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  Subjects -> CHEMISTRY (Total: 845 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (596 journals)
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CHEMISTRY (596 journals)                  1 2 3 | 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: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 31)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 22)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 38)
ACS Nano     Full-text available via subscription   (Followers: 216)
ACS Photonics     Full-text available via subscription   (Followers: 10)
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: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 48)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 12)
Advances in Chemistry     Open Access   (Followers: 12)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 18)
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: 10)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 65)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 25)
American Journal of Plant Physiology     Open Access   (Followers: 12)
American Mineralogist     Full-text available via subscription   (Followers: 12)
Analyst     Full-text available via subscription   (Followers: 39)
Angewandte Chemie     Hybrid Journal   (Followers: 150)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 205)
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: 22)
Applied Surface Science     Hybrid Journal   (Followers: 24)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemistry     Full-text available via subscription   (Followers: 267)
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: 18)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 106)
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: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 2)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 11)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 68)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 170)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 15)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 131)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 17)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 8)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 43)
Chemistry of Materials     Full-text available via subscription   (Followers: 183)
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: 2)
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: 22)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 10)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 3)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 48)
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: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 7)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 19)
Enzyme Research     Open Access   (Followers: 4)

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [150 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  [1589 journals]
  • Asymmetric Total Synthesis of Hispidanin A
    • Authors: Heping Deng; Wei Cao, Rong Liu, Yanhui Zhang, Bo Liu
      Abstract: Asymmetric total synthesis of the dimeric diterpenoid hispidanin A was accomplished by non-catalytic Diels–Alder cycloaddition at room temperature. The synthesis relies on iron-catalyzed coupling to construct a Z-configured trisubstituted alkene, an iron-catalyzed radical cascade to generate a labdane-type diene, and both Yamamoto cationic polyene cyclization and palladium-catalyzed Stille coupling to generate a totarane-type dienophile.Radikaler Ansatz: Eine asymmetrische Totalsynthese des dimeren Diterpenoids Hispidanin A beruht auf einer [4+2]-Cycloaddition, die spontan und ohne Katalysator bei Raumtemperatur stattfindet. Das Dien-Fragment wird über eine radikalische Polyen-Cyclisierung, ausgelöst durch einen metallkatalysierten Wasserstoffatomtransfer aufgebaut. Eine asymmetrische kationische Polyen-Cyclisierung führt dann das Dienophil-Fragment ein.
      PubDate: 2017-04-20T03:43:30.058554-05:
      DOI: 10.1002/ange.201700958
       
  • A Highly Active Manganese Catalyst for Enantioselective Ketone and Ester
           Hydrogenation
    • Authors: Magnus B. Widegren; Gavin J. Harkness, Alexandra M. Z. Slawin, David B. Cordes, Matthew L. Clarke
      Abstract: A new hydrogenation catalyst based on a manganese complex of a chiral P,N,N ligand has been found to be especially active for the hydrogenation of esters down to 0.1 mol % catalyst loading, and gives up to 97 % ee in the hydrogenation of pro-chiral deactivated ketones at 30–50 °C.Unedles Metall für eine kostbare Katalyse: Ein neuer Mangan-Katalysator wurde entwickelt, der die enantioselektive Hydrierung von Ketonen ermöglicht (siehe Schema). Der „unedle” Katalysator hydriert auch Ester bei sehr niedrigen Katalysatorkonzentrationen.
      PubDate: 2017-04-20T01:10:58.446945-05:
      DOI: 10.1002/ange.201702406
       
  • Enantioselective Synthesis of (+)-Mitomycin K by a Palladium-Catalyzed
           Oxidative Tandem Cyclization
    • Authors: Qiang-Shuai Gu; Dan Yang
      Abstract: The mitomycins, a family of bioactive natural products, feature a compact 6/5/5-fused polycyclic ring structure densely decorated with highly reactive and/or fragile quinone, amino ketal, and aziridine as well as carbamate moieties. It is this striking feature that has defeated numerous synthetic attempts towards these apparently small molecules, rendering them one of the most formidable targets for total synthesis. We herein report the first enantioselective synthesis of (+)-mitomycin K, a representative of G series mitomycins. The key step of this synthesis is an enantioselective oxidative cyclization catalyzed by a palladium/(+)-sparteine system that had previously been developed by our group. The robustness of this method bodes well for further applications in the asymmetric total synthesis of natural products, particularly those with characteristic 6/5/5-fused pyrroloindole skeletons.Endlich enantioselektiv: Jahrzehnte nach seiner Isolierung gelang die erste enantioselektive Synthese von Mitomycin K durch eine asymmetrische Palladium-katalysierte oxidative Tandemcyclisierung zum Aufbau des Ringgerüsts mit hoher Enantioselektivität. Anschließende mehrstufige Umsetzungen führten schließlich zu (+)-Mitomycin K mit 97 % ee.
      PubDate: 2017-04-20T01:10:52.066841-05:
      DOI: 10.1002/ange.201701895
       
  • Control of Vicinal Stereocenters through Nickel-Catalyzed
           Alkyl–Alkyl Cross-Coupling
    • Authors: Xin Mu; Yu Shibata, Yusuke Makida, Gregory C. Fu
      Abstract: Vicinal stereocenters are found in many natural and unnatural compounds. Although metal-catalyzed cross-coupling reactions of unactivated alkyl electrophiles are emerging as a powerful tool in organic synthesis, there have been virtually no reports of processes that generate, much less control, vicinal stereocenters. In this investigation, we establish that a chiral nickel catalyst can mediate doubly stereoconvergent alkyl–alkyl cross-coupling, specifically, reactions of a racemic pyrrolidine-derived nucleophile with cyclic alkyl halides (as mixtures of stereoisomers) to produce vicinal stereocenters with very good stereoselectivity.Seite an Seite: Ein chiraler Nickelkatalysator vermittelt die zweifach stereokonvergente Alkyl-Alkyl-Kreuzkupplung zwischen racemischen Pyrrolidin-Derivaten als Nukleophilen und cyclischen Alkylhalogeniden, die jeweils als Stereoisomerengemisch eingesetzt werden. Die Produkte enthalten vicinale Stereozentren, die hoch stereoselektiv eingeführt werden.
      PubDate: 2017-04-19T01:17:54.669456-05:
      DOI: 10.1002/ange.201702402
       
  • Degradation of the BAF Complex Factor BRD9 by Heterobifunctional Ligands
    • Authors: David Remillard; Dennis L. Buckley, Joshiawa Paulk, Gerard L. Brien, Matthew Sonnett, Hyuk-Soo Seo, Shiva Dastierdi, Martin Wühr, Sirano Dhe-Paganon, Scott A. Armstrong, James E. Bradner
      Abstract: The bromodomain-containing protein BRD9, a subunit of the human BAF (SWI/SNF) nucleosome remodeling complex, has emerged as an attractive therapeutic target in cancer. Despite the development of chemical probes targeting the BRD9 bromodomain, there is a limited understanding of BRD9 function beyond acetyl-lysine recognition. We have therefore created the first BRD9-directed chemical degraders, through iterative design and testing of heterobifunctional ligands that bridge the BRD9 bromodomain and the cereblon E3 ubiquitin ligase complex. Degraders of BRD9 exhibit markedly enhanced potency compared to parental ligands (10- to 100-fold). Parallel study of degraders with divergent BRD9-binding chemotypes in models of acute myeloid leukemia resolves bromodomain polypharmacology in this emerging drug class. Together, these findings reveal the tractability of non-BET bromodomain containing proteins to chemical degradation, and highlight lead compound dBRD9 as a tool for the study of BRD9.Niedermolekulare Abbaureagentien, die schnell, wirksam und selektiv das Bromodomänenprotein BRD9 aus dem BAF-Komplex eliminieren, wurden mithilfe einer iterativen, strukturbasierten Designstrategie entwickelt. In Modellen akuter myeloischer Leukämie zeigen diese ersten Abbaureagentien für Bromodomänen außerhalb der BET-Familie eine deutlich höhere Wirkung als existierende BRD9-Sonden.
      PubDate: 2017-04-18T08:55:51.6209-05:00
      DOI: 10.1002/ange.201611281
       
  • Enantioselective Heck–Matsuda Arylations through Chiral Anion
           Phase-Transfer of Aryl Diazonium Salts
    • Authors: Carolina M. Avila; Jigar S. Patel, Yernaidu Reddi, Masato Saito, Hosea M. Nelson, Hunter P. Shunatona, Matthew S. Sigman, Raghavan B. Sunoj, F. Dean Toste
      Abstract: A mild, asymmetric Heck–Matsuda reaction of five-, six- and seven-membered ring alkenes and aryl diazonium salts is presented. High yields and enantioselectivities were achieved using Pd0 and chiral anion co-catalysts, the latter functioning as a chiral anion phase-transfer (CAPT) reagent. For certain substrate classes, the chiral anion catalysts were modulated to minimize the formation of undesired by-products. More specifically, BINAM-derived phosphoric acid catalysts were shown to prevent alkene isomerization in cyclopentene and cycloheptene starting materials. DFT(B3LYP-D3) computations revealed that increased product selectivity resulted from a chiral anion dependent lowering of the activation barrier for the desired pathway.Capt'n Catalysis: Eine asymmetrische Heck-Matsuda-Reaktion von Cyclopenten-, Cyclohexen- und Cyclohepten-Derivaten wurde basierend auf einer Phasentransferkatalyse mit chiralem Anion entwickelt (CAPT-Katalyse). Die Studien demonstrieren, dass CAPT-Katalye zur Steuerung der Enantio- und Chemoselektivität der Heck-Matsuda-Reaktion eingesetzt werden kann.
      PubDate: 2017-04-18T07:00:57.951768-05:
      DOI: 10.1002/ange.201702107
       
