligands (and fluorophores) to the nucleoli. By contrast, SPAAC yielded similar nucleoplasmic labelling patterns in fixed and live cells. Our findings demonstrate the need for great care when using CuAAC to localise drugs in cells, and show that SPAAC gives results that are more consistent between fixed and live cells.
      PubDate: 2017-07-12T09:40:33.651433-05:
      DOI: 10.1002/ange.201703783
       
  • Catalytic intermolecular dicarbofunctionalization of styrenes with CO2 and
           radical precursors
    • Authors: Ruben Martin; Veera Reddy Yatham, Yangyang Shen
      Abstract: A redox-neutral intermolecular dicarbofunctionalization of styrenes with CO2 at atmospheric pressure and carbon-centered radicals is described. This mild protocol results in multiple C-C bond-forming reactions from simple precursors in the absence of stoichiometric reductants, thus exploiting a previously unrecognized opportunity that complements existing catalytic carboxylation events
      PubDate: 2017-07-12T08:40:23.234236-05:
      DOI: 10.1002/ange.201706263
       
  • Titelbild: A Twisted Nanographene Consisting of 96 Carbon Atoms (Angew.
           Chem. 31/2017)
    • Authors: Kwan Yin Cheung; Chi Kit Chan, Zhifeng Liu, Qian Miao
      Pages: 9031 - 9031
      Abstract: Dreidimensionale Kohlenstoffstrukturen … mit negativer Krümmung sollen durch Einbindung von Sieben- und Achtecken in ein Graphit-Gitter zugänglich sein, die Synthese dieser Strukturen steht aber noch aus. In ihrer Zuschrift auf S. 9131 ff. beschreiben Q. Miao et al. ein neuartiges, verdrehtes Nanographen, das als Segment negativ gekrümmter Kohlenstoffstrukturen betrachtet werden kann. Das aus 96 sp2-hybridisierten Kohlenstoffatomen bestehende Nanographen ist in zwei Richtungen im Kristall verdreht.
      PubDate: 2017-06-08T07:05:46.158495-05:
      DOI: 10.1002/ange.201704990
       
  • Innentitelbild: Natural Abundance 17O DNP NMR Provides Precise O−H
           Distances and Insights into the Brønsted Acidity of Heterogeneous
           Catalysts (Angew. Chem. 31/2017)
    • Authors: Frédéric A. Perras; Zhuoran Wang, Pranjali Naik, Igor I. Slowing, Marek Pruski
      Pages: 9032 - 9032
      Abstract: Brønsted-saure aktive Zentren auf Katalysatoroberflächen werden mit dynamischer 17O-NMR-Spektroskopie mit Kernpolarisationsverstärkung untersucht. Bei dieser Methode werden die Kerne durch Mikrowellen-induzierte Elektronensättigung hyperpolarisiert. M. Pruski et al. berichten in ihrer Zuschrift auf S. 9293 ff. über die Messung von O-H-Abständen mit Subpikometergenauigkeit. Die Länge der O-H-Bindung hängt direkt mit der Brønsted-Säurestärke zusammen und ist auch ein Indiz für die Bildung intramolekularer Wasserstoffbrücken.
      PubDate: 2017-06-09T04:05:21.083613-05:
      DOI: 10.1002/ange.201704989
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 31/2017
    • Pages: 9035 - 9050
      PubDate: 2017-07-19T02:33:35.322636-05:
      DOI: 10.1002/ange.201783111
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 31/2017
    • Pages: 9052 - 9055
      PubDate: 2017-07-19T02:33:31.524374-05:
      DOI: 10.1002/ange.201783113
       
  • Takeaki Iwamoto
    • Pages: 9056 - 9056
      Abstract: „Mein Lieblingsort auf der Welt ist Bora Bora auf Tahiti. Das Wichtigste, was ich von meinen Eltern gelernt habe, ist Güte ...“ Dies und mehr von und über Takeaki Iwamoto finden Sie auf Seite 9056.
      PubDate: 2017-03-21T03:55:26.690681-05:
      DOI: 10.1002/ange.201702167
       
  • Dreyfus-Preis für Chemie: M. Parrinello / FCI-Dozentenpreis: J. Strunk /
           Wissenschaftspreis des Stifterverbands: P. H. Seeberger /
           Günther-Laukien-Preis: B. Reif / Humboldt-, Siemens- und
           Bessel-Forschungspreise 2016/2017
    • Pages: 9057 - 9058
      PubDate: 2017-07-05T07:21:27.820411-05:
      DOI: 10.1002/ange.201706380
       
  • Die Form folgt der Funktion: Designer-Chemie auf der 52.
           Bürgenstock-Konferenz
    • Authors: Philipp Heretsch
      Pages: 9059 - 9062
      Abstract: Die 52. Bürgenstock-Konferenz über Stereochemie fand vom 30. April bis 4. Mai 2017 statt und zeigte, wie vielschichtig sich mit Chemie gestalten lässt (wie das Foto des Bauhausarchivs in Berlin illustrieren soll). In diesem Tagungsbericht fasst Philipp Heretsch das diesjährige Programm zusammen.
      PubDate: 2017-07-04T04:58:03.574677-05:
      DOI: 10.1002/ange.201705476
       
  • Eisen im Rampenlicht: mesoionische Carbene als privilegierte Liganden in
           der Photochemie
    • Authors: Biprajit Sarkar; Lisa Suntrup
      Pages: 9064 - 9066
      Abstract: Licht ins Dunkel der Eisenzeit: Mesoionische Carbene stabilisieren einen Eisen(III)-Komplex, der eine Rekordlebensdauer des angeregten Zustands aufweist und einen beispiellosen spinerlaubten strahlenden Zerfall eines 2LMCT-Zustands zeigt. Die Ergebnisse bereiten den Weg für eine nachhaltige Zukunft der neuen „Eisenzeit”.
      PubDate: 2017-06-01T13:36:13.988673-05:
      DOI: 10.1002/ange.201704522
       
  • Enantioselektive Chemo- und Biokatalyse: Partner in der Retrosynthese
    • Authors: Moritz Hönig; Philipp Sondermann, Nicholas J. Turner, Erick M. Carreira
      Pages: 9068 - 9100
      Abstract: In diesem Aufsatz werden neue Entwicklungen auf den Gebieten der biokatalytischen und chemokatalytischen Synthese diskutiert. Der Beitrag soll als Anleitung für die Verwendung biokatalytischer Methoden in der chemischen Synthese dienen, insbesondere bei retrosynthetischen Überlegungen und Analysen. Die Gliederung dieses Aufsatzes ist nach den Bindungsknüpfungen und ihren jeweiligen synthetischen Methoden strukturiert.Partner in der Synthese: Die Verwendung biokatalytischer Methoden in der chemischen Synthese gewinnt immer mehr an Bedeutung, insbesondere bei retrosynthetischen Überlegungen und Analysen. Dieser Aufsatz soll als Leitfaden für die Anwendung dieser Methoden dienen und ein besseres Verständnis der Merkmale und Unterschiede dieser beiden komplementären Ansätze ermöglichen.
      PubDate: 2017-06-23T03:35:57.164333-05:
      DOI: 10.1002/ange.201612462
       
  • Water Transport with Ultralow Friction through Partially Exfoliated g-C3N4
           Nanosheet Membranes with Self-Supporting Spacers
    • Authors: Yanjie Wang; Libo Li, Yanying Wei, Jian Xue, Huang Chen, Li Ding, Jürgen Caro, Haihui Wang
      Pages: 9102 - 9108
      Abstract: Two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C3N4 nanosheets in a stack with elaborate structures. In water purification the g-C3N4 membrane shows a better separation performance than commercial membranes. The g-C3N4 membrane has a water permeance of 29 L m−2 h−1 bar−1 and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C3N4 nanosheets and the spacers between the partially exfoliated g-C3N4 nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C3N4 membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3N4 nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.Eine g-C3N4-Membran mit geringer Reibung für die Wasseraufbereitung besteht aus gestapelten zweidimensionalen Nanoblättern und ist chemisch und mechanisch stabil. Die Schichten enthalten intrinsische (P1) und künstliche (P2) Nanoporen, und zwischen ihnen befinden sich selbsttragende Abstandhalter (S), die auf nicht entfernte Fragmente zurückgehen.
      PubDate: 2017-06-07T06:40:31.523945-05:
      DOI: 10.1002/ange.201701288
       
  • Suppression of the Charge Density Wave State in Two-Dimensional 1T-TiSe2
           by Atmospheric Oxidation
    • Authors: Lifei Sun; Chuanhui Chen, Qinghua Zhang, Christian Sohrt, Tianqi Zhao, Guanchen Xu, Jinghui Wang, Dong Wang, Kai Rossnagel, Lin Gu, Chenggang Tao, Liying Jiao
      Pages: 9109 - 9113
      Abstract: Two-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe2, have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe2 undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase-transition behavior. We comprehensively investigate the oxidation process of 2D TiSe2 by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium-assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices.Das Oxidationsverhalten und der Effekt der Oxidation auf das Phasenübergangsverhalten der Ladungsdichtewellen in 2D-TiSe2 wurden untersucht (siehe Bild; Ti violett, Se gelb, O blau). Die Ergebnisse bieten Einblick in den Oxidationsmechanismus ultradünner Schichtmaterialien und ebnen den Weg für die Nutzung der ungewöhnlichen Eigenschaften dieser Materialien.
      PubDate: 2017-06-27T06:58:09.235004-05:
      DOI: 10.1002/ange.201612605
       
  • Thermally Stable and Regenerable Platinum–Tin Clusters for Propane
           Dehydrogenation Prepared by Atom Trapping on Ceria
    • Authors: Haifeng Xiong; Sen Lin, Joris Goetze, Paul Pletcher, Hua Guo, Libor Kovarik, Kateryna Artyushkova, Bert M. Weckhuysen, Abhaya K. Datye
      Pages: 9114 - 9119
      Abstract: Ceria (CeO2) supports are unique in their ability to trap ionic platinum (Pt), providing exceptional stability for isolated single atoms of Pt. The reactivity and stability of single-atom Pt species was explored for the industrially important light alkane dehydrogenation reaction. The single-atom Pt/CeO2 catalysts are stable during propane dehydrogenation, but are not selective for propylene. DFT calculations show strong adsorption of the olefin produced, leading to further unwanted reactions. In contrast, when tin (Sn) is added to CeO2, the single-atom Pt catalyst undergoes an activation phase where it transforms into Pt–Sn clusters under reaction conditions. Formation of small Pt–Sn clusters allows the catalyst to achieve high selectivity towards propylene because of facile desorption of the product. The CeO2-supported Pt–Sn clusters are very stable, even during extended reaction at 680 °C. Coke formation is almost completely suppressed by adding water vapor to the feed. Furthermore, upon oxidation the Pt–Sn clusters readily revert to the atomically dispersed species on CeO2, making Pt–Sn/CeO2 a fully regenerable catalyst.Isolierte einzelne Platinatome sind aktiv, aber nicht selektiv in der Alkandehydrierung und aggregieren während der Reaktion zu subnanometergroßen Pt-Zn-Clustern. Der verbrauchte Katalysator kann durch oxidative Behandlung wieder in einen atomar dispergierten Zustand umgewandelt werden, ohne dass Zusatz von Chlor nötig wäre.
      PubDate: 2017-06-28T06:12:16.273818-05:
      DOI: 10.1002/ange.201701115
       
