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  Subjects -> CHEMISTRY (Total: 849 journals)
    - ANALYTICAL CHEMISTRY (47 journals)
    - CHEMISTRY (604 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (65 journals)

CHEMISTRY (604 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 6)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 25)
ACS Catalysis     Full-text available via subscription   (Followers: 29)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 16)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 24)
ACS Macro Letters     Full-text available via subscription   (Followers: 22)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 36)
ACS Nano     Full-text available via subscription   (Followers: 197)
ACS Photonics     Full-text available via subscription   (Followers: 8)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 20)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 8)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 1)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 4)
Advanced Functional Materials     Hybrid Journal   (Followers: 45)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 52)
Advances in Chemical Science     Open Access   (Followers: 11)
Advances in Chemistry     Open Access   (Followers: 11)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 17)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 8)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 13)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 16)
Advances in Nanoparticles     Open Access   (Followers: 12)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 17)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 7)
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)
Alchemy : Jurnal Penelitian Kimia     Open Access  
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 65)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 24)
American Journal of Plant Physiology     Open Access   (Followers: 12)
American Mineralogist     Full-text available via subscription   (Followers: 8)
Anadolu University Journal of Science and Technology     Open Access  
Analyst     Full-text available via subscription   (Followers: 42)
Angewandte Chemie     Hybrid Journal   (Followers: 144)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 193)
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: 7)
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: 6)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 23)
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: 6)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemistry     Full-text available via subscription   (Followers: 253)
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: 3)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 114)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 99)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 17)
Biosensors     Open Access   (Followers: 1)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 26)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 2)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 8)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 64)
Catalysis for Sustainable Energy     Open Access   (Followers: 5)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 6)
Cellulose     Hybrid Journal   (Followers: 5)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 11)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 71)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 21)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 18)
Chemical Reviews     Full-text available via subscription   (Followers: 155)
Chemical Science     Open Access   (Followers: 19)
Chemical Technology     Open Access   (Followers: 14)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 53)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 5)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 4)
Chemistry - A European Journal     Hybrid Journal   (Followers: 126)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 14)
Chemistry and Materials Research     Open Access   (Followers: 15)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 4)
Chemistry in Education     Open Access   (Followers: 3)
Chemistry International     Hybrid Journal   (Followers: 1)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 164)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
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: 8)
ChemPlusChem     Hybrid Journal   (Followers: 1)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 3)
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: 8)
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: 1)
Composite Interfaces     Hybrid Journal   (Followers: 5)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 1)
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: 10)
Current Catalysis     Hybrid Journal   (Followers: 1)
Current Metabolomics     Hybrid Journal   (Followers: 3)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 8)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 15)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 46)
Dalton Transactions     Full-text available via subscription   (Followers: 18)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 11)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 3)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 2)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EDUSAINS     Open Access  
Elements     Full-text available via subscription   (Followers: 1)
Environmental Chemistry     Hybrid Journal   (Followers: 5)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 2)

        1 2 3 4 | Last

Journal Cover Angewandte Chemie
  [144 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  [1605 journals]
  • Fulvene Synthesis by Rhodium(I)-Catalyzed [2+2+1] Cycloaddition: Synthesis
           and Catalytic Activity of Tunable Cyclopentadienyl Rhodium(III) Complexes
           with Pendant Amides
    • Authors: Soichi Yoshizaki; Yu Shibata, Ken Tanaka
      Abstract: It has been established that a RhI+/segphos complex catalyzes the [2+2+1] cycloaddition of 1,6-diynes with cyclopropylideneacetamides to give substituted fulvenes in good yields. The reductive complexation of the product fulvenes with RhCl3 in EtOH furnished the corresponding dinuclear cyclopentadienyl RhIII complexes bearing a pendant amide moiety. These RhIII complexes were highly active catalysts for oxidative annulation and cyclization through C(sp2)−H and C(sp3)−H functionalization.Ful-minante Reaktion: Ein RhI+/segphos-Komplex katalysiert die [2+2+1]-Cycloaddition von 1,6-Diinen mit Cyclopropylidenacetamiden zur Bildung von substituierten Fulvenen. Die reduktive Komplexierung dieser Produkte mit RhCl3 in EtOH liefert die entsprechenden zweikernigen Cyclopentadienyl-RhIII-Komplexe (siehe Schema), die hoch aktive Katalysatoren für oxidative Anellierungen und Cyclisierungen über C(sp2)-H- und C(sp3)-H-Funktionalisierungen sind.
      PubDate: 2017-02-20T08:55:31.899677-05:
      DOI: 10.1002/ange.201612590
       
  • Catalytic Reaction Rates Controlled by Metal Oxidation State: C−H Bond
           Cleavage in Methane over Nickel-Based Catalysts
    • Authors: Fanglin Che; Su Ha, Jean-Sabin McEwen
      Abstract: Reiten auf einer Welle aus Positivität: Die C-H-Aktivierung von Methan an Nickelclustern wird durch niedrig konzentrierten Oberflächenkohlenstoff, Grenzflächen-Carbidspezies oder eine Erhöhung der lokalen Oxidationsstufe von Nickel als Reaktion auf ein positives elektrisches Feld begünstigt. In ihrer Zuschrift (
      DOI : 10.1002/ange.201611796) bieten J.-S. McEwen, S. Ha und F. Che grundlegende Einblicke in die Rolle von Oberflächenkohlenstoff und elektrischem Feld als Teil eines elektrochemischen Systems zur Kohlenwasserstoffkonversion.
      PubDate: 2017-02-20T08:50:27.774319-05:
       
  • Neue Polymere: schöne Strukturen, aber wie bringt man sie in den
           Markt?
    • Authors: Brigitte Voit
      Abstract: … Kein Polymerwissenschaftler zweifelt daran, dass Polymere die Materialien des 21. Jahrhunderts sind, die Entwicklung von Zukunftstechnologien voranbringen und unseren Lebensstandard und unser Wohlbefinden im Kontext einer alternden Bevölkerung und der Energiewende garantieren. Jedoch muss man zwischen Polymer und Kunststoff (plastics) unterscheiden … Welche Konsequenzen diese Sicht hat, lesen Sie im Gast-Editorial von Brigitte Voit.
      PubDate: 2017-02-20T08:50:25.260319-05:
      DOI: 10.1002/ange.201700811
       
  • Understanding of Strain Effect in Electrochemical Reduction of CO2: Using
           Pd Nanostructures as an Ideal Platform
    • Authors: Hongwen Huang; Huanhuan Jia, Zhao Liu, Pengfei Gao, Jiangtao Zhao, Zhenlin Luo, Jinlong Yang, Jie Zeng
      Abstract: Tuning the surface strain of heterogeneous catalysts represents a powerful strategy to engineer their catalytic properties by altering the electronic structures. However, a clear and systematic understanding of strain effect in electrochemical reduction of carbon dioxide is still lacking, which restricts the use of surface strain as a tool to optimize the performance of electrocatalysts. Herein, we demonstrate the strain effect in electrochemical reduction of CO2 by using Pd octahedra and icosahedra with similar sizes as a well-defined platform. The Pd icosahedra/C catalyst shows a maximum Faradaic efficiency for CO production of 91.1 % at −0.8 V versus reversible hydrogen electrode (vs. RHE), 1.7-fold higher than the maximum Faradaic efficiency of Pd octahedra/C catalyst at −0.7 V (vs. RHE). The combination of molecular dynamic simulations and density functional theory calculations reveals that the tensile strain on the surface of icosahedra boosts the catalytic activity by shifting up the d-band center and thus strengthening the adsorption of key intermediate COOH*. This strain effect was further verified directly by the surface valence-band photoemission spectra and electrochemical analysis.Dranbleiben, wenn's spannend wird: Pd-Oktaeder und -Ikosaeder ähnlicher Größe dienen als definiertes Untersuchungssystem für den Einfluss von Oberflächenspannung auf die elektrochemische CO2-Reduktion. Dabei zeigt sich, dass Zugbelastung die katalytische Aktivität erhöht, indem das Zentrum der d-Bande verschoben und somit die Adsorption des Schlüsselintermediats COOH* verstärkt wird.
      PubDate: 2017-02-20T03:10:29.26492-05:0
      DOI: 10.1002/ange.201612617
       
  • Detection of Palladium(I) in Aerobic Oxidation Catalysis
    • Authors: Jonathan N. Jaworski; Scott D. McCann, Ilia A. Guzei, Shannon S. Stahl
      Abstract: Palladium(II)-catalyzed oxidation reactions exhibit broad utility in organic synthesis; however, they often feature high catalyst loading and low turnover numbers relative to non-oxidative cross-coupling reactions. Insights into the fate of the Pd catalyst during turnover could help to address this limitation. Herein, we report the identification and characterization of a dimeric PdI species in two prototypical Pd-catalyzed aerobic oxidation reactions: allylic C−H acetoxylation of terminal alkenes and intramolecular aza-Wacker cyclization. Both reactions employ 4,5-diazafluoren-9-one (DAF) as an ancillary ligand. The dimeric PdI complex, [PdI(μ-DAF)(OAc)]2, which features two bridging DAF ligands and two terminal acetate ligands, has been characterized by several spectroscopic methods, as well as single-crystal X-ray crystallography. The origin of this PdI complex and its implications for catalytic reactivity are discussed.Katalysator-Dimerisierung wird bei palladiumkatalysierten aeroben allylischen C-H-Acetoxylierungen und Aza-Wacker-Cyclisierungen beobachtet. Eine neue PdI-Spezies, die eindeutig in diesen katalytischen Prozessen charakterisiert wurde, gibt Einblicke in die Katalysatordesaktivierung und Anregungen für die Entwicklung von Palladiumkatalysatoren.
      PubDate: 2017-02-20T03:00:36.230174-05:
      DOI: 10.1002/ange.201700345
       
  • Authors Profile
    • PubDate: 2017-02-20T03:00:24.626595-05:
      DOI: 10.1002/ange.201700715
       
  • Frontispiz: Double Concave Cesium Encapsulation by Two Charged Sumanenyl
           Bowls
    • Authors: Sarah N. Spisak; Zheng Wei, Andrey Yu. Rogachev, Toru Amaya, Toshikazu Hirao, Marina A. Petrukhina
      Abstract: Doppelt konkave EinkapselungIn der Zuschrift auf S. 2625 ff. beschreiben A. Yu. Rogachev, T. Hirao, M. A. Petrukhina et al. die doppelt konkave Einkapselung eines Metallions durch zwei schalenförmige Sumanenyl-Carbanionen. Die ungewöhnliche [Cs(C21H11−)2]−-Spezies wurde kristallographisch identifiziert.
      PubDate: 2017-02-17T08:36:14.919981-05:
      DOI: 10.1002/ange.201781061
       
  • Palladium-Catalyzed Direct Stereoselective Synthesis of Deoxyglycosides
           from Glycals
    • Authors: Abhijit Sau; Ryan Williams, Carlos Palo-Nieto, Antonio Franconetti, Sandra Medina, M. Carmen Galan
      Abstract: Palladium(II) in combination with a monodentate phosphine ligand enables the unprecedented direct and α-stereoselective catalytic synthesis of deoxyglycosides from glycals. Initial mechanistic studies suggest that in the presence of N-phenyl-2-(di-tert-butylphosphino)pyrrole as the ligand, the reaction proceeds via an alkoxy palladium intermediate that increases the proton acidity and oxygen nucleophilicity of the alcohol. The method is demonstrated with a wide range of glycal donors and acceptors, including substrates bearing alkene functionalities.Ein Katalysatorsystem aus Palladium(II) und einem einzähnigen Phosphanliganden ermöglicht die direkte, α-stereoselektive katalytische Synthese von Desoxyglykosiden aus Glykalen. Mechanistischen Studien zufolge verläuft die Reaktion in Gegenwart von N-Phenyl-2-(di-tert-butylphosphanyl)pyrrol über ein Alkoxypalladium-Intermediat, das die Protonenacidität und Sauerstoffnucleophilie des Alkohols erhöht.
      PubDate: 2017-02-17T04:45:37.476334-05:
      DOI: 10.1002/ange.201612071
       
  • One-Pot Assembly of Amino Acid Bridged Hybrid Macromulticyclic Cages
           through Multiple Multicomponent Macrocyclizations
    • Authors: Ludger A. Wessjohann; Oliver Kreye, Daniel G. Rivera
      Abstract: An important development in the field of macrocyclization strategies towards molecular cages is described. The approach comprises the utilization of a double Ugi four-component macrocyclization for the assembly of macromulticycles with up to four different tethers, that is, hybrid cages. The innovation of this method rests on setting up the macromulticycle connectivities not through the tethers but through the bridgeheads, which in this case involve N-substituted amino acids. Both dilution and metal-template-driven macrocyclization conditions were implemented with success, enabling the one-pot formation of cryptands and cages including steroidal, polyether, heterocyclic, peptidic, and aryl tethers. This method demonstrates substantial complexity-generating character and is suitable for applications in molecular recognition and catalysis.Vier gewinnt: Eine neue Multimakrocyclisierungs-Strategie ermöglicht durch reaktionsbasierte Selbstorganisation die Eintopf-Mehrkomponentensynthese hybrider Molekülkäfige. Unter Verdünnung oder durch Metalltemplat-gesteuerte Makrocyclisierung wurde bei geringen Synthesekosten in einer Vierkomponentenreaktion (4CR) effizient eine hohe Komplexität bei den entstehenden Polycyclen erzielt.
      PubDate: 2017-02-17T04:45:33.033202-05:
      DOI: 10.1002/ange.201610801
       
  • Low-Temperature Anharmonicity in Cesium Chloride (CsCl)
    • Authors: Mattia Sist; Karl Frederik Færch Fischer, Hidetaka Kasai, Bo Brummerstedt Iversen
      Abstract: Anharmonic lattice vibrations govern heat transfer in materials, and anharmonicity is commonly assumed to be dominant at high temperature. The textbook cubic ionic defect-free crystal CsCl is shown to have an unexplained low thermal conductivity at room temperature (ca. 1 W/(m K)), which increases to around 13  W/(m K) at 25 K. Through high-resolution X-ray diffraction it is unexpectedly shown that the Cs atomic displacement parameter becomes anharmonic at 20 K.Kalt erwischt: Bei Raumtemperatur zeigt Caesiumchlorid eine sehr geringe Wärmeleitfähigkeit, die aber bei tieferen Temperaturen ansteigt. Durch hochauflösende Einkristallröntgenbeugung wurde unerwartet ein Anstieg der Anharmonizität unterhalb von 100 K aufgedeckt.
      PubDate: 2017-02-17T04:42:18.3683-05:00
      DOI: 10.1002/ange.201700638
       
  • Ein stabiles Hexakis(guanidino)benzol: Synthese des stärksten neutralen
           organischen Vier-Elektronen-Donors
    • Authors: Benjamin Eberle; Elisabeth Kaifer, Hans-Jörg Himmel
      Abstract: Die wachsende Nachfrage nach effizienten Batterien hat die Suche nach redoxaktiven organischen Verbindungen mit mehrstufigem Redoxverhalten als Materialien mit großer Ladungskapazität angeregt. Wir berichten hier über die Synthese und Eigenschaften des ersten Hexakis(guanidino)benzol-Derivats, eines starken neutralen organischen Elektronendonors mit reversiblem mehrstufigem Redoxverhalten und dem niedrigsten bekannten Redoxpotential für die Abgabe von vier Elektronen. Die detaillierte strukturelle und spektroskopische Charakterisierung dreier Redoxzustände (0, +2 und +4) belegt dessen einzigartigen elektronischen Eigenschaften. Trotz ihres Stickstoffreichtums ist die Verbindung thermisch stabil und lässt sich durch Sublimation reinigen.Mehrstufiger Elektronendonor: Das erste Hexakis(guanidino)benzol-Derivat gibt vier Elektronen beim niedrigsten bekannten Redoxpotential ab.
      PubDate: 2017-02-17T04:42:11.29285-05:0
      DOI: 10.1002/ange.201611189
       
  • Hydronium-Ion Batteries with Perylenetetracarboxylic Dianhydride Crystals
           as an Electrode
    • Authors: Xingfeng Wang; Clement Bommier, Zelang Jian, Zhifei Li, Raghu S. Chandrabose, Ismael A. Rodríguez-Pérez, P. Alex Greaney, Xiulei Ji
      Abstract: Eine saure wässrige Lösung als Elektrolyt in einer Hydroniumionen-Batterie mit H3O+ als Ladungsträger: X. L. Ji et al. bieten in ihrer Zuschrift (
      DOI : 10.1002/ange.201700148) Belege dafür, dass Hydroniumionen reversibel in 3,4,9,10-Perylentetracarbonsäuredianhydrid (PTCDA) inseriert und aus ihm extrahiert werden können. Die Expansion und Kontraktion des PTCDA-Gerüsts entspricht der H3O+-Interkalation bzw. -Deinterkalation, wie Ex-situ-Röntgenbeugungsstudien und Dichtefunktionalrechnungen ergaben.
      PubDate: 2017-02-17T04:35:28.83337-05:0
       
  • Photoelectrochemical Reduction of Carbon Dioxide to Methanol through a
           Highly Efficient Enzyme Cascade
    • Authors: Su Keun Kuk; Raushan K Singh, Dong Heon Nam, Ranjitha Singh, Jung-Kul Lee, Chan Beum Park
      Abstract: Ein künstliches Photosynthesesystem wurde durch Kombination einer photoelektrochemischen Zelle mit einer Multienzymkaskade konstruiert. J. K. Lee, C. B. Park und Mitarbeiter nutzen in ihrer Zuschrift (
      DOI : 10.1002/ange.201611379) Wasser als Elektronendonor, eine Hämatit-Photoanode und eine Bismutferrit-Photokathode zur Regenerierung von NADH mit sichtbarem Licht sowie eine Kaskade aus drei Dehydrogenasen für die hoch selektive und schnelle Umwandlung von Kohlendioxid in Methanol.
      PubDate: 2017-02-17T02:50:48.967835-05:
       
  • Energy Transfer Dynamics of Formate Decomposition on Cu(110)
    • Authors: Jiamei Quan; Takahiro Kondo, Guichang Wang, Junji Nakamura
      Abstract: Molekulare Metamorphose: Bei der thermischen Zersetzung von Formiat wird eine große Menge an Energie freigesetzt, die in innere Energie von CO2 umgewandelt wird. In ihrer Zuschrift (
      DOI : 10.1002/ange.201611342) beschreiben J. Nakamura et al., wie naszierende CO2-Moleküle von einer Kupferoberfläche desorbieren, wobei sie Translations- und Schwingungsenergie mitnehmen – wie frisch geschlüpfte Schmetterlinge, die sich mit ihren ersten Flügelschlägen von einem Zweig in die Lüfte erheben. Der Berg im Hintergrund versinnbildlicht die Energetik der Formiat-Zersetzung.
      PubDate: 2017-02-17T02:50:41.110899-05:
       
  • Katalytisch-asymmetrische intramolekulare [4+2]-Cycloaddition von
           in situ generierten ortho-Chinonmethiden
    • Authors: Youwei Xie; Benjamin List
      Abstract: Die erste katalytisch-asymmetrische intramolekulare [4+2]-Cycloaddition von in situ generierten ortho-Chinonmethiden wurde entwickelt. Katalysiert durch eine abgeschirmte chirale Imidodiphosphorsäure, reagieren diverse Salicylaldehyde mit Dienylalkoholen zu kurzlebigen ortho-Chinonmethid-Intermediaten, die durch intramolekulare [4+2]-Cycloaddition zu hoch funktionalisierten Furan- und Pyranchromanen mit exzellenten Diastereo- und Enantioselektivitäten umgewandelt werden.Chromansynthese: Eine neue organokatalytische asymmetrische intramolekulare [4+2]-Cycloaddition verläuft über in situ generierte ortho-Chinonmethide. In Gegenwart eines chiralen Imidodiphosphorsäure-Katalysators (HX*) reagierten verschiedene Salicylaldehyde mit Dienylalkoholen zu hoch funktionalisierten Furanchromanen und Pyranchromanen mit exzellenten Diastereo- und Enantioselektivitäten.
      PubDate: 2017-02-17T02:50:39.328469-05:
      DOI: 10.1002/ange.201612149
       
  • Applications of the Wittig-Still rearrangement in organic synthesis
    • Authors: Lukas Rycek; Tomas Hudlicky
      Abstract: This review traces the discovery of the Wittig-Still rearrangement and its applications in organic synthesis. Its relationship to Wittig rearrangements is discussed along with detailed analysis of E/Z- and diastereoselectivity. Modifications of the products arising from the Wittig-Still rearrangement are reviewed in the context of increased complexity in intermediates potentially useful in target oriented synthesis. Early applications of the Wittig-Still rearrangement to modifications of steroids are reviewed as are applications to various terpene and alkaloid natural product targets and miscellaneous compounds. To the best of our knowledge, the literature is covered through December 2016.
      PubDate: 2017-02-16T22:00:28.05727-05:0
      DOI: 10.1002/ange.201611329
       
  • Enantioselective Aza-Ene-type Reactions of Enamides with Gold Carbenes
           Generated from α-Diazoesters
    • Authors: Feng Zhao; Nan Li, Tao Zhang, Zhi-Yong Han, Shi-Wei Luo, Liu-Zhu Gong
      Abstract: Carbophile Goldcarbene, die aus α-Diazoestern gewonnen wurden, reagieren mit Enamiden in einer neuen Aza-En-artigen Reaktion. In ihrer Zuschrift (
      DOI : 10.1002/ange.201612208) zeigen S.-W. Luo, L.-Z. Gong et al., dass die Gegenwart von 0.1 Mol-% einer chiralen Brønsted-Säure ausreicht, um synthetisch interessante γ-Ketoester in exzellenten Ausbeuten und Enantioselektivitäten zu erhalten.
      PubDate: 2017-02-16T10:21:04.526188-05:
       
  • Carbonyls as Latent Alkyl Carbanions for Conjugate Additions
    • Authors: Xi-Jie Dai; Haining Wang, Chao-Jun Li
      Abstract: Conjugate addition of carbon nucleophiles to electron-deficient olefins is one of the most powerful methods for forming carbon–carbon bonds. Despite great achievements in controlling the selectivity, variation of the carbon nucleophiles remains largely underexplored, with this approach relying mostly on organometallic reagents. Herein, we report that naturally abundant carbonyls can act as latent carbon nucleophiles for conjugate additions through a ruthenium-catalyzed process, with water and nitrogen as innocuous byproducts. The key to our success is homogeneous ruthenium(II) catalysis, combined with phosphines as spectator ligands and hydrazine as the reducing agent. This chemistry allows the incorporation of highly functionalized alkyl fragments into a vast array of electron-deficient olefins under mild reaction conditions in a reaction complementary to the classical organometallic-reagent-based conjugate additions mediated or catalyzed by “soft” transition metals.Verborgene Talente: Carbonylverbindungen wirken als latente Kohlenstoffnucleophile für konjugierte Additionen über einen Ru-katalysierten Prozess. Die Reaktion beruht auf einer homogenen RuII-Katalyse mit Phosphanen als Zuschauerliganden und Hydrazin als Reduktionsmittel und ermöglicht den Einbau hoch funktionalisierter Alkylfragmente in elektronenarme Olefine unter milden Reaktionsbedingungen.
      PubDate: 2017-02-16T10:21:03.744909-05:
      DOI: 10.1002/ange.201700059
       