  • B(C6F5)3-Catalyzed Cascade Reduction of Pyridines
    • Authors: Zhi-Yun Liu; Zhi-Hui Wen, Xiao-Chen Wang
      Abstract: B(C6F5)3 has been found to be an effective catalyst for reduction of pyridines and other electron-deficient N-heteroarenes with hydrosilanes (or hydroboranes) and amines as the reducing reagents. The success of this development hinges upon the realization of a cascade process of dearomative hydrosilylation (or hydroboration) and transfer hydrogenation. The broad functional-group tolerance (e.g. ketone, ester, unactivated olefins, nitro, nitrile, heterocycles, etc.) implies high practical utility.Reduktionskaskade: Eine leicht ausführbare B(C6F5)3-katalysierte Pyridinreduktion beruht auf einer Kaskade aus dearomatisierender Hydrosilylierung (oder Hydroborierung) und Transferhydrierung. Bemerkenswert ist die Verträglichkeit des Verfahrens mit vielen funktionellen Gruppen.
      PubDate: 2017-04-18T06:50:55.587606-05:
      DOI: 10.1002/ange.201702304
       
  • Hydroniumionenbatterien: eine nachhaltige Lösung zur
           Energiespeicherung
    • Authors: Yun-hai Zhu; Xu Yang, Xin-bo Zhang
      Abstract: Hydroniumionen sind zum ersten Mal reversibel in einer Elektrode aus kristallinem 3,4,9,10-Perylentetracarbonsäuredianhydrid (PTCDA) gespeichert worden. Dabei wurde ein äußerst reversibles Lade-Entlade-Verhalten von PTCDA in einem wässrigen sauren Elektrolyten aus 1 m H2SO4 beobachtet. Die Kapazität und die Betriebspotentiale ähneln denen der Natriumionen-Speicherung in der gleichen Elektrode.
      PubDate: 2017-04-18T06:50:36.264393-05:
      DOI: 10.1002/ange.201702160
       
  • A Facile and Versatile Synthesis of Energetic Furazan-Functionalized
           5-Nitroimino-1,2,4-Triazoles
    • Authors: Zhen Xu; Guangbin Cheng, Hongwei Yang, Xuehai Ju, Ping Yin, Jiaheng Zhang, Jean'ne M. Shreeve
      Abstract: An analogue-oriented synthetic route for the formulation of furazan-functionalized 5-nitroimino-1,2,4-triazoles has been explored. The process was found to be straightforward, high yielding, and highly efficient, and scalable. Nine compounds were synthesized and the physicochemical and energetic properties, including density, thermal stability, and sensitivity, were investigated, as well as the energetic performance (e.g., detonation velocities and detonation pressures) as evaluated by using EXPLO5 code. Among the new materials, compounds 4–6 and 11 possess high densities, acceptable sensitivities, and good detonation performances, and thereby demonstrate the potential applications as new secondary explosives.Energiegeladen: Eine Analoga-orientierte Syntheseroute für die Titelverbindungen wurde erarbeitet. Der effiziente Prozess, der die Produkte direkt und in hohen Ausbeuten liefert, ist für die Synthese leistungsfähiger energetischer Materialien im größeren Maßstab geeignet.
      PubDate: 2017-04-18T06:40:53.663526-05:
      DOI: 10.1002/ange.201701659
       
  • Von zweizähnigen Gallium-Lewis-Säuren zu supramolekularen
           Komplexen
    • Authors: Jan Horstmann; Mentor Hyseni, Andreas Mix, Beate Neumann, Hans-Georg Stammler, Norbert W. Mitzel
      Abstract: Zweizähnige Gallium Lewis-Säuren wurden ausgehend von Diethinyldiphenylsilan in reinem Trimethyl- oder Triethylgallium dargestellt. Bis[(dimethylgallanyl)ethinyl]diphenylsilan (1) und dessen Diethylgallanyl-Derivat 2 wurden als Et2O- oder Pyridin-Addukte NMR-spektroskopisch charakterisiert; 2⋅2 Py wurde isoliert. Die Lewis-Säuren 1 und 2 bilden Wirt-Gast-Addukte mit zweizähnigen Stickstoffbasen; dabei bilden sich nur bei passendem N⋅⋅⋅N-Abstand cyclische 1:1-Addukte aus 1 und 4,4′-Dimethyl-3,3′-bipyridylacetylen (3), Bis[(pyrid-3-yl)ethinyl]diphenylsilan (4) oder Bis[(2-methylpyrid-5-yl)ethyinyl]diphenylsilan (5). Die cyclischen Addukte 1⋅3, 1⋅4 und 1⋅5 wurde mittels Röntgenbeugungsexperimenten identifiziert. 2⋅2 Py reagiert mit DABCO zur polymeren Spezies (DABCO-2-)n.Supramolekulare Wirt-Gast-Komplexe aus zweizähnigen Bis[(dialkylgallanyl)ethinyl]diphenylsilan-Lewis-Säuren (Alkyl=Me, Et) mit festen Ga⋅⋅⋅Ga-Abständen und zweizähnigen Lewis-Basen unterschiedlicher N⋅⋅⋅N-Abstände zeigen, dass unpassende Abstände zu polymeren Produkten führen, maßgeschneiderte Gäste hingegen cyclische 1:1-Addukte bilden.
      PubDate: 2017-04-18T03:51:42.701888-05:
      DOI: 10.1002/ange.201701303
       
  • An Iterative Module in the Azalomycin F Polyketide Synthase Contains a
           Switchable Enoylreductase Domain
    • Authors: Wei Xu; Guifa Zhai, Yuanzhen Liu, Yuan Li, Yanrong Shi, Kui Hong, Hui Hong, Peter F. Leadlay, Zixin Deng, Yuhui Sun
      Abstract: Detailed analysis of the modular Type I polyketide synthase (PKS) involved in the biosynthesis of the marginolactone azalomycin F in mangrove Streptomyces sp. 211726 has shown that only nineteen extension modules are required to accomplish twenty cycles of polyketide chain elongation. Analysis of the products of a PKS mutant specifically inactivated in the dehydratase domain of extension-module 1 showed that this module catalyzes two successive elongations with different outcomes. Strikingly, the enoylreductase domain of this module can apparently be “toggled” off and on : it functions in only the second of these two cycles. This novel mechanism expands our understanding of PKS assembly-line catalysis and may explain examples of apparent non-colinearity in other modular PKS systems.An und aus: Der Biosyntheseweg von Azalomycin F enthält eine an und ausschaltbare Enoylreduktase(ER)-Domäne in einem iterativen Polyketidsynthase(PKS)-Modul für Verlängerungen des Polyketidrückgrats. Die ER-Domäne schaltet von nicht-funktional („aus”, schwarz) im ersten Verlängerungsprozess zu funktional („an”, rot) im zweiten. LM=Lademodul.
      PubDate: 2017-04-18T03:51:36.132995-05:
      DOI: 10.1002/ange.201701220
       
  • Catalytic Enantioselective Synthesis of 2,5-Dihydrooxepines
    • Authors: Su Yong Shim; Soo Min Cho, Anipireddy Venkateswarlu, Do Hyun Ryu
      Abstract: A Michael addition initiated cyclopropanation/retro-Claisen rearrangement tandem reaction was developed for the enantioselective synthesis of highly functionalized 2,5-dihydrooxepines. In the presence of a chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeds to give good yields and high enantioselectivity.Runde Sache: Eine durch eine Michael-Addition ausgelöste Tandemreaktion aus einer Cyclopropanierung und einer Retro-Claisen-Umlagerung ermöglicht die enantioselektive Synthese von hoch funktionalisierten 2,5-Dihydrooxepinen. Die Reaktion läuft in Gegenwart eines chiralen Oxazaborolidiniumions (COBI) als Katalysator mit guten Ausbeuten und hoher Enantioselektivität ab.
      PubDate: 2017-04-18T03:51:16.409025-05:
      DOI: 10.1002/ange.201700890
       
  • Assembly of a Benzo-Fused Bridged Ketone Scaffold from 1,5,10-Enediynes
           through One-Pot Ruthenium-Catalyzed Cyclization/Iodine-Mediated Oxidative
           Ring Expansion
    • Authors: Yoshihiko Yamamoto; Kei-ichiro Nishimura, Shota Mori, Masatoshi Shibuya
      Abstract: In the presence of a cationic Ru catalyst, 1,6-diynes bearing a terminal styryl moiety underwent [2+2+2] cyclization to produce dehydrobiphenylenes fused with a five-membered ring. Although the cycloadducts were unstable toward purification, their one-pot iodine-mediated ring expansion successfully afforded unprecedented bridged ketone products containing a benzo-fused bicyclo[3.2.1] framework.Brücken bauen: Ein ungewöhnliches verbrücktes Ketongerüst wurde durch eine Ruthenium-katalysierte Eintopf-Tandemreaktion aus [2+2+2]-Cyclisierung und Iod-vermittelter oxidativer Ringerweiterung hergestellt. Die [2+2+2]-Cyclisierung läuft in Gegenwart eines kationischen Ru-Katalysators bei Raumtemperatur ab, die anschließende Ringerweiterung wird durch die Zugabe von N-Iodsuccinimid (NIS) und MeOH ausgelöst.
      PubDate: 2017-04-18T03:50:52.675178-05:
      DOI: 10.1002/ange.201700493
       
  • Cu/Pd Synergistic Dual Catalysis: Asymmetric α-Allylation of an
           α-CF3 Amide
    • Authors: Akira Saito; Naoya Kumagai, Masakatsu Shibasaki
      Abstract: Despite the burgeoning demand for fluorine-containing chemical entities, the construction of CF3-containing stereogenic centers has remained elusive. Herein, we report the strategic merger of CuI/base-catalyzed enolization of an α-CF3 amide and Pd0-catalyzed allylic alkylation in an enantioselective manner to deliver chiral building blocks bearing a stereogenic carbon center connected to a CF3, an amide carbonyl, and a manipulable allylic group. The phosphine complexes of CuI and Pd0 engage in distinct catalytic roles without ligand scrambling to render the dual catalysis operative to achieve asymmetric α-allylation of the amide. The stereoselective cyclization of the obtained α-CF3-γ,δ-unsaturated amides to give tetrahydropyran and γ-lactone-fused cyclopropane skeletons highlights the synthetic utility of the present catalytic method as a new entry to non-racemic CF3-containing compounds.Der strategische Zusammenschluss von CuI/Base-katalysierter Enolisierung eines α-CF3-Amids und Pd0-katalysierter allylischer Alkylierung ermöglicht die enantioselektive α-Allylierung von Amiden. Als Produkte entstehen chirale Bausteine mit einem CF3-, Amidcarbonyl- und allylsubstituierten Stereozentrum. In dieser kooperativen dualen Katalyse erfüllen Phosphankomplexe von CuI und Pd0 bestimmte Funktionen, ohne dass es zu Ligandenvermischung kommt.
      PubDate: 2017-04-18T03:46:07.355371-05:
      DOI: 10.1002/ange.201702113
       