  • Bioorthogonal Labeling of Human Prostate Cancer Tissue Slice Cultures for
           Glycoproteomics
    • Authors: David R. Spiciarich; Rosalie Nolley, Sophia L. Maund, Sean C. Purcell, Jason Herschel, Anthony T. Iavarone, Donna M. Peehl, Carolyn R. Bertozzi
      Pages: 9120 - 9125
      Abstract: Sialylated glycans are found at elevated levels in many types of cancer and have been implicated in disease progression. However, the specific glycoproteins that contribute to the cancer cell-surface sialylation are not well characterized, specifically in bona fide human disease tissue. Metabolic and bioorthogonal labeling methods have previously enabled the enrichment and identification of sialoglycoproteins from cultured cells and model organisms. Herein, we report the first application of this glycoproteomic platform to human tissues cultured ex vivo. Both normal and cancerous prostate tissues were sliced and cultured in the presence of the azide-functionalized sialic acid biosynthetic precursor Ac4ManNAz. The compound was metabolized to the azidosialic acid and incorporated into cell surface and secreted sialoglycoproteins. Chemical biotinylation followed by enrichment and mass spectrometry led to the identification of glycoproteins that were found at elevated levels or uniquely in cancerous prostate tissue. This work therefore extends the use of bioorthogonal labeling strategies to problems of clinical relevance.Durch metabolische Markierung von humanen Prostatakrebs-Gewebeschnitten in Kultur wurde azidfunktionalisierte Sialinsäure in Zelloberflächen- und Sekret-Glykoproteine eingeführt. Eine chemische Biotinylierung mit anschließender Anreicherung und massenspektrometrischer Analyse führte zur Identifizierung von Glykoproteinen, die ausschließlich oder in erhöhter Konzentration in Prostatakrebsgewebe vorkommen.
      PubDate: 2017-06-26T02:03:54.573994-05:
      DOI: 10.1002/ange.201701424
       
  • A Binary Bivalent Supramolecular Assembly Platform Based on
           Cucurbit[8]uril and Dimeric Adapter Protein 14-3-3
    • Authors: Pim J. de Vink; Jeroen M. Briels, Thomas Schrader, Lech-Gustav Milroy, Luc Brunsveld, Christian Ottmann
      Pages: 9126 - 9130
      Abstract: Interactions between proteins frequently involve recognition sequences based on multivalent binding events. Dimeric 14-3-3 adapter proteins are a prominent example and typically bind partner proteins in a phosphorylation-dependent mono- or bivalent manner. Herein we describe the development of a cucurbit[8]uril (Q8)-based supramolecular system, which in conjunction with the 14-3-3 protein dimer acts as a binary and bivalent protein assembly platform. We fused the phenylalanine–glycine–glycine (FGG) tripeptide motif to the N-terminus of the 14-3-3-binding epitope of the estrogen receptor α (ERα) for selective binding to Q8. Q8-induced dimerization of the ERα epitope augmented its affinity towards 14-3-3 through a binary bivalent binding mode. The crystal structure of the Q8-induced ternary complex revealed molecular insight into the multiple supramolecular interactions between the protein, the peptide, and Q8.Binäres bivalentes Binden: Die Kombination eines bivalenten Cucurbit[8]uril(Q8)-Wirt-Gast-Komplexes mit dem bivalenten Protein 14-3-3 ergibt eine binäre Assemblierungsplattform. Supramolekular induziertes Schalten zwischen mono- und bivalenten Proteinbindungsweisen wurde beobachtet, und die Aufklärung der ersten Q8-Protein-Kokristallstruktur wird berichtet (siehe Bild).
      PubDate: 2017-06-29T07:36:17.002114-05:
      DOI: 10.1002/ange.201701807
       
  • A Twisted Nanographene Consisting of 96 Carbon Atoms
    • Authors: Kwan Yin Cheung; Chi Kit Chan, Zhifeng Liu, Qian Miao
      Pages: 9131 - 9135
      Abstract: Herein we report synthesis, structure and properties of a new type of twisted nanographene, which contains an [8]circulene moiety in a polycyclic framework of 96 sp2 carbon atoms. The key steps in this synthesis are the Diels–Alder reaction of a macrocyclic diyne and the subsequent Scholl reaction forming the [8]circulene moiety. Two incompletely cyclized products were isolated from the Scholl reaction, providing insight into the cyclization of the strained octagon. This nanographene is twisted along two directions with end-to-end twists of 142.4° and 140.2° as revealed by X-ray crystallography, and is flexible at room temperature as found from the computational and experimental studies.Ein neuartiges, verdrehtes Nanographen mit einem [8]Circulen-Rest in einem polycyclischen Gerüst aus 96 sp2-Kohlenstoffatomen wurde aus einem macrocyclischen Diine (siehe Bild) synthetisiert. Seine Struktur wurde mit Röntgenkristallographie und DFT-Rechnungen untersucht.
      PubDate: 2017-05-16T03:00:35.016505-05:
      DOI: 10.1002/ange.201703754
       
  • Differences between G-Protein-Stabilized Agonist–GPCR Complexes and
           their Nanobody-Stabilized Equivalents
    • Authors: Noureldin Saleh; Passainte Ibrahim, Timothy Clark
      Pages: 9136 - 9140
      Abstract: Protein nanobodies have been used successfully as surrogates for unstable G-proteins in order to crystallize G-protein-coupled receptors (GPCRs) in their active states. We used molecular dynamics (MD) simulations, including metadynamics enhanced sampling, to investigate the similarities and differences between GPCR–agonist ternary complexes with the α-subunits of the appropriate G-proteins and those with the protein nanobodies (intracellular binding partners, IBPs) used for crystallization. In two of the three receptors considered, the agonist-binding mode differs significantly between the two alternative ternary complexes. The ternary-complex model of GPCR activation entails enhancement of ligand binding by bound IBPs: Our results show that IBP-specific changes can alter the agonist binding modes and thus also the criteria for designing GPCR agonists.Lagebetrachtung: Moleküldynamik(MD)-Simulationen weisen darauf hin, dass die Proteinnanokörper, die oft zur Erzeugung von Kristallen G-Protein-gekoppelter Rezeptoren verwendet werden, zu leicht unterschiedlichen Ligandenlagen und Änderungen der orthosterischen Bindestelle im Vergleich zum nativen G-Protein führen. MD-Simulationen sind derzeit die einzige Möglichkeit, solche Unterschiede aufzuzeigen.
      PubDate: 2017-07-03T08:00:47.042786-05:
      DOI: 10.1002/ange.201702468
       
  • Inorganic-Macroion-Induced Formation of Bicontinuous Block Copolymer
           Nanocomposites with Enhanced Conductivity and Modulus
    • Authors: Liying Zhang; Tingting Cui, Xiao Cao, Chengji Zhao, Quan Chen, Lixin Wu, Haolong Li
      Pages: 9141 - 9145
      Abstract: A facile and electrostatically driven approach has been developed to prepare bicontinuous polymer nanocomposites that is based on the polyoxometalate (POM) macroion induced phase transition of PS-b-P2VP from an initial lamellar phase to a stable bicontinuous phase. The multi-charged POMs can electrostatically cross-link P2VP blocks and give rise to bicontinuous phases in which the POM hybrid conductive domains occupy a large volume fraction of more than 50 %. Furthermore, the POMs can give rise to high proton conductivity and serve as nanoenhancers, endowing the bicontinuous nanocomposites with a conductivity of 0.1 mS cm−1 and a Young's modulus of 7.4 GPa at room temperature; these values are greater than those of pristine PS-b-P2VP by two orders of magnitude and a factor of 1.8, respectively. This approach can provide a new concept based on electrostatic control to design functional bicontinuous polymer materials.Polymer-Nanokomposite: Bikontinuierliche Nanokomposite wurden durch eine von Polyoxometallat-Makroionen induzierte Phasenumwandlung aus Blockcopolymeren erhalten. Die resultierenden Nanokomposite zeichnen sich bei Raumtemperatur durch ein anteilig großes leitfähiges Volumen von über 50 %, eine erhöhte Leitfähigkeit von bis zu 0.1 mS cm−1 und einen verstärkten Young-Modul von 7.4 GPa aus.
      PubDate: 2017-06-30T01:56:13.829701-05:
      DOI: 10.1002/ange.201702785
       
  • Low-Dimensional Organic Tin Bromide Perovskites and Their Photoinduced
           Structural Transformation
    • Authors: Chenkun Zhou; Yu Tian, Mingchao Wang, Alyssa Rose, Tiglet Besara, Nicholas K. Doyle, Zhao Yuan, Jamie C. Wang, Ronald Clark, Yanyan Hu, Theo Siegrist, Shangchao Lin, Biwu Ma
      Pages: 9146 - 9150
      Abstract: Hybrid organic–inorganic metal halide perovskites possess exceptional structural tunability, with three- (3D), two- (2D), one- (1D), and zero-dimensional (0D) structures on the molecular level all possible. While remarkable progress has been realized in perovskite research in recent years, the focus has been mainly on 3D and 2D structures, with 1D and 0D structures significantly underexplored. The synthesis and characterization of a series of low-dimensional organic tin bromide perovskites with 1D and 0D structures is reported. Using the same organic and inorganic components, but at different ratios and reaction conditions, both 1D (C4N2H14)SnBr4 and 0D (C4N2H14Br)4SnBr6 can be prepared in high yields. Moreover, photoinduced structural transformation from 1D to 0D was investigated experimentally and theoretically in which photodissociation of 1D metal halide chains followed by structural reorganization leads to the formation of a more thermodynamically stable 0D structure.Kontrollierte Synthesen niederdimensionaler (1D oder 0D) organischer Zinnbromid-Perowskite werden vorgestellt. Die nichtstrahlende 1D-Struktur, die als kinetisch begünstigtes Produkt erhalten wird, kann lichtinduziert in eine thermodynamisch stabile 0D-Struktur mit außergewöhnlicher Lumineszenz übergehen.
      PubDate: 2017-07-03T07:10:47.897954-05:
      DOI: 10.1002/ange.201702825
       
  • Switching Between Giant Positive and Negative Thermal Expansions of a
           YFe(CN)6-based Prussian Blue Analogue Induced by Guest Species
    • Authors: Qilong Gao; Jun Chen, Qiang Sun, Dahu Chang, Qingzhen Huang, Hui Wu, Andrea Sanson, Ruggero Milazzo, He Zhu, Qiang Li, Zhanning Liu, Jinxia Deng, Xianran Xing
      Pages: 9151 - 9156
      Abstract: The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K+) and molecules (H2O) can substantially switch thermal expansion of YFe(CN)6 from negative (αv=−33.67×10−6 K−1) to positive (αv=+42.72×10−6 K−1)—a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests.Ehrengast: Das thermische Ausdehnungsverhalten eines offenen YFe(CN)6-Gerüsts kann durch Einlagerung von Kaliumionen oder H2O-Molekülen von stark negativ auf positiv umgeschaltet werden. Die Gastspezies dämpfen Transversalschwingungen der Stickstoff- und Kohlenstoffatome und wirken so der negativen thermischen Ausdehnung entgegen.
      PubDate: 2017-06-23T03:35:27.84798-05:0
      DOI: 10.1002/ange.201702955
       
  • Initiator-Loaded Gold Nanocages as a Light-Induced Free-Radical Generator
           for Cancer Therapy
    • Authors: Xiao-Qiang Wang; Fan Gao, Xian-Zheng Zhang
      Pages: 9157 - 9161
      Abstract: Tumor hypoxia greatly suppresses the therapeutic efficacy of photodynamic therapy (PDT), mainly because the generation of toxic reactive oxygen species (ROS) in PDT is highly oxygen-dependent. In contrast to ROS, the generation of oxygen-irrelevant free radicals is oxygen-independent. A new therapeutic strategy based on the light-induced generation of free radicals for cancer therapy is reported. Initiator-loaded gold nanocages (AuNCs) as the free-radical generator were synthesized. Under near-infrared light (NIR) irradiation, the plasmonic heating effect of AuNCs can induce the decomposition of the initiator to generate alkyl radicals (R.), which can elevate oxidative-stress (OS) and cause DNA damages in cancer cells, and finally lead to apoptotic cell death under different oxygen tensions. As a proof of concept, this research opens up a new field to use various free radicals for cancer therapy.Goldener Käfig gegen Krebs: Eine neue Strategie für die Krebstherapie beruht auf Initiator-beladenen Gold-Nanokäfigen zur lichtinduzierten, sauerstoffunabhängigen Bildung freier Radikale. Der Wirkmechanismus der gebildeten freien Radikale wurde aufgeklärt.
      PubDate: 2017-06-28T06:07:04.977433-05:
      DOI: 10.1002/ange.201703159
       