  • Visible-Light-Promoted Asymmetric Cross-Dehydrogenative Coupling of
           Tertiary Amines to Ketones by Synergistic Multiple Catalysis
    • Authors: Qi Yang; Long Zhang, Chen Ye, Sanzhong Luo, Li-Zhu Wu, Chen-Ho Tung
      Abstract: Reported herein is an unprecedented photocatalytic asymmetric cross-dehydrogenative coupling reaction between tertiary amines and simple ketones, and it proceeds by synergistic multiple catalysis with substoichiometric amounts of a hydrogen acceptor. This process is enabled by a simple chiral primary amine catalyst through the coupling of a catalytic enamine intermediate and an iminium cation intermediate in situ generated from tetrahydroisoquinoline derivatives by coupled Ru/Co catalysis.Gemeinschaftsproduktion: Synergistische Katalysezyklen ermöglichen die asymmetrische dehydrierende Kreuzkupplung von tertiären Aminen mit einfachen Ketonen unter Bestrahlung mit sichtbarem Licht. Der hoch diastereo- und enantioselektive Prozess nutzt ein chirales primäres Amin als Katalysator und beruht auf der Kupplung eines intermediären Enamins mit einem Iminiumkation, das in situ aus einem Tetrahydroisochinolin-Derivat unter Ru/Co-Katalyse erzeugt wird.
      PubDate: 2017-02-16T10:21:01.904808-05:
      DOI: 10.1002/ange.201700572
       
  • Palladium-Catalyzed Oxidative Cascade Carbonylative Spirolactonization of
           Enallenols
    • Authors: Youai Qiu; Bin Yang, Tuo Jiang, Can Zhu, Jan-E. Bäckvall
      Abstract: A highly selective palladium-catalyzed oxidative carbonylation/carbocyclization/alkoxycarbonylation of enallenols to afford spirolactones bearing an all-carbon quaternary center was developed. This transformation involves the overall formation of three C−C bonds and one C−O bond through a cascade insertion of carbon monoxide (CO), an olefin, and CO. Preliminary experiments on chiral anion-induced enantioselective carbonylation/carbocyclization of enallenols afforded spirolactones with moderate enantioselectivity.Plus zwei CO: Eine hoch selektive Reaktionskaskade zur C-C/C-O-Verknüpfung durch palladiumkatalysierte oxidative Carbonylierung, Carbocyclisierung und Alkoxycarbonylierung von Enallenolen liefert Spirolactone mit einem vollständig kohlenstoffsubstituierten quartären Zentrum. In Ansätzen zur enantioselektiven carbonylierende Carbocyclisierung erwies sich eine chirale Phosphorsäure vom VAPOL-Typ als guter anionischer Kokatalysator.
      PubDate: 2017-02-16T10:20:58.711433-05:
      DOI: 10.1002/ange.201612384
       
  • (Aminomethyl)pyridine Complexes for the Cobalt-Catalyzed Anti-Markovnikov
           Hydrosilylation of Alkoxy- or Siloxy(vinyl)silanes with Alkoxy- or
           Siloxyhydrosilanes
    • Authors: Kangsang L. Lee
      Abstract: Cobalt-catalyzed anti-Markovnikov reactions that involve siloxy- or alkoxy(vinyl)silanes and siloxy- or alkoxyhydrosilanes are disclosed. More than 25 new cobalt–(aminomethyl)pyridine complexes were developed as catalysts for the hydrosilylation of industry-relevant and challenging siloxy- or alkoxy-terminated vinylsilanes. These transformations typically proceed in the presence of 0.25 mol % of the cobalt complex with 0.75 mol % of the alkylating agent to afford the desired products in up to >98 % yield with >98 % anti-Markovnikov selectivity in 30 min. The current protocol shows a broad substrate scope, delivering more than 25 siloxanes with siloxy or alkoxy functional groups at both termini, and can also be applied to polymeric vinyl- and hydrosiloxanes.Mehr als 25 Siloxane mit Siloxy- oder Alkoxygruppen als funktionellen Einheiten an beiden Enden werden mit einem Cobaltkatalysator, der sich von einem (Aminomethyl)pyridin-Liganden und CoBr2 ableitet, in hoher Ausbeute erhalten (siehe Schema). Dieser Ansatz eignet sich auch für die Hydrosilylierung polymerer Vinylsilane durch Hydrosilane bei der Herstellung von Silikonen.
      PubDate: 2017-02-16T10:20:57.060242-05:
      DOI: 10.1002/ange.201612460
       
  • Synthesis of Active Hexafluoroisopropyl Benzoates through
           Hydrogen-Bond-Enabled Palladium(II)-Catalyzed C−H Alkoxycarbonylation
           Reaction
    • Authors: Yang Wang; Vladimir Gevorgyan
      Abstract: A PdII-catalyzed ortho C−H alkoxycarbonylation reaction of aryl silanes toward active hexafluoroisopropyl (HFIP) benzoate esters has been developed. This efficient reaction features high selectivity and good functional-group tolerance. Notably, given the general nature of the silyl-tethered directing group, this method delivers products bearing two independently modifiable sites. NMR studies reveal the presence of hydrogen bonding between HFIP and a pyrimidine nitrogen atom of the directing group, and it is thought to be crucial for the success of this alkoxycarbonylation reaction.Aktiv werden: Die Titelreaktion von Arylsilanen zu aktiven Hexafluorisopropyl(HFIP)-Benzoesäureestern verläuft hoch selektiv, auch in Gegenwart von funktionellen Gruppen. Die Produkte enthalten zwei unabhängig voneinander modifizierbare Stellen. NMR-Studien belegen Wasserstoffbrücken zwischen HFIP und einem Pyrimidin-Stickstoffatom der dirigierenden Gruppe (DG), die als entscheidend für den Erfolg dieser Alkoxycarbonylierung betrachtet werden.
      PubDate: 2017-02-16T10:20:52.99035-05:0
      DOI: 10.1002/ange.201611757
       
  • Supramolecularly Engineered Amphiphilic Macromolecules: Molecular
           Interaction Overrules Packing Parameters
    • Authors: Prithankar Pramanik; Debes Ray, Vinod K. Aswal, Suhrit Ghosh
      Abstract: We report molecular interaction-driven self-assembly of supramolecularly engineered amphiphilic macromolecules (SEAM) containing a single supramolecular structure-directing unit (SSDU) consisting of an H-bonding group connected to a naphthalene diimide chromophore. Two such SEAMs, P1-50 and P2-50, having the identical chemical structure and hydrophobic/hydrophilic balance, exhibit distinct self-assembled structures (polymersome and cylindrical micelle, respectively) due to a difference in the H-bonding group (hydrazide or amide, respectively) of the single SSDU. When mixed together, P1-50 and P2-50 adopted self-sorted assembly. For either series of polymers, variation in the hydrophobic/hydrophilic balance does not alter the morphology reconfirming that self-assembly is primarily driven by directional molecular interaction which is capable of overruling the existing norms in packing parameter-dependent morphology control in an immiscibility-driven block copolymer assembly.Amphiphile Blockcopolymere: Eine gerichtete, molekulare Wechselwirkung setzt klassische Packungsparameter außer Kraft und steuert in neuer Form die Selbstorganisation von supramolekular entworfenen, amphiphilen Polymeraggregaten. Die Selbstorganisation wird durch ein spezifisches Wasserstoffbrückenmotiv dirigiert, das entlang der ganzen Polymerkette vorhanden ist.
      PubDate: 2017-02-16T10:20:48.788786-05:
      DOI: 10.1002/ange.201611715
       
  • Selective Arene Cleavage by Direct Insertion of Iridium into the Aromatic
           Ring
    • Authors: Martin Jakoobi; Nathan Halcovitch, George F. S. Whitehead, Alexey G. Sergeev
      Abstract: We report an unprecedented selective cleavage of aromatic C−C bonds through the insertion of well-defined iridium complexes into the aromatic ring of simple alkylarenes. The insertion occurs at 50–100 °C without the activation of weaker C−H and C−C bonds and gives unique metallacycles in high yields. Key to the success of this approach is metal-induced deformation of the arene ring, which creates temporary ring strain and promotes direct and selective insertion of the metal into the otherwise inert arene ring C−C bonds.Nur die Schwachen überleben: Bei der milden und selektiven Insertion eines Metallzentrums in einen Arenring spaltet das einfache Cp*Ir-Fragment starke aromatische C-C-Bindungen in Alkylarenen ohne Auswirkungen auf schwächere C-H- und C-C-Bindungen. Dies ist eine konzeptionell neue Art von Reaktivität mit potentieller Bedeutung für eine Reihe industrieller Prozesse, wie die Produktion von Chemikalien und Brennstoffen aus Kohle und pflanzlicher Biomasse.
      PubDate: 2017-02-16T10:20:45.15267-05:0
      DOI: 10.1002/ange.201611409
       
  • Michael Polanyi: Vater der chemischen Dynamik und des impliziten Wissens
    • Authors: Dudley R. Herschbach
      Abstract: Connecting Science and the Humanities war der Titel eines Symposiums über Michael Polanyi, das im Oktober 2016 an der Technischen Universität Berlin stattfand. Der Vortrag, den Herschbach bei dieser Gelegenheit hielt, ist die Grundlage des hier abgedruckten Essays. In ihm werden sowohl das wissenschaftliche Werk Polanyis als auch sein philosophisches Denken gewürdigt. Das nebenstehende Foto von ihm stammt aus dem Jahr 1931.
      PubDate: 2017-02-16T10:20:34.835258-05:
      DOI: 10.1002/ange.201610968
       
  • Die erste stereoselektive Totalsynthese eines dimeren γ-Lacton-
           anellierten Pyranonaphthochinons: (+)-γ-Actinorhodin
    • Authors: Markus Neumeyer; Reinhard Brückner
      Abstract: Uns gelang die erste Totalsynthese von einem isomerenreinen dimeren γ-Lacton-anellierten Pyranonaphthochinon, (+)-γ-Actinorhodin. Unsere elf Stufen umfassende Synthese nutzt zwei Mal ein Paar peri-ständiger Methoxygruppen als Mediatoren einer ungewöhnlichen Selektivitätssteuerung durch einen weit entfernten Brom- oder Iodsubstituenten. Dessen Sperrigkeit gaben die Methoxygruppen an die beiden Naphthalinpositionen weiter, an denen wir Ar-SE-Reaktionen vornahmen. Das ermöglichte bei einer Kernbromierung eine perfekte Regiokontrolle und bei einer Oxa-Pictet-Spengler-Cyclisierung die gewünschte Diastereokontrolle. Die Absolutkonfiguration unseres Zielmoleküls legte die Sharpless-Dihydroxylierung eines β,γ-ungesättigten Esters fest, der einer Heck-Kupplung entstammte. Sie ergab den γ-Hydroxylactonteil eines Bromnaphthalins, der als Substrat der Oxa-Pictet-Spengler-Reaktion fungierte. Zum γ-Actinorhodingerüst führte eine dimerisierende Suzuki-Kupplung.peri-Ständige Methoxygruppen als Mediatoren ermöglichten es weit entfernten Halogensubstituenten, bei elektrophilen Naphthalinfunktionalisierungen Regio- und Diastereokontrolle auszuüben. Das verhalf zu einem γ-Lacton-anellierten Pyrano(bromnaphthalin). Es wurde per Suzuki-Kupplung dimerisiert. Oxidation und Demethylierung führten nach insgesamt elf Stufen zu isomerenreinem totalsynthetischem (+)-γ-Actinorhodin.
      PubDate: 2017-02-16T10:20:29.89095-05:0
      DOI: 10.1002/ange.201611183
       
  • Energy Transfer Dynamics of Formate Decomposition on Cu(110)
    • Authors: Jiamei Quan; Takahiro Kondo, Guichang Wang, Junji Nakamura
      Abstract: Energy transfer dynamics of formate (HCOOa) decomposition on a Cu(110) surface has been studied by measuring the angle-resolved intensity and translational energy distributions of CO2 emitted from the surface in a steady-state reaction of HCOOH and O2. The angular distribution of CO2 shows a sharp collimation with the direction perpendicular to the surface, as represented by cosnθ (n=6). The mean translational energy of CO2 is measured to be as low as 100 meV and is independent of the surface temperature (Ts). These results clearly indicate that the decomposition of formate is a thermal non-equilibrium process in which a large amount of energy released by the decomposition reaction of formate is transformed into the internal energies of CO2 molecules. The thermal non-equilibrium features observed in the dynamics of formate decomposition support the proposed Eley–Rideal (ER)-type mechanism for formate synthesis on copper catalysts.Die CO2-Desorption bei der Formiat-Zersetzung in der stationären Reaktion von HCOOH mit O2 auf Cu(110) ist ein thermischer Nichtgleichgewichtsprozess. Bei der Formiat-Zersetzung wird eine große Menge der freiwerdenden Energie in interne Energie der CO2-Moleküle umgewandelt, was für einen Eley-Rideal-artigen Mechanismus der Formiat-Synthese auf Kupfer-Katalysatoren spricht.
      PubDate: 2017-02-16T10:20:25.253868-05:
      DOI: 10.1002/ange.201611342
       
  • Determining the Origin of Rate-Independent Chemoselectivity in CuAAC
           Reactions: An Alkyne-Specific Shift in Rate-Determining Step
    • Authors: Ciaran P. Seath; Glenn A. Burley, Allan J. B. Watson
      Abstract: We report a kinetic and spectroscopic analysis of alkyne-dependent chemoselectivity in the copper-catalyzed azide–alkyne click (CuAAC) reaction. Studies of six alkyne subtypes reveal that the rate-determining step (RDS) of an aromatic ynamine class is shifted from acetylide formation to the azide ligation/migratory insertion event allowing chemoselectivity independent of overall rate.Kehrtwendung: Eine kinetische Analyse der vom Alkin abhängigen Chemoselektivität in der Cu-katalysierten Azid-Alkin-Reaktion (CuAAC) wird vorgestellt. Untersuchungen von sechs Alkintypen ergeben, dass sich bei einer aromatischen Inaminklasse der geschwindigkeitsbestimmende Schritt (RDS) von der Acetylidbildung zur Azidligation/migratorischen Insertion verschiebt, woraus eine von der Gesamtgeschwindigkeit unabhängige Selektivität resultiert.
      PubDate: 2017-02-16T05:35:44.718361-05:
      DOI: 10.1002/ange.201612288
       
  • Template-Assisted meta-C−H Alkylation and Alkenylation of Arenes
    • Authors: Sukdev Bag; Ramasamy Jayarajan, Rahul Mondal, Debabrata Maiti
      Abstract: To expand the scope of meta-functionalization, a pyrimidine-based template effective for the formation of β-aryl aldehydes and ketones, using allyl alcohols, by meta-C−H activation of benzylsulfonyl esters is described. In addition, α,β-unsaturated aldehydes were generated by in situ olefination and deprotection of allyl benzyl ethers. These new functionalizations at the meta-position of an arene have also been successfully implemented in benzylphosphonate, phenethyl carbonyl, and phenethylsulfonyl ester scaffolds. Key to these successful new functionalizations is the creation of an electropositive palladium center by accepting the electron cloud from the metal to the energetically low-lying π-orbitals of pyrimidine ring, and it favors coordination of allyl alcohol to the metal center.Zielgenau: Die durch Pyrimidin-Template unterstützte meta-C-H-Alkylierung und -Alkenylierung mit Allylalkoholen und geschützten Allylalkoholen gelingt mit Sulfonyl-, Carbonyl- und Phosphonylester-Gruppen als Linkern zwischen der dirigierenden Gruppe (DG) und der anvisierten meta-C-H-Bindung am Arenring.
      PubDate: 2017-02-16T05:35:38.256891-05:
      DOI: 10.1002/ange.201611360
       
  • Patchy Nanofibers from the Thin Film Self-Assembly of a Conjugated Diblock
           Copolymer
    • Authors: Emily L. Kynaston; Yuan Fang, Joseph G. Manion, Nimrat K. Obhi, Jane Y. Howe, Dmitrii F. Perepichka, Dwight S. Seferos
      Abstract: An unexpected morphology comprising patchy nanofibers can be accessed from the self-assembly of an all-conjugated, polyselenophene-block-polythiophene copolymer. This morphology consists of very small (
      PubDate: 2017-02-16T05:35:32.106995-05:
      DOI: 10.1002/ange.201700134
       
  • Outer-Sphere 2 e−/2 H+ Transfer Reactions of Ruthenium(II)-Amine and
           Ruthenium(IV)-Amido Complexes
    • Authors: Mauricio Cattaneo; Scott A. Ryken, James M. Mayer
      Abstract: A diverse set of 2 e−/2 H+ reactions are described that interconvert [RuII(bpy)(en*)2]2+ and [RuIV(bpy)(en-H*)2]2+ (bpy=2,2′-bipyridine, en*=H2NCMe2CMe2NH2, en*-H=H2NCMe2CMe2NH−), forming or cleaving different O−H, N−H, S−H, and C−H bonds. The reactions involve quinones, hydrazines, thiols, and 1,3-cyclohexadiene. These proton-coupled electron transfer reactions occur without substrate binding to the ruthenium center, but instead with precursor complex formation by hydrogen bonding. The free energies of the reactions vary over more than 90 kcal mol−1, but the rates are more dependent on the type of X−H bond involved than the associated ΔG°. There is a kinetic preference for substrates that have the transferring hydrogen atoms in close proximity, such as ortho-tetrachlorobenzoquinone over its para-isomer and 1,3-cyclohexadiene over its 1,4-isomer, perhaps hinting at the potential for concerted 2 e−/2 H+ transfers.Mehrelektronenredoxprozesse sind von zentraler Bedeutung für viele Anwendungen in der Katalyse und Energiespeicherung. Die vorgestellten 2 e−/2 H+-Reaktionen von Substraten, die zwei O-H-, N-H-, S-H- oder C-H-Bindungen bilden oder enthalten, wandeln RuII-Bis(amin)- und RuIV-Bis(amido)-Komplexe ineinander um.
      PubDate: 2017-02-16T05:25:32.283583-05:
      DOI: 10.1002/ange.201612642
       
  • Palladium-Mediated Arylation of Lysine in Unprotected Peptides
    • Authors: Hong Geun Lee; Guillaume Lautrette, Bradley L. Pentelute, Stephen L. Buchwald
      Abstract: A mild method for the arylation of lysine in an unprotected peptide is presented. In the presence of a preformed biarylphosphine-supported palladium(II)–aryl complex and a weak base, lysine amino groups underwent C−N bond formation at room temperature. The process generally exhibited high selectivity for lysine over other amino acids containing nucleophilic side chains and was applicable to the conjugation of a variety of organic compounds, including complex drug molecules, with an array of peptides. Finally, this method was also successfully applied to the formation of cyclic peptides by macrocyclization.Schutzlos ausgeliefert: In Gegenwart eines vorgebildeten Biarylphosphan-Palladium(II)-Arylkomplexes und einer schwachen Base gehen Lysin-Aminogruppen in ungeschützten Peptiden eine C-N-Bindungbildung bei Raumtemperatur ein (siehe Schema). Der Prozess konnte zur Konjugation verschiedener organischer Verbindungen, einschließlich komplexer Wirkstoffmoleküle, an Peptide verwendet werden, ebenso auch zur Bildung cyclischer Peptide durch Makrocyclisierung.
      PubDate: 2017-02-16T05:15:49.849494-05:
      DOI: 10.1002/ange.201611202
       
  • Proteintemplat-gesteuerte Bildung eines Inhibitors des Koagulationsfaktors
           Xa durch eine Amidierung ohne Hintergrundreaktion
    • Authors: Mike Jaegle; Torsten Steinmetzer, Jörg Rademann
      Abstract: Proteintemplat-gesteuerte Reaktionen ermöglichen eine “Ziel-geleitete Synthese” von Proteinliganden ausgehend von reaktiven Fragmenten – im Idealfall ohne jegliche Hintergrundreaktion. Hier wird die Templat-unterstützte Bildung von Amiden untersucht. Ein nukleophiles Fragment, das an Koagulationsfaktor Xa bindet, wurde mit dem Protein und 13 unterschiedlich aktivierten Dipeptiden inkubiert. Das Protein induzierte eine nicht-katalytische Templat-unterstützte Reaktion des Phenyl- und Trifluorethylesters; für Letzteren konnte eine vollständig Hintergrund-freie Amidierung nachgewiesen werden. Ausgehend von zwei Startfragmenten mit mm Affinität wurde ein 29 nm superadditiver Inhibitor gebildet. Die Fragmentligation wurde mit hoher Empfindlichkeit über einen Enzymaktivitätsassay und Massenspektrometrie detektiert. Der Reaktionsfortschritt und die Autoinhibierung der Templat-gesteuerten Reaktion durch das gebildete Ligationsprodukt wurden bestimmt, und die Struktur des Protein-Inhibitor-Komplexes wurde aufgeklärt.Ein Protein formt seinen eigenen Mörder: Koagulationsfaktor Xa induziert die Verknüpfung zweier schwach bindender Fragmente zu einem hochpotenten, superadditiven Inhibitor unter Bildung einer Amidbindung (siehe Schema, unten; gelb: aktiviertes Carbonsäurederivat, grün: nukleophiles Aminfragment). Geeignete Aktivester reagieren auf der Proteinoberfläche über einen nicht-katalytischen, auto-inhibierten Mechanismus ohne Auftreten einer Hintergrundreaktion in freier Lösung.
      PubDate: 2017-02-15T15:21:11.564254-05:
      DOI: 10.1002/ange.201611547
       
  • Photoresponsive Nanosheets of Polyoxometalates Formed by Controlled
           Self-Assembly Pathways
    • Authors: Keita Ishiba; Takao Noguchi, Hiroaki Iguchi, Masa-aki Morikawa, Kenji Kaneko, Nobuo Kimizuka
      Abstract: Anionic Keggin polyoxometalates (POMs) and ether linkage-enriched ammonium ions spontaneously self-assemble into rectangular ultrathin nanosheets in aqueous media. The structural flexibility of the cation is essential to form oriented nanosheets; as demonstrated by single-crystal X-ray diffraction measurements. The difference in initial conditions exerts significant influence on selecting for self-assembly pathways in the energy landscape. Photoillumination of the POM sheets in pure water causes dissolution of reduced POMs, which allowed site-specific etching of nanosheets using laser scanning microscopy. By contrast, photoetching was suppressed in aqueous AgNO3 and site-selective deposition of silver nanoparticles occurred as a consequence of electron transfer from the photoreduced POMs to Ag+ ions on the nanosheet surface.Unter kontrollierten Bedingungen bilden Polyoxometallate und Ammoniumionen mit veretherten Substituenten in Wasser spontan rechteckige Nanoplättchen, die bei Bestrahlung mit Licht reduziert werden. Ortsspezifisches photochemisches Ätzen und Abscheidung von Silbernanopartikeln werden demonstriert.
      PubDate: 2017-02-15T15:21:06.830129-05:
      DOI: 10.1002/ange.201612473
       
  • Mechanical Trap Surface-Enhanced Raman Spectroscopy for Three-Dimensional
           Surface Molecular Imaging of Single Live Cells
    • Authors: Qianru Jin; Ming Li, Beril Polat, Santosh K. Paidi, Aimee Dai, Amy Zhang, Jayson V. Pagaduan, Ishan Barman, David H. Gracias
      Abstract: Reported is a new shell-based spectroscopic platform, named mechanical trap surface-enhanced Raman spectroscopy (MTSERS), for simultaneous capture, profiling, and 3D microscopic mapping of the intrinsic molecular signatures on the membrane of single live cells. By leveraging the functionalization of the inner surfaces of the MTs with plasmonic gold nanostars, and conformal contact of the cell membrane, MTSERS permits excellent signal enhancement, reliably detects molecular signatures, and allows non-perturbative, multiplex 3D surface imaging of analytes, such as lipids and proteins on the surface of single cells. The demonstrated ability underscores the potential of MTSERS to perform 3D spectroscopic microimaging and to furnish biologically interpretable, quantitative, and dynamic molecular maps in live cell populations.Einzelne Zellen werden durch mit Au-Nanosternen beschichtete mikromechanische Fallen eingefangen, die die Zelle greifen und zugleich als Sensor für die oberflächenverstärkte Raman-Spektroskopie dienen. Diese nichtinvasive markierungsfreie Methode ermöglicht die Identifizierung von Proteinen und Lipiden auf der Zelloberfläche, und die Spektren können zur Rekonstruktion eines 3D-Bildes der chemischen Zusammensetzung der Zelloberfläche genutzt werden.
      PubDate: 2017-02-15T15:21:00.437065-05:
      DOI: 10.1002/ange.201700695
       