  • Lewis Acid Promoted Single C–F Bond Activation of the CF3 Group:
           SN1′-Type 3,3-Difluoroallylation of Arenes with
           2-Trifluoromethyl-1-alkenes
    • Authors: Kohei Fuchibe; Hibiki Hatta, Ken Oh, Rie Oki, Junji Ichikawa
      Abstract: Activation of the sp3 C−F bond in 2-trifluoromethyl-1-alkenes was accomplished through treatment with a Lewis acid. In the presence of an equimolar amount of EtAlCl2, the (trifluoromethyl)alkenes readily underwent an SN1′-type reaction with arenes through a Friedel–Crafts-type mechanism via elimination of a fluoride ion to afford 3,3-difluoroallylated arenes in good yields. This selective activation of one C−F bond of the CF3 group provides a synthetic method for accessing biologically and synthetically important 1,1-difluoro-1-alkenes.Einmaliges Ereignis: In Gegenwart der Lewis-Säure EtAlCl2 spalten Trifluormethylalkene bereitwillig ein F−-Ion ab und liefern über eine SN1′-artige Friedel-Crafts-Reaktion mit Arenen die 3,3-difluorallylierten Produkte in guten Ausbeuten. Diese selektive Aktivierung einer einzigen Csp3-F-Bindung der CF3-Gruppe führt glatt zu 1,1-Difluor-1-alkenen.
      PubDate: 2017-04-18T03:45:40.411538-05:
      DOI: 10.1002/ange.201701985
       
  • Frontispiz: Ein achtkerniger metallosupramolekularer Würfel mit
           Spin-Crossover-Eigenschaften
    • Authors: Niklas Struch; Christoph Bannwarth, Tanya K. Ronson, Yvonne Lorenz, Bernd Mienert, Norbert Wagner, Marianne Engeser, Eckhard Bill, Rakesh Puttreddy, Kari Rissanen, Johannes Beck, Stefan Grimme, Jonathan R. Nitschke, Arne Lützen
      Abstract: Metallosupramolekulare ChemieA. Lützen und Mitarbeiter beschreiben in ihrer Zuschrift auf S. 5012 die Synthese und Eigenschaften eines achtkernigen supramolekularen Käfigs mit Spin-Crossover-Verhalten in Lösung.
      PubDate: 2017-04-18T03:15:43.243201-05:
      DOI: 10.1002/ange.201781861
       
  • Enantioselective Chemo- and Biocatalysis: Partners in Retrosynthesis
    • Authors: Erick Moran Carreira; Nicholas Turner, Moritz Hönig, Philipp Sondermann
      Abstract: Abstract: Recent developments of biocatalytic and chemocata-lytic methods are discussed. The review provides a guide to the use of biocatalytic methods in the area of chemical synthesis with focused attention on retrosynthetic considerations and analysis. The methods presented are organized according to bond disconnections and attendant synthetic methods. The review is expected to lead to better understanding of the charac-teristics and distinctions of the two complementary approaches. It depicts for researchers in bio- and chemocatalysis a road map of challenges and opportunities for the evolution (and at times revolution) in chemical synthesis.
      PubDate: 2017-04-13T12:33:11.466244-05:
      DOI: 10.1002/ange.201612462
       
  • Fluorophores for Excited-State Intramolecular Proton Transfer by an
           Yttrium Triflate-Catalyzed Reaction of Isocyanides with Thiocarboxylic
           Acids
    • Authors: Shuo Tong; Shun Zhao, Qing He, Qian Wang, Mei-Xiang Wang, Jieping Zhu
      Abstract: Discovery of new chemical reactivity of a given functional group can often result in innovative synthesis of important chemical entities that possess unprecedented properties. We designed and developed a one-step synthesis of 5-amino-4-carboxamidothiazoles 1 by an yttrium-triflate-catalyzed reaction of thiocarboxylic acids 2 with isocyanides 3. In this reaction, both reactants 2 and 3 deviated from their normal reactivities because of metal coordination. The resulting heterocycles are novel prototypical structures for the double ESIPT process. Some of them were excited by visible light irradiation and emitted fluorescence at the NIR region with large Stokes shift, high quantum yield, and strong solvatochromism.Farbenfrohe Reaktivität: Die Reaktion von Thiocarbonsäuren mit Isocyaniden in Anwesenheit einer katalytischen Menge von Yttriumtriflat ergab 5-Amino-4-carboxamidothiazole in guter bis exzellenter Ausbeute. Einige dieser Heterocyclen wurden mit sichtbarem Licht angeregt und emittierten Fluoreszenz im Nahinfrarotbereich mit einer großen Stokes-Verschiebung, hoher Quantenausbeute und einer starker positiver Solvatochromie.
      PubDate: 2017-04-13T12:11:14.318325-05:
      DOI: 10.1002/ange.201702488
       
  • Vom Aufspießen des Benzols
    • Authors: Quang H. Luu; Tobias Fiedler, John A. Gladysz
      Abstract: Go Aggies! Go Chemiker! Das Wort „gig” beschreibt ein mehrzackiges metallenes Werkzeug für die Jagd auf Frösche und Fische. Es ist Teil eines Schlachtrufs, „gig ’em”, der Texas A&M Aggies zu Triumphen in sportlichen und wissenschaftlichen Wettbewerben anspornt. Dieses Highlight behandelt jüngste Triumphe auf dem Gebiet der C....._C-Bindungsspaltung des Benzols. Diese wird durch vierzackige Iridium-Spieße ermöglicht und resultiert in norbornadienartigen Strukturen, die unter signifikanter Ringspannung stehen.
      PubDate: 2017-04-13T12:08:30.240786-05:
      DOI: 10.1002/ange.201702942
       
  • Iridium-Catalyzed Regio- and Enantioselective Hydroarylation of Alkenyl
           Ethers by Olefin Isomerization
    • Authors: Yusuke Ebe; Mitsuki Onoda, Takahiro Nishimura, Hideki Yorimitsu
      Abstract: Iridium-catalyzed hydroarylation of alkenyl ethers, such as allylic and homoallylic ethers, by C−H bond activation gave high yields of the corresponding addition products, where the aryl groups were selectively installed at the α-carbon atom to the alkoxy group. The reaction involves an isomerization of the alkenyl ethers into the corresponding 1-alkenyl ethers, which then undergo the regio- and enantioselective hydroarylation.Treffpunkt α: Die iridiumkatalysierte Hydroarylierung von Alkenylethern, beispielsweise (Homo)Allylethern, unter C-H-Aktivierung liefert die entsprechenden Additionsprodukte in hohen Ausbeuten. Die Arylgruppen werden selektiv am Kohlenstoffatom in α-Stellung zur Alkoxygruppe eingeführt. ArF= 3,5-(CF3)2C6H3.
      PubDate: 2017-04-13T12:08:28.19294-05:0
      DOI: 10.1002/ange.201702286
       
  • Toroid Formation through a Supramolecular “Cyclization
           Reaction” of Rodlike Micelles
    • Authors: Chaoying Yang; Liang Gao, Jiaping Lin, Liquan Wang, Chunhua Cai, Yuhan Wei, Zhibo Li
      Abstract: Constructing polymeric toroids with a uniform, tunable size is challenging. Reported herein is the formation of uniform toroids from poly(γ-benzyl-l-glutamate)-graft-poly(ethylene glycol) (PBLG-g-PEG) graft copolymers by a two-step self-assembly process. In the first step, uniform rodlike micelles are prepared by dialyzing the polymer dissolved in tetrahydrofuran (THF)/N,N′-dimethylformamide (DMF) against water. With the addition of THF in the second step, the rodlike micelles curve and then close end-to-end to form uniform toroids, which resemble a cyclization reaction.Stabförmige Mizellen, die durch Selbstorganisation von Polypeptid-Pfropfcopolymeren mit starrem Rückgrat entstehen, können als Antwort auf Lösungsmittel- und Temperaturstimuli ihre beiden Enden nach Art einer Cyclisierung unter Ringbildung verbinden.
      PubDate: 2017-04-13T12:08:14.088311-05:
      DOI: 10.1002/ange.201701978
       
  • An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a
           Molybdenum-Based Layer for Overall Water Splitting
    • Authors: Angel T. Garcia-Esparza; Tatsuya Shinagawa, Samy Ould-Chikh, Muhammad Qureshi, Xuyuan Peng, Nini Wei, Dalaver H. Anjum, Alain Clo, Tsu-Chien Weng, Dennis Nordlund, Dimosthenis Sokaras, Jun Kubota, Kazunari Domen, Kazuhiro Takanabe
      Abstract: For overall water-splitting systems, it is essential to establish O2-insensitive cathodes that allow cogeneration of H2 and O2. An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2. In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx/Pt/SrTiO3 with inhibited water formation from H2 and O2, which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.Wasserstoff in Gegenwart von Sauerstoff: Molybdänspezies hemmen die Wasserbildung auf Platin- und anderen Metallkatalysatoren. Eine In-operando-Charakterisierung zeigt, dass Platin bei der selektiven Wasserstoffentwicklung durch elektro- und photokatalytische Wasserspaltung in Gegenwart von Sauerstoff durch eine amorphe hydratisierte Oxyhydroxid-Struktur aus polyanionischen Trimolybdän(IV)-Einheiten geschützt wird.
      PubDate: 2017-04-13T12:07:45.453057-05:
      DOI: 10.1002/ange.201701861
       