  • Energy Transfer between Spatially Separated Entangled Molecules
    • Authors: Xiaolan Zhong; Thibault Chervy, Lei Zhang, Anoop Thomas, Jino George, Cyriaque Genet, James A. Hutchison, Thomas W. Ebbesen
      Pages: 9162 - 9166
      Abstract: Light–matter strong coupling allows for the possibility of entangling the wave functions of different molecules through the light field. We hereby present direct evidence of non-radiative energy transfer well beyond the Förster limit for spatially separated donor and acceptor cyanine dyes strongly coupled to a cavity. The transient dynamics and the static spectra show an energy transfer efficiency approaching 37 % for donor–acceptor distances ≥100 nm. In such systems, the energy transfer process becomes independent of distance as long as the coupling strength is maintained. This is consistent with the entangled and delocalized nature of the polaritonic states.Im Vakuumfeld einer optischen Kavität findet ein strahlungsloser Energietransfer zwischen räumlich getrennten verschränkten Molekülen statt. In solchen Systemen wird der Energietransferprozess unabhängig von der Entfernung, solange die Kopplungsstärke gleich bleibt. Dieses Verhalten ist im Einklang mit der verschränkten und delokalisierten Natur der polaritonischen Zustände.
      PubDate: 2017-06-28T06:42:41.755826-05:
      DOI: 10.1002/ange.201703539
       
  • Direct Mechanism of the First Carbon–Carbon Bond Formation in the
           Methanol-to-Hydrocarbons Process
    • Authors: Xinqiang Wu; Shutao Xu, Wenna Zhang, Jindou Huang, Jinzhe Li, Bowen Yu, Yingxu Wei, Zhongmin Liu
      Pages: 9167 - 9171
      Abstract: In the past two decades, the reaction mechanism of C−C bond formation from either methanol or dimethyl ether (DME) in the methanol-to-hydrocarbons (MTH) process has been a highly controversial issue. Described here is the first observation of a surface methyleneoxy analogue, originating from the surface-activated DME, by in situ solid-state NMR spectroscopy, a species crucial to the first C−C bond formation in the MTH process. New insights into the first C−C bond formation were provided, thus suggesting DME/methanol activation and direct C−C bond formation by an interesting synergetic mechanism, involving C−H bond breakage and C−C bond coupling during the initial methanol reaction within the chemical environment of the zeolite catalyst.Von Anfang an: Eine oberflächengebundene Methylenoxy-analoge Gruppe, die durch Aktivierung von Dimethylether (DME) an einer Oberfläche entsteht, konnte mit Festkörper-NMR-Spektroskopie direkt in situ beobachtet werden. Daraus ergeben sich Einblicke in den ersten C-C-Kupplungsschritt bei der Umwandlung von Methanol in Kohlenwasserstoffe.
      PubDate: 2017-05-31T03:05:29.308293-05:
      DOI: 10.1002/ange.201703902
       
  • Temperature-Dependence of the Rates of Reaction of Trifluoroacetic Acid
           with Criegee Intermediates
    • Authors: Rabi Chhantyal-Pun; Max R. McGillen, Joseph M. Beames, M. Anwar H. Khan, Carl J. Percival, Dudley E. Shallcross, Andrew J. Orr-Ewing
      Pages: 9172 - 9175
      Abstract: The rate coefficients for gas-phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240–340 K. The rate coefficients k(CH2OO + CF3COOH)=(3.4±0.3)×10−10 cm3 s−1 and k((CH3)2COO + CF3COOH)=(6.1±0.2)×10−10 cm3 s−1 at 294 K exceed estimates for collision-limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre-reactive complex. Fits to a model incorporating this complex formation give k [cm3 s−1]=(3.8±2.6)×10−18 T2 exp((1620±180)/T) + 2.5×10−10 and k [cm3 s−1]=(4.9±4.1)×10−18 T2 exp((1620±230)/T) + 5.2×10−10 for the CH2OO + CF3COOH and (CH3)2COO + CF3COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates.Criegee-Intermediate, die durch die Ozonolyse von Alkenen in der Troposphäre gebildet werden, sind potentielle Oxidantien für Spurengase. Messungen der Geschwindigkeiten der Reaktion von Trifluoressigsäure mit zwei Criegee-Intermediaten, Formaldehydoxid und Acetonoxid, verweisen auf die Relevanz dieser Spezies als wichtige atmosphärische Senke für diesen persistenten Luftschadstoff.
      PubDate: 2017-06-29T01:35:27.27683-05:0
      DOI: 10.1002/ange.201703700
       
  • (NHC)NiH-Catalyzed Intermolecular Regio- and Diastereoselective
           Cross-Hydroalkenylation of Endocyclic Dienes with α-Olefins
    • Authors: Xiaoyan Lian; Weihao Chen, Liang Dang, Yuchen Li, Chun-Yu Ho
      Pages: 9176 - 9180
      Abstract: Highly selective cross-hydroalkenylations of endocyclic 1,3-dienes at the least substituted site with α-olefins were achieved with a set of neutral (NHC)NiIIH(OTf) catalysts and cationic NiII catalysts with a novel NHC ligand. Under heteroatom assistance, skipped dienes were obtained in good yields, often from equal amounts of the two substrates and at a catalyst loading of 2–5 mol %. Rare 4,3-product selectivity (i.e., with the H atom at C4 and the alkenyl group at C3 of the diene) was observed, which is different from the selectivity of known dimerizations of α-olefins with both acyclic Co and Fe systems. The influence of the various substituents on the NHC, 1,3-diene, and α-olefin on the chemo-, regio-, and diastereoselectivity was studied. High levels of chirality transfer were observed with chiral cyclohexadiene derivatives.Heteroatom-Effekte: 1,4-Diene mit exo-Methylengruppen wurden durch Nickel-katalysierte Kreuzhydroalkenylierungen in hohen Ausbeuten erhalten, sodass endocyclische 1,3-Diene mit eingebauten Chiralitätszentren nun mit α-Olefinen kompatibel sind. Sterische Effekte der NHC-Liganden und Produkte verhindern eine Isomerisierung. DIPP=2,6-Diisopropylphenyl.
      PubDate: 2017-06-16T03:16:03.719966-05:
      DOI: 10.1002/ange.201703706
       
  • A Simple Nanocellulose Coating for Self-Cleaning upon Water Action:
           Molecular Design of Stable Surface Hydrophilicity
    • Authors: Shu Huang; Dayang Wang
      Pages: 9181 - 9185
      Abstract: Coating solid surfaces with cellulose nanofibril (CNF) monolayers via physical deposition was found to keep the surfaces free of a variety of oils, ranging from viscous engine oil to polar n-butanol, upon water action. The self-cleaning function was well correlated with the unique molecular structure of the CNF, in which abundant surface carboxyl and hydroxy groups are uniformly, densely, and symmetrically arranged to form a polar corona on a crystalline nanocellulose strand. This isotropic core–corona configuration offers new and easily adoptable guidance to design self-cleaning surfaces at the molecular level. Thanks to its excellent self-cleaning behavior, the CNF coating converted conventional meshes into highly effective membranes for oil–water separation with no prior surface treatment required.Eine Monoschicht aus Cellulose-Nanofasern (CNFs) verleiht Oberflächen selbstreinigende Eigenschaften. Durch die isotrope Molekülkonfiguration wirkt sich die Orientierung der einzelnen CNFs bezüglich der Oberflächenebene kaum auf das Wasserbenetzungsverhalten der Beschichtung aus, sodass verschiedenartige Öle leicht mit Wasser abgespült werden können.
      PubDate: 2017-06-28T06:42:34.368969-05:
      DOI: 10.1002/ange.201703913
       
  • Highly Stable, Low Gas Crossover, Proton-Conducting Phenylated
           Polyphenylenes
    • Authors: Michael Adamski; Thomas J. G. Skalski, Benjamin Britton, Timothy J. Peckham, Lukas Metzler, Steven Holdcroft
      Pages: 9186 - 9189
      Abstract: Two classes of novel sulfonated phenylated polyphenylene ionomers are investigated as polyaromatic-based proton exchange membranes. Both types of ionomer possess high ion exchange capacities yet are insoluble in water at elevated temperatures. They exhibit high proton conductivity under both fully hydrated conditions and reduced relative humidity, and are markedly resilient to free radical attack. Fuel cells constructed with membrane-electrode assemblies containing each ionomer membrane yield high in situ proton conductivity and peak power densities that are greater than obtained using Nafion reference membranes. In situ chemical stability accelerated stress tests reveal that this class of the polyaromatic membranes allow significantly lower gas crossover and lower rates of degradation than Nafion benchmark systems. These results point to a promising future for molecularly designed sulfonated phenylated polyphenylenes as proton-conducting media in electrochemical technologies.Stresstest bestanden: Zwei Klassen neuartiger sulfonierter Polyphenylenionomere wurden als Protonenaustauschmembranen entwickelt. Beide Ionomertypen besitzen hohe Ionenaustauschkapazitäten und sind dabei unlöslich in Wasser. Sie zeigen hohe Protonenleitfähigkeiten sowohl unter vollständig hydratisierten Bedingungen als auch bei reduzierter Feuchtigkeit und sind bemerkenswert widerstandsfähig gegen freie Radikale.
      PubDate: 2017-06-27T06:13:16.402618-05:
      DOI: 10.1002/ange.201703916
       
  • Discovery of a Calcium-Dependent Enzymatic Cascade for the Selective
           Assembly of Hapalindole-Type Alkaloids: On the Biosynthetic Origin of
           Hapalindole U
    • Authors: Qin Zhu; Xinyu Liu
      Pages: 9190 - 9194
      Abstract: Hapalindole U (4) is a validated biosynthetic precursor to ambiguine alkaloids (Angew. Chem. Int. Ed. 2016, 55, 5780), of which biogenetic origin remains unknown. The recent discovery of AmbU4 (or FamC1) protein encoded in the ambiguine biosynthetic pathway (J. Am. Chem. Soc. 2015, 137, 15366), an isomerocyclase that can rearrange and cyclize geranylated indolenine (2) to a previously unknown 12-epi-hapalindole U (3), raised the question whether 3 is a direct precursor to 4 or an artifact arising from the limited in vitro experiments. Here we report a systematic approach that led to the discovery of an unprecedented calcium-dependent AmbU1-AmbU4 enzymatic complex for the selective formation of 4. This discovery refuted the intermediacy of 3 and bridged the missing links in the early-stage biosynthesis of ambiguines. This work further established the isomerocyclases involved in the biogenesis of hapalindole-type alkaloids as a new family of calcium-dependent enzymes, where the metal ions are shown critical for their enzymatic activities and selectivities.Calcium als Schlüsselkomponente: Die Suche nach der enzymatischen Basis für Hapalindol U, einer validierten biogenetischen Vorstufe der Ambiguin-Alkaloide, führte zu einem beispiellosen Calcium-abhängigen Isomerocyclase-Komplex. Diese Entdeckung ermöglichte die Etablierung von Isomerocyclasen, die als neue Familie Calcium-abhängiger Enzyme die Biogenese Hapalindol-artiger Verbindungen erlauben.
      PubDate: 2017-06-29T07:35:33.75946-05:0
      DOI: 10.1002/ange.201703932
       