  • (Ge4Bi14)4−: Ein Fall von “Element-Entmischung” auf
           molekularer Skala
    • Authors: Robert J. Wilson; Stefanie Dehnen
      Abstract: (Ge4Bi14)4− ist das größte Hauptgruppenelementpolyanion mit Bismutatomen, das weder von Liganden noch durch endohedrale Atome stabilisiert wird. Es enthält Strukturmotive kleinerer Polybismutidanionen wie Bi73− oder Bi113−, die räumlich klar von einer Ge4-Taille separiert sind – im Unterschied zu binären Verwandten mit homologen Elementkombinationen, bei denen gemäß DFT-Rechnungen mehr heteroatomare Bindungen bevorzugt werden, wie S. Dehnen und R. J. Wilson in ihrer Zuschrift (
      DOI : 10.1002/ange.201611422) berichten.
      PubDate: 2017-02-15T15:20:52.632721-05:
       
  • Cation-Selective Channel Regulated by Anions According to Their Hofmeister
           Ranking
    • Authors: Philip A. Gurnev; Torri C. Roark, Horia I. Petrache, Alexander J. Sodt, Sergey M. Bezrukov
      Abstract: Specificity of small ions, the Hofmeister ranking, is long-known and has many applications including medicine. Yet it evades consistent theoretical description. Here we study the effect of Hofmeister anions on gramicidin A channels in lipid membranes. Counterintuitively, we find that conductance of this perfectly cation-selective channel increases about two-fold in the H2PO4−
      PubDate: 2017-02-15T07:46:04.228602-05:
      DOI: 10.1002/ange.201611335
       
  • Remote Regulation of Membrane Channel Activity by Site-Specific
           Localization of Lanthanide-Doped Upconversion Nanocrystals
    • Authors: Xiangzhao Ai; Linna Lyu, Yang Zhang, Yanxia Tang, Jing Mu, Fang Liu, Yixi Zhou, Zhenghong Zuo, Gang Liu, Bengang Xing
      Abstract: Räumlich und zeitlich gesteuerte Aktivität von Membrankanälen in lebenden Systemen anhand von Nah-IR-Bestrahlung (λ=808 nm) ist das Thema der Zuschrift von B. Xing und Mitarbeitern (
      DOI : 10.1002/ange.201612142). Im Zuge der Glykan-Biosynthese werden Lanthanoid-dotierte aufwärtskonvertierende Nanokristalle (UCNs) über kupferfreie Klick-Cyclisierung an der Zelloberfläche angebracht. Der Kationen-Einstrom ist durch Bestrahlung steuerbar, und membranassoziierte Aktivitäten wurden in lebenden Zellen und Zebrafischen manipuliert.
      PubDate: 2017-02-15T04:45:28.770601-05:
       
  • Organoselenium-Catalyzed Regioselective C−H Pyridination of
           1,3-Dienes and Alkenes
    • Authors: Lihao Liao; Ruizhi Guo, Xiaodan Zhao
      Abstract: Ein Geschenk der Mondgöttinnen Selene und Chang'e: Pyridiniumsalze entstehen bei einer organoseleniumkatalysierten regioselektiven C-H-Pyridinierung von Alkenen, wie X. Zhao et al. in ihrer Zuschrift (
      DOI : 10.1002/ange.201610657) beschreiben. Die neuen Pyridiniumsalze wurden aus 1,3-Dienen und Fluorpyridiniumsalzen mithilfe von Diselenidkatalysatoren synthetisiert, die durch die Mondgöttinnen Selene (griechisch) und Chang'e (chinesisch) personifiziert werden.
      PubDate: 2017-02-15T04:35:31.086828-05:
       
  • By-Product-Free Siloxane-Bond Formation and Programmed One-Pot
           Oligosiloxane Synthesis
    • Authors: Kazuhiro Matsumoto; Kappam Veettil Sajna, Yasushi Satoh, Kazuhiko Sato, Shigeru Shimada
      Abstract: Oligosiloxane können auf programmierte Weise in einem einzigen Reaktionsgefäß synthetisiert werden. S. Shimada und Mitarbeiter berichten in ihrer Zuschrift (
      DOI : 10.1002/ange.201611623) über eine neuartige Ein-Topf-Synthese von Oligosiloxanen bestehend aus drei Folgereaktionen: Iridium-katalysierte Hydrosilylierung, Bor-katalysierte Umlagerung und Bor-katalysierte Kreuzkupplung. Die Abfolge der SiR2-Einheiten im Oligosiloxanprodukt kann einfach durch Ändern der Reihenfolge der Hydrosilanzugabe gesteuert werden.
      PubDate: 2017-02-15T04:35:27.860078-05:
       
  • Die erste biokatalytische Bildung von Kohlenstoff-Silicium-Bindungen
    • Authors: Stephan Lütz
      Abstract: Verknüpfung zweier Welten: Das Repertoire biokatalytischer Reaktionen wurde kürzlich bemerkenswert erweitert, und zwar um die Carben-Insertion in Si-H-Bindungen in Gegenwart des katalytischen Hämproteins Cytochrom C (siehe Schema). Die Reaktion verspricht den hochselektiven Einbau von Silicium in kohlenstoffbasierte Moleküle ohne Schutzgruppenoperationen.
      PubDate: 2017-02-15T04:35:25.785172-05:
      DOI: 10.1002/ange.201612543
       
  • A Stable Saddle-Shaped Polycyclic Hydrocarbon with an Open-Shell Singlet
           Ground State
    • Authors: Ji Ma; Junzhi Liu, Martin Baumgarten, Yubin Fu, Yuan-Zhi Tan, Karl Sebastian Schellhammer, Frank Ortmann, Gianaurelio Cuniberti, Hartmut Komber, Reinhard Berger, Klaus Müllen, Xinliang Feng
      Abstract: Diindeno-fused bischrysene, a new diindeno-based polycyclic hydrocarbon (PH), was synthesized and characterized. It was elucidated in detailed experimental and theoretical studies that this cyclopenta-fused PH possesses an open-shell singlet biradical structure in the ground state and exhibits high stability under ambient conditions (t1/2=39 days). The crystal structure unambiguously shows a novel saddle-shaped π-conjugated carbon skeleton due to the steric hindrance of the central cove-edged bischrysene unit. UV/Vis spectral measurements revealed that the title molecule has a very narrow optical energy gap of 0.92 eV, which is consistent with the electrochemical analysis and further supported by density functional theory (DFT) calculations.Im Sattel bleiben: Ein gekrümmter polycyclischer Kohlenwasserstoff, der durch Erweiterung des verdrehten Bischrysen-Kerns mit zwei Inden-Einheiten synthetisiert wurde, zeigt eine stabile Singulett-Biradikalstruktur im Grundzustand. Eine röntgenkristallographische Analyse belegt eindeutig dessen sattelförmige Konformation.
      PubDate: 2017-02-15T03:26:03.626904-05:
      DOI: 10.1002/ange.201611689
       
  • Rapid and Complete Surface Modification with Strain-Promoted
           Oxidation-Controlled Cyclooctyne-1,2-Quinone Cycloaddition (SPOCQ)
    • Authors: Rickdeb Sen; Jorge Escorihuela, Floris van Delft, Han Zuilhof
      Abstract: Strain-promoted oxidation-controlled cyclooctyne-1,2-quinone cycloaddition (SPOCQ) between functionalized bicyclo[6.1.0]non-4-yne (BCN) and surface-bound quinones revealed an unprecedented 100 % conjugation efficiency. In addition, monitoring by direct analysis in real time mass spectrometry (DART-MS) revealed the underlying kinetics and activation parameters of this immobilization process in dependence on its microenvironment.Mr. 100 %: Die spannungsvermittelte und oxidationskontrollierte Cyclooctin-1,2-Chinon-Cycloaddition (abgekürzt „SPOCQ”) zwischen Bicyclo[6.1.0]nonin (BCN) und einem oberflächengebundenen Chinon verläuft mit 100 % Konjugationseffizienz.
      PubDate: 2017-02-15T03:20:53.609324-05:
      DOI: 10.1002/ange.201612037
       
  • In Vivo Gold Complex Catalysis within Live Mice
    • Authors: Kazuki Tsubokura; Kenward K. H. Vong, Ambara R. Pradipta, Akihiro Ogura, Sayaka Urano, Tsuyoshi Tahara, Satoshi Nozaki, Hirotaka Onoe, Yoichi Nakao, Regina Sibgatullina, Almira Kurbangalieva, Yasuyoshi Watanabe, Katsunori Tanaka
      Abstract: Metal complex catalysis within biological systems is largely limited to cell and bacterial systems. In this work, a glycoalbumin–AuIII complex was designed and developed that enables organ-specific, localized propargyl ester amidation with nearby proteins within live mice. The targeted reactivity can be imaged through the use of Cy7.5- and TAMRA-linked propargyl ester based fluorescent probes. This targeting system could enable the exploitation of other metal catalysis strategies for biomedical and clinical applications.Die erste Metall-katalysierte Reaktion in lebenden Mäusen basiert auf der Verwendung von Glycanen. Glycoalbumin-AuIII-Komplexe akkumulieren in spezifischen Organen, wo sie die Amidbildung zwischen einer Propargylestersonde und einem Amin eines nahen Proteins katalysieren. Die Organselektivität wurde durch Ganzkörperfluoreszenzbildgebung und die Analyse sezierter Gewebe bestätigt.
      PubDate: 2017-02-15T03:20:44.822189-05:
      DOI: 10.1002/ange.201610273
       
  • Cation Translocation around Single Polyoxometalate–Organic Hybrid
           Cluster Regulated by Electrostatic and Cation–π Interactions
    • Authors: Dong Li; Zhuonan Liu, Jie Song, Hui Li, Baofang Zhang, Panchao Yin, Zhaoxiong Norm Zheng, James E. Roberts, Mesfin Tsige, Craig L. Hill, Tianbo Liu
      Abstract: We report herein an interesting dynamic translocation process of countercations around one polyoxometalate(POM)–organic hybrid anionic cluster at various concentrations and temperatures. It was found that both electrostatic interactions and cation–π interactions regulate the position of small countercations around single clusters. The dynamic geometry and the symmetry of the hybrid macroions are largely affected by the type of counterions, as shown by nuclear magnetic resonance (NMR) spectroscopy studies and all-atom molecular dynamics simulation. It is also shown that electrostatic interactions dominate over cation–π interactions in determining the locations of the counterions in the current system.Nah und fern: Spektroskopische und theoretische Studien zur dynamischen Verschiebung der Kationen um einen molekularen anionischen Polyoxometallat-organischen Hybridcluster zeigen, dass elektrostatische und Kation-π-Wechselwirkungen die Positionen der kleinen Gegenionen in Bezug auf den Cluster bestimmen.
      PubDate: 2017-02-15T03:20:39.112268-05:
      DOI: 10.1002/ange.201612008
       
  • Oxygen Activated, Palladium Nanoparticle Catalyzed, Ultrafast
           Cross-Coupling of Organolithium Reagents
    • Authors: Dorus Heijnen; Filippo Tosi, Carlos Vila, Marc C. A. Stuart, Philip H. Elsinga, Wiktor Szymanski, Ben L. Feringa
      Abstract: The discovery of an ultrafast cross-coupling of alkyl- and aryllithium reagents with a range of aryl bromides is presented. The essential role of molecular oxygen to form the active palladium catalyst was established; palladium nanoparticles that are highly active in cross-coupling reactions with reaction times ranging from 5 s to 5 min are thus generated in situ. High selectivities were observed for a range of heterocycles and functional groups as well as for an expanded scope of organolithium reagents. The applicability of this method was showcased by the synthesis of the [11C]-labeled PET tracer celecoxib.Kein Sauerstoff, keine Kupplung: Molekular Sauerstoff ist die entscheidende Komponente für die hier beschriebene schnelle Palladium-katalysierte Kreuzkupplung von Organolithium-Reagentien. Reaktionszeiten von bis zu 5 s ermöglichen die Anwendung der Reaktion in der Synthese radiomarkierter Verbindungen.
      PubDate: 2017-02-14T04:35:58.22492-05:0
      DOI: 10.1002/ange.201700417
       
  • An Electron Acceptor with Porphyrin and Perylene Bisimides for Efficient
           Non-Fullerene Solar Cells
    • Authors: Andong Zhang; Cheng Li, Fan Yang, Jianqi Zhang, Zhaohui Wang, Zhixiang Wei, Weiwei Li
      Abstract: Ein sternförmiges porphyrinbasiertes Molekül mit vier Perylenbisimid-Armen (PBI-Por) wurde als Nichtfulleren-Elektronenakzeptor für Solarzellen entworfen. In ihrer Zuschrift (
      DOI : 10.1002/ange.201612090) zeigen Z. Wang, W. Li et al., dass die Kombination eines Donorpolymers mit PBI-Por in einer Solarzelle eine Photoantwort im Bereich λ=300 bis 850 nm auslöst, die eine maximale externe Quanteneffizienz (EQE) von fast 0.70 und eine vielversprechende Umwandlungseffizienz von 7.4 % aufweist.
      PubDate: 2017-02-14T04:35:41.191418-05:
       
  • Synthetic Channel Specifically Inserts into the Lipid Bilayer of
           Gram-Positive Bacteria but not that of Mammalian Erythrocytes
    • Authors: Min Zhang; Ping-Ping Zhu, Pengyang Xin, Wen Si, Zhan-Ting Li, Jun-Li Hou
      Abstract: Synthetische Transmembrankanäle, eine Art rational entworfener Moleküle, die Ionen durch die Bildung von Nanoporen, die die Lipiddoppelschicht durchspannen, transportieren können, bieten eine alternative Strategie für die Entwicklung membranaktiver antimikrobieller Stoffe. Doch nur wenige Kanäle sind membranselektiv. In ihrer Zuschrift (
      DOI : 10.1002/ange.201612093) berichten J.-L Hou et al. über einen Kanal, der sich spezifisch in die Lipiddoppelschichten von Gram-positiven Bakterien einschiebt, nicht aber in die von Säuger-Erythrocyten.
      PubDate: 2017-02-14T04:35:36.840212-05:
       
  • Unerwartete Ge-Ge-Kontakte in der zweidimensionalen Phase Ge4Se3Te und
           Analyse ihres chemischen Ursprungs mittels Energiedichte(DOE)-Funktion
    • Authors: Michael Küpers; Philipp M. Konze, Stefan Maintz, Simon Steinberg, Antonio M. Mio, Oana Cojocaru-Mirédin, Min Zhu, Merlin Müller, Martina Luysberg, Joachim Mayer, Matthias Wuttig, Richard Dronskowski
      Abstract: Im ternären System Ge-Se-Te ist seit den 1960er Jahren eine hexagonale Phase mit der annähernden Zusammensetzung GeSe0.75Te0.25 bekannt, aber ihre Struktur blieb ungeklärt. Durch chemischen Transport gelang nun die Zucht von Einkristallen zur Bestimmung der Ge4Se3Te-Struktur. Diese besteht aus Schichten, die – wie elektronenmikroskopische Analysen erhärten – über van-der-Waals-artige schwache Chalkogen-Chalkogen-, aber auch über unerwartete Ge-Ge-Wechselwirkungen verbunden sind. Die Art der elektronischen Struktur von Ge4Se3Te wurde durch Analyse der chemischen Bindungen bestimmt, speziell mithilfe der neu eingeführten Energiedichte(DOE)-Funktion. Die bindenden Ge-Ge-Wechselwirkungen dienen der Aufnahme von Elektronen, die ansonsten antibindende Ge-Te-Zustände einnähmen.Ge-Ge-Kontakte und die DOE: Ge4Se3Te, eine Schichtstruktur mit Van-der-Waals-Wechselwirkungen und unerwarteten Ge-Ge-Kontakten, wurde kristallisiert, strukturell charakterisiert und auch elektronenmikroskopisch untersucht. Die Art der elektronischen Struktur wird durch Analyse der chemischen Bindungen und mithilfe der neu eingeführten Energiedichte(DOE)-Funktion bestimmt.
      PubDate: 2017-02-14T04:30:46.593321-05:
      DOI: 10.1002/ange.201612121
       
  • Synthesis of Enantiopure C3-Symmetric Triangular Molecules
    • Authors: Tomoya Miura; Takayuki Nakamuro, Scott G. Stewart, Yuuya Nagata, Masahiro Murakami
      Abstract: An asymmetric synthesis of C3-symmetric triangular macrocycles is reported. 1-Methylsulfonyl-4-(4-vinylphenyl)-1,2,3-triazole undergoes a rhodium(II)-catalyzed cyclotrimerization to establish an enantiopure C3-symmetric triangular macrocycle motif. This method can be applied to the synthesis of an enantiopure hydrocarbon, which owes its chirality to asymmetric distribution of H/D atoms on the benzene rings.Mein Hut, der hat drei Ecken: Enantiomerenreine C3-symmetrische dreieckförmige Makrocyclen wurden über eine dreifache asymmetrische Cyclopropanierung synthetisiert. Die Methode konnte auf die Synthese eines enantiomerenreinen Kohlenwasserstoffs übertragen werden, dessen Chiralität auf der asymmetrischen Verteilung von H/D-Atomen an den Benzolringen zurückzuführen ist.
      PubDate: 2017-02-14T04:25:57.538546-05:
      DOI: 10.1002/ange.201612585
       
  • A Ruthenium Complex–Porphyrin–Fullerene-Linked Molecular Pentad as an
           Integrative Photosynthetic Model
    • Authors: Masanori Yamamoto; Jens Föhlinger, Jonas Petersson, Leif Hammarström, Hiroshi Imahori
      Abstract: A ruthenium complex, porphyrin sensitizer, fullerene acceptor molecular pentad has been synthesized and a long-lived hole–electron pair was achieved in aqueous solution by photoinduced multistep electron transfer: Upon irradiation by visible light, the excited-state of a zinc porphyrin (1ZnP*) was quenched by fullerene (C60) to afford a radical ion pair, 1,3(ZnP.+-C60.−). This was followed by the subsequent electron transfer from a water oxidation catalyst unit (RuII) to ZnP.+ to give the long-lived charge-separated state, RuIII-ZnP-C60.−, with a lifetime of 14 μs. The ZnP worked as a visible-light-harvesting antenna, while the C60 acted as an excellent electron acceptor. As a consequence, visible-light-driven water oxidation by this integrated photosynthetic model compound was achieved in the presence of sacrificial oxidant and redox mediator.Gib mir fünf: Ein Ruthenium-basierter Wasseroxidationskatalysator wurde synthetisiert und in Form einer molekularen Pentade mit Porphyrin-Fulleren-Einheiten verknüpft. Den transienten Absorptionsspektren zufolge erzeugt der photoinduzierte mehrstufige Elektronentransfer ein langlebiges Elektron-Loch-Paar, und die photokatalytische Wasseroxidation durch die Pentade wurde in Gegenwart eines sakrifiziellen Oxidationsmittels erreicht.
      PubDate: 2017-02-14T04:25:54.109769-05:
      DOI: 10.1002/ange.201612456
       
  • A General and Highly Selective Cobalt-Catalyzed Hydrogenation of
           N-Heteroarenes under Mild Reaction Conditions
    • Authors: Rosa Adam; Jose R. Cabrero-Antonino, Anke Spannenberg, Kathrin Junge, Ralf Jackstell, Matthias Beller
      Abstract: Herein, a general and efficient method for the homogeneous cobalt-catalyzed hydrogenation of N-heterocycles, under mild reaction conditions, is reported. Key to success is the use of the tetradentate ligand tris(2-(diphenylphosphino)phenyl)phosphine). This non-noble metal catalyst system allows the selective hydrogenation of heteroarenes in the presence of a broad range of other sensitive reducible groups.Reduktion! Chinoline und ähnliche N-Heteroarene können mithilfe von [Co]/L hydriert werden. Die Reaktionen verlaufen hoch selektiv unter milden Bedingungen.
      PubDate: 2017-02-14T04:25:52.017429-05:
      DOI: 10.1002/ange.201612290
       
  • Inversion of the Side-Chain Stereochemistry of Indvidual Thr or Ile
           Residues in a Protein Molecule: Impact on the Folding, Stability, and
           Structure of the ShK Toxin
    • Authors: Bobo Dang; Rong Shen, Tomoya Kubota, Kalyaneswar Mandal, Francisco Bezanilla, Benoit Roux, Stephen B. H. Kent
      Abstract: ShK toxin is a cysteine-rich 35-residue protein ion-channel ligand isolated from the sea anemone Stichodactyla helianthus. In this work, we studied the effect of inverting the side chain stereochemistry of individual Thr or Ile residues on the properties of the ShK protein. Molecular dynamics simulations were used to calculate the free energy cost of inverting the side-chain stereochemistry of individual Thr or Ile residues. Guided by the computational results, we used chemical protein synthesis to prepare three ShK polypeptide chain analogues, each containing either an allo-Thr or an allo-Ile residue. The three allo-Thr or allo-Ile-containing ShK polypeptides were able to fold into defined protein products, but with different folding propensities. Their relative thermal stabilities were measured and were consistent with the MD simulation data. Structures of the three ShK analogue proteins were determined by quasi-racemic X-ray crystallography and were similar to wild-type ShK. All three ShK analogues retained ion-channel blocking activity.Der Faltung auf der Spur: Auf der Grundlage von Moleküldynamikrechnungen wurde chemische Proteinsynthese eingesetzt, um den Effekt von Allo-Thr- und Allo-Ile-Substitutionen für einzelne Thr- und Ile-Reste auf die Faltung, Kristallstruktur und Stabilität des ShK-Proteins zu erforschen. Die experimentell gefundenen Faltungen und thermischen Stabilitätsdaten stimmen gut mit den Computerergebnissen überein.
      PubDate: 2017-02-14T04:25:49.974411-05:
      DOI: 10.1002/ange.201612398
       
  • Steering Siglec–Sialic Acid Interactions on Living Cells using
           Bioorthogonal Chemistry
    • Authors: Christian Büll; Torben Heise, Niek van Hilten, Johan F. A. Pijnenborg, Victor Bloemendal, Lotte Gerrits, Esther D. Kers-Rebel, Tina Ritschel, Martijn H. den Brok, Gosse J. Adema, Thomas J. Boltje
      Abstract: Sialic acid sugars that terminate cell-surface glycans form the ligands for the sialic acid binding immunoglobulin-like lectin (Siglec) family, which are immunomodulatory receptors expressed by immune cells. Interactions between sialic acid and Siglecs regulate the immune system, and aberrations contribute to pathologies like autoimmunity and cancer. Sialic acid/Siglec interactions between living cells are difficult to study owing to a lack of specific tools. Here, we report a glycoengineering approach to remodel the sialic acids of living cells and their binding to Siglecs. Using bioorthogonal chemistry, a library of cells with more than sixty different sialic acid modifications was generated that showed dramatically increased binding toward the different Siglec family members. Rational design reduced cross-reactivity and led to the discovery of three selective Siglec-5/14 ligands. Furthermore, glycoengineered cells carrying sialic acid ligands for Siglec-3 dampened the activation of Siglec-3+ monocytic cells through the NF-κB and IRF pathways.Immunsystem ausgeklickt: Eine neue Methode zu schnellen Umprogrammierung der Bindung von Sialinsäurezuckern auf Lebendzellen an ihre jeweiligen Siglec-Rezeptoren beruht auf Glykoengineering und Klick-Chemie. Die Bindung lässt sich selektiv um einen Faktor >100 verbessern. Die modifizierten Zellen zeigen wirksame Immunsuppressionsaktivität als Ergebnis starker Signalgebung durch Siglecs auf Immunzellen.
      PubDate: 2017-02-14T04:25:45.786012-05:
      DOI: 10.1002/ange.201612193
       