  • Binding CO2 by a Cr8 Metallacrown
    • Authors: Iñigo J. Vitórica-Yrezábal; Daniel Florin Sava, Grigore A. Timco, Martyn S. Brown, Mathew Savage, Harry G. W. Godfrey, Florian Moreau, Martin Schröder, Flor Siperstein, Lee Brammer, Sihai Yang, Martin P. Attfield, Joseph J. W. McDouall, Richard E. P. Winpenny
      Abstract: The {Cr8} metallacrown [CrF(O2CtBu)2]8, containing a F-lined internal cavity, shows high selectivity for CO2 over N2. DFT calculations and absorption studies support the multiple binding of F-groups to the C-center of CO2 (C⋅⋅⋅F 3.190(9)–3.389(9) Å), as confirmed by single-crystal X-ray diffraction.Die grüne Krone: Ein Ring mit 8 Cr-Atomen bindet CO2 stark und selektiv über C⋅⋅⋅F-Wechselwirkungen. Cr grün, F gelb, O rot, C grau.
      PubDate: 2017-04-13T12:07:43.788208-05:
      DOI: 10.1002/ange.201701726
       
  • Uncovering the Atomistic Mechanism for Calcite Step Growth
    • Authors: Marco De La Pierre; Paolo Raiteri, Andrew G. Stack, Julian D. Gale
      Abstract: Determining a complete atomic-level picture of how minerals grow from aqueous solution remains a challenge as macroscopic rates can be a convolution of many reactions. For the case of calcite (CaCO3) in water, computer simulations have been used to map the complex thermodynamic landscape leading to growth of the two distinct steps, acute and obtuse, on the basal surface. The carbonate ion is found to preferentially adsorb at the upper edge of acute steps while Ca2+ only adsorbs after CO32−. In contrast to the conventional picture, ion pairs prefer to bind at the upper edge of the step with only one ion, at most, coordinated to the step and lower terrace. Migration of the first carbonate ion to a growth site is found to be rate-limiting for kink nucleation, with this process having a lower activation energy on the obtuse step.Computersimulationen wurden eingesetzt, um die initiale Thermodynamik für das Stufenwachstum auf einer Calcit-Oberfläche in wässriger Lösung zu quantifizieren und die konkurrierenden atomistischen Reaktionswege zu identifizieren. Der wachstumslimitierende Schritt ist die Umlagerung adsorbierter Ionenpaare von den exponierten Ecken der Stufenkante zu Kinkstellen.
      PubDate: 2017-04-13T12:02:19.138151-05:
      DOI: 10.1002/ange.201701701
       
  • Designed Spiroketal Protein Modulation
    • Authors: Marcel Scheepstra; Sebastian A. Andrei, M. Yagiz Unver, Anna K. H. Hirsch, Seppe Leysen, Christian Ottmann, Luc Brunsveld, Lech-Gustav Milroy
      Abstract: Spiroketals are structural motifs found in many biologically active natural products, which has stimulated considerable efforts toward their synthesis and interest in their use as drug lead compounds. Despite this, the use of spiroketals, and especially bisbenzanulated spiroketals, in a structure-based drug discovery setting has not been convincingly demonstrated. Herein, we report the rational design of a bisbenzannulated spiroketal that potently binds to the retinoid X receptor (RXR) thereby inducing partial co-activator recruitment. We solved the crystal structure of the spiroketal–hRXRα–TIF2 ternary complex, and identified a canonical allosteric mechanism as a possible explanation for the partial agonist behavior of our spiroketal. Our co-crystal structure, the first of a designed spiroketal–protein complex, suggests that spiroketals can be designed to selectively target other nuclear receptor subtypes.Strukturbasiertes Design, Synthese sowie biochemische und strukturelle Validierung eines Proteinmodulators werden vorgestellt. Die Ergebnisse sprechen dafür, dass das doppelt benzanellierte Spiroketal als starker partieller Agonist des Retinoid-X-Rezeptors wirkt. Dadurch zeigt sich das Potenzial von Spiroketalen als Leitstrukturen für neue Wirkstoffe.
      PubDate: 2017-04-13T12:01:40.437944-05:
      DOI: 10.1002/ange.201612504
       
  • Water-Soluble N-Heterocyclic Carbene-Protected Gold Nanoparticles:
           Size-Controlled Synthesis, Stability, and Optical Properties
    • Authors: Kirsi Salorinne; Renee W. Y. Man, Chien-Hung Li, Masayasu Taki, Masakazu Nambo, Cathleen M. Crudden
      Abstract: NHC-AuI complexes were used to prepare stable, water-soluble, NHC-protected gold nanoparticles. The water-soluble, charged nature of the nanoparticles permitted analysis by polyacrylamide gel electrophoresis (PAGE), which showed that the nanoparticles were highly monodisperse, with tunable core diameters between 2.0 and 3.3 nm depending on the synthesis conditions. Temporal, thermal, and chemical stability of the nanoparticles were determined to be high. Treatment with thiols caused etching of the particles after 24 h; however larger plasmonic particles showed greater resistance to thiol treatment. These water-soluble, bio-compatible nanoparticles are promising candidates for use in photoacoustic imaging, with even the smallest nanoparticles giving reliable photoacoustic signals.Goldwasser: Wasserlösliche NHC-funktionalisierte Au-Nanopartikel (NPs) mit Kerndurchmessern von 2.0 bis 3.3 nm wurden aus molekularen Vorstufen hergestellt. Die NPs sind chemisch sehr beständig und in Wasser über zwei Monate haltbar. Durch Thiole jedoch werden sie geätzt. Alle untersuchten NPs lieferten photoakustische Signale, die zur NP-Konzentration proportional waren.
      PubDate: 2017-04-13T11:40:29.353214-05:
      DOI: 10.1002/ange.201701605
       
  • Synthesis of Long Oxahelicenes by Polycyclization in a Flow Reactor
    • Authors: Jindřich Nejedlý; Michal Šámal, Jiří Rybáček, Miroslava Tobrmanová, Florence Szydlo, Christophe Coudret, Maria Neumeier, Jaroslav Vacek, Jana Vacek Chocholoušová, Miloš Buděšínský, David Šaman, Lucie Bednárová, Ladislav Sieger, Irena G. Stará, Ivo Starý
      Abstract: A series of oxahelicenes composed of ortho/meta-annulated benzene/pyridine and 2H-pyran rings were synthesized on the basis of the cobalt(I)-mediated (or rhodium(I)- or nickel(0)-mediated) double, triple, or quadruple [2+2+2] cycloisomerization of branched aromatic hexa-, nona-, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyclization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]-, [13]-, [17]- and [19]helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single-molecule conductivity was studied by the mechanically controllable break-junction method with a pyridooxa[9]helicene.Große Ziele setzen: Oxahelicene aus bis zu 19 kondensierten Ringen (siehe Beispiel) wurden durch mehrfache Cobalt(I)-vermittelte Cycloisomerisierungen von Oligoinen in einem Strömungsreaktor synthetisiert. Die stereogenen Zentren in enantiomerenreinen Substraten dirigierten die diastereoselektiven Polycyclisierungen. Die Einzelmolekülleitfähigkeit eines Pyridooxa[9]helicens wurde mit der Break-Junction-Methode untersucht.
      PubDate: 2017-04-13T10:58:09.752646-05:
      DOI: 10.1002/ange.201700341
       
  • Oxidative Cross-Coupling Reactions. Von Aiwen Lei, Wei Shi, Chao Liu, Wei
           Liu, Hua Zhang und Chuan He.
    • Authors: Jin-Heng Li
      Abstract: Wiley-VCH, Weinheim, 2016. 229 S., geb., 129.00 €.—ISBN 978-3527336883
      PubDate: 2017-04-13T10:57:39.560343-05:
      DOI: 10.1002/ange.201703272
       
  • Oxidation-Initiated Cyclizations of Pentadienyl Ethers: An Alternative
           Entry to the Nazarov Reaction
    • Authors: Ryan J. Fradette; Minkyu Kang, F. G. West
      Abstract: Oxidation-initiated Nazarov reactions of 1,4-pentadien-3-yl ethers take place in the presence of DDQ. Termination by regioselective elimination preserves both stereocenters created during electrocyclization, providing cyclopentanone products bearing an exocyclic methylene unit. Use of catalytic DDQ with MnO2 as terminal oxidant is also described.Dehydrierende Nazarov-Reaktion: 1,4-Pentadien-3-ylether unterliegen der oxidativen Umwandlung in 3-Alkoxypentadienylkationen, gefolgt von einer glatten Nazarov-Cyclisierung und regioselektiven exocyclischen Eliminierung zur Bildung der Alkylidencyclopentenolether unter Verlust von H2. Die Methode bietet einen milden Zugang zu Nazarov-Produkten, wobei die in der Elektrocyclisierung gebildeten stereogenen Zentren erhalten bleiben.
      PubDate: 2017-04-13T10:53:25.057058-05:
      DOI: 10.1002/ange.201701748
       