  • Synthesis and Characterization of a Metallacyclic Framework with Three
           Fused Five-membered Rings
    • Authors: Congqing Zhu; Jingjing Wu, Shenyan Li, Yuhui Yang, Jun Zhu, Xin Lu, Haiping Xia
      Pages: 9195 - 9199
      Abstract: Polycyclic complexes containing a bridgehead transition metal are interesting species because the transition metal is shared by all the rings simultaneously. In this study, we present a novel osmium–bridgehead system with three fused five-membered rings. This novel framework can be viewed as a 10-atom carbon chain coordinating to the osmium center. In sharp contrast to the nonplanar organic analogue, this unique metallacycle exhibits good planarity, which was unambiguously verified by means of X-ray diffraction. Interestingly, preliminary DFT calculations show that the aromaticity in the three 5MRs of these osmatricycles can be easily tuned by the ligand substitution. Finally, the broad UV/Vis absorption spectra of these novel polycyclic complexes were also reported.Das hat noch gefehlt! Ein Gerüst mit drei kondensierten Fünfringen (im Kästchen gezeigt) wurde ausgehend von einer 10-atomigen Kette durch äquatoriale Koordination an ein Übergangsmetallzentrum aufgebaut. Die Struktur vervollständigt die Reihe aus Metallapentalin sowie Metallapentalen-kondensiertem Dreiring, Vierring und Sechsring.
      PubDate: 2017-07-19T02:33:24.250049-05:
      DOI: 10.1002/ange.201704057
       
  • Gluing Ionic Liquids to Oxide Surfaces: Chemical Anchoring of
           Functionalized Ionic Liquids by Vapor Deposition onto Cobalt(II) Oxide
    • Authors: Tao Xu; Tobias Waehler, Julia Vecchietti, Adrian Bonivardi, Tanja Bauer, Johannes Schwegler, Peter S. Schulz, Peter Wasserscheid, Joerg Libuda
      Pages: 9200 - 9204
      Abstract: Ionic liquids (IL) hold a great potential as novel electrolytes for applications in electronic materials and energy technology. The functionality of ILs in these applications relies on their interface to semiconducting nanomaterials. Therefore, methods to control the chemistry and structure of this interface are the key to assemble new IL-based electronic and electrochemical materials. Here, we present a new method to prepare a chemically well-defined interface between an oxide and an IL film. An imidazolium-based IL, which is carrying an ester group, is deposited onto cobalt oxide surface by evaporation. The IL binds covalently to the surface by thermally activated cleavage of the ester group and formation of a bridging carboxylate. The anchoring reaction shows high structure sensitivity, which implies that the IL film can be adhered selectively to specific oxide surfaces.An der Oberfläche bleiben: Eine funktionalisierte ionische Flüssigkeit auf Imidazolium-Basis wurde aus der Gasphase auf einer Oxidoberfläche abgeschieden und kovalent verankert. Dabei bindet die ionische Flüssigkeit in einer stark strukturabhängigen Reaktion über thermisch aktivierte Esterspaltung und Bildung eines verbrückenden Carboxylats.
      PubDate: 2017-06-28T06:42:18.607849-05:
      DOI: 10.1002/ange.201704107
       
  • Rational Engineering of a Dynamic, Entropy-Driven DNA Nanomachine for
           Intracellular MicroRNA Imaging
    • Authors: Cheng-Pin Liang; Pei-Qiang Ma, Hui Liu, Xinggang Guo, Bin-Cheng Yin, Bang-Ce Ye
      Pages: 9205 - 9209
      Abstract: We rationally engineered an elegant entropy-driven DNA nanomachine with three-dimensional track and applied it for intracellular miRNAs imaging. The proposed nanomachine is activated by target miRNA binding to drive a walking leg tethered to gold nanoparticle with a high density of DNA substrates. The autonomous and progressive walk on the DNA track via the entropy-driven catalytic reaction of intramolecular toehold-mediated strand migration leads to continuous disassembly of DNA substrates, accompanied by the recovery of fluorescence signal due to the specific release of a dye-labeled substrate from DNA track. Our nanomachine outperforms the conventional intermolecular reaction-based gold nanoparticle design in the context of an improved sensitivity and kinetics, attributed to the enhanced local effective concentrations of working DNA components from the proximity-induced intramolecular reaction. Moreover, the nanomachine was applied for miRNA imaging inside living cells.Spaziergang auf einem DNA-Weg: Eine Entropie-getriebene DNA-Nanomaschine mit einem dreidimensionalen Laufweg wurde hergestellt (siehe Bild). Die Nanomaschine wurde zur Bildgebung von microRNA in lebenden Zellen verwendet.
      PubDate: 2017-06-28T06:46:51.769124-05:
      DOI: 10.1002/ange.201704147
       
  • Proton Transport in the Outer-Membrane Flavocytochrome Complex Limits the
           Rate of Extracellular Electron Transport
    • Authors: Akihiro Okamoto; Yoshihide Tokunou, Shafeer Kalathil, Kazuhito Hashimoto
      Pages: 9210 - 9214
      Abstract: The microbial transfer of electrons to extracellularly located solid compounds, termed extracellular electron transport (EET), is critical for microbial electrode catalysis. Although the components of the EET pathway in the outer membrane (OM) have been identified, the role of electron/cation coupling in EET kinetics is poorly understood. We studied the dynamics of proton transport associated with EET in an OM flavocytochrome complex in Shewanella oneidensis MR-1. Using a whole-cell electrochemical assay, a significant kinetic isotope effect (KIE) was observed following the addition of deuterated water (D2O). The removal of a flavin cofactor or key components of the OM flavocytochrome complex significantly increased the KIE in the presence of D2O to values that were significantly larger than those reported for proton channels and ATP synthase, thus indicating that proton transport by OM flavocytochrome complexes limits the rate of EET.Elektrifizierend: Der direkte Elektronentransport über eine Elektronenschaltung aus Multihäm und Flavin in einem integralen Außenmembran(OM)-Flavocytochromkomplex ist entscheidend für den Katalyseprozess an einer mikrobiellen Elektrode. Studien des kinetischen Isotopeneffekts ergeben, dass der Protonentransport durch das OM-Flavocytochrom den Elektronentransport im Eisen-reduzierenden Bakterium Shewanella oneidensis MR-1 bestimmt.
      PubDate: 2017-06-29T07:36:09.690103-05:
      DOI: 10.1002/ange.201704241
       
  • A Modular Approach to Inorganic Phosphazane Macrocycles
    • Authors: Alex J. Plajer; Raúl García-Rodríguez, Callum G. M. Benson, Peter D. Matthews, Andrew D. Bond, Sanjay Singh, Lutz H. Gade, Dominic S. Wright
      Pages: 9215 - 9218
      Abstract: Inorganic macrocycles, based on non-carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host–guest and supramolecular chemistry. Here we demonstrate a new high-yielding modular approach to a broad range of trimeric and hexameric S- and Se-bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(μ-NR)]2. The method involves the in situ generation of the key intermediate [E....._(S....._)P(μ-NR)]22−(E=S, Se) dianion, which can be reacted with electrophilic [ClP(μ-NR)]2 to give PIII/PV hexameric rings or reacted with I2 to give trimeric PV variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air-stable and chiral inorganic macrocycles.Nimm diesen Ring: Neue S- und Se- verbrückte Phosphazan-Makrocyclen wurden aus den dimeren Dianionen [S=(Se)P(μ-NtBu)]22− erhalten, entweder durch Reaktionen mit den Dichlorphosphazandimeren [ClP(μ-NR)]2 oder durch Oxidation mit I2. Dieser Ansatz ermöglicht erstmals ein Variieren der organischen Substituenten bei dieser Klasse anorganischer Makromoleküle, sowie die Einführung von Chiralität.
      PubDate: 2017-04-21T03:16:15.93194-05:0
      DOI: 10.1002/ange.201702558
       
  • Facile and Reversible Formation of Iron(III)–Oxo–Cerium(IV) Adducts
           from Nonheme Oxoiron(IV) Complexes and Cerium(III)
    • Authors: Apparao Draksharapu; Waqas Rasheed, Johannes E. M. N. Klein, Lawrence Que
      Pages: 9219 - 9223
      Abstract: Ceric ammonium nitrate (CAN) or CeIV(NH4)2(NO3)6 is often used in artificial water oxidation and generally considered to be an outer-sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)FeIII-O-CeIV(OH2)(NO3)4]+ (3), a complex obtained from the reaction of [(N4Py)FeII(NCMe)]2+ with 2 equiv CAN or [(N4Py)FeIV=O]2+ (2) with CeIII(NO3)3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the FeIV and CeIV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S=1 FeIV in 2 to S=5/2 in 3, which is found to be facile despite the formal spin-forbidden nature of this process. This observation suggests that FeIV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier.Cer auf frischer Redox-Tat erwischt: CeIII reagiert mit FeIV(O)-Komplexen in Acetonitril und bildet FeIII-O-CeIV-Addukte. Durch Zugabe von Wasser kann die Transformation leicht umgekehrt werden. Das Gleichgewicht wird einfach durch die Liganden am Ce-Zentrum eingestellt, und seine Existenz belegt, dass die CeIV/III- und FeIV/III-Potentiale im Bereich von 0.9–1.1 V (ges. Kalomelelektrode) liegen müssen.
      PubDate: 2017-06-27T06:13:02.411239-05:
      DOI: 10.1002/ange.201704322
       
  • Unified Asymmetric Total Syntheses of (−)-Alotaketals A–D and
           (−)-Phorbaketal A
    • Authors: Hang Cheng; Zhihong Zhang, Hongliang Yao, Wei Zhang, Jingxun Yu, Rongbiao Tong
      Pages: 9224 - 9228
      Abstract: The novel tricyclic spiroketal alotane-type sesterterpenoids showed strikingly different biological activities and potency with subtle structural alterations. Asymmetric total syntheses of the tricyclic sesterterpenoids (−)-alotaketals A–D and (−)-phorbaketal A were accomplished [29–31 steps from (−)-malic acid] in a collective way for the first time. The key features of the strategy included 1) a new cascade cyclization of vinyl epoxy δ-keto-alcohols to forge the common tricyclic spiroketal intermediate, 2) a late-stage allylic C−H oxidation, and 3) olefin cross-metathesis to install the different side chains.Alleskönner: Ein gemeinsamer Ansatz für die Totalsynthesen der tricyclischen Sesterterpenoide (−)-Alotaketal A–D und (−)-Phorbaketal A liefert die Produkte in 29–31 Stufen ausgehend von (−)-Äpfelsäure. Dabei stehen eine neue Cyclisierungskaskade von Vinylepoxy-δ-ketoalkoholen, eine späte C-H-Oxidation und eine Olefin-Kreuzmetathese im Vordergrund.
      PubDate: 2017-06-26T02:39:38.895299-05:
      DOI: 10.1002/ange.201704628
       
  • Automated Quantum Mechanical Predictions of Enantioselectivity in a
           Rhodium-Catalyzed Asymmetric Hydrogenation
    • Authors: Yanfei Guan; Steven E. Wheeler
      Pages: 9229 - 9233
      Abstract: A computational toolkit (AARON: An automated reaction optimizer for new catalysts) is described that automates the density functional theory (DFT) based screening of chiral ligands for transition-metal-catalyzed reactions with well-defined reaction mechanisms but multiple stereocontrolling transition states. This is demonstrated for the Rh-catalyzed asymmetric hydrogenation of (E)-β-aryl-N-acetyl enamides, for which a new C2-symmetric phosphorus ligand is designed.Die Computerressource AARON – die englische Abkürzung für eine „automatische Reaktionsoptimierung neuer Katalysatoren” – evaluiert Hunderte von Übergangszustandsstrukturen, wie es für eine zuverlässige Voraussage des stereochemischen Verlaufs übergangsmetallkatalysierter Reaktionen erforderlich ist. Als Beispiel wurde eine Rh-katalysierte asymmetrische Hydrierung von (E)-β-Aryl-N-acetylenamiden gewählt.
      PubDate: 2017-06-28T06:47:12.444961-05:
      DOI: 10.1002/ange.201704663
       