  • Enantioselective Aza-Ene-type Reactions of Enamides with Gold Carbenes
           Generated from α-Diazoesters
    • Authors: Feng Zhao; Nan Li, Tao Zhang, Zhi-Yong Han, Shi-Wei Luo, Liu-Zhu Gong
      Abstract: Carbophilic gold carbenes generated from the decomposition of α-diazoesters show high reactivity towards enamides, leading to an unprecedented aza-ene-type reaction. The presence of 0.1 mol % of a chiral Brønsted acid co-catalyst is sufficient to give synthetically relevant γ-keto esters in excellent yields and selectivities (up to 99 % yield, 97 % ee).Aus α-Diazoestern gewonnene carbophile Goldcarbene reagieren mit Enamiden in einer neuen Aza-En-artigen Reaktion. Die Gegenwart von 0.1 Mol-% einer chiralen Brønsted-Säure reicht aus, um exzellente Ausbeuten und Enantioselektivitäten zu erzielen.
      PubDate: 2017-02-14T04:25:27.978216-05:
      DOI: 10.1002/ange.201612208
       
  • Zur Gold-katalysierten Erzeugung von Vinylkationen aus 1,5-Diinen
    • Authors: Thomas Wurm; Janina Bucher, Sarah B. Duckworth, Matthias Rudolph, Frank Rominger, A. Stephen K. Hashmi
      Abstract: Konjugierte 1,5-Diin-Systeme mit zwei aromatischen Resten an den terminalen Positionen der Alkine wurden in Anwesenheit eines Gold-Katalysators umgesetzt. Unter milden Bedingungen werden arylsubstituierte Dibenzopentalene erzeugt. Berechnungen sagen aurierte Vinylkationen als Schlüsselintermediate der Reaktion voraus. Eine bidirektionale Reaktion lieferte selektiv das angular anellierte Produkt in hoher Ausbeute, was über Berechnungen erklärt werden kann.Positives zu C=C-Gruppen: Durch Kombination von nicht terminalen 1,5-Diinen mit kationischen Gold-Komplexen gelingt die Erzeugung von hochreaktiven Vinylkationen, die für die Synthese von unsymmetrisch substituierten Dibenzopentalenen genutzt werden können. Quantenchemische Betrachtungen weisen auf ein schnelles Valenztautomerengleichgewicht zwischen einem Gold-Alkin-Komplex und dem Vinylkation hin.
      PubDate: 2017-02-14T04:20:41.22486-05:0
      DOI: 10.1002/ange.201700057
       
  • Enzyme-Initiated Free-Radical Polymerization of Molecularly Imprinted
           Polymer Nanogels on a Solid Phase with an Immobilized Radical Source
    • Authors: Mira Daoud Attieh; Yi Zhao, Assem Elkak, Aude Falcimaigne-Cordin, Karsten Haupt
      Abstract: An enzyme-mediated synthetic approach is described for the preparation of molecularly imprinted polymer nanoparticles (MIP-NPs) in aqueous media. Horseradish peroxidase (HRP) was used to initiate the polymerization of methacrylate or vinyl monomers and cross-linkers by catalyzing the generation of free radicals. To prevent entrapment of the enzyme in the cross-linked polymer, and to enable it to be reused, HRP was immobilized on a solid support. MIPs based on 4-vinylpyridine and 1,4-bis(acryloyl)piperazine for the recognition of 2,4-dichlorophenoxyacetic acid (2,4-D) and salicylic acid were synthesized in an aqueous medium. MIPs for the protein trypsin were also synthesized. MIP nanoparticles with sizes between 50 and 300 nm were obtained with good binding properties, a good imprinting effect, and high selectivity for the target molecule. The reusability of immobilized HRP for MIP synthesis was shown for several batches.Immobilisierte Meerrettich-Peroxidase (HRP) initiiert die radikalische Polymerisation von Methacrylat- oder Vinylmonomeren mit Vernetzungsreagentien zur Bildung von Nanogelen molekular geprägter Polymere (MIPs) in wässrigen Medien (siehe Schema). MIP-Nanopartikel mit Größen zwischen 50 und 300 nm wurden erhalten, die gute Bindungseigenschaften und hohe Selektivität für das Zielmolekül, das Herbizid 2,4-Dichlorphenoxyessigsäure, zeigen.
      PubDate: 2017-02-14T04:20:30.732707-05:
      DOI: 10.1002/ange.201612667
       
  • Enantioselective Dearomatization of Naphthol Derivatives with Allylic
           Alcohols by Cooperative Iridium and Brønsted Acid Catalysis
    • Authors: Dan Shen; Qiliang Chen, Peipei Yan, Xiaofei Zeng, Guofu Zhong
      Abstract: The combination of a transition-metal catalyst and organocatalyst was designed to achieve a highly enantioselective system for the allylic dearomatization reaction of naphthols with racemic secondary allylic alcohols. The desired β-naphthalenones, bearing an all-carbon quaternary center, were obtained in good yields with high chemo- and enantioselectivities. The cooperative catalytic system, involving a chiral iridium complex and phosphoric acid, provided measurable improvements in yields, and chemo- and enantioselectivities relative to single-catalyst systems. Control experiments indicated that the chiral iridium complex functions as a key species in the control of the absolute configuration, thus enabling the formation of both β-naphthalenone enantiomers by simply employing opposite enantiomeric ligands.Ein kooperatives Katalysesystem aus einem chiralen Iridiumkomplex und einem Phosphorsäurederivat ergibt hoch enantioselektive allylierende Desaromatisierungen von Naphtholen mit racemischen sekundären Allylalkoholen. Die gewünschten β-Naphthalinone mit vollständig kohlenstoffsubstituiertem quartärem Zentrum werden in guten Ausbeuten erhalten. Durch den Einsatz der entsprechenden Ligand-Enantiomere sind beide β-Naphthalinon-Enantiomere zugänglich.
      PubDate: 2017-02-14T03:55:45.688416-05:
      DOI: 10.1002/ange.201609693
       
  • (Ge4Bi14)4−: Ein Fall von “Element-Entmischung” auf
           molekularer Skala
    • Authors: Robert J. Wilson; Stefanie Dehnen
      Abstract: Die Extraktion eines Feststoffs der nominalen Zusammensetzung “K2GeBi” mit 1,2-Diaminoethan (en) in Gegenwart von 4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosan (crypt-222) führte zur Bildung des Salzes [K(crypt-222)]4(Ge4Bi14). Das 18-atomige Zintl-Anion (Ge4Bi14)4− darin hat eine bislang unbekannte Topologie, die sich als formales Kondensationsprodukt zweier E113−-Käfige entlang einer gemeinsamen Ge4-“Taille” verstehen lässt. (Ge4Bi14)4− stellt somit das größte und strukturell komplexeste Polyanion mit Bismutatomen dar. Wir beschreiben seine schrittweise Bildung, die geometrische und elektronische Struktur und diskutieren relative Stabilitäten der Isomere mit unterschiedlicher Verteilung der vier Germaniumatome auf den 18 Atompositionen, die wir mittels DFT-Rechnungen untersucht haben.Nach Extraktion von „K2GeBi” mit en/crypt-222 entsteht (Ge4Bi14)4−, das größte Hauptgruppenelement-Polyanion mit Bismutatomen, das weder von Liganden noch durch endohedrale Atome stabilisiert wird. Die Einkristallstruktur belegt eine räumliche Trennung von Germanium- und Bismutatomen – gemäß DFT-Rechnungen ein Spezifikum für Ge (und Si) als „Heteroatome”, während Homologe mit Sn und Pb mehr heteroatomare Kontakte bevorzugen.
      PubDate: 2017-02-14T03:50:52.351708-05:
      DOI: 10.1002/ange.201611422
       
  • Reversible Stereoselective Folding/Unfolding Fueled by the Interplay of
           Photoisomerism and Hydrogen Bonding
    • Authors: Christopher R. Opie; Naoya Kumagai, Masakatsu Shibasaki
      Abstract: A linear molecular architecture equipped with complementary three-fold hydrogen-bonding units embedded with a photoswitchable trans-tetrafluoroazobenzene moiety was synthesized. The transto cis photoisomerism of the azobenzene unit induced drastic changes in the molecular architecture as a result of intramolecular hydrogen bonding as evidenced by NMR spectroscopy and size exclusion chromatography. A minute stereogenic element in the linear trans state enabled stereoselective folding into the cis state, thus producing a globular architecture with enhanced chiroptical property.Ein lineares Molekül mit komplementären Einheiten für dreifache Wasserstoffbrücken und einer photoschaltbaren trans-Tetrafluorazobenzol-Einheit wurde synthetisiert. Die trans-cis-Photoisomerisierung der Azobenzol-Einheit induziert Änderungen der Molekülform infolge veränderter intramolekularer Wasserstoffbrücken. Dies wird durch NMR-Spektroskopie und Größenausschlusschromatographie belegt.
      PubDate: 2017-02-14T03:50:50.245103-05:
      DOI: 10.1002/ange.201610279
       
  • A Tale of Two Elements: The Lewis Acidity/Basicity Umpolung of Boron and
           Phosphorus
    • Authors: Douglas Wade Stephan
      Abstract: This mini-review focuses on the Lewis acidity/basicity "umpolung" of B-based nucleophiles and P-based electrophiles.
      PubDate: 2017-02-13T06:15:30.294519-05:
      DOI: 10.1002/ange.201700721
       
  • New Modalities for Challenging Targets in Drug Discovery
    • Authors: Herbert Waldmann; Eric Valeur, Stéphanie M. Guéret, Hélène Adihou, Ranganath Gopalakrishnan, Malin Lemurell, Tom N. Grossmann, Alleyn T. Plowright
      Abstract: An ever increasing understanding of biological systems is providing a range of exciting novel biological targets whose modulation may enable novel therapeutic options in many diseases. These targets include protein-protein and protein-nucleic acid interactions, which are, however, often refractory to classical small molecule approaches. Other types of molecules, or modalities, are therefore required to address these targets, which has led several academic research groups and pharmaceutical companies to increasingly use the concept of so-called 'New Modalities'. This review defines for the first time the scope of this term, which includes novel peptidic scaffolds, oligonucleotides, hybrids, molecular conjugates as well as new uses of classical small molecules. We provide herein a journey through the most representative examples of these modalities to target large binding surface areas such as those found in protein-protein interactions and for biological processes at the center of cell regulation.
      PubDate: 2017-02-10T07:10:33.631609-05:
      DOI: 10.1002/ange.201611914
       
  • Erste Preise von Air Liquide für essenzielle kleine Moleküle/Wolf-Preis
           für Chemie für Robert G. Bergman/Preise der Schweizerischen Chemischen
           Gesellschaft/Kurz gemeldet
    • PubDate: 2017-02-10T04:15:26.519379-05:
      DOI: 10.1002/ange.201700844
       
  • Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and
           Production
    • Authors: Walter Leitner; Jürgen Klankermayer, Stefan Pischinger, Heinz Pitsch, Katharina Kohse-Höinghaus
      Abstract: Sustainably produced biofuels are being discussed intensively as one possible component in the energy scenarios for future ground transportation, especially when they are derived from lignocellulosic biomass. Traditionally, research activities on their production focus on the synthesis process, while leaving their combustion properties to subsequent evaluation by a different community. The present article adopts an integrative view of engine combustion and fuel synthesis, focusing on the chemical aspects as the common denominator. We wish to demonstrate that fundamental understanding of the combustion process can be instrumental to derive design criteria for the molecular structure of fuel candidates that can then be targets for the analysis of synthetic pathways and the development of catalytic production routes. With such an integrative approach to fuel design, it will be possible to improve systematically the entire system, spanning biomass feedstock, conversion process, fuel, engine, and pollutants with a perspective to improve the carbon footprint, increase efficiency, and reduce emissions of the transportation sector along the whole value chain.
      PubDate: 2017-02-10T03:25:57.689265-05:
      DOI: 10.1002/ange.201607257
       
  • Enolonium Species—Umpoled Enolates
    • Authors: Shlomy Arava; Jayprakash N. Kumar, Shimon Maksymenko, Mark A. Iron, Keshaba N. Parida, Peter Fristrup, Alex M. Szpilman
      Abstract: Enolonium species/iodo(III)enolates of carbonyl compounds have been suggested to be intermediates in a wide variety of hypervalent iodine induced chemical transformations of ketones, including α-C−O, α-C−N, α-C−C, and α-carbon–halide bond formation, but they have never been characterized. We report that these elusive umpoled enolates may be made as discrete species that are stable for several minutes at −78 °C, and report the first spectroscopic identification of such species. It is shown that enolonium species are direct intermediates in C−O, C−N, C−Cl, and C−C bond forming reactions. Our results open up chemical space for designing a variety of new transformations. We showcase the ability of enolonium species to react with prenyl, crotyl, cinnamyl, and allyl silanes with absolute regioselectivity in up to 92 % yield.Sowohl Enolonium-Spezies (5) als auch Keton-Derivate (4) von Carbonylverbindungen wurden als Zwischenstufen durch hypervalente Iodverbindungen induzierter Transformationen von Ketonen vorgeschlagen (u. a. Oxygenierung, Aminierung, Chlorierung, Enoldimerisierung und Allylation). Umgepolte Enolate konnten nun als diskrete Spezies erzeugt und charakterisiert werden, und Enolonium-Spezies wurden als direkte Zwischenstufen der Reaktionen etabliert.
      PubDate: 2017-02-09T06:16:39.020252-05:
      DOI: 10.1002/ange.201610274
       
  • Double Concave Cesium Encapsulation by Two Charged Sumanenyl Bowls
    • Authors: Sarah N. Spisak; Zheng Wei, Andrey Yu. Rogachev, Toru Amaya, Toshikazu Hirao, Marina A. Petrukhina
      Abstract: The controlled reaction of Na and Cs, two alkali metals of different ionic sizes and binding abilities, with sumanene (C21H12) affords a novel type of organometallic sandwich [Cs(C21H11−)2]−, which crystallized as a solvent-separated ion pair with a [Na(18-crown-6)(THF)2]+ cation (where THF=tetrahydrofuran). The unprecedented double concave encapsulation of a metal ion by two bowl-shaped sumanenyl anions in [Cs(C21H11−)2]− was revealed crystallographically. Evaluation of bonding and energetics of the remarkable product was accomplished computationally (B2PLYP-D/TZVP/ZORA), providing insights into its formation.Von beiden Seiten: Zwei konkav bindende schalenförmige Carbanionen kapseln ein Metallion ein. Die Synthese dieser Struktur nutzt die unterschiedliche Bindungsfähigkeit von Natrium- und Caesiumionen bezüglich der gebogenen π-Oberflächen.
      PubDate: 2017-02-07T08:25:33.704208-05:
      DOI: 10.1002/ange.201610696
       
  • Nanostructured Materials for Heterogeneous Electrocatalytic CO2 Reduction
           and Related Reaction Mechanisms
    • Authors: Jinlong Gong; Lei Zhang, Zhi-Jian Zhao
      Abstract: The gradually increased concentration of carbon dioxide (CO2) in the atmosphere has been recognized as the primary culprit for the raise of the global mean temperature, thus resulting in the aggravated desert formation and extinction of species. In recent years, development of the routes for highly efficient conversion of CO2 has received numerous attentions. Among them, the reduction of CO2 with electric power is an important transformation route with high application prospect, due to its high environmental compatibility and good combination with other renewable energy sources such as solar and wind energy. This review describes recent progress on the design and synthesis of solid state catalysts (i.e., heterogeneous catalysts) and their emerging catalytic performances in the CO2 reduction. The significance for catalytic conversion of CO2 and the advantages of CO2 electroreduction will be presented in the introduction section, followed by the general parameters for CO2 electroreduction and the summary of reaction apparatus. We also discuss various types of solid catalysts according to CO2 conversion mechanisms. Furthermore, we summarize the crucial factors (particle size, surface structure, composition and etc.) determining the performance for electroreduction. These studies in improvement of solid state catalysts for CO2 reduction offer numerous experiences for developing potential industrialized CO2 electroreduction catalysts in the future. Additionally, the abundant experience for controllable synthesis of solid state catalysts could effectively guide the rational design of catalysts for other electrocatalytic reactions.
      PubDate: 2017-02-06T22:20:26.596093-05:
      DOI: 10.1002/ange.201612214
       
  • Catalytic Dearomatization of N-Heteroarenes with Silicon and Boron
           Compounds
    • Authors: Sukbok Chang; Sehoon Park
      Abstract: Dearomatized N-heterocycles provide a class of structural motifs important in the fields of synthetic organic chemistry and chemical biology. The catalytic dearomative reduction of unactivated N-heteroarenes using silicon and/or boron-containing compounds as a reductant is one of the most straightforward alternatives to hydrogenation. However, scattered precedents on the catalytic reduction of N-heteroaromatics with silane or borane reducing agents have been reported thus far, and a handful of elegant catalytic procedures for the reduction of N-aromatics have emerged only recently as a viable tool in organic synthesis. This review presents recent advances in the catalytic reduction of unactivated N-heteroarenes using hydrosilanes, hydroboranes, silaboranes, and diboranes. The focus presents the general chemical behavior and selectivity of transition-metal or metal-free organocatalyst systems for the dearomative homogeneous reduction of N-heteroarenes. In addition, the working modes of these catalysis will be described particularly on the basis of the experimental mechanistic insights.
      PubDate: 2017-02-05T22:21:02.01778-05:0
      DOI: 10.1002/ange.201612140
       
  • Modern Inorganic Aerogels
    • Authors: Alexander Eychmüller; Christoph Ziegler, André Wolf, Wei Liu, Anne-Kristin Herrmann, Nikolai Gaponik
      Abstract: Essentially, the term aerogel describes a special geometric structure of matter. It is neither limited to any material nor to any synthesis procedure. Hence, the possible variety of materials and therefore the multitude of their applications are almost unbounded. In fact, the same applies for nanoparticles. These are also just defined by their geometrical properties. In the past decades nano-sized materials were intensively studied and possible applications appeared in nearly all areas of natural sciences. To date a large variety of metal, semiconductor, oxide and other nanoparticles are available from colloidal synthesis. However, for many applications of these materials an assembly into macroscopic structures is needed. Here we present a comprehensive picture of the developments that enabled the fusion of the colloidal nanoparticle and the aerogel world. This became possible by the controlled destabilization of pre-formed nanoparticles, which leads to their assembly into three-dimensional macroscopic networks. This revolutionary approach makes it possible to use precisely controlled nanoparticles as building blocks for macroscopic porous structures with programmable properties.
      PubDate: 2017-02-03T12:11:09.703588-05:
      DOI: 10.1002/ange.201611552
       
  • Uniform Supersonic Chemical Reactors: 30 Years of Astrochemical History
           and Future Challenges
    • Authors: Alexey Potapov; André Canosa, Elena Jiménez, Bertrand Rowe
      Abstract: The interstellar medium attracts our great attention, as the place where stars and planets are born and from where, probably, the molecular precursors of life have come to Earth. To understand the chemical pathways to the formation of stars, planets, and biological molecules, astronomical observations, astrochemical modelling, and laboratory astrochemistry should go hand in hand. In this paper we review the laboratory experiments devoted to investigations of the reaction dynamics of species of astrochemical interest at the temperatures of the interstellar medium and performed by using one of the most popular techniques in the field, CRESU. We discuss new technical developments and scientific ideas for CRESU, which, if realized, will bring us one more step closer to an understanding of the astrochemical history and future of our Universe.
      PubDate: 2017-02-03T04:06:24.845538-05:
      DOI: 10.1002/ange.201611240
       
  • Luminescence, Plasmonic and Magnetic Properties of Doped Semiconductor
           Nanocrystals: Current Developments and Future Prospects
    • Authors: Narayan Pradhan; Samrat Das Adhikari, Angshuman Nag, D D Sarma
      Abstract: Introducing few atoms of impurities or dopants in semiconductor nanocrystals can drastically alter the existing or even introduce new properties. For example, mid-gap states created by doping tremendously affect photocatalytic activities and surface controlled redox reactions, generate new emission centres, show thermometric optical switching, make suitable FRET donors by enhancing the excited state lifetime and also create localized surface plasmon resonance induced low energy absorption. In addition, researchers have more recently started focusing their attention on doped nanocrystals as an important and alternative material for solar energy conversion in order to meet the current demand for renewable energy. Moreover, electrical as well as magnetic properties of the host are also strongly altered on doping. These dopant-induced beneficial changes in material properties suggest that doped nanocrystals with proper selections of dopant-host pairs may be helpful for generating designer materials for a wide range of current technological needs. Such exciting properties related to various aspects of doping a variety of semiconductor nanocrystals are summarized and reported in this mini review.
      PubDate: 2017-02-02T05:31:07.03112-05:0
      DOI: 10.1002/ange.201611526
       
  • Protein-templated fragment ligations - from molecular recognition to drug
           discovery
    • Authors: Mike Jaegle; Ee Lin Wong, Carolin Tauber, Eric Nawrotzky, Christoph Arkona, Jörg Rademann
      Abstract: The understanding and manipulation of molecular recognition events is the key to modern approaches in drug discovery. Protein-templated fragment ligation is a novel concept to support drug discovery and can help to improve the efficacy of already existing protein ligands. Protein-templated fragment ligations are chemical reactions between small molecules ("fragments") that utilize a protein´s surface as a template to combine and to form a protein ligand with increased binding affinity. The approach exploits the molecular recognition of reactive small molecule fragments by proteins both for ligand assembly and for the identification of bioactive fragment combinations. Chemical synthesis and bioassay are thus integrated in one single step. In this article we portrait the biophysical basis of reversible and irreversible fragment ligations and the available methods to detect protein-templated ligation products. The scope of known chemical reactions providing templated ligation products is reviewed and the possibilities to extend the reaction portfolio are discussed. Selected recent applications of the method in protein ligand discovery are reported. Finally, the strengths and limitations of the concept are discussed and an outlook on the future impact of templated fragment ligations on the drug discovery process is given.
      PubDate: 2017-01-24T08:45:33.189727-05:
      DOI: 10.1002/ange.201610372
       
  • Black Phosphorus Rediscovered: From Bulk to Monolayer
    • Authors: Rui Gusmao; Zdenek Sofer, Martin Pumera
      Abstract: Phosphorus is a non-metal with several allotropes, from the highly reactive white phosphorus to the thermodynamically stable black phosphorus (BP) with a puckered orthorhombic layered structure. The bulk form of BP was synthesized for the first time more than a century ago, in 1914, not receiving much attention until very recently rediscovered, in 2014, joining the new wave of 2D layered nanomaterials. BP can be exfoliated to a single sheet structure with tunable direct band, semiconducting, high carrier mobility at room temperature and in-plane anisotropic layered structure. Surface chemistry degradation can still be a holdback for the advancement of BP applications, thus compelling efforts to achieve effective BP passivation are ongoing, such as its integration in van der Waals heterostructures. Currently, BP has been tested as a novel nanomaterial in batteries, transistors, sensors and photonics related fields. In this review we take a look back at BP origin story, taking the path from bulk to nowadays few/single layer. Physical and chemical properties are summarized, highlighting the state-of-the-art in BP applications.
      PubDate: 2017-01-23T02:35:58.618983-05:
      DOI: 10.1002/ange.201610512
       
  • Xenobiology meets enzymology: Exploring the potential of unnatural
           building blocks in biocatalysis
    • Authors: Nediljko Budisa; Jan-Stefan Völler, Beate Koksch, Carlos G. Acevedo-Rocha, Vladimir Kubyshkin, Federica Agostini
      Abstract: Xenobiology (XB) aims to design biological systems endowed with unusual biochemistries, while enzymology concerns the study of enzymes, the workhorses of biocatalysis. Biocatalysis employs enzymes and organisms to perform useful biotransformations in synthetic chemistry and biotechnology. During the past years, the effects of incorporating noncanonical amino acids (ncAAs) into enzymes with potential applications in biocatalysis have been increasingly investigated. Here we provide an overview of the effects of new chemical functionalities that have been introduced into proteins to improve various facets of enzymatic catalysis. We also discuss future research avenues that will complement unnatural mutagenesis with the standard protein-engineering toolbox for producing novel and versatile biocatalysts with applications in synthetic organic chemistry and biotechnology.
      PubDate: 2017-01-13T14:20:35.017578-05:
      DOI: 10.1002/ange.201610129
       