  • Gezielte Spaltung von durch direktes Laserschreiben hergestellten
           Mikrostrukturen
    • Authors: Markus M. Zieger; Patrick Mueller, Alexander S. Quick, Martin Wegener, Christopher Barner-Kowollik
      Abstract: Basierend auf einem neuartigen Photolack wurden 3D-Mikrostrukturen durch direktes Laserschreiben (DLW) hergestellt, die gezielt und vollständig spaltbar sind. Die Netzwerke bestehen ausschließlich aus reversiblen Bindungen, die unter Bestrahlung eines Phenacylsulfid-Vernetzers entstehen. In einer radikalfreien Stufenwachstumsreaktion zwischen den sich bildenden reaktiven Thioaldehyden und einer Thiol-Komponente bilden sich Disulfidbrücken. Die Reaktion wurde in Lösung durch ESI-MS nachgewiesen. Induziert wird die Spaltung durch einen Thiol-Disulfidbrücken-Austausch mit Dithiothreitol, der die geschriebenen Strukturen “löscht”. Die milde Spaltung des Disulfidbrücken-Netzwerkes ist z. B. orthogonal zu Acrylat-basierten DLW-Strukturen. Um diesen Aspekt hervorzuheben, wurden DLW-Strukturen hergestellt, die reversible Strukturelemente in nicht-reversible Acrylat-basierte Standardgerüste integrieren. Im Anschluss wurde die selektive Spaltung gezeigt. Die Erreichbarkeit hoher lateraler Auflösung wurde durch Anfertigen definierter Liniengitter mit Linienabständen bis 300 nm nachgewiesen.Nichts hält ewig: Ein neuer Photolack ermöglicht die gezielte Spaltung von Mikrostrukturen, die mithilfe von direktem Laserschreiben (DLW) hergestellt wurden. Die neuartigen, Phenacylsulfid-basierten Netzwerke sind ausschließlich durch Disulfidbrücken vernetzt. Dies wird durch einen wohldefinierten Stufenwachstumsmechanismus mithilfe von Thiol-Vernetzern erreicht. Die gezielte Spaltung wird durch einen einfachen chemischen Auslöser eingeleitet.
      PubDate: 2017-04-13T10:52:18.950254-05:
      DOI: 10.1002/ange.201701593
       
  • Protein Dimerization on a Phosphonated Calix[6]arene Disc
    • Authors: Martin L. Rennie; Aishling M. Doolan, Colin L. Raston, Peter B. Crowley
      Abstract: Complex formation between cationic cytochrome c and the water-soluble, poly-anionic p-phosphonatocalix[6]arene (pclx6) was investigated. A crystal structure (at 1.8 Å resolution) revealed a remarkable dimeric disc of pclx6 that acts like glue to mediate a symmetric (C2) protein dimer. The calixarene disc has a diameter of about 1.5 nm and masks about 360 Å2 of protein surface. The key protein–calixarene contacts occur via two linchpin lysines, with additional contacts provided by a small hydrophobic patch. The protein–calixarene supramolecular assemblies were observed in solution by size-exclusion chromatography with multi-angle light scattering and NMR spectroscopy. Using isothermal titration calorimetry and NMR data, an apparent Kd in the low micromolar range was determined for the charge-rich protein–calixarene complex. In contrast to p-sulfonatocalix[4]arene, the larger pclx6 has a single, well-defined binding site that mediates the assembly of cytochrome c in solution.Calixarenkontakt: Phosphonatocalix[6]aren wirkt als molekularer Klebstoff für die Anordnung von Cytochrom c bei niedrigen und hohen Salzkonzentrationen. Eine Kristallstrukturanalyse zeigt eine dimere Scheibe des Calixarens eingefügt zwischen zwei Proteinmolekülen. Die Selbstorganisation in Lösung wurde durch Größenausschlusschromatographie, NMR-Spektroskopie und isotherme Titrationskalorimetrie untersucht.
      PubDate: 2017-04-13T10:52:04.911243-05:
      DOI: 10.1002/ange.201701500
       
  • Flexible Li-CO2 Batteries with Liquid-Free Electrolyte
    • Authors: Xiaofei Hu; Zifan Li, Jun Chen
      Abstract: Developing flexible Li-CO2 batteries is a promising approach to reuse CO2 and simultaneously supply energy to wearable electronics. However, all reported Li-CO2 batteries use liquid electrolyte and lack robust electrolyte/electrodes structure, not providing the safety and flexibility required. Herein we demonstrate flexible liquid-free Li-CO2 batteries based on poly(methacrylate)/poly(ethylene glycol)-LiClO4-3 wt %SiO2 composite polymer electrolyte (CPE) and multiwall carbon nanotubes (CNTs) cathodes. The CPE (7.14×10−2 mS cm−1) incorporates with porous CNTs cathodes, displaying stable structure and small interface resistance. The batteries run for 100 cycles with controlled capacity of 1000 mAh g−1. Moreover, pouch-type flexible batteries exhibit large reversible capacity of 993.3 mAh, high energy density of 521 Wh kg−1, and long operation time of 220 h at different degrees of bending (0–360°) at 55 °C.Biegsame Batterie: Eine leistungsfähige flüssigkeitsfreie wiederaufladbare Li-CO2-Batterie kann unter Verwendung eines Gel-artigen Kompositpolymerelektrolyts (CPE) und einer Kathode aus mehrwandigen Kohlenstoff-Nanoröhren (CNTs) hergestellt werden. Die Batterie ist biegsam und eignet sich dadurch für elastische Funktionseinheiten.
      PubDate: 2017-04-13T10:00:56.793339-05:
      DOI: 10.1002/ange.201701928
       
  • Grain-Boundary-Free Super-Proton Conduction of a Solution-Processed
           Prussian-Blue Nanoparticle Film
    • Authors: Kenta Ono; Manabu Ishizaki, Katsuhiko Kanaizuka, Takanari Togashi, Teppei Yamada, Hiroshi Kitagawa, Masato Kurihara
      Abstract: A porous crystal family has been explored as alternatives of Nafion films exhibiting super-proton conductivities of ≥10−2 S cm−1. Here, the proton-conduction natures of a solution-processed film of nanoparticles (NPs) have been studied and compared to those of a Nafion film. A mono-particle film of Prussian-blue NPs is spontaneously formed on a self-assembled monolayer substrate by a one-step solution process. A low-temperature heating process of the densely packed, pinhole-free mono-particle NP film enables a maximum 105-fold enhancement of proton conductivity, reaching ca. 10−1 S cm−1. The apparent highest conductivity, compared to previously reported data of the porous crystal family, remains constant against humidity changes by an improved water-retention ability of the film. In our proposed mechanism, the high-performing solution-processed NP film suggests that heating leads to the self-restoration of hydrogen-bonding networks throughout their innumerable grain boundaries.Ein dicht gepackter, lochfreier Film aus Preußischblau-Nanopartikeln wurde auf einem Substrat erzeugt. Durch eine Niedertemperaturbehandlung kann die Protonenleitfähigkeit des Films auf fast 10−1 S cm−1 erhöht werden. Offenbar ermöglicht der Heizvorgang die Selbstrekonstruktion der H-Brücken-Netzwerke über die unzähligen Korngrenzen hinweg.
      PubDate: 2017-04-13T09:59:50.290596-05:
      DOI: 10.1002/ange.201701759
       
  • Copper-Catalyzed Aminothiolation of 1,3-Dienes via a Dihydrothiazine
           Intermediate
    • Authors: Christopher E. Sleet; Uttam K. Tambar
      Abstract: Heteroatom-containing organic molecules are of particular interest to medicinal chemists and materials scientists. A strategy to reach these architectures via direct difunctionalization of abundant 1,3-dienes is especially attractive. Herein, we describe the development of a regio- and diastereoselective 1,4-aminothiolation of 1,3-dienes with a sulfur diimide reagent, a copper catalyst, and alkyl Grignard reagents. This unique protocol provides remote nitrogen and sulfur functionalities with high levels of stereocontrol. The reaction proceeds via a tandem hetero-Diels–Alder cycloaddition of N,N′-bis(benzenesulfonyl)sulfur diimide with 1,3-diene followed by copper-catalyzed Grignard substitution. Mechanistic studies support a copper catalyzed formation of an unprecedented [10-S-4] sulfurane that reductively eliminates to afford a 3,6-dihydrothiazine, which is selectively converted to 1,4-aminothiols.Eine katalytische Methode für die regio- und diastereoselektive 1,4-Aminothiolierung von 1,3-Dienen nutzt ein Schwefeldiimid-Reagens, einen Kupferkatalysator und Alkyl-Grignard-Reagentien. Die Stickstoff- und Schwefelfunktionalitäten werden hoch stereokontrolliert eingeführt. Mechanistische Studien sprechen für die Cu-katalysierte Bildung eines [10-S-4]-Sulfurans, das durch reduktive Eliminierung ein 3,6-Dihydrothiazin bildet.
      PubDate: 2017-04-13T09:59:38.632604-05:
      DOI: 10.1002/ange.201701796
       
  • Japan-Preis/Japanischer Spezialpreis für organische
           Synthesechemie/CNRS-Medaillen
    • PubDate: 2017-04-12T12:58:36.661693-05:
      DOI: 10.1002/ange.201703151
       
  • “Molecular Activity Painting”: schaltbare, lichtgesteuerte
           Manipulation in lebenden Zellen
    • Authors: Xi Chen; Muthukumaran Venkatachalapathy, Dominic Kamps, Simone Weigel, Ravi Kumar, Michael Orlich, Ruben Garrecht, Michael Hirtz, Christof M. Niemeyer, Yao-Wen Wu, Leif Dehmelt
      Abstract: Menschen auf der ganzen Welt schnitzen ihre Initialen in Bäume als Zeichen ewiger Liebe. Diese Schnitzereien sind eine Million Mal größer als die Malereien in lebenden Zellen, die Y.-W. Wu, L. Dehmelt und Mitarbeiter in ihrer Zuschrift (http://doi.org/10.1002/ange.201611432) vorstellen. Und auch wenn diese Zellmalereien nicht für die Ewigkeit sind, halten sie doch mehrere Stunden – eine sehr lange Zeit in der dynamischen Umgebung einer lebenden Zelle. Die Malereien dienen nicht dem bloßen Vergnügen, sondern werden zur Manipulation von Zellfunktionen genutzt, um damit ein besseres Verständnis von komplexen Krankheitsprozessen wie Krebsmetastase zu gewinnen.
      PubDate: 2017-04-12T10:35:40.389668-05:
      DOI: 10.1002/ange.201703450
       