  • Pentagon-Embedded Cycloarylenes with Cylindrical Shapes
    • Authors: Shunpei Hitosugi; Sota Sato, Taisuke Matsuno, Takashi Koretsune, Ryotaro Arita, Hiroyuki Isobe
      Pages: 9234 - 9238
      Abstract: Cylinder-shaped graphitic networks in carbon nanotubes have attracted interest from scientists in various disciplines. The chemical synthesis of segments thereof is considered as a challenging and appealing subject in chemistry, and deepens our understanding of curved and conjugated arrays of hexagons. We herein report the synthesis of cylinder-shaped molecules containing non-hexagon bridges in their conjugated systems. Multiple pentagon units were embedded in the cylinder-shaped discrete molecules, and the stereoisomerism originating from their helical carbon arrangements was studied. Structural analysis by NMR, UV/Vis absorption spectroscopy, and single-crystal X-ray diffraction provided fundamental experimental information on the curved systems with conjugation across the pentagons. This study provides the first experimental guide for further explorations of anomalous non-hexagon arrays of graphitic carbon materials with cylindrical shapes.Mehrere Pentagone wurden in zylinderförmige Moleküle eingebaut, um Segmente von Haeckelit-Nanoröhren mit defekthaltigen Wabenmustern zu erhalten. Diese zylinderförmigen Moleküle zeichnen sich durch Konjugation über die Pentagon-Brücken aus. Sie dienen zudem als Intermediate für retrosynthetische Analysen und als Inspiration für neuartige defekthaltige Kohlenstoffnanoröhren.
      PubDate: 2017-06-29T07:40:54.646753-05:
      DOI: 10.1002/ange.201704676
       
  • Antimony Complexes for Electrocatalysis: Activity of a Main-Group Element
           in Proton Reduction
    • Authors: Jianbing Jiang; Kelly L. Materna, Svante Hedström, Ke R. Yang, Robert H. Crabtree, Victor S. Batista, Gary W. Brudvig
      Pages: 9239 - 9243
      Abstract: Main-group complexes are shown to be viable electrocatalysts for the H2-evolution reaction (HER) from acid. A series of antimony porphyrins with varying axial ligands were synthesized for electrocatalysis applications. The proton-reduction catalytic properties of TPSb(OH)2 (TP=5,10,15,20-tetra(p-tolyl)porphyrin) with two axial hydroxy ligands were studied in detail, demonstrating catalytic H2 production. Experiments, in conjunction with quantum chemistry calculations, show that the catalytic cycle is driven via the redox activity of both the porphyrin ligand and the Sb center. This study brings insight into main group catalysis and the role of redox-active ligands during catalysis.Antimon-Porphyrinkomplexe wurden hergestellt und in der katalytischen Protonenreduktion erprobt. Die Komplexe katalysieren die elektrochemische Produktion von Wasserstoffgas und könnten als Grundlage für die Entwicklung neuer Hauptgruppenkatalysatoren dienen.
      PubDate: 2017-07-04T04:56:59.391036-05:
      DOI: 10.1002/ange.201704700
       
  • Catalysis of Extracellular Deamination by a FAD-Linked Oxidoreductase
           after Prodrug Maturation in the Biosynthesis of Saframycin A
    • Authors: Li-Qiang Song; Ying-Ying Zhang, Jin-Yue Pu, Man-Cheng Tang, Chao Peng, Gong-Li Tang
      Pages: 9244 - 9248
      Abstract: The biosynthesis of antibiotics in bacteria is usually believed to be an intracellular process, at the end of which the matured compounds are exported outside the cells. The biosynthesis of saframycin A (SFM-A), an antitumor antibiotic, requires a cryptic fatty acyl chain to guide the construction of a pentacyclic tetrahydroisoquinoline scaffold; however, the follow-up deacylation and deamination steps remain unknown. Herein we demonstrate that SfmE, a membrane-bound peptidase, hydrolyzes the fatty acyl chain to release the amino group; and SfmCy2, a secreted oxidoreductase covalently associated with FAD, subsequently performs an oxidative deamination extracellularly. These results not only fill in the missing steps of SFM-A biosynthesis, but also reveal that a FAD-binding oxidoreductase catalyzes an unexpected deamination reaction through an unconventional extracellular pathway in Streptmyces bacteria.Ein sekretiertes Protein, SfmCy2, das kovalent an FAD bindet, katalysiert die extrazelluläre oxidative Deaminierung als letzten Schritt in der Biosynthese von Saframycin A. Voraus geht eine Prodrug-Reifung durch die membrangebundene Peptidase SfmE (siehe Schema; Saframycin A trägt eine Cyanogruppe anstelle der Hydroxygruppe im Vorläufer Saframycin S).
      PubDate: 2017-07-04T04:57:26.735568-05:
      DOI: 10.1002/ange.201704726
       
  • Carbon Dioxide Electroreduction into Syngas Boosted by a Partially
           Delocalized Charge in Molybdenum Sulfide Selenide Alloy Monolayers
    • Authors: Jiaqi Xu; Xiaodong Li, Wei Liu, Yongfu Sun, Zhengyu Ju, Tao Yao, Chengming Wang, Huanxin Ju, Junfa Zhu, Shiqiang Wei, Yi Xie
      Pages: 9249 - 9253
      Abstract: Structural parameters of ternary transition-metal dichalcogenide (TMD) alloy usually obey Vegard law well, while interestingly it often exhibits boosted electrocatalytic performances relative to its two pristine binary TMDs. To unveil the underlying reasons, we propose an ideal model of ternary TMDs alloy monolayer. As a prototype, MoSeS alloy monolayers are successfully synthesized, in which X-ray absorption fine structure spectroscopy manifests their shortened Mo−S and lengthened Mo−Se bonds, helping to tailor the d-band electronic structure of Mo atoms. Density functional theory calculations illustrate an increased density of states near their conduction band edge, which ensures faster electron transfer confirmed by their lower work function and smaller charge-transfer resistance. Energy calculations show the off-center charge around Mo atoms not only benefits for stabilizing COOH* intermediate confirmed by its most negative formation energy, but also facilitates the rate-limiting CO desorption step verified by CO temperature programmed desorption and electro-stripping tests. As a result, MoSeS alloy monolayers attain the highest 45.2 % Faradaic efficiency for CO production, much larger than that of MoS2 monolayers (16.6 %) and MoSe2 monolayers (30.5 %) at −1.15 V vs. RHE. This work discloses how the partially delocalized charge in ternary TMDs alloys accelerates electrocatalytic performances at atomic level, opening new horizons for manipulating CO2 electroreduction properties.CO2-Konvertierung: Monolagen einer MoSeS-Legierung wurden mithilfe einer durch flüssig/flüssig-Grenzflächen vermittelten Strategie synthetisiert. Röntgenabsorptionsspektroskopie offenbart verkürzte Mo-S- und verlängerte Mo-Se-Bindungen, und Berechnungen zeigen, dass die seitlich versetzte Ladung an den Mo-Atomen das COOH*-Intermediat stabilisiert und den geschwindigkeitsbestimmenden CO-Desorptionsschritt erleichtert.
      PubDate: 2017-06-29T07:50:36.480311-05:
      DOI: 10.1002/ange.201704928
       
  • A Rechargeable Li-CO2 Battery with a Gel Polymer Electrolyte
    • Authors: Chao Li; Ziyang Guo, Bingchang Yang, Yao Liu, Yonggang Wang, Yongyao Xia
      Pages: 9254 - 9258
      Abstract: The utilization of CO2 in Li-CO2 batteries is attracting extensive attention. However, the poor rechargeability and low applied current density have remained the Achilles’ heel of this energy device. The gel polymer electrolyte (GPE), which is composed of a polymer matrix filled with tetraglyme-based liquid electrolyte, was used to fabricate a rechargeable Li-CO2 battery with a carbon nanotube-based gas electrode. The discharge product of Li2CO3 formed in the GPE-based Li-CO2 battery exhibits a particle-shaped morphology with poor crystallinity, which is different from the contiguous polymer-like and crystalline discharge product in conventional Li-CO2 battery using a liquid electrolyte. Accordingly, the GPE-based battery shows much improved electrochemical performance. The achieved cycle life (60 cycles) and rate capability (maximum applied current density of 500 mA g−1) are much higher than most of previous reports, which points a new way to develop high-performance Li-CO2 batteries.Auf dem Weg zur Hochleistungsbatterie: Eine wiederaufladbare Li-CO2-Batterie wurde mit einem Gelpolymerelektrolyt (GPE) hergestellt. Die Batterie weist eine hohe Ratenkapazität (bei einer maximalen Stromdichte von 500 mA g−1) und lange Zyklenstabilität (60 Zyklen) auf.
      PubDate: 2017-06-30T01:56:46.173578-05:
      DOI: 10.1002/ange.201705017
       
  • Water-Catalyzed Oxidation of Few-Layer Black Phosphorous in a Dark
           Environment
    • Authors: Zehua Hu; Qiang Li, Bo Lei, Qionghua Zhou, Du Xiang, Zhiyang Lyu, Fang Hu, Junyong Wang, Yinjuan Ren, Rui Guo, Eda Goki, Li Wang, Cheng Han, Jinlan Wang, Wei Chen
      Pages: 9259 - 9263
      Abstract: Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.Ein neuer Oxidationsmechanismus für schwarzen Phosphor (BP), die wasserkatalysierte Oxidation im Dunkeln, wurde durch In-situ-Experimente aufgeklärt. DFT-Rechnungen zeigen, dass der Polarisationseffekt von Wasser das Energieniveau des Sauerstoffs absenkt, wodurch der Oxidationsprozess katalysiert wird.
      PubDate: 2017-06-30T01:56:31.314105-05:
      DOI: 10.1002/ange.201705012
       
  • Anion Exchange Renders Hydrophobic Capsules and Cargoes Water-Soluble
    • Authors: Edmundo G. Percástegui; Jesús Mosquera, Jonathan R. Nitschke
      Pages: 9264 - 9268
      Abstract: Control over the solubility properties of container molecules is a central challenge in host–guest chemistry. Herein we present a simple anion-exchange protocol that allows the dissolution in water of various hydrophobic metal–organic container molecules prepared by iron(II)-templated subcomponent self-assembly. Our process involved the exchange of less hydrophilic trifluoromethanesulfonate anions for hydrophilic sulfate; the resulting water-soluble cages could be rendered water-insoluble through reverse anion exchange. Notably, this strategy allowed cargoes within capsules, including polycyclic aromatic compounds and complex organic drugs, to be brought into water. Hydrophobic effects appeared to enhance binding, as many of these cargoes were not bound in non-aqueous media. Studies of the scope of this method revealed that cages containing tetratopic and tritopic ligands were more stable in water, whereas cages with ditopic ligands disassembled.Rein ins Wasser: Verschiedene hydrophobe selbstorganisierte Kapseln lassen sich durch Anionenaustausch in Wasser in Lösung bringen. Sie verkapseln dort eine breite Reihe von Gästen, die in Acetonitril nicht gebunden werden. Die erhaltenen wasserlöslichen Käfige können durch umgekehrten Anionenaustausch wasserunlöslich gemacht werden (siehe Schema).
      PubDate: 2017-06-27T06:14:14.887222-05:
      DOI: 10.1002/ange.201705093
       