  • Carbon-Carbon Bond Formation in a Weak Ligand Field: Leveraging Open Shell
           First Row Transition Metal Catalysts
    • Authors: Paul James Chirik
      Abstract: Unique features of Earth abundant transition metal catalysts are reviewed in the context of catalytic carbon-carbon bond forming reactions. Aryl-substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open shell iron and cobalt alkyl complexes have been synthesized that serve as single component olefin polymerization catalysts. Reduced bis(imino)pyridine iron- and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Electronic structure studies support open shell intermediates, a deviation from traditional strong field organometallic compounds that promote catalytic C-C bond formation.
      PubDate: 2017-01-12T14:45:24.350363-05:
      DOI: 10.1002/ange.201611959
       
  • Fullerenes in space
    • Authors: John Paul Maier; Ewen Kyle Campbell
      Abstract: In 1985 the football structure of $\textrm{C}_{60}$, buckminsterfullerene was proposed and subsequently confirmed following its macroscopic synthesis in 1990. From the very beginning the role of $\textrm{C}_{60}$ and $\textrm{C}_{60}^{+}$ in space was considered, particularly in the context of the enigmatic diffuse interstellar bands. These are absorption features found in the spectra of reddened star light. The first astronomical observations were made around one hundred years ago and despite significant efforts none of the interstellar molecules responsible have been identified. The absorption spectrum of $\textrm{C}_{60}^{+}$ was measured in a $5\,\textrm{K}$ neon matrix in 1993 and two prominent bands near $9583\,\textrm{\AA}$ and $9645\,\textrm{\AA}$ were observed. On the basis of this data the likely wavelength range in which the gas phase $\textrm{C}_{60}^{+}$ absorptions should lie was predicted. In 1994 two diffuse interstellar bands were found in this spectral region and proposed to be due to $\textrm{C}_{60}^{+}$. It took over 20 years to measure the absorption spectrum of $\textrm{C}_{60}^{+}$ under conditions similar to those prevailing in diffuse clouds. In 2015, sophisticated laboratory experiments led to the confirmation that these two interstellar bands are indeed caused by $\textrm{C}_{60}^{+}$, providing the first answer to this century old puzzle. Here, we describe the experiments, concepts and astronomical observations that led to the detection of $\textrm{C}_{60}^{+}$ in interstellar space.
      PubDate: 2017-01-10T04:20:29.09953-05:0
      DOI: 10.1002/ange.201612117
       
  • Titelbild: Protonierung kontra Oxoniumsalz-Bildung: Abstimmung der
           Basizität und Stabilität von Cyanoborat-Anionen (Angew. Chem. 10/2017)
    • Authors: Christoph Kerpen; Jan A. P. Sprenger, Lorena Herkert, Marius Schäfer, Lisa A. Bischoff, Pierre Zeides, Matthias Grüne, Rüdiger Bertermann, Franziska A. Brede, Klaus Müller-Buschbaum, Nikolai V. Ignat'ev, Maik Finze
      Pages: 2557 - 2557
      Abstract: Salze mit Hydridoborat-Anionen … … wie [BH3(CN)]− sind Reduktions- und Hydrierungsreagentien. Der Austausch von H gegen CN führt zu starker Verminderung des Hydridcharakters, sodass [BH2(CN)2]− äußerst schwach hydridisch ist, was M. Finze et al. in der Zuschrift auf S. 2839 ff. anhand der Synthese von H[BH2(CN)2] zeigen. Das H-Atom von [BH(CN)3]− ist aufgrund der drei CN-Gruppen protisch, und starke nichtnucleophile Basen deprotonieren das Anion zum Dianion B(CN)32−, worüber die gleiche Arbeitsgruppe in einer zweiten Zuschrift auf S. 2844 ff. berichtet.
      PubDate: 2017-01-27T07:15:56.975223-05:
      DOI: 10.1002/ange.201700515
       
  • Innentitelbild: Anaerobe-Inspired Anticancer Nanovesicles (Angew. Chem.
           10/2017)
    • Authors: Chenggen Qian; Peijian Feng, Jicheng Yu, Yulei Chen, Quanyin Hu, Wujin Sun, Xuanzhong Xiao, Xiuli Hu, Adriano Bellotti, Qun-Dong Shen, Zhen Gu
      Pages: 2558 - 2558
      Abstract: Anaerobe Bakterien dienten als Vorlage für ein Wirkstofftransportsystem, das von Q. D. Shen, Z. Gu et al. in der Zuschrift auf S. 2632 ff. beschrieben wird. Die biomimetischen Nanovesikel sind in Zellen mit einer normalen physiologischen Redox- und Sauerstoffbilanz stabil. Bei Lichteinstrahlung brechen sie auf und entfalten ihre duale synergistische Antikrebswirkung mit erhöhter therapeutischer Wirkung.
      PubDate: 2017-02-15T15:20:55.356222-05:
      DOI: 10.1002/ange.201701131
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 10/2017
    • Pages: 2561 - 2573
      PubDate: 2017-02-17T08:36:15.738857-05:
      DOI: 10.1002/ange.201781011
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 10/2017
    • Pages: 2576 - 2579
      PubDate: 2017-02-17T08:36:17.298128-05:
      DOI: 10.1002/ange.201781013
       
  • Synthesis of Best-Seller Drugs. Von Ruben Vardanyan und Victor Hruby.
    • Authors: Jie Jack Li
      Pages: 2583 - 2583
      Abstract: Academic Press, 2016. 868 S., Broschur, 199.95 $.– ISBN 978-0124114920
      PubDate: 2017-01-18T03:15:21.433387-05:
      DOI: 10.1002/ange.201700015
       
  • Wertmetalle – Gewinnungsverfahren, aktuelle Trends und
           Recyclingstrategien
    • Authors: Peter Fröhlich; Tom Lorenz, Gunther Martin, Beate Brett, Martin Bertau
      Pages: 2586 - 2624
      Abstract: Dieser Aufsatz gibt einen Überblick über Wertmetalle, deren Versorgungslage für Europa als kritisch eingestuft wird. Aufbauend auf einer Darstellung des Stands der Technik werden neue Ansätze, vornehmlich seit 2005, zur Gewinnung aus Primärrohstoffen vorgestellt und die Recyclingverfahren diskutiert. Ausgehend von den jeweiligen Lagerstätten sowie der Mineralchemie wird aufgezeigt, welche Strategien zur Gewinnung der Metalle verfolgt werden. Außerdem wird auf die wirtschaftliche Bedeutung und Verwendung der Metalle eingegangen.Wertmetalle – ohne geht es nicht: Die Ausfuhrbeschränkung für Seltenerdmetalle hat uns die Abhängigkeit von Rohstoffen deutlich ins Bewusstsein gerufen. Dieser Aufsatz gibt einen Überblick über die Rohstoffsituation, die wirtschaftliche Bedeutung sowie die Herstell- und Recyclingverfahren für technisch relevante Wertmetalle und stellt die Neuentwicklungen der letzten zehn Jahre vor.
      PubDate: 2017-01-27T07:32:35.555739-05:
      DOI: 10.1002/ange.201605417
       
  • Anaerobe-Inspired Anticancer Nanovesicles
    • Authors: Chenggen Qian; Peijian Feng, Jicheng Yu, Yulei Chen, Quanyin Hu, Wujin Sun, Xuanzhong Xiao, Xiuli Hu, Adriano Bellotti, Qun-Dong Shen, Zhen Gu
      Pages: 2632 - 2637
      Abstract: Anaerobic bacteria, such as Clostridium and Salmonella, can selectively invade and colonize in tumor hypoxic regions (THRs) and deliver therapeutic products to destroy cancer cells. Herein, we present an anaerobe nanovesicle mimic that can not only be activated in THRs but also induce hypoxia in tumors by themselves. Moreover, inspired by the oxygen metabolism of anaerobes, we construct a light-induced hypoxia-responsive modality to promote dissociation of vehicles and activation of bioreductive prodrugs simultaneously. In vitro and in vivo experiments indicate that this anaerobe-inspired nanovesicle can efficiently induce apoptotic cell death and significantly inhibit tumor growth. Our work provides a new strategy for engineering stimuli-responsive drug delivery systems in a bioinspired and synergistic fashion.Biomimetische Vesikel imitieren den natürlichen Mechanismus der Tumorerkennung und des Wirkstofftransports anaerober Bakterien. Die Nanovesikel sind in Zellen mit einer normalen physiologischen Redox- und Sauerstoffbilanz stabil. Bei Lichteinstrahlung brechen sie auf und entfalten ihre duale synergistische Antikrebswirkung mit erhöhter therapeutischer Wirksamkeit.
      PubDate: 2017-02-01T02:10:41.134858-05:
      DOI: 10.1002/ange.201611783
       
  • Growth of Stable Surface Oxides on Pt(111) at Near-Ambient Pressures
    • Authors: Donato Fantauzzi; Sandra Krick Calderón, Jonathan E. Mueller, Mathias Grabau, Christian Papp, Hans-Peter Steinrück, Thomas P. Senftle, Adri C. T. van Duin, Timo Jacob
      Pages: 2638 - 2642
      Abstract: Detailed knowledge of the structure and degree of oxidation of platinum surfaces under operando conditions is essential for understanding catalytic performance. However, experimental investigations of platinum surface oxides have been hampered by technical limitations, preventing in situ investigations at relevant pressures. As a result, the time-dependent evolution of oxide formation has only received superficial treatment. In addition, the amorphous structures of many surface oxides have hindered realistic theoretical studies. Using near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) we show that a time scale of hours (t≥4 h) is required for the formation of platinum surface oxides. These experimental observations are consistent with ReaxFF grand canonical Monte Carlo (ReaxFF-GCMC) calculations, predicting the structures and coverages of stable, amorphous surface oxides at temperatures between 430–680 K and an O2 partial pressure of 1 mbar.Stabile Oberflächenoxide: Stabile Oberflächenoxide auf Pt(111) nahe Umgebungsdruck wurden theoretisch vorhergesagt und ihre Existenz durch Röntgen-Photoelektronenspektroskopie bestätigt. Die Anwesenheit stabiler Oberflächenoxide hat gravierende Auswirkungen auf Pt-Katalysatoren, da ihre katalytischen Eigenschaften sich deutlich von denen blanker Pt-Oberflächen unterscheiden.
      PubDate: 2017-01-25T03:10:38.746954-05:
      DOI: 10.1002/ange.201609317
       
  • Ferromagnetic Interactions in Highly Stable, Partially Reduced TiO2: The
           S=2 State in Anatase
    • Authors: Mario Chiesa; Stefano Livraghi, Elio Giamello, Elisa Albanese, Gianfranco Pacchioni
      Pages: 2648 - 2651
      Abstract: We report direct evidence for quintuplet spin states in a particular kind of reduced TiO2 anatase obtained by the mild oxidation of TiB2 under hydrothermal conditions. Continuous-wave and pulse EPR spectroscopy at X and Q band frequencies provide compelling evidence for the presence of S=2 states, stable in a wide range of temperatures up to room temperature. A tentative model, corroborated by spin-polarized DFT calculations, is proposed, which consists of four ferromagnetically interacting Ti3+ ions with distances ranging from 0.5 nm to 0.8 nm and tetrahedral arrangement.Spinoff: Die solvothermale Oxidation von TiB2 erzeugt ferromagnetisch wechselwirkende Ti3+-Zentren, die stabile S=2-Zustände in Anatas-TiO2 ergeben. Dieses Nanomaterial entspricht einer besonderen Form von blauem reduziertem TiO2 (siehe Strukturbild und Ausschnitt eines 2D-EPR-Spektrums).
      PubDate: 2017-01-27T05:35:45.638534-05:
      DOI: 10.1002/ange.201610973
       
  • Anisotropically Swelling Gels Attained through Axis-Dependent Crosslinking
           of MOF Crystals
    • Authors: Takumi Ishiwata; Kenta Kokado, Kazuki Sada
      Pages: 2652 - 2656
      Abstract: Anisotropically deforming objects have attracted considerable interest for use in molecular machines and artificial muscles. Herein, we focus on a new approach based on the crystal crosslinking of organic ligands in a pillared-layer metal–organic framework (PLMOF). The approach involves the transformation from crosslinked PLMOF to polymer gels through hydrolysis of the coordination bonds between the organic ligands and metal ions, giving a network polymer that exhibits anisotropic swelling. The anisotropic monomer arrangement in the PLMOF underwent axis-dependent crosslinking to yield anisotropically swelling gels. Therefore, the crystal crosslinking of MOFs should be a useful method for creating actuators with designable deformation properties.Dehnbare MOFs: Ein neuer Ansatz für die anisotrope Verformung von Objekten wird vorgestellt, der auf der Quervernetzung von organischen Liganden in einem säulenförmigen Metall-organischen Kristallgerüst (PLMOF) basiert. Die anisotrope Anordnung der Monomere im PLMOF ist für die achsenabhängige Quervernetzung verantwortlich, die zu anisotrop anschwellenden Gelen führt.
      PubDate: 2017-01-27T07:21:33.944859-05:
      DOI: 10.1002/ange.201611338
       
  • Supramolecular Graft Copolymerization of a Polyester by Guest-Selective
           Encapsulation of a Self-Assembled Capsule
    • Authors: Yuta Tsunoda; Mei Takatsuka, Ryo Sekiya, Takeharu Haino
      Pages: 2657 - 2662
      Abstract: Repeating guest units of polyesters poly-(R)-2 were selectively encapsulated by capsule 1(BF4)4 to produce supramolecular graft polymers. The encapsulation of the guest units was confirmed by 1H NMR spectroscopy. The graft polymer structures were confirmed by the increase in the hydrodynamic radii and the solution viscosities of the polyesters upon complexation of the capsule. After the capsule was formed, atomic force microscopy showed extension of the polyester chains. The introduction of the graft chains onto poly-(R)-2 resulted in the main chain of the polymer having an M-helical morphology. The complexation of copolymers poly-[(R)-2-co-(S)-2] by the capsule gave rise to the unique chiral amplification known as the majority-rules effect.Der selektive Einschluss repetitiv in Polyester eingebauter Gasteinheiten in selbstorganisierten Kapseln liefert supramolekulare Pfropfcopolymere mit induzierter M-Helizität. Eine beispiellose Chiralitätsverstärkung wurde für die molekulare Erkennung durch die Kapsel beobachtet.
      PubDate: 2017-01-25T03:05:52.89664-05:0
      DOI: 10.1002/ange.201611394
       
  • A Boronic Acid Conjugate of Angiogenin that Shows ROS-Responsive
           Neuroprotective Activity
    • Authors: Trish T. Hoang; Thomas P. Smith, Ronald T. Raines
      Pages: 2663 - 2666
      Abstract: Angiogenin (ANG) is a human ribonuclease that is compromised in patients with amyotrophic lateral sclerosis (ALS). ANG also promotes neovascularization, and can induce hemorrhage and encourage tumor growth. The causal neurodegeneration of ALS is associated with reactive oxygen species, which are also known to elicit the oxidative cleavage of carbon–boron bonds. We have developed a synthetic boronic acid mask that restrains the ribonucleolytic activity of ANG. The masked ANG does not stimulate endothelial cell proliferation but protects astrocytes from oxidative stress. By differentiating between the two dichotomous biological activities of ANG, this strategy could provide a viable pharmacological approach for the treatment of ALS.Ein Defekt der Ribonuclease Angiogenin in Patienten mit amyotropher Lateralsklerose führt unter anderem zu oxidativem Stress. Ein halbsynthetisches Angiogenin wurde hergestellt, in dem eine wichtige Position des aktiven Zentrums mit einer Boronsäure maskiert ist, um systemische Nebenwirkungen zu vermeiden. Unter oxidativem Stress maskiert H2O2 das Angiogeninkonjugat, das daraufhin neuroprotektiv wirkt.
      PubDate: 2017-01-25T03:00:28.506638-05:
      DOI: 10.1002/ange.201611446
       
  • Hyper-Crosslinkers Lead to Temperature- and pH-Responsive Polymeric
           Nanogels with Unusual Volume Change
    • Authors: Ning Zhou; Xiaoyan Cao, Xuewen Du, Huaimin Wang, Ming Wang, Shuang Liu, Khang Nguyen, Klaus Schmidt-Rohr, Qiaobing Xu, Gaolin Liang, Bing Xu
      Pages: 2667 - 2671
      Abstract: Hydrogels consisting of carboxylic acid groups and N-isopropylacrylamide as pendants on their polymeric network usually exhibit volume expansion upon deprotonation or volume contraction when being heated. Demonstrated here is an anti-intuitive case of a hydrogel containing multiple carboxylic acid groups at each crosslinking point in the polymeric network, which shrinks upon increasing pH from 1 to 7 at 37 °C or expands upon heating from 25 to 37 °C at pH 1. The unexpected volume change originates from the high percentage of the crosslinker in the polymers, as detected by solid-state 13C NMR spectroscopy. In addition, the volume changes are thermally reversible. As the first example of the use of functional hyper-crosslinkers to control the pH and thermal responses of nanogels, this work illustrates a new way to design soft materials with unusual behaviors.Flexibler Zusammenhalt: Filament-Vernetzer werden oft für Zytoskelette entworfen, im Zusammenhang mit synthetischer weicher Materie wird eine entsprechende Strategie aber weitaus seltener angewendet. Hier führen Hypervernetzer ungewöhnliche Formänderungen von Hydrogelen als Antwort auf pH- und Temperaturänderungen herbei.
      PubDate: 2017-01-27T07:21:28.968591-05:
      DOI: 10.1002/ange.201611479
       
  • N2-Substituted 2′-Deoxyguanosine Triphosphate Derivatives as Selective
           Substrates for Human DNA Polymerase κ
    • Authors: A. S. Prakasha Gowda; Marietta Lee, Thomas E. Spratt
      Pages: 2672 - 2675
      Abstract: N2-Alkyl-2′-deoxyguanosine triphosphate (N2-alkyl-dGTP) derivatives with methyl, butyl, benzyl, or 4-ethynylbenzyl substituents were prepared and tested as substrates for human DNA polymerases. N2-Benzyl-dGTP was equal to dGTP as a substrate for DNA polymerase κ (pol κ), but was a poor substrate for pols β, δ, η, ι, or ν. In vivo reactivity was evaluated through incubation of N2-4-ethynylbenzyl-dG with wild-type and pol κ deficient mouse embryonic fibroblasts. CuAAC reaction with 5(6)-FAM-azide demonstrated that only cells containing pol κ were able to incorporate N2-4-ethynylbenzyl-dG into the nucleus. This is the first instance of a Y-family-polymerase-specific dNTP, and this method could be used to probe the activity of pol κ in vivo.Pol-Erkundung: N2-Alkyl-2′-desoxyguanosintriphosphat-Derivate (N2-alkyl-dGTP) mit Methyl-, Butyl-, Benzyl- oder 4-Ethinylbenzyl-Substituenten wurden als Substrate für humane DNA-Polymerasen getestet. N2-Benzyl-dGTP war gleich wie dGTP ein Substrat der DNA-Polymerase κ (pol κ), aber ein schlechtes Substrat für pol β, δ, η, ι oder ν. Nur lebende Zellen, die pol κ enthielten, konnten N2-4-Ethinylbenzyl-dG in ihrem Zellkern inkorporieren.
      PubDate: 2017-02-01T02:10:28.016977-05:
      DOI: 10.1002/ange.201611607
       
  • Rational Design and Synthesis of Efficient Sunscreens To Boost the Solar
           Protection Factor
    • Authors: Raúl Losantos; Ignacio Funes-Ardoiz, José Aguilera, Enrique Herrera-Ceballos, Cristina García-Iriepa, Pedro J. Campos, Diego Sampedro
      Pages: 2676 - 2679
      Abstract: Skin cancer incidence has been increasing in the last decades, but most of the commercial formulations used as sunscreens are designed to protect only against solar erythema. Many of the active components present in sunscreens show critical weaknesses, such as low stability and toxicity. Thus, the development of more efficient components is an urgent health necessity and an attractive industrial target. We have rationally designed core moieties with increased photoprotective capacities and a new energy dissipation mechanism. Using these scaffolds, we have synthesized a series of compounds with tunable properties suitable for their use in sunscreens, and enhanced properties in terms of stability, light energy dissipation, and toxicity. Moreover, some representative compounds were included in final sunscreen formulations and a relevant solar protection factor boost was measured.Schützt euch! Eine neue Familie wirkungsvoller Lichtschutzmittel wurde nach dem Vorbild natürlicher Verbindungen gezielt entworfen und snythetisiert. Tests der Lichtschutzeigenschaften ergaben einen drastisch erhöhten Schutzfaktor in realen Proben.
      PubDate: 2017-01-27T07:20:59.355573-05:
      DOI: 10.1002/ange.201611627
       
  • Highly Multiplexed Single-Cell In Situ Protein Analysis with
           Cleavable Fluorescent Antibodies
    • Authors: Manas Mondal; Renjie Liao, Lu Xiao, Taylor Eno, Jia Guo
      Pages: 2680 - 2683
      Abstract: Limitations on the number of proteins that can be quantified in single cells in situ impede advances in our deep understanding of normal cell physiology and disease pathogenesis. Herein, we present a highly multiplexed single-cell in situ protein analysis approach that is based on chemically cleavable fluorescent antibodies. In this method, antibodies tethered to fluorophores through a novel azide-based cleavable linker are utilized to detect their protein targets. After fluorescence imaging and data storage, the fluorophores coupled to the antibodies are efficiently cleaved without loss of protein target antigenicity. Upon continuous cycles of target recognition, fluorescence imaging, and fluorophore cleavage, this approach has the potential to quantify over 100 different proteins in individual cells at optical resolution. This single-cell in situ protein profiling technology will have wide applications in signaling network analysis, molecular diagnosis, and cellular targeted therapies.Mehrmals markiert: Bestimmte Proteine wurden mit Antikörpern, die über einen chemisch spaltbaren Linker an Fluorophore gebunden waren, angefärbt. Durch wiederholte Zyklen von Markierung, Fluoreszenzbildgebung und Fluorophor-Abspaltung wurde eine große Anzahl unterschiedlicher Proteine in situ in einzelnen Zellen detektiert.
      PubDate: 2017-01-27T07:32:24.201889-05:
      DOI: 10.1002/ange.201611641
       
  • Structure of the Ribosomal RNA Decoding Site Containing a
           Selenium-Modified Responsive Fluorescent Ribonucleoside Probe
    • Authors: Ashok Nuthanakanti; Mark A. Boerneke, Thomas Hermann, Seergazhi G. Srivatsan
      Pages: 2684 - 2688
      Abstract: Comprehensive understanding of the structure–function relationship of RNA both in real time and at atomic level will have a profound impact in advancing our understanding of RNA functions in biology. Here, we describe the first example of a multifunctional nucleoside probe, containing a conformation-sensitive fluorophore and an anomalous X-ray diffraction label (5-selenophene uracil), which enables the correlation of RNA conformation and recognition under equilibrium and in 3D. The probe incorporated into the bacterial ribosomal RNA decoding site, fluorescently reports antibiotic binding and provides diffraction information in determining the structure without distorting native RNA fold. Further, by comparing solution binding data and crystal structure, we gained insight on how the probe senses ligand-induced conformational change in RNA. Taken together, our nucleoside probe represents a new class of biophysical tool that would complement available tools for functional RNA investigations.Doppelfunktion: Eine Ribonucleotid-Hybridsonde mit einem konformationssensitiven Fluorophor und einem Röntgenbeugungsmarker (5-Selenophenuracil) wurde in das bakterielle ribosomale RNA-Dekodierungszentrum eingeführt und ermöglicht so die direkte Korrelation von antibiotikainduzierten Konformationsänderungen in Echtzeit und auf atomarer Ebene, ohne die native RNA-Faltung zu stören.
      PubDate: 2017-02-03T02:20:27.476158-05:
      DOI: 10.1002/ange.201611700
       