  • Signal-Induced Release of Guests from a Photolatent Metal–Phenolic
           Supramolecular Cage and Its Hybrid Assemblies
    • Authors: Chiyoung Park; Beom Joo Yang, Ki Beom Jeong, Chae Bin Kim, Seunghyun Lee, Bon-Cheol Ku
      Abstract: Mesoporöse Siliciumdioxid-Nanopartikel wurden mit einem Photosäuregenerator und Gastmolekülen beladen und mit einer Schale aus Gerbsäure und CuII-Ionen ummantelt. In ihrer Zuschrift (
      DOI : 10.1002/ange.201701152) beschreiben C. Park et al. eine schnelle und einfache Methode für die Herstellung solcher photoresponsiver Nanocontainer und verschiedener Hybridstrukturen, wie Dünnfilme und adaptive Hydrogele. Dieser neue Ansatz könnte in der Synthese von adaptiven Kompositverbindungen und den Materialwissenschaften Anwendung finden.
      PubDate: 2017-04-12T10:35:36.932425-05:
       
  • Isolated Single Iron Atoms Anchored on N-Doped Porous Carbon as an
           Efficient Electrocatalyst for the Oxygen Reduction Reaction
    • Authors: Yuanjun Chen; Shufang Ji, Yanggang Wang, Juncai Dong, Wenxing Chen, Zhi Li, Rongan Shen, Lirong Zheng, Zhongbin Zhuang, Dingsheng Wang, Yadong Li
      Abstract: The development of low-cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable isolated single-atom Fe/N-doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half-wave potential (E1/2) of 0.900 V, which outperformed commercial Pt/C and most non-precious-metal catalysts reported to date. Besides exceptionally high kinetic current density (Jk) of 37.83 mV cm−2 at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.Gemeinsam allein: Isolierte Eisenatome, die über eine Pyrolysestrategie ausgehend von verkapselten Käfigen auf N-dotiertem porösem Kohlenstoff verankert wurden, zeigen exzellente Eigenschaften in der Sauerstoffreduktion (ORR), gute Methanoltoleranz und herausragende Stabilität. Kontrollexperimente und theoretische Studien belegen, dass die ORR-Aktivität aus dem atomar dispergierten Eisen resultiert.
      PubDate: 2017-04-12T08:02:26.992396-05:
      DOI: 10.1002/ange.201702473
       
  • From Two- to Three-Dimensional Structures of a Supertetrahedral Boran
           Using Density Functional Calculations
    • Authors: Iliya V. Getmanskii; Ruslan M. Minyaev, Dmitrii V. Steglenko, Vitaliy V. Koval, Stanislav A. Zaitsev, Vladimir I. Minkin
      Abstract: With help of the DFT calculations and imposing of periodic boundary conditions the geometrical and electronic structures were investigated of two- and three-dimensional boron systems designed on the basis of graphane and diamond lattices in which carbons were replaced with boron tetrahedrons. The consequent studies of two- and three-layer systems resulted in the construction of a three-dimensional supertetrahedral borane crystal structure. The two-dimensional supertetrahedral borane structures with less than seven layers are dynamically unstable. At the same time the three-dimensional superborane systems were found to be dynamically stable. Lack of the forbidden electronic zone for the studied boron systems testifies that these structures can behave as good conductors. The low density of the supertetrahedral borane crystal structures (0.9 g cm−3) is close to that of water, which offers the perspective for their application as aerospace and cosmic materials.Leitfähige Materialien: Die geometrischen und elektronischen Strukturen zwei- und dreidimensionaler Bor-Systeme mit Graphan- und Diamant-artigen Gittern, in denen Kohlenstoffatome durch Bor-Tetraeder ersetzt wurden, wurden untersucht. Weitergehende Studien zwei- und dreilagiger Systeme führten zur Konstruktion einer dreidimensionalen supertetraedrischen Boran-Kristallstruktur.
      PubDate: 2017-04-12T08:01:42.056364-05:
      DOI: 10.1002/ange.201701225
       
  • A Plastic–Crystal Electrolyte Interphase for All-Solid-State Sodium
           Batteries
    • Authors: Hongcai Gao; Leigang Xue, Sen Xin, Kyusung Park, John B. Goodenough
      Abstract: The development of all-solid-state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. Comparison of solid-state sodium cells with 1) solid electrolyte Na3Zr2(Si2PO4) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all-solid-state battery cells.Der Grenzflächenwiderstand an der Kathode in einer Natrium-Festkörperbatterie wird durch den Einsatz eines plastischen Kristalls als Interphasenelektrolyt zwischen Kathodenpartikeln und dem festen Elektrolyt stark verringert. Eine entsprechende Natrium-Festkörperbatterie verfügte über Zyklenstabilität und hervorragende Belastungsfähigkeit.
      PubDate: 2017-04-12T08:01:35.188447-05:
      DOI: 10.1002/ange.201702003
       
  • The Reactivity of Benzyl Lithium Species is Regulated by Intermediate
           Structures
    • Authors: Ulrike Kroesen; Lena Knauer, Carsten Strohmann
      Abstract: The reaction of benzyl lithiums is an important aspect in organic and organometallic synthesis. Reported herein are detailed insights into the reactivity of benzyl lithiums as regulated by intermediate structures. By discussing the carbometalation of allylamines and the reaction of the formed benzyl-lithium compounds with electrophiles, the influence of the metal as well as the solvent on the electronic structure of the intermediate is described. This molecular structure strongly influences the reactivity of these intermediates. By choosing the appropriate reaction conditions, the regioselectivity of reactions with electrophiles can be regulated. With trimethylchlorosilane in n-pentane a selective reaction at the para-position takes place. In contrast, selective reaction at the benzylic position, with trimethylchlorostannane in tetrahydrofuran (THF) as a solvent, is accomplished.Ein Benzyllithiumkomplex mit zwei Lithiumzentren in nichtäquivalenten Umgebungen geht in para-Stellung unerwartete regioselektive Reaktionen mit Elektrophilen (E+) ein. Der Wechsel zu Tetrahydrofuran als Lösungsmittel führt zur Bildung eines Monomers, das mit Elektrophilen in Benzylstellung reagiert.
      PubDate: 2017-04-12T08:01:07.291977-05:
      DOI: 10.1002/ange.201702377
       
  • Magneto-Adaptive Surfactants Showing Anti-Curie Behavior and Tunable
           Surface Tension as Porogens for Mesoporous Particles with 12-Fold Symmetry
           
    • Authors: Stefanie Hermann; Martin Wessig, Dennis Kollofrath, Melanie Gerigk, Kay Hagedorn, James A. Odendal, Matthias Hagner, Markus Drechsler, Philipp Erler, Mikhail Fonin, Georg Maret, Sebastian Polarz
      Abstract: Gaining external control over self-organization is of vital importance for future smart materials. Surfactants are extremely valuable for the synthesis of diverse nanomaterials. Their self-assembly is dictated by microphase separation, the hydrophobic effect, and head-group repulsion. It is desirable to supplement surfactants with an added mode of long-range and directional interaction. Magnetic forces are ideal, as they are not shielded in water. We report on surfactants with heads containing tightly bound transition-metal centers. The magnetic moment of the head was varied systematically while keeping shape and charge constant. Changes in the magnetic moment of the head led to notable differences in surface tension, aggregate size, and contact angle, which could also be altered by an external magnetic field. The most astonishing result was that the use of magnetic surfactants as structure-directing agents enabled the formation of porous solids with 12-fold rotational symmetry.Magnetische Seife: Kopfgruppen mit paramagnetischen Übergangsmetallen ergeben Tenside, die an zusätzlichen, nichtklassischen langreichweitigen Wechselwirkungen teilnehmen. Solche Systeme ermöglichen neue Arten supramolekularer Selbstorganisation sowie die Steuerung der Schlüsselparameter des Tensids durch ein äußeres Magnetfeld.
      PubDate: 2017-04-12T07:55:51.810125-05:
      DOI: 10.1002/ange.201612416
       
  • Complementary Lock-and-Key Ligand Binding of a Triplet Transmitter to a
           Nanocrystal Photosensitizer
    • Authors: Xin Li; Alexander Fast, Zhiyuan Huang, Dmitry A. Fishman, Ming Lee Tang
      Abstract: Owing to the difficulty in comprehensively characterizing nanocrystal (NC) surfaces, clear guidance for ligand design is lacking. In this work, a series of bidentate bis(pyridine) anthracene isomers (2,3-PyAn, 3,3-PyAn, 2,2-PyAn) that differ in their binding geometries were designed to find the best complementary fit to the NC surface. The efficiency of triplet energy transfer (TET) from the CdSe NC donor to a diphenylanthracene (DPA) acceptor mediated by these isomers was used as a proxy for the efficacy of orbital overlap and therefore ligand binding. 2,3-PyAn, with an intramolecular N–N distance of 8.2 Å, provided the best match to the surface of CdSe NCs. When serving as a transmitter for photon upconversion, 2,3-PyAn yielded the highest upconversion quantum yield (QY) of 12.1±1.3 %, followed by 3,3-PyAn and 2,2-PyAn. The TET quantum efficiencies determined by ultrafast transient absorption measurements showed the same trend.Transmitteroptimierung: Eine Serie von zweizähnigen Bis(pyridin)anthracenen mit unterschiedlichen Bindungsgeometrien wurde synthetisiert, um die am besten passende Spezies für die Oberfläche von CdSe-Nanokristallen zu finden. Die Effizienz des Triplettenergietransfers vom CdSe-NC-Donor zu einem Diphenylanthracen-Akzeptor über diese Transmitter wurde als Maß für die Orbitalüberlappung und Ligandenbindung genutzt.
      PubDate: 2017-04-12T07:53:42.647155-05:
      DOI: 10.1002/ange.201701929
       
  • An Ion-Responsive Pincer-Crown Ether Catalyst System for Rapid and
           Switchable Olefin Isomerization
    • Authors: Matthew R. Kita; Alexander J. M. Miller
      Abstract: Rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with a macrocyclic “pincer-crown ether” ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding.Von null auf tausend: Vollständig steuerbar ist die Aktivität der Olefinisomerisierung mit dem hier vorgestellten System. Nach mechanistischen Studien tragen Kationen zur Steuerung bei, indem sie mit dem hemilabilen Makrocyclus von „Pinzetten-Kronenether”-Liganden wechselwirken. Beschleunigung mit einem geeigneten Kation und Verlangsamung mit Ether- oder Chloridquellen ermöglichen eine ausgezeichnete Steuerung der katalytischen Aktivität.
      PubDate: 2017-04-12T07:53:32.99898-05:0
      DOI: 10.1002/ange.201701006
       