  • An Intrinsically Stretchable and Compressible Supercapacitor Containing a
           Polyacrylamide Hydrogel Electrolyte
    • Authors: Yan Huang; Ming Zhong, Fukuan Shi, Xiaoying Liu, Zijie Tang, Yukun Wang, Yang Huang, Haoqing Hou, Xuming Xie, Chunyi Zhi
      Pages: 9269 - 9273
      Abstract: Stretchability and compressibility of supercapacitors is an essential element of modern electronics, such as flexible, wearable devices. Widely used polyvinyl alcohol-based electrolytes are neither very stretchable nor compressible, which fundamentally limits the realization of supercapacitors with high stretchability and compressibility. A new electrolyte that is intrinsically super-stretchable and compressible is presented. Vinyl hybrid silica nanoparticle cross-linkers were introduced into polyacrylamide hydrogel backbones to promote dynamic cross-linking of the polymer networks. These cross-linkers serve as stress buffers to dissipate energy when strain is applied, providing a solution to the intrinsically low stretchability and compressibility shortcomings of conventional supercapacitors. The newly developed supercapacitor and electrolyte can be stretched up to an unprecedented 1000 % strain with enhanced performance, and compressed to 50 % strain with good retention of the initial performance.Streck Dich! Ein leicht herstellbarer Polyacrylamid-Hydrogelelektrolyt verleiht einem Superkondensator eine intrinsische und beispiellose Streckfähigkeit von 1000 % bei erhöhter Leistung sowie eine hohe Kompressibilität von 50 % bei gleichbleibender Kapazität.
      PubDate: 2017-06-29T07:50:55.183341-05:
      DOI: 10.1002/ange.201705212
       
  • An Interconnected Ternary MIn2S4 (M=Fe, Co, Ni) Thiospinel Nanosheet
           Array: A Type of Efficient Platinum-Free Counter Electrode for
           Dye-Sensitized Solar Cells
    • Authors: Wenjing Hou; Yaoming Xiao, Gaoyi Han
      Pages: 9274 - 9278
      Abstract: The ternary iron-group thiospinels of metal diindium sulfides (MIn2S4, M=Fe, Co, Ni) with a vertically aligned nanosheet array structure are fabricated through an in situ solvothermal method on F-doped tin oxide (FTO) substrates, which are employed as one type of platinum (Pt)-free counter electrodes (CEs) in structure-dependent dye-sensitized solar cells (DSSCs). A DSSC assembled with ternary CoIn2S4 CE achieves an photoelectric conversion efficiency (PCE) of 8.83 %, outperforming than that of FeIn2S4 (7.18 %) and NiIn2S4 (8.27 %) CEs under full sunlight illumination (100 mW cm−2, AM 1.5 G), which is also comparable with that of the Pt CE (8.19 %). Putting aside that the interconnected nanosheet array provides fast electron transfer and electrolyte diffusion channels, the highest PCE of CoIn2S4 based DSSC results from its largest specific surface area (144.07 m2 g−1), providing abundant active sites and the largest electron injection efficiency from CE to electrolyte.Ternäre Sulfide (MIn2S4, M=Fe, Co, Ni) mit einer Anordnung in Form vertikal orientierter Nanoschichten wurden auf Substraten aus F-dotiertem Zinnoxid (FTO) durch eine einfache In-situ-Solvothermalmethode hergestellt. Die Struktur enthält zahlreiche aktive Zentren sowie Kanäle für einen schnellen Elektronentransfer zur I3−-Reduktion.
      PubDate: 2017-07-04T04:58:01.038498-05:
      DOI: 10.1002/ange.201705399
       
  • The Existence of an Isolated Hydronium Ion in the Interior of Proteins
    • Authors: Takuya Ikeda; Keisuke Saito, Ryo Hasegawa, Hiroshi Ishikita
      Pages: 9279 - 9282
      Abstract: Neutron diffraction analysis studies reported an isolated hydronium ion (H3O+) in the interior of d-xylose isomerase (XI) and phycocyanobilin-ferredoxin oxidoreductase (PcyA). H3O+ forms hydrogen bonds (H-bonds) with two histidine side-chains and a backbone carbonyl group in PcyA, whereas H3O+ forms H-bonds with three acidic residues in XI. Using a quantum mechanical/molecular mechanical (QM/MM) approach, we analyzed stabilization of H3O+ by the protein environment. QM/MM calculations indicated that H3O+ was unstable in the PcyA crystal structure, releasing a proton to an H-bond partner His88, producing H2O and protonated His88. On the other hand, H3O+ was stable in the XI crystal structure. H-bond partners of isolated H3O+ would be practically limited to acidic residues such as aspartic and glutamic acids in the protein environment.Hydronium allein: H3O+ wird häufig eine Rolle in enzymatischen Reaktionen zugeschrieben. Um zu verstehen, wie die Proteinumgebung ein isoliertes H3O+ stabilisieren kann, wurden die Potentialenergieprofile von H-Brücken in postulierten H3O+-bindenden Molekülteilen mittels QM/MM ausgehend von der Neutronenbeugungsstruktur der Phycocyanobilin-Ferredoxin-Oxidoreduktase (PcyA) und der d-Xylose-Isomerase (XI) analysiert.
      PubDate: 2017-06-30T03:50:33.380162-05:
      DOI: 10.1002/ange.201705512
       
  • Dendronized Semiconducting Polymer as Photothermal Nanocarrier for Remote
           Activation of Gene Expression
    • Authors: Yan Lyu; Dong Cui, He Sun, Yansong Miao, Hongwei Duan, Kanyi Pu
      Pages: 9283 - 9287
      Abstract: Regulation of transgene systems is needed to develop innovative medicines. However, noninvasive remote control of gene expression has been rarely developed and remains challenging. We herein synthesize a near-infrared (NIR) absorbing dendronized semiconducting polymer (DSP) and utilize it as a photothermal nanocarrier not only to efficiently deliver genes but also to spatiotemporally control gene expression in conjunction with heat-inducible promoter. DSP has a high photothermal conversion efficiency (44.2 %) at 808 nm, permitting fast transduction of NIR light into thermal signals for intracellular activation of transcription. Such a DSP-mediated remote activation can rapidly and safely result in 25- and 4.5-fold increases in the expression levels of proteins in living cells and mice, respectively. This study thus provides a promising approach to optically regulate transgene systems for on-demand therapeutic transgene dosing.Gen-Genie: Ein im nahen Infrarot (NIR) absorbierendes dendronisiertes Halbleiterpolymer (DSP) wurde synthetisiert und als photothermischer Nanoträger genutzt – nicht nur zum effizienten Gentransport, sondern auch zur räumlich und zeitlich präzisen photothermischen Steuerung der Genexpression.
      PubDate: 2017-07-03T07:11:00.519792-05:
      DOI: 10.1002/ange.201705543
       
  • Bright, Multi-responsive, Sky-Blue Platinum(II) Phosphors Based on a
           Tetradentate Chelating Framework
    • Authors: Lijie Liu; Xiang Wang, Nan Wang, Tai Peng, Suning Wang
      Pages: 9288 - 9292
      Abstract: A new class of highly efficient and stable, blue-phosphorescent PtII complexes based on a tetradentate chelating framework has been found to exhibit highly sensitive and reversible responses to multiple external stimuli including temperature, pressure, and UV irradiation with distinct phosphorescent color switching—from blue to red or white. Intermolecular excimer formation is the main origin of this intriguing multi-response phenomenon. Highly efficient singlet-oxygen sensitization by the PtII compounds yields UV-light-induced phosphorescence enhancement and color switching.Eine starrere Struktur erwies sich als hoch effektiv, um effizient und stabil phosphoreszierende PtII-Komplexe mit dualer Emission zu erhalten. Die Komplexe ändern Farbe und Intensität als Antwort auf Temperatur, Druck und UV-Licht/Sauerstoff.
      PubDate: 2017-06-27T06:12:10.968637-05:
      DOI: 10.1002/ange.201705785
       
  • Natural Abundance 17O DNP NMR Provides Precise O−H Distances and
           Insights into the Brønsted Acidity of Heterogeneous Catalysts
    • Authors: Frédéric A. Perras; Zhuoran Wang, Pranjali Naik, Igor I. Slowing, Marek Pruski
      Pages: 9293 - 9297
      Abstract: Heterogeneous Brønsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Brønsted acid sites can be directly observed at natural abundance by 17O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O−H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material. Experiments performed on materials impregnated with pyridine also allow for the direct detection of intermolecular hydrogen bonding interactions through the lengthening of O−H bonds.Der einsame Reporter: Oberflächenverstärkte 17O-NMR-Spektroskopie mit dynamischer Kernpolarisation wurde verwendet, um 17O-1H-Abstände mit natürlicher Isotopenhäufigkeit in Quarz und Quarz/Aluminiumoxid-Materialien mit Subpikometergenauigkeit zu messen. Die hochpräzise Messung der O-H-Bindungslängen wurde genutzt, um die Brønsted-Azidität der Oxidoberflächen zu ermitteln und die Bildung intermolekularer Wasserstoffbrücken nachzuweisen.
      PubDate: 2017-06-06T08:15:24.185643-05:
      DOI: 10.1002/ange.201704032
       
  • A Strategy for Creating Organisms Dependent on Noncanonical Amino Acids
    • Authors: Weimin Xuan; Peter G. Schultz
      Pages: 9298 - 9301
      Abstract: The use of noncanonical amino acids (ncAAs) to control the viability of an organism provides a strategy for the development of conditional “kill switches” for live vaccines or engineered human cells. We report an approach inspired by the posttranslational acetylation/deacetylation of lysine residues, in which a protein encoded by a gene with an in-frame nonsense codon at an essential lysine can be expressed in its native state only upon genetic incorporation of N-ϵ-acetyl-l-Lys (AcK), and subsequent enzymatic deacetylation in the host cell. We applied this strategy to two essential E. coli enzymes: the branched-chain aminotransferase BCAT and the DNA replication initiator protein DnaA. We also devised a barnase-based conditional suicide switch to further lower the escape frequency of the host cells. This strategy offers a number of attractive features for controlling host viability, including a single small-molecule-based kill switch, low escape frequency, and unaffected protein function.Kein Entkommen: Eine PTM-Strategie ermöglicht die Erschaffung von Organismen, die von nichtkanonischen Aminosäuren abhängen. Ein Protein, für das ein Gen mit einem Nonsense-Codon an einem Lysin ohne Leserasterverschiebung codiert, wird in seinem nativen Zustand nur bei gentechnischem Einbau von N-ϵ-Acetyl-l-Lys (AcK) und nachfolgender enzymatischer Desacetylierung exprimiert. Ein Barnase-basierter Suizidschalter reduziert ferner das Entkommen der Wirtzellen.
      PubDate: 2017-06-27T06:12:50.411802-05:
      DOI: 10.1002/ange.201703553
       
  • DOSY Analysis of Micromolar Analytes: Resolving Dilute Mixtures by SABRE
           Hyperpolarization
    • Authors: Indrek Reile; Ruud L. E. G. Aspers, Jean-Max Tyburn, James G. Kempf, Martin C. Feiters, Floris P. J. T. Rutjes, Marco Tessari
      Pages: 9302 - 9305
      Abstract: DOSY is an NMR spectroscopy technique that resolves resonances according to the analytes’ diffusion coefficients. It has found use in correlating NMR signals and estimating the number of components in mixtures. Applications of DOSY in dilute mixtures are, however, held back by excessively long measurement times. We demonstrate herein, how the enhanced NMR sensitivity provided by SABRE hyperpolarization allows DOSY analysis of low-micromolar mixtures, thus reducing the concentration requirements by at least 100-fold.Die DOSY-Analyse einer Mischung mit niedrigen mikromolaren Konzentrationen gelingt über die Kombination mit Kernspin-Hyperpolarisierung. SABRE-Hyperpolarisierung verstärkt NMR-Signale um zwei Größenordnungen, sodass sechs verdünnte Analyte in einem 35-minütigen SABRE-DOSY-Experiment erfasst werden konnten.
      PubDate: 2017-06-28T06:42:45.606788-05:
      DOI: 10.1002/ange.201703577
       