  • Cycloparaphenylenes and Their Catenanes: Complex Macrocycles Unveiled by
           Ion Mobility Mass Spectrometry
    • Authors: Wen Zhang; Ali Abdulkarim, Florian E. Golling, Hans Joachim Räder, Klaus Müllen
      Pages: 2689 - 2692
      Abstract: The insoluble product mixture obtained from cycloparaphenylene (CPP) synthesis from Suzuki coupling and reductive aromatization was analyzed. Traditional mass spectrometry suggests a homologous series of macrocycles with 12 to 84 phenylene units. Ion-mobility mass spectrometry, however, unravels an unexpected complexity of isomers with identical chemical formula, but different topologies. Whereas macrocycles containing up to 30 phenylene units show only one structure, the homologue with 36 phenylene units forms at least four different isomers with significant molecular size differences. They can be assigned to catenanes composed of CPPs with 2×18 and 12+24 phenylene units together with the ordinary [36]CPP macrocycle. Most likely, a trefoil knot of the CPP with 36 moieties is also present. For the first time, catenanes can be elucidated in a simple reaction mixture by analyzing their ions in the gas phase, an analysis which lies beyond the scope of traditional analytical methods.Ring auf Ring: Lösungsmittelfreie MALDI-Ionenmobilitätsmassenspektrometrie wurde verwendet, um ein unlösliches Produktgemisch von Cycloparaphenylenen zu analysieren. Zum ersten Mal können Monocyclen und isomere Catenane in einem einfachen Reaktionsgemisch nachgewiesen werden, in dem nur Monocyclen erwartet werden konnten.
      PubDate: 2017-01-27T07:21:42.535148-05:
      DOI: 10.1002/ange.201611943
       
  • Surface-Enhanced Raman Spectra Promoted by a Finger Press in an
           All-Solid-State Flexible Energy Conversion and Storage Film
    • Authors: Haitao Li; Han Dai, Yihe Zhang, Wangshu Tong, Hua Gao, Qi An
      Pages: 2693 - 2698
      Abstract: Electrochemically up-regulated surface-enhanced Raman spectroscopy (E-SERS) effectively increases Raman signal intensities. However, the instrumental requirements and the conventional measurement conditions in an electrolyte cell have hampered its application in fast and on-site detection. To circumvent the inconveniences of E-SERS, we propose a self-energizing substrate that provides electrical potential by converting film deformation from a finger press into stored electrical energy. The substrate combines an energy conversion film and a SERS-active Ag nanowire layer. A composite film prepared from a piezoelectric polymer matrix and surface-engineered rGO that simultaneously presents high permittivity and low dielectric loss is the key component herein. Using our substrate, increased E-SERS signals up to 10 times from a variety of molecules were obtained in the open air. Various tests on real-life sample surfaces demonstrated the potentials of the substrate in fast on-site detection.Energie per Fingerdruck: Ein selbstverstärkendes SERS-aktives Trägermaterial wurde durch Kombination eines piezoelektrischen Kompositfilms hoher Permittivität mit Silbernanodrahtschichten erhalten (SERS=oberflächenverstärkte Raman-Streuung). Der polymere Kompositfilm speichert Druck mit dem Finger als elektrische Energie und steigert die SERS-Intensität um eine Größenordnung.
      PubDate: 2017-01-12T04:25:47.729503-05:
      DOI: 10.1002/ange.201610737
       
  • Supramolecular Vesicles Coassembled from Disulfide-Linked Benzimidazolium
           Amphiphiles and Carboxylate-Substituted Pillar[6]arenes that Are
           Responsive to Five Stimuli
    • Authors: Long Jiang; Xuan Huang, Dong Chen, Hua Yan, Xueyuan Li, Xuezhong Du
      Pages: 2699 - 2703
      Abstract: Novel supramolecular vesicles based on host–guest systems were coassembled from carboxylate-substituted pillar[6]arene (CPA[6]) and disulfide-linked benzimidazolium amphiphiles, and the microstructures of the CPA-based supramolecular vesicles were clearly elaborated. The supramolecular vesicles showed controlled drug release in response to five stimuli, with glutathione, pH, CO2, Zn2+ ions, and hexanediamine, leading to cleavage of the disulfide bonds, protonation of the carboxylate groups, metal chelation, and competitive binding. This is the first case of a smart pillararene-based supramolecular vesicle being integrated with five stimuli-responsive functions to meet the diverse requirements of controlled drug release. Importantly, each of the five stimuli is closely related to microenvironments of tumors and diseases of the human body. The smart stimuli-responsive supramolecular vesicles have promising applications in drug therapy of tumors and relevant diseases.Viele Wege zum Ziel: Carboxylat-substituierte Pillar[6]arene und Disulfid-verknüpfte Benzimidazolium-Amphiphile bilden gemeinsam supramolekulare Vesikel, die unter Einwirkung von Glutathion, CO2, Zn2+ und Hexandiamin sowie ausgelöst durch pH-Änderungen einen verkapselten Wirkstoff freisetzen können. Diese fünf Stimuli stehen in engem Zusammenhang mit der Mikroumgebung von Tumoren und Krankheitszuständen.
      PubDate: 2017-02-01T02:10:46.512657-05:
      DOI: 10.1002/ange.201611973
       
  • Transformation of Dipeptide-Based Organogels into Chiral Crystals by
           Cryogenic Treatment
    • Authors: Xingcen Liu; Jinbo Fei, Anhe Wang, Wei Cui, Pengli Zhu, Junbai Li
      Pages: 2704 - 2707
      Abstract: Controlled molecular assembly is an important approach for the synthesis of single-component materials with diverse functions. Unlike traditional heat treatment or solvent modulation, cryogenic treatment at 77 K enabled the tunable transition of a self-assembled diphenylalanine organogel into a hexagonal crystal. Under these conditions, the assembled molecules undergo an internal rearrangement in the solid state to form a well-defined chiral crystal structure. Moreover, these assemblies exhibit enhanced emission. This strategy for the synthesis of single-component supramolecular assemblies can create new functions by manipulating phase transitions.Durch Kühlen auf 77 K kann ein selbstorganisiertes Dipeptid-Organogel in einen chiralen hexagonalen Kristall mit verstärkter intrinsischer Emission überführt werden. Diese universelle Strategie bietet einen neuen Ansatz, um das Phasenverhalten supramolekularer Einkomponentensysteme zu beeinflussen.
      PubDate: 2017-02-01T02:10:32.654292-05:
      DOI: 10.1002/ange.201612024
       
  • Four-Shell Polyoxometalates Featuring High-Nuclearity Ln26 Clusters:
           Structural Transformations of Nanoclusters into Frameworks Triggered by
           Transition-Metal Ions
    • Authors: Zhong Li; Xin-Xiong Li, Tao Yang, Zhen-Wen Cai, Shou-Tian Zheng
      Pages: 2708 - 2713
      Abstract: A series of polyoxometalates (POMs) that incorporate the highest-nuclearity Ln clusters that have been observed in such structures to date (Ln26 , Ln=La and Ce) are described, which exhibit giant multishell configurations (Ln⊂W6⊂Ln26⊂W100). Their structures are remarkably different from known giant POMs that feature multiple Ln ions. In particular, the incorporated Ln–O clusters with a nuclearity of 26 are significantly larger than known high-nuclearity (≤10) Ln–O clusters in POM chemistry. Furthermore, they also contain the largest number of La and Ce centers for any POM reported to date and represent a new kind of rare giant POMs with more than 100 W atoms. Interestingly, the La26-containing POM can undergo a single-crystal to single-crystal structural transformation in the presence of various transition-metal ions, such as Cu2+, Co2+, and Ni2+, from an inorganic molecular nanocluster into an inorganic–organic hybrid extended framework that is built from POM building blocks with even higher-nuclearity La28 clusters bridged by transition-metal complexes.Vierschalige heterometallische Polyoxowolframate, die Ln26-Cluster mit hoher Nuklearität beinhalten, wurden synthetisiert. Diese können 3d-Metallionen einschließen, während ihre Einkristall-Einkristall-Transformation zu einer neuen Klasse an Polyoxometallaten (POMs) mit ausgedehnten Strukturen führt, die auf Ln28 enthaltenden POMs basieren (TM=Übergangsmetall).
      PubDate: 2017-01-27T07:15:40.797159-05:
      DOI: 10.1002/ange.201612046
       
  • Catalytic Enantioselective Synthesis of Lactams through Formal [4+2]
           Cycloaddition of Imines with Homophthalic Anhydride
    • Authors: Claire L. Jarvis; Jennifer S. Hirschi, Mathew J. Vetticatt, Daniel Seidel
      Pages: 2714 - 2718
      Abstract: An amide-thiourea compound, operating through a novel ion pairing mechanism, is an efficient organocatalyst for the asymmetric reaction of homophthalic anhydride with imines. N-aryl and N-alkyl imines readily undergo formal [4+2] cycloaddition to provide lactams with high levels of enantio- and diastereoselectivity. The nature of the key chiral ion pair intermediate was elucidated by DFT calculations.Paarbildung: Ein Amid-Thioharnstoff-Organokatalysator vermittelt effizient die asymmetrische Reaktion von Homophthalsäureanhydrid mit Iminen über einen neuartigen Ionenpaarungsmechanismus. N-Aryl- und N-Alkylimine gehen glatt und mit hoher Enantio- und Diastereoselektivität die formale [4+2]-Cycloaddition zu Lactamen ein. Das entscheidende Ionenpaarintermediat wurde mithilfe von DFT-Rechnungen charakterisiert.
      PubDate: 2017-01-27T07:32:26.229807-05:
      DOI: 10.1002/ange.201612148
       
  • Controlled Covalent Functionalization of Thermally Reduced Graphene Oxide
           To Generate Defined Bifunctional 2D Nanomaterials
    • Authors: Abbas Faghani; Ievgen S. Donskyi, Mohammad Fardin Gholami, Benjamin Ziem, Andreas Lippitz, Wolfgang E. S. Unger, Christoph Böttcher, Jürgen P. Rabe, Rainer Haag, Mohsen Adeli
      Pages: 2719 - 2723
      Abstract: A controlled, reproducible, gram-scale method is reported for the covalent functionalization of graphene sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. The reaction between commercially available 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized sheets. The different reactivities of the chlorine substituents on the functionalized graphene allow stepwise post-modification by manipulating the temperature. This new method provides unique access to defined bifunctional 2D nanomaterials, as exemplified by chiral surfaces and multifunctional hybrid architectures.Einfach und mild: Die Reaktion von 2,4,6-Trichlor-1,3,5-triazin und Natriumazid mit thermisch reduziertem Graphenoxid liefert definierte Dichlortriazin-funktionalisierte Schichten. Da die Chlorsubstituenten am funktionalisierten Graphen unterschiedlich reaktiv sind, gelingen temperaturgesteuert stufenweise Modifizierungen. Das Ergebnis sind definierte difunktionelle 2D-Nanomaterialien.
      PubDate: 2017-02-06T04:55:49.540776-05:
      DOI: 10.1002/ange.201612422
       
  • Bioelectrochemical Haber–Bosch Process: An Ammonia-Producing H2/N2
           Fuel Cell
    • Authors: Ross D. Milton; Rong Cai, Sofiene Abdellaoui, Dónal Leech, Antonio L. De Lacey, Marcos Pita, Shelley D. Minteer
      Pages: 2724 - 2727
      Abstract: Nitrogenases are the only enzymes known to reduce molecular nitrogen (N2) to ammonia (NH3). By using methyl viologen (N,N′-dimethyl-4,4′-bipyridinium) to shuttle electrons to nitrogenase, N2 reduction to NH3 can be mediated at an electrode surface. The coupling of this nitrogenase cathode with a bioanode that utilizes the enzyme hydrogenase to oxidize molecular hydrogen (H2) results in an enzymatic fuel cell (EFC) that is able to produce NH3 from H2 and N2 while simultaneously producing an electrical current. To demonstrate this, a charge of 60 mC was passed across H2 /N2 EFCs, which resulted in the formation of 286 nmol NH3 mg−1 MoFe protein, corresponding to a Faradaic efficiency of 26.4 %.Elektrifizierter Haber-Bosch-Prozess: Die bioelektrochemische Verknüpfung von Nitrogenase und Hydrogenase ergibt eine enzymatische Brennstoffzelle, die aus H2 und N2 elektrische Energie gewinnt und gleichzeitig NH3 als nützlichen chemischen Grundstoff generiert. Methylviologen wurde in diesem Prozess als Elektronentransferreagens eingesetzt.
      PubDate: 2017-02-03T02:30:43.025424-05:
      DOI: 10.1002/ange.201612500
       
  • Efficient Solar Light Harvesting CdS/Co9S8 Hollow Cubes for Z-Scheme
           Photocatalytic Water Splitting
    • Authors: Bocheng Qiu; Qiaohong Zhu, Mengmeng Du, Linggang Fan, Mingyang Xing, Jinlong Zhang
      Pages: 2728 - 2732
      Abstract: Hollow structures with an efficient light harvesting and tunable interior component offer great advantages for constructing a Z-scheme system. Controlled design of hollow cobalt sulfide (Co9S8) cubes embedded with cadmium sulfide quantum dots (QDs) is described, using hollow Co(OH)2 as the template and a one-pot hydrothermal strategy. The hollow CdS/Co9S8 cubes utilize multiple reflections of light in the cubic structure to achieve enhanced photocatalytic activity. Importantly, the photoexcited charge carriers can be effectively separated by the construction of a redox-mediator-free Z-scheme system. The hydrogen evolution rate over hollow CdS/Co9S8 is 134 and 9.1 times higher than that of pure hollow Co9S8 and CdS QDs under simulated solar light irradiation, respectively. Moreover, this is the first report describing construction of a hollow Co9S8 based Z-scheme system for photocatalytic water splitting, which gives full play to the advantages of light-harvesting and charges separation.Gut hohl: Ein CdS/Co9S8-Katalysator zur effizienten Lichtsammlung für die direkte photokatalytische Wasserspaltung wurde entwickelt. Hohle Co9S8-Würfel schließen die für reine CdS-Quantenpunkte übliche Photokorrosion aus und erhöhen die Ausbeute an Sonnenlicht für eine stark verbesserte photokatalytische H2-Entwicklung.
      PubDate: 2017-02-01T02:06:36.040752-05:
      DOI: 10.1002/ange.201612551
       
  • A Stimuli-Responsive Smart Lanthanide Nanocomposite for Multidimensional
           Optical Recording and Encryption
    • Authors: Xiang Li; Yujie Xie, Bo Song, Hao-Li Zhang, Hao Chen, Huijuan Cai, Weisheng Liu, Yu Tang
      Pages: 2733 - 2737
      Abstract: A stimuli-responsive lanthanide-based smart nanocomposite has been fabricated by supramolecular assembly and applied as an active material in multidimensional memory materials. Conjugation of the lanthanide complexes with carbon dots provides a stimuli response that is based on the modulation of the energy level of the ligand and affords microsecond-to-nanosecond fluorescence lifetimes, giving rise to intriguing memory performance in the spatial and temporal dimension. The present study points to a new direction for the future development of multidimensional memory materials based on inorganic–organic hybrid nanosystems.Farbenspiel: Stimuliresponsive Nanokomposite wurden durch die Funktionalisierung von Kohlenstoffpunkten mit Lanthanoid-Komplexen erhalten und in einer multidimensionalen Speichereinheit eingesetzt. Farbe und Lebensdauer der Fluoreszenz können durch Modulation der Energieniveaus des Lanthanoid-Liganden verändert werden.
      PubDate: 2017-02-01T02:06:44.638618-05:
      DOI: 10.1002/ange.201700011
       
  • An Electron Acceptor with Porphyrin and Perylene Bisimides for Efficient
           Non-Fullerene Solar Cells
    • Authors: Andong Zhang; Cheng Li, Fan Yang, Jianqi Zhang, Zhaohui Wang, Zhixiang Wei, Weiwei Li
      Pages: 2738 - 2742
      Abstract: A star-shaped electron acceptor based on porphyrin as a core and perylene bisimide as end groups was constructed for application in non-fullerene organic solar cells. The new conjugated molecule exhibits aligned energy levels, good electron mobility, and complementary absorption with a donor polymer. These advantages facilitate a high power conversion efficiency of 7.4 % in non-fullerene solar cells, which represents the highest photovoltaic performance based on porphyrin derivatives as the acceptor.Eine Armlänge voraus: Ein sternförmiges Porphyrin mit vier Perylenbisimid-Armen (PBI-Por) wurde als Elektronenakzeptor für Anwendungen in Solarzellen entworfen. Die Kombination eines Donorpolymers mit PBI-Por in einer Solarzelle resultierte in einer Photoantwort im Spektralbereich λ=300–850 nm, bei einer maximalen externen Quantenausbeute (EQE) von fast 0.70 und einem vielversprechenden Wirkungsgrad von 7.4 %.
      PubDate: 2017-01-27T07:15:54.154251-05:
      DOI: 10.1002/ange.201612090
       
  • Electrocatalytic Synthesis of Ammonia at Room Temperature and Atmospheric
           Pressure from Water and Nitrogen on a Carbon-Nanotube-Based
           Electrocatalyst
    • Authors: Shiming Chen; Siglinda Perathoner, Claudio Ampelli, Chalachew Mebrahtu, Dangsheng Su, Gabriele Centi
      Pages: 2743 - 2747
      Abstract: Ammonia is synthesized directly from water and N2 at room temperature and atmospheric pressure in a flow electrochemical cell operating in gas phase (half-cell for the NH3 synthesis). Iron supported on carbon nanotubes (CNTs) was used as the electrocatalyst in this half-cell. A rate of ammonia formation of 2.2×10−3 gNH3 m−2 h−1 was obtained at room temperature and atmospheric pressure in a flow of N2, with stable behavior for at least 60 h of reaction, under an applied potential of −2.0 V. This value is higher than the rate of ammonia formation obtained using noble metals (Ru/C) under comparable reaction conditions. Furthermore, hydrogen gas with a total Faraday efficiency as high as 95.1 % was obtained. Data also indicate that the active sites in NH3 electrocatalytic synthesis may be associated to specific carbon sites formed at the interface between iron particles and CNT and able to activate N2, making it more reactive towards hydrogenation.Nachhaltige industrielle Chemie: Ammoniak wurde direkt aus Wasser und N2 bei Raumtemperatur und Atmosphärendruck in einer elektrochemischen Durchflusszelle in der Gasphase synthetisiert (Halbzelle für die NH3-Synthese). Eisen auf Kohlenstoffnanoröhrenträger wurde als Elektrokatalysator in dieser Halbzelle verwendet.
      PubDate: 2017-01-27T07:25:43.311604-05:
      DOI: 10.1002/ange.201609533
       
  • Individual (f,tA)- and (f,tC)-Fullerene-Based Nickel(II) Glycinates:
           Protected Chiral Amino Acids Directly Linked to a Chiral π-Electron
           System
    • Authors: Oleg A. Levitskiy; Yuri K. Grishin, Olesya O. Semivrazhskaya, Asmik A. Ambartsumyan, Konstantin A. Kochetkov, Tatiana V. Magdesieva
      Pages: 2748 - 2752
      Abstract: Stereoselective electrosynthesis of the first individual (f,tA)- and (f,tC)-1,4-fullerene derivatives with a non-inherently chiral functionalization pattern is described, as well as the first example of an optically pure protected primary amino acid directly linked to the fullerene through only the chiral α-amino-acid carbon atom. An application of an auxiliary chiral nickel-Schiff base moiety as derivatizing agent allowed separation of (f,tA)- and (f,tC)-1,4-fullerene derivatives using an achiral stationary phase, a separation which has never been done before.Unzertrennliches getrennt: (f,tA)- und (f,tC)-1,4-Fulleren-Derivate konnten unter Anwendung einer achiralen stationären Phase getrennt werden. Dadurch wurden Verbindungen erhalten, in denen eine optisch reine, geschützte primäre Aminosäure ausschließlich über das Kohlenstoff-Chiralitätszentrum in α-Stellung direkt mit einem Fulleren verknüpft ist.
      PubDate: 2017-02-01T02:16:14.992881-05:
      DOI: 10.1002/ange.201609792
       
  • ZnAl-Hydrotalcite-Supported Au25 Nanoclusters as Precatalysts for
           Chemoselective Hydrogenation of 3-Nitrostyrene
    • Authors: Yuan Tan; Xiao Yan Liu, Leilei Zhang, Aiqin Wang, Lin Li, Xiaoli Pan, Shu Miao, Masatake Haruta, Haisheng Wei, Hua Wang, Fangjun Wang, Xiaodong Wang, Tao Zhang
      Pages: 2753 - 2757
      Abstract: Chemoselective hydrogenation of 3-nitrostyrene to 3-vinylaniline is quite challenging because of competitive activation of the vinyl group and the nitro group over most supported precious-metal catalysts. A precatalyst comprised of thiolated Au25 nanoclusters supported on ZnAl-hydrotalcite yielded gold catalysts of a well-controlled size (ca. 2.0 nm)—even after calcination at 500 °C. The catalyst showed excellent selectivity (>98 %) with respect to 3-vinylaniline, and complete conversion of 3-nitrostyrene over broad reaction duration and temperature windows. This result is unprecedented for gold catalysts. In contrast to traditional catalysts, the gold catalyst is inert with respect to the vinyl group and is only active with regard to the nitro group, as demonstrated by the results of the control experiments and attenuated total reflection infrared spectra. The findings may extend to design of gold catalysts with excellent chemoselectivity for use in the synthesis of fine chemicals.Gold-Nanokatalysatoren einer bestimmten Größe werden durch einen thiolierten Au25-Präkatalysator auf ZnAl-Hydrotalcit-Träger bereitgestellt. Schwefelreste und epitaktische Wechselwirkungen zwischen Gold und Träger stabilisieren den Katalysator gegen Calcinieren bei hohen Temperaturen und ermöglichen eine vollständige und hoch selektive Umwandlung der Nitrogruppe von 3-Nitrostyrol in eine Aminogruppe.
      PubDate: 2017-01-31T03:31:20.15451-05:0
      DOI: 10.1002/ange.201610736
       
  • Stereoselective Copolymerization of Unprotected Polar and Nonpolar
           Styrenes by an Yttrium Precursor: Control of Polar-Group Distribution and
           Mechanism
    • Authors: Dongtao Liu; Meiyan Wang, Zichuan Wang, Chunji Wu, Yupeng Pan, Dongmei Cui
      Pages: 2758 - 2763
      Abstract: Styrene underwent unprecedented coordination–insertion copolymerization with naked polar monomers (ortho-/meta-/para-methoxystyrene) in the presence of a pyridyl methylene fluorenyl yttrium catalyst. High activity (1.26×106 g molY−1 h−1) and excellent syndioselectivity were observed, and high-molecular-weight copolymers (24.6×104 g mol−1) were obtained. The insertion rate of the polar monomers could be adjusted in the full range of 0–100 % simply by changing the loading of the polar styrene monomer. Strikingly, the copolymers had tapered, gradient, and even random sequence distributions, depending on the position of the polar methoxy group on the phenyl ring and thus on its mode of coordination to the active metal center, as shown by tracking the polymerization process and DFT calculations.Alles unter Kontrolle: Methoxystyrole copolymerisieren mit Styrol durch Koordination/Insertion in Gegenwart eines kationischen Yttrium-Katalysators und ergeben je nach Stellung des Methoxysubstituenten verschiedenartige Sequenzverteilungen (siehe Bild). Der Anteil des polaren Styrols konnte einfach durch die Beladung mit diesem Monomer zwischen 0 und 100 % eingestellt werden.
      PubDate: 2017-01-27T07:25:52.022436-05:
      DOI: 10.1002/ange.201611066
       