  • Photo- and Electronically Switchable Spin-Crossover Iron(II)
           Metal–Organic Frameworks Based on a Tetrathiafulvalene Ligand
    • Authors: Hai-Ying Wang; Jing-Yuan Ge, Carol Hua, Cheng-Qi Jiao, Yue Wu, Chanel F. Leong, Deanna M. D'Alessandro, Tao Liu, Jing-Lin Zuo
      Abstract: A major challenge is the development of multifunctional metal–organic frameworks (MOFs), wherein magnetic and electronic functionality can be controlled simultaneously. Herein, we rationally construct two 3D MOFs by introducing the redox active ligand tetra(4-pyridyl)tetrathiafulvalene (TTF(py)4) and spin-crossover FeII centers. The materials exhibit redox activity, in addition to thermally and photo-induced spin crossover (SCO). A crystal-to-crystal transformation induced by I2 doping has also been observed and the resulting intercalated structure determined. The conductivity could be significantly enhanced (up to 3 orders of magnitude) by modulating the electronic state of the framework via oxidative doping; SCO behavior was also modified and the photo-magnetic behavior was switched off. This work provides a new strategy to tune the spin state and conductivity of framework materials through guest-induced redox-state switching.Ein FeII-organisches 3D-Gerüst mit Tetrathiafulvalentetrapyridyl-Ligand sowie eine I2-dotierte Variante wurden hergestellt. Die TTF-Einheiten verleihen Redoxaktivität, und die I2-Dotierung erhöht die Leitfähigkeit. Dotierung oder Bestrahlung verändern die magnetischen Eigenschaften des Materials deutlich, was auf elektronisch und durch Licht schaltbares Spin-Crossover-Verhalten hindeutet.
      PubDate: 2017-04-12T07:35:55.971955-05:
      DOI: 10.1002/ange.201611824
       
  • Non-Thermal Plasma Activation of Gold-Based Catalysts for Low-Temperature
           Water–Gas Shift Catalysis
    • Authors: Cristina E. Stere; James A. Anderson, Sarayute Chansai, Juan Jose Delgado, Alexandre Goguet, Willam G. Graham, C. Hardacre, S. F. Rebecca Taylor, Xin Tu, Ziyun Wang, Hui Yang
      Abstract: Non-thermal plasma activation has been used to enable low-temperature water-gas shift over a Au/CeZrO4 catalyst. The activity obtained was comparable with that attained by heating the catalyst to 180 °C providing an opportunity for the hydrogen production to be obtained under conditions where the thermodynamic limitations are minimal. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), structural changes associated with the gold nanoparticles in the catalyst have been observed which are not found under thermal activation indicating a weakening of the Au−CO bond and a change in the mechanism of deactivation.Ein Weg zur Wasserstoffproduktion durch die Wassergas-Shift-Reaktion wurde mit einem heterogenem Katalysator gekoppelt mit einer Plasmaentladung erforscht. Strukturänderungen wurden beobachtet, die bei thermischer Aktivierung nicht auftreten, was auf eine Schwächung der Au-CO-Bindung, einen Wechsel des Aktivierungsmechanismus und einen alternativen Reaktionsweg hindeutet.
      PubDate: 2017-04-12T07:35:50.643854-05:
      DOI: 10.1002/ange.201612370
       
  • Switch in Catalyst State: Single Bifunctional Bi-State Catalyst for Two
           Different Reactions
    • Authors: Shrivats Semwal; Joyanta Choudhury
      Abstract: Disclosed here is a molecular switch which responds to acid-base stimuli and serves as a bi-state catalyst for two different reactions. The two states of the switch serve as a highly active and poorly active catalyst for two catalytic reactions (namely a hydrogenation and a dehydrogenative coupling) but in a complementary manner. The system was used in an assisted tandem catalysis set-up involving dehydrogenative coupling of an amine and then hydrogenation of the resulting imine product by switching between the respective states of the catalyst.Wandlungsfähig: Ein Säure-Base-responsiver Zweizustandskatalysator gibt die Geschwindigkeiten zweier verschiedener katalytischer Prozesse in sich ergänzender Weise vor. Auf dieser Grundlage wurde eine Tandemkatalyse entwickelt, bei der zwischen den Katalysatorzuständen geschaltet wird, um die gewünschte Reaktionsfolge zu erhalten.
      PubDate: 2017-04-12T06:45:59.079209-05:
      DOI: 10.1002/ange.201702142
       
  • Shape-Shifting Patchy Particles
    • Authors: Xiaolong Zheng; Mingzhu Liu, Mingxin He, David J. Pine, Marcus Weck
      Abstract: A facile method to synthesize shape-shifting patchy particles on the colloidal scale is described. The design is based on the solvent-induced shifting of the patch shape between concave and convex features. The initial concave patchy particles were synthesized in a water suspension by a swelling-induced buckling process. Upon exposure to different solvents, the patches were tuned reversibly to be either concave or convex. These particles can be assembled into chained, branched, zigzag, and cyclic colloidal superstructures in a highly site-specific manner by surface–liquid capillary bridging. The biphasic nature of the particles also enables site-selective surface functionalization.Formverändernde Partikel wurden in kolloidalem Maßstab entwickelt. Das Design beruht auf der solvensinduzierten Änderung der Kappen der Partikel zwischen konkav und konvex. Diese Partikel („patchy particles”) lassen sich ortsspezifisch über ihre Kappen durch Oberflächen-Flüssigkeits-Verbrückung zu größeren Architekturen anordnen, wobei konkave Kappen anschwellen und heraustreten.
      PubDate: 2017-04-12T06:41:27.564899-05:
      DOI: 10.1002/ange.201701456
       
  • A Vicinal Electrophilic Diborylation Reaction Furnishes Doubly Boron-Doped
           Polycyclic Aromatic Hydrocarbons
    • Authors: Alexandra John; Michael Bolte, Hans-Wolfram Lerner, Matthias Wagner
      Abstract: Ten examples of unsymmetrically benzannulated, boron-doped polycyclic aromatic hydrocarbons (B-PAHs) were prepared by a one-pot protocol using 4,5-dichloro-1,2-bis(trimethylsilyl)benzene (1), BBr3, and selected PAHs—among them anthracene, benzo[a]pyrene, biphenylene, and fluoranthene. After mesitylation at the boron centers, the resulting air- and water-stable products were investigated by 1H/11B{1H}/13C{1H} NMR spectroscopy, X-ray crystallography, cyclic voltammetry, and UV/Vis absorption/emission spectroscopy. The experiments were augmented by DFT calculations. Most of the B-PAHs are brightly luminescent (ΦPL up to 90 %) and undergo reversible reduction at moderate half-wave potentials. The two chloro substituents of 1 are not only mandatory for accomplishing efficient diborylation, but can subsequently be used for Stille-type coupling reactions to introduce 2-thienyl moieties. Alternatively, Cl/H exchange is achievable with HSiEt3 in a quantitative, Pd-catalyzed transformation.Vicinal Bor-dotierte polycyclische aromatische Kohlenwasserstoffe (B-PAKs) wurden in einer Dreikomponentenreaktion aus einem PAK, BBr3 und einem elektronenarmen 1,2-Bis(trimethylsilyl)benzol hergestellt. Der Ansatz liefert ein Screening-Instrument für B-PAK-Bibliotheken.
      PubDate: 2017-04-12T06:41:12.442481-05:
      DOI: 10.1002/ange.201701591
       
  • A Fully Phosphane-Substituted Disilene
    • Authors: Keith Izod; Peter Evans, Paul G. Waddell
      Abstract: There is growing interest in compounds containing functionalized E=E multiple bonds (E=Si, Ge, Sn, Pb) because of their potential to exhibit novel physical and chemical properties. However, compounds containing multiple functionalizations are rare, with scarcity increasing with increasing degree of substitution. The first ditetrelene R2E=ER2 in which the E=E bond is substituted by four heteroatoms (other than Si) is described. The tetraphosphadisilene {(Mes)2P}2Si=Si{P(Mes)2}2 (7) is readily isolated from the reaction between SiBr4 and [(Mes)2P]Li, the latter of which acts as a sacrificial reducing agent. The structure of 7 is presented, while the bonding in, and stability of 7 were probed using DFT calculations.Das Tetraphosphadisilen {(Mes)2P}2Si=Si{P(Mes)2}2 ist leicht zugänglich und im festen Zustand stabil. Darin unterscheidet es sich von Tetraaminodisilenen (R2N)2Si=Si(NR2)2, die in der Regel instabil gegen Zersetzung in die monomeren Silylene (R2N)2Si sind. Mit dem Tetraphosphadisilene konnte erstmals ein Ditetrelen strukturell charakterisiert werden, das mehr als zwei Nicht-Silicium-Heteroatomsubstituenten trägt.
      PubDate: 2017-04-12T06:41:07.360045-05:
      DOI: 10.1002/ange.201701867
       
  • Anisotropic Polymer Nanoparticles with Tunable Emission Wavelengths by
           Intersegmental Chain Packing
    • Authors: Julian D. Ruiz Perez; Stefan Mecking
      Abstract: The shape of nanoparticles is decisive for their self-assembly properties, as well as for the behavior of individual particles in many instances. The introduction and control of anisotropy is well-known for inorganic nanocrystals but a largely unresolved problem for polymer nanoparticles, especially for conjugated polymers. Here, we report a reproducible preparation method using heterophase polymerization for a range of stable dispersions of ellipsoidal conjugated polymer nanoparticles with sizes in the range of 50 to 180 nm and narrow size and shape distributions. The nanoparticles show a bright fluorescence with tunable emission wavelengths and quantum yields as high as ϕ=78 %. Structural investigations reveal the nanoparticles to be composed of a highly ordered β- and α′-phase within a nematic matrix. Preliminary studies on the origin of particle anisotropy suggest a concerted mechanism in which anisotropic shape evolves from intersegmental packing that occurs along with progressing chain formation by polymerization.Polymere Nanopartikel: Eine Reihe stabiler Dispersionen ellipsoidaler konjugierter Polymernanopartikel mit Größen von 50 bis 180 nm und einer schmalen Größen- und Formverteilung wurden mithilfe einer reproduzierbaren, auf einer Heterophasenpolymerisation basierenden Präparationsmethode hergestellt. Die Nanopartikel zeigen eine helle Fluoreszenz und große Quantenausbeuten von bis zu ϕ=78 %.
      PubDate: 2017-04-12T06:41:05.783065-05:
      DOI: 10.1002/ange.201701000
       