  • Poly(oligo(ethylene glycol) vinyl acetate)s: A Versatile Class of
           Thermoresponsive and Biocompatible Polymers
    • Authors: Guillaume G. Hedir; Maria C. Arno, Marvin Langlais, Jonathan T. Husband, Rachel K. O'Reilly, Andrew P. Dove
      Pages: 9306 - 9310
      Abstract: Polymers with a thermally triggered phase transition are important in the design of materials for biological applications, where their behavior can be used to trigger release or (dis)assembly events. Despite their advantages, a system with tunable thermal response, end-group reactive sites, low toxicity, and controlled main-chain degradability has not been realized, yet this would be a significant advance. The versatile new poly(oligo(ethylene glycol) vinyl acetate)s are presented with excellent control over their molecular properties obtained through RAFT/MADIX polymerization. Furthermore, we demonstrate structure-controlled thermal transitions, conjugation to human lysozyme through the retained end-group, and moreover show that this class of polymers can uniquely be copolymerized with 2-methylene-1,3-dioxepane (MDO) to generate polymers in which the degradability and cloud point can be independently tuned to create materials that display the same cloud point but degrade differently.Smarte Acetate: Die kontrollierte Polymerisation einer Familie PEGylierter Vinylacetate ergibt Polymere mit thermoresponsivem Verhalten, das durch Wahl des (Co)monomers einstellbar ist und die unabhängige Abstimmung von Responsivität und Zersetzung ermöglicht. Die ausgeprägte Endgruppenretention eröffnet zudem neue Möglichkeiten für die Protein-Polymer-Konjugation.
      PubDate: 2017-06-30T03:46:43.917093-05:
      DOI: 10.1002/ange.201703763
       
  • Synthesis of [5,6]-Bicyclic Heterocycles with a Ring-Junction Nitrogen
           Atom: Rhodium(III)-Catalyzed C−H Functionalization of Alkenyl Azoles
    • Authors: Kim Søholm Halskov; Howard S. Roth, Jonathan A. Ellman
      Pages: 9311 - 9315
      Abstract: The first syntheses of privileged [5,6]-bicyclic heterocycles, with ring-junction nitrogen atoms, by transition metal catalyzed C−H functionalization of C-alkenyl azoles is disclosed. Several reactions are applied to alkenyl imidazoles, pyrazoles, and triazoles to provide products with nitrogen incorporated at different sites. Alkyne and diazoketone coupling partners give azolopyridines with various substitution patterns. In addition, 1,4,2-dioxazolone coupling partners yield azolopyrimidines. Furthermore, the mechanisms for the reactions are discussed and the utility of the developed approach is demonstrated by iterative application of C−H functionalization for the rapid synthesis of a patented drug candidate.Stickstoffbicyclen: Die Titelreaktion liefert ein breites Spektrum von [5,6]-bicyclischen Stickstoffheterocyclen. Alkenylimidazole, -pyrazole und -triazole als C-H-aktivierbare Substrate in Kombination mit Alkinen, Diazoketonen oder 1,4,2-Dioxazolonen als Reaktionspartnern ermöglichen die Bildung dieser privilegierten Heterocyclenklasse mit hoch diversen Substitutionsmustern und Stickstoff-Funktionalitäten.
      PubDate: 2017-07-05T12:34:07.771774-05:
      DOI: 10.1002/ange.201703967
       
  • Synthesis and Structural Characterization of Butadienylcalcium-based Heavy
           Grignard Reagents and a Ca4[O] Inverse Crown Ether Complex
    • Authors: Baosheng Wei; Liang Liu, Wen-Xiong Zhang, Zhenfeng Xi
      Pages: 9316 - 9320
      Abstract: The structure elucidation of heavy Grignard reagents (RAeX, Ae=Ca, Sr, and Ba, X=halides) has been greatly strived after, mainly because of their inaccessibility and remarkable instability. The synthesis of a series of butadienylcalcium compounds is presented, including 1-calcio-4-lithio-1,3-butadiene, 1,4-dicalcio-1,3-butadiene, and a Ca4[O] inverse crown ether complex, via the reaction between 1,4-dilithio-1,3-butadienes and calcium iodide in THF. Single-crystal X-ray analysis of these unprecedented heavy Grignard reagents revealed unique structural characteristics and bonding modes. Preliminary reaction chemistry was investigated. This study provides a novel class of alkenyl heavy Grignard reagents and a useful synthetic strategy for otherwise unavailable reactive organometallic compounds.Schwere Grignard-Reagentien: Eine Reihe von Butadienylcalciumverbindungen wurde durch Metallaustausch zwischen 1,4-Dilithio-1,3-butadienen und Calciumiodid in THF synthetisiert. Einkristall-Röntgenstrukturanalysen dieser schweren Grignard-Reagentien zeigen einzigartige Bindungsverhältnisse. Zusätzlich wurde ein inverser Kronenetherkomplex vom Ca4[O]-Typ entdeckt.
      PubDate: 2017-06-29T07:40:26.5355-05:00
      DOI: 10.1002/ange.201704176
       
  • Nitrogen–Carbon Bond Formation by Reactions of a Titanium–Potassium
           Dinitrogen Complex with Carbon Dioxide, tert-Butyl Isocyanate, and
           Phenylallene
    • Authors: Yusuke Nakanishi; Yutaka Ishida, Hiroyuki Kawaguchi
      Pages: 9321 - 9325
      Abstract: Nitrogen–carbon bond-forming reactions at coordinated dinitrogen in a bifunctional titanium–potassium system are reported. A titanium atrane complex with a tris(aryloxide)methyl ligand (1) was treated with two equivalents of potassium naphthalenide under N2 atmosphere to generate a bifunctional complex (2) in which N2 binds end-on to two titanium centers and side-on to three potassium cations. Dinitrogen complex 2 reacted with carbon dioxide, tert-butyl isocyanate, and phenylallene, forming nitrogen–carbon bonds and affording diverse N-functionalized products. The reaction of 2 with CO2 followed by addition of Me3SiCl resulted in the formation of the starting complex 1 with concomitant release of silylated carboxyl hydrazines while the reaction with two equivalents of tert-butyl isocyanate proceeded by insertion into the Ti−N bonds. Treatment of 2 with phenylallene afforded vinyl-substituted hydrazido complexes.Ein Titan-Atran-Komplex mit einem Tris(aryloxid)-Liganden wurde mit Kaliumnaphthalid unter N2-Atmosphäre reduziert. Der erhaltene Stickstoffkomplex, in dem N2 „end-on” an Titan und „side-on” an Kalium bindet, reagiert mit CO2, tBuNCO und Phenylallen unter Bildung von Stickstoff-Kohlenstoff-Bindungen zu diversen N-funktionalisierten Produkten.
      PubDate: 2017-06-14T06:40:31.879777-05:
      DOI: 10.1002/ange.201704286
       
  • Reversible Photothermal Isomerization of Carborane-Fused Azaborole to
           Borirane: Synthesis and Reactivity of Carbene-Stabilized Carborane-Fused
           Borirane
    • Authors: Hao Wang; Jiji Zhang, Zuowei Xie
      Pages: 9326 - 9329
      Abstract: A fully reversible photothermal isomerization between carborane-fused trigonal-planar azaborole (dark-purple) and tetrahedral borirane (pale-yellow) has been observed, leading to the isolation and structural characterization of the first example of carborane-fused borirane. DFT calculations indicate that the azaborole is thermodynamically more stable than the borirane by 11.2 kcal mol−1, and the energy barrier for the thermal conversion from azaborole to borirane is 35.5 kcal mol−1. The reactivity studies show that the B−C(cage) bond in borirane can be broken in the reaction with CuCl, HCl, or elemental sulfur.Ein Kind des Lichts: Eine vollständig reversible photochemisch-thermische Isomerisierung zwischen einem Carboran-kondensierten trigonal-planaren Azaborol (violett) und Boriran (hellgelb) wurde beobachtet. Das Carboran-kondensierte Boriran wurde isoliert und strukturanalytisch charakterisiert. Es reagiert mit CuCl, HCl und elementarem Schwefel unter Spaltung der C(Käfig)-B-Bindung.
      PubDate: 2017-06-26T01:52:39.790292-05:
      DOI: 10.1002/ange.201704642
       
  • Frustrated Lewis Pair Mediated 1,2-Hydrocarbation of Alkynes
    • Authors: Valerio Fasano; Liam D. Curless, James E. Radcliffe, Michael J. Ingleson
      Pages: 9330 - 9334
      Abstract: Frustrated Lewis pair (FLP) chemistry enables a rare example of alkyne 1,2-hydrocarbation with N-methylacridinium salts as the carbon Lewis acid. This 1,2-hydrocarbation process does not proceed through a concerted mechanism as in alkyne syn-hydroboration, or through an intramolecular 1,3-hydride migration as operates in the only other reported alkyne 1,2-hydrocarbation reaction. Instead, in this study, alkyne 1,2-hydrocarbation proceeds by a novel mechanism involving alkyne dehydrocarbation with a carbon Lewis acid based FLP to form the new C−C bond. Subsequently, intermolecular hydride transfer occurs, with the Lewis acid component of the FLP acting as a hydride shuttle that enables alkyne 1,2-hydrocarbation.Hohe Kochkunst: Eine seltene 1,2-Hydrocarbierung von Alkinen wurde unter Verwendung frustrierter Lewis-Paare (FLPs) entwickelt (siehe Bild). Die Reaktion verläuft über einen neuartigen Mechanismus bestehend aus einer FLP-vermittelten Dehydrocarbierung des Alkins, der sich ein Hydridtransfer unter der Einwirkung eines intermolekularen Hydridshuttles sowie schließlich eine Protonierung anschließen.
      PubDate: 2017-07-04T04:57:45.491926-05:
      DOI: 10.1002/ange.201705100
       
  • Asymmetric Yttrium-Catalyzed C(sp3)−H Addition of 2-Methyl Azaarenes
           to Cyclopropenes
    • Authors: Yong Luo; Huai-Long Teng, Masayoshi Nishiura, Zhaomin Hou
      Pages: 9335 - 9338
      Abstract: An enantioselective C−H addition to a C=C bond represents the most atom-efficient route for the construction of chiral carbon–carbon skeletons, a central research topic in organic synthesis. We herein report the enantioselective yttrium-catalyzed C(sp3)−H bond addition of 2-methyl azaarenes, such as 2-methyl pyridines, to various substituted cyclopropenes and norbornenes. This process efficiently afforded a new family of chiral pyridylmethyl-functionalized cyclopropane and norbornane derivatives in high yields and high enantioselectivities (up to 97 % ee).Enantioselektive C(sp3)-H-Additionen von 2-Methylazaarenen, wie z. B. 2-Methylpyridinen, an verschiedene substituierte Cyclopropene und Norbornene gelangen mit einem chiralen Yttrium-Katalysator mit Halbsandwich-Struktur. Auf diesem Weg wurden chirale Pyridylmethyl-substituierte Cyclopropane und Norbornane in guten Ausbeuten, mit hoher Enantioselektivität und vollständiger Atomeffizienz erhalten.
      PubDate: 2017-07-04T00:37:44.72144-05:0
      DOI: 10.1002/ange.201705431
       