  • An NHC–Silyl–NHC Pincer Ligand for the Oxidative Addition of C−H,
           N−H, and O−H Bonds to Cobalt(I) Complexes
    • Authors: Jian Sun; Lun Luo, Yi Luo, Liang Deng
      Pages: 2764 - 2768
      Abstract: N-Heterocyclic carbene based pincer ligands bearing a central silyl donor, [CSiC]−, have been envisioned as a class of strongly σ-donating ligands that can be used for synthesizing electron-rich transition-metal complexes for the activation of inert bonds. However, this type of pincer ligand and complexes thereof have remained elusive owing to their challenging synthesis. We herein describe the first synthesis of a CSiC pincer ligand scaffold through the coupling of a silyl–NHC chelate with a benzyl–NHC chelate induced by one-electron oxidation in the coordination sphere of a cobalt complex. The monoanionic CSiC ligand stabilizes the CoI dinitrogen complex [(CSiC)Co(N2)] with an unusual coordination geometry and enables the challenging oxidative addition of E−H bonds (E=C, N, O) to CoI to form CoIII complexes. The structure and reactivity of the cobalt(I) complex are ascribed to the unique electronic properties of the CSiC pincer ligand, which provides a strong trans effect and pronounced σ-donation.Ein stark elektronenschiebender NHC-Silyl-NHC-Pinzettenligand wurde durch eine Cobalt-vermittelte und oxidationsinduzierte reduktive Eliminierung unter Si-C-Verknüpfung synthetisiert. Dieser Pinzettenligand ermöglicht die oxidative Addition von E-H-Bindungen (E=C, N, O) an Cobalt(I)-Komplexe, die mit anderen Ligandengerüsten kaum gelingt.
      PubDate: 2017-01-27T07:32:19.085718-05:
      DOI: 10.1002/ange.201611162
       
  • One-Pot N-Deprotection and Catalytic Intramolecular Asymmetric Reductive
           Amination for the Synthesis of Tetrahydroisoquinolines
    • Authors: Huan Zhou; Yuan Liu, Suhua Yang, Le Zhou, Mingxin Chang
      Pages: 2769 - 2773
      Abstract: A one-pot N-Boc deprotection and catalytic intramolecular reductive amination protocol for the preparation of enantiomerically pure tetrahydroisoquinoline alkaloids is described. The iodine-bridged dimeric iridium complexes displayed superb stereoselectivity to give tetrahydroisoquinolines, including several key pharmaceutical drug intermediates, in excellent yields under mild reaction conditions. Three additives played important roles in this reaction: Titanium(IV) isopropoxide and molecular iodine accelerated the transformation of the intermediate imine to the tetrahydroisoquinoline product; p-toluenesulfonic acid contributed to the stereocontrol.Coole Kombi: N-Boc-Entschützung und eine direkte asymmetrische intramolekulare reduktive Aminierung lieferten in einem Eintopfprozess biologisch aktive chirale 1-substituierte Tetrahydroisochinoline (siehe Schema). Der Iod-verbrückte dimere Komplex [{Ir(H)[(R)-SEGPHOS]}2(μ-I)3]+I− war ein sehr effektiver Katalysator in dieser Umsetzung, bei der die Additive Ti(OiPr)4, p-Toluolsulfonsäure und I2 wichtige Rollen spielen.
      PubDate: 2017-02-01T02:16:24.01387-05:0
      DOI: 10.1002/ange.201611181
       
  • N-Heterocyclic-Carbene-Catalyzed Umpolung of Imines
    • Authors: Atanu Patra; Subrata Mukherjee, Tamal Kanti Das, Shailja Jain, Rajesh G. Gonnade, Akkattu T. Biju
      Pages: 2774 - 2778
      Abstract: N-Heterocyclic carbene (NHC) catalysis has been widely used for the umpolung of aldehydes, and recently for the umpolung of Michael acceptors. Described herein is the umpolung of aldimines catalyzed by NHCs, and the reaction likely proceeds via aza-Breslow intermediates. The NHC-catalyzed intramolecular cyclization of aldimines bearing a Michael acceptor resulted in the formation of biologically important 2-(hetero)aryl indole 3-acetic-acid derivatives in moderate to good yields. The carbene generated from the bicyclic triazolium salt was found to be efficient for this transformation.Umgepolt: Die NHC-katalysierte intramolekulare Cyclisierung von Aldiminen mit Michael-Akzeptoreinheit liefert biologisch bedeutsame 2-(Hetero)arylindol-3-essigsäure-Derivate in mittleren bis guten Ausbeuten. Die Erzeugung eines Carbens aus dem bicyclischen Triazoliumsalz ist entscheidend für den erfolgreichen Reaktionsverlauf.
      PubDate: 2017-01-27T07:26:01.111566-05:
      DOI: 10.1002/ange.201611268
       
  • From Genome to Proteome to Elucidation of Reactions for All Eleven Known
           Lytic Transglycosylases from Pseudomonas aeruginosa
    • Authors: Mijoon Lee; Dusan Hesek, David A. Dik, Jennifer Fishovitz, Elena Lastochkin, Bill Boggess, Jed F. Fisher, Shahriar Mobashery
      Pages: 2779 - 2783
      Abstract: An enzyme superfamily, the lytic transglycosylases (LTs), occupies the space between the two membranes of Gram-negative bacteria. LTs catalyze the non-hydrolytic cleavage of the bacterial peptidoglycan cell-wall polymer. This reaction is central to the growth of the cell wall, for excavating the cell wall for protein insertion, and for monitoring the cell wall so as to initiate resistance responses to cell-wall-acting antibiotics. The nefarious Gram-negative pathogen Pseudomonas aeruginosa encodes eleven LTs. With few exceptions, their substrates and functions are unknown. Each P. aeruginosa LT was expressed as a soluble protein and evaluated with a panel of substrates (both simple and complex mimetics of their natural substrates). Thirty-one distinct products distinguish these LTs with respect to substrate recognition, catalytic activity, and relative exolytic or endolytic ability. These properties are foundational to an understanding of the LTs as catalysts and as antibiotic targets.Die lytischen Transglykosylasen (LTs) sind glykosidspaltende Enzyme in Gram-negativen Bakterien. Trotz ihrer vielfältigen Strukturen haben sie ein gemeinsames Substrat: das Peptidoglykan der bakteriellen Zellwand. Durch systematische Evaluierung synthetischer Peptidoglykane und des polymeren Peptidoglykans wurden 11 LTs aus Pseudomonas aeruginosa bezüglich ihrer Substraterkennung, katalytischen Aktivität und exolytischen oder endolytischen Präferenz charakterisiert.
      PubDate: 2017-01-27T07:21:35.75745-05:0
      DOI: 10.1002/ange.201611279
       
  • Automated Synthesis of Well-Defined Polymers and Biohybrids by Atom
           Transfer Radical Polymerization Using a DNA Synthesizer
    • Authors: Xiangcheng Pan; Sushil Lathwal, Stephanie Mack, Jiajun Yan, Subha R. Das, Krzysztof Matyjaszewski
      Pages: 2784 - 2787
      Abstract: A DNA synthesizer was successfully employed for preparation of well-defined polymers by atom transfer radical polymerization (ATRP), in a technique termed AutoATRP. This method provides well-defined homopolymers, diblock copolymers, and biohybrids under automated photomediated ATRP conditions. PhotoATRP was selected over other ATRP methods because of mild reaction conditions, ambient temperature, tolerance to oxygen, and no need to introduce reducing agents or radical initiators. Both acrylate and methacrylate monomers were successfully polymerized with excellent control in the DNA synthesizer. Diblock copolymers were synthesized with different targeted degrees of polymerization and with high retention of chain-end functionality. Both hydrophobic and hydrophilic monomers were grafted from DNA. The DNA-polymer hybrids were characterized by SEC and DLS. The AutoATRP method provides an efficient route to prepare a range of different polymeric materials, especially polymer-biohybrids.Radikal automatisiert: Die lichtinduzierte radikalische Atomtransferpolymerisation in einem DNA-Syntheseautomat liefert wohldefinierte Homopolymere, Diblockcopolymere und Biohybride. Mit dieser Technik steht ein sauber arbeitendes und sauerstofftolerantes System für Polymerisationen bei Raumtemperatur bereit.
      PubDate: 2017-02-06T05:00:38.246728-05:
      DOI: 10.1002/ange.201611567
       
  • Chemical Synthesis of Diubiquitin-Based Photoaffinity Probes for
           Selectively Profiling Ubiquitin-Binding Proteins
    • Authors: Jun Liang; Lin Zhang, Xiang-Long Tan, Yun-Kun Qi, Shan Feng, Haiteng Deng, Yijing Yan, Ji-Shen Zheng, Lei Liu, Chang-Lin Tian
      Pages: 2788 - 2792
      Abstract: Biochemical studies of cellular processes involving polyubiquitin have gained increasing attention. More tools are needed to identify ubiquitin (Ub)-binding proteins. We report diazirine-based photoaffinity probes that can capture Ub-binding proteins in cell lysates, and show that diazirines are preferable to aryl azides as the photo-crosslinking group, since they decrease non-selective capture. Photoaffinity probes containing at least two Ub units were required to effectively capture Ub-binding proteins. Different capture selectivity was observed for probes containing diubiquitin moieties with different types of linkages, thus indicating the potential to develop linkage-dependent probes for selectively profiling Ub-binding proteins under various cellular conditions.Wählerisch: Photoaffinitätssonden für Ubiquitin(Ub)-bindende Proteine mit K48- und K63-verknüpftem Diubiquitin wurden entwickelt. Dabei war die Diazirin-Funktion eine bessere Photovernetzungsgruppe als ein Arylazid, da sie unselektiven Einfang vermeidet. Sonden mit verschiedenartigen Linkern unterschieden sich bezüglich der Einfangselektivität, was zur Profilierung Ub-bindender Proteine genutzt werden könnte.
      PubDate: 2017-02-01T05:50:32.133042-05:
      DOI: 10.1002/ange.201611659
       
  • Highly para-Selective C−H Alkylation of Benzene Derivatives with
           2,2,2-Trifluoroethyl α-Aryl-α-Diazoesters
    • Authors: Ben Ma; Zhaowei Chu, Ben Huang, Zhenli Liu, Lu Liu, Junliang Zhang
      Pages: 2793 - 2797
      Abstract: Compared to the most popular directing-group-assisted strategy, the “undirected” strategy for C−H bond functionalization represents a more flexible but more challenging approach. Reported herein is a gold-catalyzed highly site-selective C(sp2)−H alkylation of unactivated arenes with 2,2,2-trifluoroethyl α-aryl-α-diazoesters. This protocol demonstrates that high site-selective C−H bond functionalization can be achieved without the assistance of a directing group. In this transformation, both the gold catalyst and trifluoroethyl group on the ester of the diazo compound play vital roles for achieving the chemo- and regioselectivity.Auf der anderen Seite: Eine hoch para-selektive goldkatalysierte C-H-Funktionalisierung nichtaktivierter Arene durch 2,2,2-α-Aryl-α-diazoessigsäuretrifluorethylester führt unter milden Bedingungen in guten Ausbeuten zu nützlichen Diarylacetaten mit modifizierbaren funktionellen Gruppen.
      PubDate: 2017-01-27T07:21:37.843524-05:
      DOI: 10.1002/ange.201611809
       
  • Bio-Inspired Fragmentations: Rapid Assembly of Indolones, 2-Quinolinones,
           and (−)-Goniomitine
    • Authors: Haokun Li; Peng Cheng, Long Jiang, Jin-Liang Yang, Liansuo Zu
      Pages: 2798 - 2801
      Abstract: Inspired by the biogenetic origin of goniomitine, new synthetic bio-inspired fragmentation strategies for the synthesis of functionalized 2-quinolinones and indolones have been developed. Remarkable synthetic efficiency was achieved by telescoping several transformations into one-pot reactions, allowing for the direct coupling of 2-alkynyl-anilines and diazo ketones. The synthetic utility was demonstrated by the 5-step asymmetric total synthesis of (−)-goniomitine from 2-ethyl-cyclopentanone.Die konvergente Kupplung eines 2-Alkinylanilins mit einem α-Diazoketon unter N-H-Insertion, intramolekularer Michael-Addition, Fragmentierung und regioselektiver N-Cyclisierung ebnet den Weg für die asymmetrische Totalsynthese von (−)-Goniomitin in nur fünf Stufen (vier Arbeitsschritten) ausgehend von leicht zugänglichen Verbindungen.
      PubDate: 2017-01-27T07:15:33.380748-05:
      DOI: 10.1002/ange.201611830
       
  • Encapsulation and Dynamic Behavior of Methanol and Formaldehyde inside
           Open-Cage C60 Derivatives
    • Authors: Tsukasa Futagoishi; Michihisa Murata, Atsushi Wakamiya, Yasujiro Murata
      Pages: 2802 - 2806
      Abstract: Methanol (CH3OH) and formaldehyde (H2CO) molecules were inserted into an open-cage C60 derivative with a large opening, under high-pressure and high-temperature conditions in solution. Isolation of their molecular complexes in pure form was achieved by the use of recycling HPLC with Buckyprep columns. 1H NMR spectroscopy, single-crystal X-ray diffraction studies, and DFT calculations revealed the orientation of the encapsulated CH3OH and H2CO, both in solution and in the solid state, and the results show that the CH3 group of the CH3OH and the carbonyl group of the H2CO point to the bottom of the cages. Furthermore, the dynamic behavior of the CH3OH and H2CO were studied at the molecular level.Es kann nur eine geben: In offenen C60-Käfigstrukturen wurden CH3OH und H2CO verkapselt, deren Orientierungen in Lösung und im festen Zustand NMR-spektroskopisch, röntgenographisch und durch DFT-Rechnungen bestimmt wurden. Jede Spezies zeigt nur eine Orientierung: Die CH3-Gruppe von CH3OH befindet sich auf der Krümmung des Kohlenstoffkäfigs, und die CH2-Gruppe von H2CO zeigt in Richtung der Öffnung.
      PubDate: 2017-01-31T03:36:00.832522-05:
      DOI: 10.1002/ange.201611903
       
  • Design of Artificial Glycosidases: Metallopeptides that Remove H Antigen
           from Human Erythrocytes
    • Authors: Zhen Yu; James Allan Cowan
      Pages: 2807 - 2810
      Abstract: Catalysts that promote carbohydrate degradation have a wide range of potential applications, but the use of either enzyme glycosidases or small-molecule catalysts in biological systems raises significant challenges. Herein, we demonstrate a novel strategy for the design of synthetic agents that mimic natural glycosidases and address current problems for biological use. This strategy is illustrated by application to the development of potential blood substitutes for the rare Bombay blood type that is characterized by a deficiency of H2 antigen. Metallopeptides with 16 to 20 amino acids were constructed as artificial fucosidases that exhibit selective carbohydrate cleavage reactivity toward l-fucose over d-glucose. Selective fucose cleavage from the H2-antigen saccharide enables efficient removal of H2 antigen from erythrocytes and thereby accomplishes the conversion of regular human type-O blood into a potential blood substitute for the rare Bombay blood type.Blutzuckerspielchen: Metallopeptide wurden als künstliche Fucosidasen entworfen, die l-Fucose selektiv gegenüber d-Glucose spalten. Die selektive Spaltung von Fucose (Fuc) im H2-Antigen-Trisaccharid (Fucα1-2Galβ1-4GlcNAcβ) ermöglicht die Entfernung des H2-Antigens aus Humanerythrozyten, wodurch Gruppe-0-Blut möglicherweise in einen Ersatz für die seltene Bombay-Blutgruppe umgewandelt werden könnte.
      PubDate: 2017-01-27T07:15:29.834164-05:
      DOI: 10.1002/ange.201612079
       
  • Modular Assembly of Spirocarbocyclic Scaffolds through Pd0-Catalyzed
           Intermolecular Dearomatizing [2+2+1] Annulation of Bromonaphthols with
           Aryl Iodides and Alkynes
    • Authors: Zhijun Zuo; Hui Wang, Liangxin Fan, Jingjing Liu, Yaoyu Wang, Xinjun Luan
      Pages: 2811 - 2815
      Abstract: A novel palladium(0)-catalyzed dearomatizing [2+2+1] spiroannulation of 1-bromo-2-naphthols with aryl iodides and alkynes was developed for the rapid assembly of spiro[indene-1,1′-naphthalen]-2′-ones. This three-component cascade reaction was realized through consecutive Catellani-type C−H activation, unsymmetrical biaryl coupling, alkyne migratory insertion, and arene dearomatization. The potential utility of our method is illustrated by the one-step construction of the polycyclic skeletons of dalesconols A and B from alkyne-tethered aryl iodides and 1-bromo-2-naphthol.Spiro[inden-1,1′-naphthalin]-2′-one sind über die Titelreaktion ausgehend von 1-Brom-2-naphtholen, Aryliodiden und Alkinen schnell zugänglich. Die Dreikomponentenkaskade verläuft als Sequenz aus Catellani-C-H-Aktivierung, unsymmetrischer Biarylkupplung, migratorischer Alkininsertion und Dearomatisierung.
      PubDate: 2017-01-27T07:15:44.176281-05:
      DOI: 10.1002/ange.201612127
       
  • A Cationic Unsaturated Platinum(II) Complex that Promotes the
           Tautomerization of Acetylene to Vinylidene
    • Authors: Laura Ortega-Moreno; Riccardo Peloso, Joaquín López-Serrano, Javier Iglesias-Sigüenza, Celia Maya, Ernesto Carmona
      Pages: 2816 - 2819
      Abstract: Complex [PtMe2(PMe2ArDipp2)] (1), which contains a tethered terphenyl phosphine (ArDipp2=2,6-(2,6-iPr2C6H3)2C6H3), reacts with [H(Et2O)2]BArF (BArF−=B[3,5-(CF3)2C6H3]4−) to give the solvent (S) complex [PtMe(S)(PMe2ArDipp2)]+ (2⋅S). Although the solvent molecule is easily displaced by a Lewis base (e.g., CO or C2H4) to afford the corresponding adducts, treatment of 2⋅S with C2H2 yielded instead the allyl complex [Pt(η3-C3H5)(PMe2ArDipp2)]+ (6) via the alkyne intermediate [PtMe(η2-C2H2)(PMe2ArDipp2)]+ (5). Deuteration experiments with C2D2, and kinetic and theoretical investigations demonstrated that the conversion of 5 into 6 involves a PtII-promoted HC≡CH to :C=CH2 tautomerization in preference over acetylene migratory insertion into the Pt−Me bond.Der kationische Komplex [PtMe(Solvens)(PMe2Ar)]+ reagiert mit Acetylen zum Allylkomplex [Pt(η3-C3H5)(PMe2Ar)]+, der formal das Produkt einer klassischen migratorischen Insertion ist. Deuterierungsexperimente mit C2D2, kinetische und theoretische Studien zeigen jedoch, dass die Umwandlung als PtII-vermittelte Tautomerisierung von HC≡CH zu :C=CH2 verläuft.
      PubDate: 2017-02-01T02:06:39.971975-05:
      DOI: 10.1002/ange.201700087
       
  • Mechanistische Studien an zwei bakteriellen Diterpencyclasen:
           Spiroviolen-Synthase und Tsukubadien-Synthase
    • Authors: Patrick Rabe; Jan Rinkel, Etilia Dolja, Thomas Schmitz, Britta Nubbemeyer, T. Hoang Luu, Jeroen S. Dickschat
      Pages: 2820 - 2823
      Abstract: Die Mechanismen von zwei Diterpencyclasen aus Streptomyceten – eine mit unbekanntem Produkt, das als der spirocyclische Kohlenwasserstoff Spiroviolen identifiziert wurde, und eine mit dem bekannten Produkt Tsukubadien – wurden detailliert durch Isotopenmarkierungsexperimente untersucht. Obwohl die Strukturen der Produkte sehr unterschiedlich sind, beginnen die Cyclisierungsmechanismen beider Enzyme mit derselben Cyclisierungsreaktion, bevor sie auf dem Weg zu ihren individuellen Produkten divergieren. Dies spiegelt die nahe phylogenetische Verwandtschaft der Enzyme wider.Die Produkte von zwei verwandten Diterpencyclasen aus Streptomyceten wurden identifiziert. Die Mechanismen der Enzyme wurden durch extensive Markierungsexperimente untersucht. Obwohl die Strukturen der Diterpene sehr unterschiedlich sind, sind einige Schritte der Cyclisierungskaskaden sehr ähnlich, was vermuten lässt, dass geringe Konformationsänderungen des Substrates zur Bildung der einzigartigen Produkte führen.
      PubDate: 2017-02-01T02:06:22.086819-05:
      DOI: 10.1002/ange.201612439
       
  • Poly(p-phenyleniminoboran): ein Bor-Stickstoff-Analogon von
           Poly(p-phenylenvinylen)
    • Authors: Thomas Lorenz; Merian Crumbach, Thomas Eckert, Artur Lik, Holger Helten
      Pages: 2824 - 2828
      Abstract: Der isoelektronische und isostere Austausch ausgewählter CC- durch BN-Einheiten in π-konjugierten organischen Systemen (BN/CC-Isosterie) hat sich als erfolgreiche Strategie zur Entwicklung BN-dotierter polycyclischer aromatischer Kohlenwasserstoffe (PAKs) mit faszinierenden Eigenschaften und Funktionen erwiesen. Unlängst haben erste Beispiele die Nützlichkeit dieses Konzepts in der Polymerchemie gezeigt. Hier stellen wir die Synthese und Charakterisierung des ersten Poly(p-phenyleniminoborans) vor. Dieses neue anorganisch-organische Hybridpolymer kann als BN-Analogon des bekannten Poly(p-phenylenvinylens) (PPV) angesehen werden. Photophysikalische Untersuchungen am Polymer und einer Reihe von Modelloligomeren geben eindeutige Hinweise auf π-Konjugation über die B=N-Bindungen und eine Erweiterung der Konjugationslänge mit wachsender Kettenlänge. TD-DFT-Rechnungen verschaffen einen tieferen Einblick in die elektronische Struktur der neuen Materialien.Ein BN-Analogon des halbleitenden organischen Polymers Poly(p-phenylenvinylen) (PPV) wurde mittels einer hocheffizienten Si/B-Austausch-Polykondensation hergestellt. Das neue anorganisch-organische Hybridpolymer und verwandte monodisperse Oligomere zeigen ein gewisses Maß an π-Konjugation über die B=N-Einheiten entlang des Rückgrats und eine Erweiterung der Konjugationslänge mit wachsender Kettenlänge.
      PubDate: 2017-02-01T02:06:31.3013-05:00
      DOI: 10.1002/ange.201612476
       
  • Einschaltbare Fluoreszenz in Tetra-NHC-Liganden durch Versteifung bei der
           Komplexbildung: eine Alternative zu aggregationsinduzierter Emission
    • Authors: Narayan Sinha; Linda Stegemann, Tristan T. Y. Tan, Nikos L. Doltsinis, Cristian A. Strassert, F. Ekkehardt Hahn
      Pages: 2829 - 2833
      Abstract: Mit den Tetraphenylethylen(TPE)-verbrückten Tetraimidazolium-Salzen [H4L-Et](PF6)4 und [H4L-Bu](PF6)4 wurden die zweikernigen AgI- und AuI-Tetracarben-Komplexe [Ag2(L-Et)](PF6)2, [Ag2(L-Bu)](PF6)2, [Au2(L-Et)](PF6)2 und [Au2(L-Bu)](PF6)2 synthetisiert. In verdünnter Lösung zeigen die Tetraimidazolium-Salze fast keine Fluoreszenz (ΦF
      PubDate: 2017-01-27T05:30:34.450991-05:
      DOI: 10.1002/ange.201610971
       