  • Palladium-Catalyzed Asymmetric Synthesis of Silicon-Stereogenic
           5,10-Dihydrophenazasilines via Enantioselective 1,5-Palladium Migration
    • Authors: Yosuke Sato; Chihiro Takagi, Ryo Shintani, Kyoko Nozaki
      Pages: 9339 - 9344
      Abstract: A palladium-catalyzed asymmetric synthesis of silicon-stereogenic 5,10-dihydrophenazasilines was developed that proceeds via an unprecedented enantioselective 1,5-palladium migration. High enantioselectivity was achieved by employing 4,4′-bis(trimethylsilyl) (R)-Binap as the chiral ligand, and a series of mechanistic investigations were carried out to probe the catalytic cycle of this process.Eine palladiumkatalysierte asymmetrische Synthese von Si-stereogenen 5,10-Dihydrophenazasilinen wurde entwickelt, die über eine hoch enantioselektive 1,5-Palladium-Wanderung verläuft. Mechanistische Studien wurden ausgeführt, um den Katalysezyklus aufzuklären.
      PubDate: 2017-07-04T00:38:03.556663-05:
      DOI: 10.1002/ange.201705500
       
  • Catalytic Enantioselective Aza-pinacol Rearrangement
    • Authors: Yuanyuan Yu; Jingwen Li, Long Jiang, Jing-Ren Zhang, Liansuo Zu
      Pages: 9345 - 9349
      Abstract: The first catalytic enantioselective asymmetric aza-pinacol rearrangement is reported. The reactions are catalyzed by a chiral phosphoric acid and proceed via a highly organized transition state involving a cyclic aza-ortho-xylylene intermediate to afford the indoline structures with good to excellent enantioselectivity. The synthetic utility of this method is demonstrated by the asymmetric synthesis of a key intermediate to the natural product minfiensine and the identification of a chiral lead compound to repress antibiotic resistance.Ausgezeichneter Treffer: Die erste katalytische enantioselektive Azapinakol-Umlagerung wird beschrieben. Die Reaktion, die von einer chiralen Phosphorsäure katalysiert wird und über einen hoch organisierten Übergangszustand verläuft, wurde genutzt, um direkten Zugang zum Indolinkern einer Vielzahl von Naturstoffen zu erhalten. Eine vereinfachte antibiotische Leitstruktur wurde identifiziert.
      PubDate: 2017-06-29T07:45:37.755736-05:
      DOI: 10.1002/ange.201705539
       
  • Thermische Disproportionierung von Oxo-funktionalisiertem Graphen
    • Authors: Fabian Grote; Christoph Gruber, Felix Börrnert, Ute Kaiser, Siegfried Eigler
      Pages: 9350 - 9353
      Abstract: Die nasschemische Synthese von Graphen ist nach wie vor eine Herausforderung. Ein Weg führt über die kontrollierte Oxidation von Graphit unter Einführung sauerstoffhaltiger funktioneller Gruppen. Dadurch entsteht ein Material, das nach reduktiver Defunktionalisierung Graphen liefert. Obwohl die thermische Verarbeitung zu leitfähigem Kohlenstoff führt, wird das Kohlenstoffgerüst als Folge der Bildung von CO2 aufgebrochen. Hier untersuchen wir die thermische Verarbeitung von Oxo-funktionalisiertem Graphen (oxo-G) mit niedrigem (4–6 %) oder hohem Funktionalisierungsgrad (50–60 %). Aus Raman-spektroskopischen Untersuchungen und mittels Transmissionselektronenspektroskopie bei atomarer Auflösung (HRTEM) finden wir, dass die thermische Verarbeitung überwiegend zu einem intakten hexagonalen Kohlenstoffgerüst führt. Dabei liegt die Defektdichte bei 0.8 %. Wir schließen auf eine Reorganisation sauerstoffhaltiger Gruppen. Dieser Befund stellt die thermische Graphenherstellung aus oxo-G-Derivaten in Aussicht.Thermisch behandelt: Graphen kann aus Oxo-funktionalisiertem Graphen durch Erhitzen hergestellt werden. Die Defunktionalisierung zu Graphen (Weg I) ist der Hauptweg.
      PubDate: 2017-06-30T06:00:41.271097-05:
      DOI: 10.1002/ange.201704419
       
  • Ringöffnende 1-Amino-3-aminomethylierung von
           Donor-Akzeptor-substituierten Cyclopropanen über 1,3-Diazepane
    • Authors: Lennart K. B. Garve; Peter G. Jones, Daniel B. Werz
      Pages: 9354 - 9358
      Abstract: Die erste Ringöffnungsreaktion von Donor-Akzeptor-Cyclopropanen zu Diaminen wird beschrieben. Die entwickelte 1,3-Difunktionalisierung nutzt Cyclopropane und Triazinane sowie Sc(OTf)3 als Katalysator, gefolgt von einer anschließenden Umsetzung mit Säure. Die Reaktion verläuft unter sehr milden Bedingungen und toleriert eine Vielzahl an funktionellen Gruppen. Darüber hinaus konnte eine Bibliothek an verschiedenen 1,3-Diazepanen synthetisiert werden, die als Intermediat bei der Aza-[4+3]-Cycloaddition mit Donor-Akzeptor-Cyclopropanen auftreten.Doppelte Aminierung: Donor-Akzeptor-substituierte Cyclopropane konnten unter Scandium-Katalyse selektiv mit Triazinanen umgesetzt und unter leicht sauren Bedingungen zu Diaminen geöffnet werden. Zudem wurde eine Bibliothek von verschiedenen 1,3-Diazepanen synthetisiert, die als Intermediate in diesen formalen Aza-[4+3]-Cycloadditionen auftraten.
      PubDate: 2017-06-28T06:07:20.106718-05:
      DOI: 10.1002/ange.201704619
       
  • 1,4-Diphosphinine aus Imidazol-2-thionen
    • Authors: Abhishek Koner; Gregor Pfeifer, Zsolt Kelemen, Gregor Schnakenburg, László Nyulászi, Takahiro Sasamori, Rainer Streubel
      Pages: 9359 - 9363
      Abstract: 1,4-Diphosphinine, substituiert mit zwei Thioharnstoff-Gruppen, wurden aus tricyclischen 1,4-Dichlor-1,4-dihydro-1,4-diphosphininen synthetisiert. Ihre Strukturen und spektroskopischen Eigenschaften werden beschrieben. Elektrochemische Untersuchungen zeigen sehr niedrige Oxidationspotentiale, bedingt durch effektive π-Wechselwirkungen zwischen dem 1,4-Diphosphinin-Ring und den Orbitalen der beiden ylidischen C=S-Bindungen. In Übereinstimmung mit dem niedrig liegenden LUMO, das größtenteils an den zwei Phosphorzentren lokalisiert ist, wird die Dianion-Bildung stark bevorzugt. Trotz des kleinen HOMO-LUMO-Abstands, der in Einklang mit der roten Farbe der Titelverbindung ist, legen theoretische Rechnungen eine beträchtliche Aromatizität des 1,4-Diphosphinin-Ringes nahe.Tricyclische 1,4-Diphosphinine (II), substituiert mit zwei Thioharnstoff-Gruppen, wurden aus 1,4-Dichlor-1,4-dihydro-1,4-diphosphininen (I) synthetisiert. Ihre Strukturen und spektroskopischen Eigenschaften wurden untersucht, wobei ihre niedrigen Oxidationspotentiale und die große Elektronenaffinität wichtige elektrochemische Eigenschaften darstellen. Die spektroskopischen Eigenschaften und Rechnungen verweisen auf eine beträchtliche Aromatizität.
      PubDate: 2017-06-28T06:07:12.32039-05:0
      DOI: 10.1002/ange.201704070
       
  • Herstellung fester polyfunktioneller Alkinylzinkpivalate mit verbesserter
           Luft- und Feuchtigkeitsstabilität
    • Authors: Yi-Hung Chen; Carl Phillip Tüllmann, Mario Ellwart, Paul Knochel
      Pages: 9364 - 9368
      Abstract: Die Umsetzung von Alkinen mit TMPZnOPiv (TMP=2,2,6,6-Tetramethylpiperidyl) als Base liefert die entsprechenden festen und luftstabilen Alkinylzinkpivalate. Diese Organozinkpivalate werden als Pulver unter milden Bedingungen in exzellenten Ausbeuten gewonnen und können an Luft für mehrere Stunden ohne signifikante Zersetzung gehandhabt werden. Die Alkinylzinkpivalate zeigen exzellente Reaktivität in verschiedenen C-C-Verknüpfungsreaktionen und in 1,3-dipolaren Cycloadditionen. Diese Zinkreagenzien wurden verwendet, um ein Carboxyamidotriazol mit potenzieller antineoplastischer Aktivität in 8 Schritten in 38 % Gesamtausbeute herzustellen.Feste polyfunktionelle Alkinylzinkpivalate mit verbesserter Luft- und Feuchtigkeitsstabilität reagieren in Pd-katalysierten Negishi-Kreuzkupplungen und Fukuyama-Acylierungen sowie in kupferkatalysierten Allylierungen und liefern trisubstituierte Triazole über 1,3-dipolare Cycloadditionen. Eine Vierkomponentenreaktion führt zu einem potenziellen antineoplastischen Wirkstoff (38 % Gesamtausbeute über 8 Schritte).
      PubDate: 2017-06-27T06:13:34.393371-05:
      DOI: 10.1002/ange.201704400
       
  • Innenrücktitelbild: Direct Mechanism of the First Carbon–Carbon Bond
           Formation in the Methanol-to-Hydrocarbons Process (Angew. Chem. 31/2017)
    • Authors: Xinqiang Wu; Shutao Xu, Wenna Zhang, Jindou Huang, Jinzhe Li, Bowen Yu, Yingxu Wei, Zhongmin Liu
      Pages: 9369 - 9369
      Abstract: Der erste C-C-Verknüpfungsschritt bei der Umwandlung von Methanol in Kohlenwasserstoffe über Zeolithkatalysatoren wird seit 30 Jahren kontrovers diskutiert. In ihrer Zuschrift auf S. 9167 ff. schlagen Z. Liu, Y. Wei et al. einen Mechanismus für diesen Schritt vor. Ihr Postulat gründet auf dem Nachweis einer Methylenoxy-analogen Oberflächenspezies, gebildet aus aktiviertem Dimethylether oder Methanol, durch In-situ-Festkörper-NMR-Spektroskopie.
      PubDate: 2017-06-16T03:16:06.029609-05:
      DOI: 10.1002/ange.201705757
       
  • Rücktitelbild: A Modular Approach to Inorganic Phosphazane
           Macrocycles (Angew. Chem. 31/2017)
    • Authors: Alex J. Plajer; Raúl García-Rodríguez, Callum G. M. Benson, Peter D. Matthews, Andrew D. Bond, Sanjay Singh, Lutz H. Gade, Dominic S. Wright
      Pages: 9370 - 9370
      Abstract: Organische Chemie trifft Makrocyclenchemie:Die Bildung von großen anorganischen Makrocyclen mit über Schwefel- oder Selenatome verknüpften Phosphazan-Einheiten gelingt mit einer Eintopfmethode, die D. S. Wright et al. in der Zuschrift auf S. 9215 ff. beschreiben. Vielfältige organische Substituenten können eingeführt werden, sodass die gezielte Abstimmung der sterischen und elektronischen Eigenschaften erleichtert ist. Die Methode stellt einen wichtigen Schritt in der Entwicklung von Syntheseverfahren für anorganische Makromoleküle dar.
      PubDate: 2017-06-20T07:42:34.566009-05:
      DOI: 10.1002/ange.201705956
       
 
 
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