  • Eine durch Lipid-Wasser-Trennung verstärkte FRET-Sonde zur Detektion der
           Sauren Sphingomyelinase in lebenden Zellen
    • Authors: Thomas Pinkert; David Furkert, Thomas Korte, Andreas Herrmann, Christoph Arenz
      Pages: 2834 - 2838
      Abstract: Eine Echtzeit-Beobachtung der Aktivität der Sauren Sphingomyelinase (ASM) ist notwendig zur Aufklärung ihrer Rolle in Lipid-Signaltransduktionsprozessen. Mithilfe von Phosphorodichloridat-Chemie gelang die Synthese von fluoreszierenden Phosphosphingolipiden mit der Fähigkeit zum FRET. Diese Sphingomyelin-Analoga sind Substrate für die rekombinante humane ASM und ermöglichen die Verfolgung der ASM-Aktivität mittels Fluoreszenzspektroskopie. Inkubation mit Zell-Lysaten von Wildtyp- und Knockout-Mäusen zeigte eine ausschließliche Spaltung durch ASM. Darüber hinaus nutzten wir systematisch die Umgebungsempfindlichkeit der Fluorophore, um signifikante Zuwächse in der Responsivität zu erzielen. Die dabei angewendeten Konzepte könnten auch für andere zukünftige Lipase-Sonden zum Einsatz kommen. Eine mikroskopische Abbildung der ASM-Aktivität in lebenden Zellen wurde mittels Zweiphotonenanregung realisiert.Eine FRET-Sonde für die Saure Sphingomyelinase wurde entworfen. Während eine erste Sonde einer Fluoreszenzlöschung aufgrund von Umgebungsempfindlichkeit unterlag (oben), konnte in einer zweiten Sonde dasselbe Phänomen genutzt werden, um die Hintergrundfluoreszenz zu unterdrücken (unten). Diese Sonde wurde anschließend genutzt, um die Aktivität der Sauren Sphingomyelinase in vitro und in lebenden Zellen mithilfe von Zweiphotonenanregungsmikroskopie zu detektieren.
      PubDate: 2017-02-03T02:35:31.549747-05:
      DOI: 10.1002/ange.201611706
       
  • Deprotonierung eines Hydridoborat-Anions
    • Authors: Johannes Landmann; Fabian Keppner, Daniel B. Hofmann, Jan A. P. Sprenger, Mathias Häring, Sven H. Zottnick, Klaus Müller-Buschbaum, Nikolai V. Ignat'ev, Maik Finze
      Pages: 2839 - 2843
      Abstract: Die Reaktionen von [BH(CN)3]− mit starken nicht-nucleophilen Basen sind die ersten Beispiele für die Deprotonierung eines Hydridoborat-Anions. Diese liefern Alkalimetall-Salze mit dem Tricyanoborat-Dianion B(CN)32− in bis zu 97 % Ausbeute und 99.5 % Reinheit. [BH(CN)3]− ist weniger acide als (Me3Si)2NH, aber eine stärkere Säure als iPr2NH. Sterisch weniger gehinderte, stärker nucleophile Basen wie PhLi und MeLi greifen hauptsächlich die CN-Gruppen unter Bildung von Imino-Dianionen [RC(N)B(CN)3]2− an, die mit Wasser zu Ketonen vom Typ [RC(O)B(CN)3]− reagieren. Das Bor-zentrierte Nucleophil B(CN)32− reagiert mit CO2 und CN+-Reagenzien in exzellenten Ausbeuten zu Salzen mit dem [B(CN)3CO2]2−- bzw. dem Tetracyanoborat-Anion [B(CN)4]−.Angriff an B: In der erstmalig beschriebenen Deprotonierung eines Hydridoborat-Anions reagiert das leicht zugängliche [BH(CN)3]− mit starken nicht-nucleophilen Basen in hoher Reinheit und Ausbeute zum Bor-zentrierten Nucleophil B(CN)32−. Das B(CN)32−-Dianion reagiert mit CN+-Reagentien zum Tetracyanoborat-Anion und mit CO2 zum Carbonsäure-Derivat [B(CN)3CO2]2−, dessen Salze vielversprechende Reagentien für die Cyanoborat-Chemie und die Materialwissenschaften sind.
      PubDate: 2017-01-24T07:01:51.133032-05:
      DOI: 10.1002/ange.201611899
       
  • Protonierung kontra Oxoniumsalz-Bildung: Abstimmung der Basizität und
           Stabilität von Cyanoborat-Anionen
    • Authors: Christoph Kerpen; Jan A. P. Sprenger, Lorena Herkert, Marius Schäfer, Lisa A. Bischoff, Pierre Zeides, Matthias Grüne, Rüdiger Bertermann, Franziska A. Brede, Klaus Müller-Buschbaum, Nikolai V. Ignat'ev, Maik Finze
      Pages: 2844 - 2848
      Abstract: Wasserfreies H[BH2(CN)2] kristallisiert aus sauren wässrigen Lösungen des Dicyanodihydridoborat-Anions. Die Bildung von H[BH2(CN)2] ist überraschend, da die Protonierung von Nitrilen stark saure und wasserfreie Bedingungen erfordert, sie lässt sich aber auf Basis theoretischer Daten verstehen. [BX(CN)3]− (X=H, F) liefern dagegen die erwarteten Oxonium-Salze (H3O)[BX(CN)3], wohingegen (H3O)[BF2(CN)2]/H[BF2(CN)2] instabil ist. H[BH2(CN)2] schmilzt bei 54 °C und bildet im Festkörper Ketten über N−H⋅⋅⋅N-Bindungen. Lösungen von H[BH2(CN)2] in der ionischen Flüssigkeit [EMIm][BH2(CN)2] enthalten das [(NC)H2BCN-H⋅⋅⋅NCBH2(CN)]−-Anion. Aufgrund der ungewöhnlichen Stabilität der Lösungen konnten ausgewählte spektroskopische und physikalische Eigenschaften untersucht werden. [(NC)H2BCN-H⋅⋅⋅NCBH2(CN)]− reagiert langsam zu H2 und [(NC)H2BCN-BH(CN)2]−. Letztgenanntes dient als Quelle für die freie Lewis-Säure BH(CN)2, was anhand der Bildung von [BHF(CN)2]− und BH(CN)2⋅py demonstriert wurde.H[BH2(CN)2] kristallisiert als niedrig schmelzendes 1-D-Polymer aus saurer wässriger Lösung, [BX(CN)3]− (X=H, F) geben dagegen (H3O)[BX(CN)3]. Festes H[BH2(CN)2] ist unbegrenzt stabil, und in Lösung und der Schmelze zersetzt es sich nur langsam unter H2-Entwicklung, was den schwachen hydridischen Charakter von [BH2(CN)2]− belegt. H[BH2(CN)2] hat Potenzial als Reagens, weshalb seine Lösungen in [EMIm][BH2(CN)2] detailliert untersucht wurden.
      PubDate: 2017-01-27T07:32:22.365399-05:
      DOI: 10.1002/ange.201611901
       
  • Innenrücktitelbild: Surface-Enhanced Raman Spectra Promoted by a Finger
           Press in an All-Solid-State Flexible Energy Conversion and Storage Film
           (Angew. Chem. 10/2017)
    • Authors: Haitao Li; Han Dai, Yihe Zhang, Wangshu Tong, Hua Gao, Qi An
      Pages: 2849 - 2849
      Abstract: Raman-Signalverstärkung per Fingerdruck wurde durch Kombination eines flexiblen, piezoelektrischen und dielektrischen Energieumwandel- und Speicherfilms mit Silbernanodrahtschichten erhalten. In der Zuschrift auf S. 2693 ff. beschreiben Y. Zhang, Q. An et al. ein selbstanregendes SERS-Trägermaterial (SERS=oberflächenverstärkte Raman-Streuung), das Filmdeformationen in gespeicherte elektrische Energie umwandeln kann, die dann Elektronen in eine Silbernanodrahtschicht injiziert und die darin gemessenen SERS-Signale erhöht.
      PubDate: 2017-02-15T04:35:36.729348-05:
      DOI: 10.1002/ange.201701297
       
  • From composition to cure: A systems engineering approach to anti-cancer
           drug carriers
    • Authors: Sarah Reagan MacEwan; Ashutosh Chilkoti
      Abstract: The molecular complexity and heterogeneity of cancer has led to a persistent, and as yet unsolved, challenge of developing cures for this disease. Although the pharmaceutical industry focuses the bulk of its efforts on the development of new drugs, an alternative —and in many ways complementary— approach is the improvement of the delivery of existing drugs with drug carriers that can manipulate when, where, and how a drug exerts its therapeutic effect. For the treatment of solid tumors, systemically delivered drug carriers face significant challenges that are imposed by the pathophysiological barriers that lie between their site of administration and their site of therapeutic action in the tumor. Furthermore, drug carriers face additional challenges in their translation from pre-clinical validation to clinical approval and adoption. Addressing this diverse network of challenges requires a systems engineering approach to anti-cancer drug delivery. Such a perspective is needed to better enable the rational design of optimized vehicles that navigate the trade-offs of this complex system to create next generation anti-cancer drug carriers that have a realistic prospect for translation from the lab to the patient.
      PubDate: 2016-12-27T22:20:32.206682-05:
      DOI: 10.1002/ange.201610819
       
  • Gaining Momentum: Sulfonimidamides in Medicinal- and Agrochemistry
    • Authors: Praveen K Chinthakindi; Tricia Naicker, Niranjan Thota, Thavendran Govender, Hendrik G Kruger, Per I. Arvidsson
      Abstract: Synthesis and evaluation of structural analogues and isosteres represent a cornerstone methodology among the practitioners of medicinal- and agrochemistry. The sulfonamide functional group represents one of the most important amide isosteres in contemporary drug design, with some 500 compounds that has overcome both the pharmacological and regulatory hurdles that precede studies in humans. We note that mono aza-analogues of sulfonamides, i.e. sulfonimidamides, are rapidly gaining popularity as a novel functional group among molecular architects involved in the design of biologically active compounds for both pharmaceutical- and agrochemical applications. Herein, we review these recent developments with the ambition to showcase the promise of this functional group to the wider chemical community.
      PubDate: 2016-12-13T06:05:24.30595-05:0
      DOI: 10.1002/ange.201610456
       
  • Methyltransferase directed labeling of biomolecules and its applications
    • Authors: Jochem Deen; Charlotte Vranken, Volker Leen, Robert K Neely, Kris Pieter Frans Janssen, Johan Hofkens
      Abstract: Methyltransferases (MTases) compose a large family of enzymes which have the ability to methylate a diverse set of targets, ranging from the three major biopolymers DNA, RNA and protein to small molecules. Most of these MTases use the cofactor S-Adenosyl-L-Methionine (AdoMet) as their methyl source. Given the important biological role of methylation, e.g. in epigenetic regulation of gene activity and the vast potential of targeted functionalization in biology, diagnostics and nanotechnology, it should come as no surprise that recent years have seen significant efforts in the development of AdoMet analogues with the aim of transferring moieties other than simple methyl groups. Two major classes of AdoMet analogues currently exist- the doubly-activated and aziridine based molecules- each of which employs a different approach for transalkylation, as opposed to transmethylation, of the target molecule. In this review, we discuss the various strategies for labelling and functionalizing biomolecules using AdoMet-dependent MTases and AdoMet analogues. We cover the synthetic routes to AdoMet analogues, their stability in biological environments and their application in transalkylation reactions. Finally, some perspectives are presented for the potential use of AdoMet analogues in biology research, (epi)genetics and nanotechnology.
      PubDate: 2016-12-12T04:16:28.246834-05:
      DOI: 10.1002/ange.201608625
       
  • Synthetic Biology - The Synthesis of Biology
    • Authors: Simon Ausländer; David Ausländer, Martin Fussenegger
      Abstract: Synthetic biology envisages the engineering of man-made living biomachines from standardized components that can perform pre-defined functions in a (self-)controlled manner. Different research strategies and interdisciplinary efforts are pursued to implement engineering principles to biology. The "top-down" strategy exploits nature's incredible diversity of existing, natural parts to construct synthetic compositions of genetic, metabolic or signalling networks with predictable and controllable properties. This mainly application-driven approach results in living factories that produce drugs, biofuels, biomaterials and fine chemicals and results in living pills that are based on engineered cells with the capacity to autonomously detect and treat disease states in vivo. In contrast, the "bottom-up" strategy seeks to be independent of existing living systems by designing biological systems from scratch and synthesizing artificial biological entities not found in nature. This more knowledge-driven approach investigates the reconstruction of minimal biological systems that are capable of performing basic biological phenomena, such as self-organization, self-replication and self-sustainability. Moreover, the syntheses of artificial biological units, such as synthetic nucleotides or amino acids, and their implementation into polymers inside living cells currently set the boundaries between natural and artificial biological systems. In particular, the in vitro design, synthesis and transfer of complete genomes into host cells and the application of efficient genome-wide intervention techniques point to the future of synthetic biology: the creation of living designer cells with tailored desirable properties for biomedicine and biotechnology.
      PubDate: 2016-12-11T23:24:13.846386-05:
      DOI: 10.1002/ange.201609229
       
  • Modern Synthetic Avenues for the Preparation of Functional Fluorophores
    • Authors: Fabio De Moliner; Nicola Kielland, Rodolfo Lavilla, Marc Vendrell
      Abstract: Biomedical research relies on the fast and accurate profiling of specific biomolecules and cells in a non-invasive manner. Functional fluorophores have consolidated as powerful tools for such studies. Since these sophisticated structures are often difficult to access through conventional synthetic strategies, novel chemical processes have been developed in the last years. In this Minireview we describe the most recent advances in the design, preparation and fine-tuning of fluorophores by means of multicomponent reactions, C-H activation processes, cycloadditions and biomolecule-based chemical transformations.
      PubDate: 2016-12-01T15:50:42.740152-05:
      DOI: 10.1002/ange.201609394
       
  • 50 (and more) Years of Propellane Chemistry - From a Chemical Curiosity to
           "Explosive" Applications in Material Sciences and Natural Product
           Chemistry
    • Authors: Alicia Merve Dilmac; Eduard Spuling, Armin de Meijere, Stefan Bräse
      Abstract: Propellanes are a unique class of compounds with well over 10000 members with an inverted tetrahedral configuration featuring a weak single bond between two carbon atoms linked by three additional bridge. Not only structurally interesting, these propella-type compounds exhibit unusual reactivities. In this review, we highlight their synthesis and applications in material sciences, natural product chemistry and medicinal chemistry. We feature the chemistry of [1.1.1]propellane like the synthesis of oligomeric and polymeric structures derived from it such as bicyclo[1.1.1]pentanes and staffanes. A selected number of natural products are discussed in detail. Heteropropellanes and inorganic propellanes are also addressed. The historical background is given in brief showing the pioneering work of David Ginsburg, Günther Snatzke, Günter Szeimies, Kenneth Wiberg and others.
      PubDate: 2016-11-30T12:15:40.668115-05:
      DOI: 10.1002/ange.201603951
       
  • Label-free molecular imaging of biological cells and tissues by linear and
           non-linear Raman spectroscopic approaches
    • Authors: Jürgen Popp; Christoph Krafft, Michael Schmitt, Iwan Schie, Dana Cialla-May, Christian Matthaeus, Thomas Bocklitz
      Abstract: Raman spectroscopy is an emerging technique in bioanalysis and imaging of biomaterials due to its unique spectroscopic fingerprint capabilities. Imaging of cells and tissues by Raman microspectroscopy represents a non-destructive and label-free approach. All components of cells or tissues contribute to the Raman signals giving complex spectral signatures. Long acquisitions times are often required due to the relatively small Raman scattering cross sections. To overcome these limitations, Raman signal enhancing methods like resonance Raman scattering and surface enhanced Raman scattering can be applied that also reduce the spectral complexity because the enhancement is often restricted to selected bands. Raman-active labels can be introduced to increase specificity and multimodality. In addition, non-linear coherent Raman scattering such as coherent anti-Stokes Raman scattering and stimulated Raman scattering offer higher sensitivities which enable rapid imaging of larger sampling areas. Finally, fiber based imaging techniques open the way towards in vivo applications of Raman spectroscopy. This critical review summarizes theory, instrumentation, data processing and progress of medical Raman imaging since 2012.
      PubDate: 2016-11-15T16:29:42.063815-05:
      DOI: 10.1002/ange.201607604
       
  • Metal Fluorides as Analogs for Studies on Phosphoryl Transfer Enzymes
    • Authors: George Michael Blackburn; Yi Jin, Nigel G Richards, Jonathan P Waltho
      Abstract: The 1994 structure of a transition state analog with AlF4- and GDP complexed to G1, a small G protein, heralded a new field of research into structure and mechanism of enzymes that manipulate transfer of the phosphoryl (PO3-) group. The list of enzyme structures that embrace metal fluorides, MFx, as ligands that imitate either the phosphoryl group or a phosphate, is now growing at over 80 per triennium. They fall into three distinct geometrical classes: (i) Tetrahedral complexes, based on BeF3-, mimic ground state phosphates; (ii) Octahedral complexes, primarily based on AlF4-, mimic "in-line" anionic transition state for phosphoryl transfer; and (iii) Trigonal bipyramidal complexes, represented by MgF3- and putative AlF30 moieties, additionally mimic the tbp geometry of the transition state. The interpretation of these structures provides a deeper mechanistic understanding of the behavior and manipulation of phosphate monoesters in molecular biology. This review provides a comprehensive overview of these structures, their uses, and their computational development. It questions the identification of AlF30 and MgF4= as tbp species in protein complexes and discusses the relevance of physical organic chemistry and water-based model studies for understanding phosphoryl group transfer in enzymes. It describes two roles for amino acid side-chains that mediate proton transfers during phosphoryl transfer, based on the analysis of protein/MFx structures. First, they deploy hydrogen bonding to neutral oxygen nucleophiles so as to orientate them for correct orbital overlap with the electrophilic phosphorus center. Secondly, they behave as classical general acid/base catalysts.
      PubDate: 2016-11-08T11:02:56.779882-05:
      DOI: 10.1002/ange.201606474
       
  • The Stability Challenges of Oxygen Evolving Electrocatalysts: Towards a
           Common Fundamental Understanding and Mitigation of Catalyst Degradation
    • Authors: Camillo Spoeri; Jason Tai Hong Kwan, Arman Bonakdarpour, David Wilkinson, Peter Strasser
      Abstract: The electrochemical oxygen evolution reaction (OER) is an important reaction in the industrial production of numerous inorganic chemicals. However, over the last decade it has also received growing attention as scalable proton- and electron-providing process for use in the production of solar fuels, such as hydrogen, hydrocarbons, or alcohols carried out in water- and CO2-electrolyzers. To operate these devices efficiently and economically , active and stable electrocatalysts are required. While advances have been made in understanding and tuning OER efficiency and activity, the stability of OER catalysts and the reduction of their degradation continue to be major challenges. While most stability studies limit themselves to short-term testing in idealized three-electrode set ups, a much stronger focus on advancing our understanding of degradation of OER catalysts in realistic Membrane Electrode Assemblies (MEAs) with industrial current densities, is critically needed.This review addresses the technical challenges, their scientific basis, as well as recent progress and the road ahead regarding stability and degradation of OER catalysts operating at electrolyzer anodes in acidic MEA environments. First, we start clarifying the complexity associated with the term "catalyst stability", cover today's performance targets and outline major catalyst degradation mechanisms and their mitigation strategies. Then we evaluate suitable in-situ experimental methods to get insight into catalyst degradation and describe achievements in tuning OER catalyst stability. Finally, we highlight the importance of identifying universal figures of merit for stability and develop a comprehensive accelerated life test (ALT) that would yield comparable performance data across labs and catalyst types. As a whole, this review will help to disseminate and highlight the important relations between structure, composition and stability of OER catalysis under different operating conditions.
      PubDate: 2016-11-01T09:20:36.743545-05:
      DOI: 10.1002/ange.201608601
       
  • Vesicles and their multiple facets: underpinning biological and synthetic
           progress
    • Authors: Paula M. Mendes; Francisco Fernandez-Trillo, Liam Grover, Alex Stephenson-Brown, Paul Harrison
      Abstract: The important role of vesicles in many aspects of cell function is well recognised but only recently have sophisticated imaging techniques begun to reveal their ubiquity in nature. While we further our understanding of the biological properties of vesicles and their physiological functions, increasingly elegantly designed artificial vesicles are being reported for a wide range of technological applications and basic studies. Herein, we bring together both the biological and synthetic state-of-the-art on vesicles and place their biological features in the context of recent synthetic developments, providing a unique view of these complex and rapidly developing fields. The perspectives on the challenges and opportunities for future biological and synthetic progress on vesicles are also presented.
      PubDate: 2016-10-12T13:26:03.249846-05:
      DOI: 10.1002/ange.201607825
       
  • Power-to-Syngas - an enabling technology for the transition of the energy
           system? Production of tailored synfuels and chemicals using renewably
           generated electricity.
    • Authors: Severin Foit; Rüdiger-A. Eichel, Izaak C. Vinke, Lambertus G.J. de Haart
      Abstract: Power-to-X concepts promise a significant reduction of greenhouse gas emissions and simultaneously guaranteeing a safe energy supply even at high share of renewable power generation, thus becoming a cornerstone of a sustainable energy system. Power-to-Syngas, i.e. the electrochemical conversion of steam and carbon dioxide with the use of renewably generated electricity to syngas for the production of synfuels and high-value chemicals, offers an efficient technology to couple different energy-intense sectors, such as 'traffic and transportation' and 'chemical industry'. Consequently, co-electrolysis can be regarded as a key-enabling step for a transition of the energy system that offers additionally features of CO2-valorization and closed carbon cycles. In this Minireview, we outline and discuss advantages and current technical limitations of low- and high-temperature co-electrolysis. Advances in both, a fundamental understanding of the basic reaction schemes and in stable high-performance materials are essential to further promote co-electrolysis.
      PubDate: 2016-10-07T02:46:24.908026-05:
      DOI: 10.1002/ange.201607552
       
  • Surface Modification of Water Purification Membranes: a Review
    • Authors: Daniel Miller; Daniel Dreyer, Christopher Bielawski, Donald Paul, Benny Freeman
      Abstract: Polymer membranes are an energy‐efficient means of purifying water, but they suffer from fouling during filtration. Membrane surface modification is one route to mitigate membrane fouling as it helps to maintain high levels of water productivity. Here, a series of common membrane surface modification techniques are reviewed, including surface coating, grafting, and various treatment techniques such as chemical treatment, UV irradiation, and plasma treatment, among others. Historical background on membrane development and surface modification is also provided. Finally, polydopamine, an emerging material that can be easily deposited onto a wide variety of substrates, is discussed in the context of membrane modification. The chemistry of polydopamine is also reviewed.
      PubDate: 2016-09-08T06:35:42.626644-05:
      DOI: 10.1002/ange.201601509
       
  • Name Reactions in Biological Chemistry
    • Authors: Hung-wen Liu; Chia-I Lin, Reid M. McCarty
      Abstract: Chemical reactions that are named in honor of their true or at least perceived discoverers are known as "name reactions". This review is a collection of biological representatives of named chemical reactions. Emphasis is placed on reaction types and catalytic mechanisms that showcase both the chemical diversity in natural product biosynthesis as well as the parallels with synthetic organic chemistry. An attempt has been made to describe the enzymatic mechanisms of catalysis within the context of their synthetic counterparts whenever possible and to discuss the mechanistic hypotheses for those reactions that are presently active areas of investigation. This review has been categorized by reaction type, e.g., condensation, reduction and oxidation, substitution, carboxylation, radical‐mediated, and rearrangements, which are subdivided by named reactions.
      PubDate: 2016-08-09T07:30:46.620315-05:
      DOI: 10.1002/ange.201603291
       
  • Michael Schmittel
    • Pages: 2580 - 2580
      Abstract: „Was ich gerne entdeckt hätte, ist das Penicillin. Ich bin Chemiker geworden, weil die Chemie für mich ein unendliches Faszinosum ist ...“ Dies und mehr von und über Michael Schmittel finden Sie auf Seite 2580.
      PubDate: 2016-09-26T01:41:02.749548-05:
      DOI: 10.1002/ange.201608184
       
 
 
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