  • Synthesis and Bowl-in-Bowl Assembly of a Geodesic Phenylene Bowl
    • Authors: Koki Ikemoto; Ryo Kobayashi, Sota Sato, Hiroyuki Isobe
      Abstract: A phenylene multiring with a corannulenoidal skeleton was synthesized. Geodesic constraints over 20 phenylene panels resulted in its nanometer-sized, bowl-shaped molecular structure, which was unequivocally revealed by crystallographic analysis. The crystal structure also showed the presence of a bowl-in-bowl dimeric assembly, which was driven by entropic factors in solution.Nach Form sortiert: Bei der Kupplung trigonal-planarer Phenylene zu einem von fünf Fünfecken umgebenen Fünfeck bewirken geodätische Randbedingungen die Bildung einer nanometergroßen schalenförmigen Struktur. Die Packung der Moleküle wird durch Konkav-konvex-Erkennungsprozesse bestimmt. Die Formerkennung beruht auf einem Entropiegewinn bei der Anordnung der großen 120 π-Systeme.
      PubDate: 2017-04-12T06:40:53.770747-05:
      DOI: 10.1002/ange.201702063
       
  • Berichtigung: Hydroxy-Directed Ruthenium-Catalyzed Alkene/Alkyne Coupling:
           Increased Scope, Stereochemical Implications, and Mechanistic Rationale
    • Authors: Stephan M. Rummelt; Gui-Juan Cheng, Puneet Gupta, Walter Thiel, Alois Fürstner
      PubDate: 2017-04-12T06:40:51.811112-05:
      DOI: 10.1002/ange.201703197
       
  • Synthesis of Aromatic Sulfones from SO2 and Organosilanes Under Metal-free
           Conditions
    • Authors: Niklas von Wolff; Joëlle Char, Xavier Frogneux, Thibault Cantat
      Abstract: The conversion of SO2 into arylsulfones under metal-free conditions was achieved for the first time by reacting SO2 with (hetero)arylsilanes and alkylhalides in the presence of a fluoride source. The mechanism of this transformation was elucidated based on DFT calculations, which highlight the influence of SO2 in promoting C−Si bond cleavage.SOO gut: Die Umwandlung von SO2 in (Hetero)Arylsulfone durch Umsetzung mit (Hetero)Arylsilanen und Alkylhalogeniden gelingt in Gegenwart einer Fluoridquelle unter metallfreien Bedingungen. Dichtefunktionalrechnungen zum Reaktionsmechanismus unterstreichen den Einfluss des SO2 auf die C-Si-Bindungsspaltung.
      PubDate: 2017-04-12T06:40:47.511153-05:
      DOI: 10.1002/ange.201702311
       
  • Online Flowing Colloidosomes for Sequential Multi-Analyte High-Throughput
           SERS Analysis
    • Authors: Gia Chuong Phan-Quang; Elizabeth Hui Zi Wee, Fengling Yang, Hiang Kwee Lee, In Yee Phang, Xiaotong Feng, Ramón A. Alvarez-Puebla, Xing Yi Ling
      Abstract: 3D plasmonic colloidosomes are superior SERS sensors owing to their high sensitivity and excellent tolerance to laser misalignment. Herein, we incorporate plasmonic colloidosomes in a microfluidic channel for online SERS detection. Our method resolves the poor signal reproducibility and inter-sample contamination in the existing online SERS platforms. Our flow system offers rapid and continuous online detection of 20 samples in less than 5 min with excellent signal reproducibility. The isolated colloidosomes prevent cross-sample and channel contamination, allowing accurate quantification of samples over a concentration range of five orders of magnitude. Our system demonstrates high-resolution multiplex detection with fully preserved signal and Raman features of individual analytes in a mixture. High-throughput multi-assay analysis is performed, which highlights that our system is capable of rapid identification and quantification of a sequence of samples containing various analytes and concentrations.Plasmonische Kolloidosome wurden in einem Mikrofluidiksystem für die Online-SERS-Analyse multipler Proben eingesetzt. Die hohe Verkapselungseffizienz der Kolloidosome verhindert ein Vermischen der Proben und ihrer Signale sowie die Verschmutzung des Mikrokanals, sodass die präzise Quantifizierung von Proben in einem Analytkonzentrationsbereich von fünf Größenordnungen gelingt.
      PubDate: 2017-04-11T08:20:35.149003-05:
      DOI: 10.1002/ange.201702374
       
  • On-Chip-Mikrosuperkondensatoren aus Koordinationspolymeren zur
           Wechselstromnetzfilterung
    • Authors: Liang Huang; Liming Dai
      Abstract: Miniaturisierte Elektronik: On-Chip-Mikrosuperkondensatoren (MSCs) zur AC-Netzfilterung basierend auf Koordinationspolymergerüsten wurden durch eine einfache schichtweise Methode hergestellt. Die On-Chip-MSCs zeigen einen niedrigen Impedanzphasenwinkel von −73° bei 120 Hz und eine hohe Leistungsdichte von bis zu 1323 W cm−3 bei einer niedrigen Relaxationszeitkonstanten von 0.27 ms.
      PubDate: 2017-04-11T08:20:25.095846-05:
      DOI: 10.1002/ange.201702868
       
  • Rhenium-Catalyzed Construction of Polycyclic Hydrocarbon Frameworks by a
           Unique Cyclization of 1,n-Diynes Initiated by 1,1-Difunctionalization with
           Carbon Nucleophiles
    • Authors: Masahito Murai; Erika Uemura, Shunsuke Hori, Kazuhiko Takai
      Abstract: A regioselective cyclization of 1,n-diynes under rhenium catalysis was developed on the basis of a rare type of 1,1-difunctionalization of terminal alkynes with carbon nucleophiles, followed by sequential addition reactions of the resulting alkenylrhenium species. The reaction provides an efficient approach to the synthesis of complex cyclopentane-fused bi- and tricycles and spirocycles, which are useful building blocks for the construction of essential frameworks of biologically active compounds as well as functional materials, from simple starting materials by the formation of up to six new carbon–carbon bonds in a single step. The reaction proceeds under neutral conditions and does not require external ligands or additives. The key to this reactivity is the unique activation mode of the rhenium carbonyl complex, which prefers to interact with heteroatoms in polar carbon–heteroatom bonds as well as nonpolar carbon–carbon unsaturated π bonds.Wie wäre es mit einem Dominospiel? 1,n-Diine gehen unter Rheniumkatalyse 1,1-Difunktionalisierungen mit Kohlenstoffnukleophilen ein (siehe Schema). Verschiedene substituierte Bicyclen und Spiroverbindungen wurden in Dominocyclisierungen erhalten, die durch die einzigartige Aktivierungsweise des Rheniumcarbonylkomplexes ermöglicht werden. Bis zu sechs C-C-Bindungen und vier Ringe werden in einem einzigen Arbeitsgang aufgebaut.
      PubDate: 2017-04-11T07:26:09.894759-05:
      DOI: 10.1002/ange.201701159
       
  • Intramolecular Hydrogen Bonding Restricts Gd–Aqua-Ligand Dynamics
    • Authors: Eszter Boros; Raja Srinivas, Hee-Kyung Kim, Arnold M. Raitsimring, Andrei V. Astashkin, Oleg G. Poluektov, Jens Niklas, Andrew D. Horning, Bruce Tidor, Peter Caravan
      Abstract: Aqua ligands can undergo rapid internal rotation about the M−O bond. For magnetic resonance contrast agents, this rotation results in diminished relaxivity. Herein, we show that an intramolecular hydrogen bond to the aqua ligand can reduce this internal rotation and increase relaxivity. Molecular modeling was used to design a series of four Gd complexes capable of forming an intramolecular H-bond to the coordinated water ligand, and these complexes had anomalously high relaxivities compared to similar complexes lacking a H-bond acceptor. Molecular dynamics simulations supported the formation of a stable intramolecular H-bond, while alternative hypotheses that could explain the higher relaxivity were systematically ruled out. Intramolecular H-bonding represents a useful strategy to limit internal water rotational motion and increase relaxivity of Gd complexes.Angehalten: Bei Gd3+-Komplexen für die Kernspintomographie führt die schnelle Rotation des Aqua-Liganden um die Gd-O-Bindung zu einer Verringerung der Relaxivität. Diese innere Bewegung kann durch eine intramolekulare Wasserstoffbrücke zum Aqua-Liganden angehalten werden.
      PubDate: 2017-04-11T07:25:54.395133-05:
      DOI: 10.1002/ange.201702274
       
  • Formal (4+1) Cycloaddition and Enantioselective Michael–Henry Cascade
           Reactions To Synthesize Spiro[4,5]decanes and Spirooxindole Polycycles
    • Authors: Ji-Rong Huang; Muhammad Sohail, Tohru Taniguchi, Kenji Monde, Fujie Tanaka
      Abstract: Spiro[4,5]decanes and polycyclic compounds bearing spiro[4,5]decane systems are important biofunctional molecules. Described are diastereoselective formal (4+1) cycloaddition reactions to afford oxindole-functionalized spiro[4,5]decanes and organocatalytic enantioselective Michael–Henry cascade reactions of the (4+1) cycloaddition products to generate spirooxindole polycyclic derivatives bearing the spiro[4,5]decane system. Spiro[4,5]decanes bearing oxindoles containing three stereogenic centers and spirooxindole polycycles having seven stereogenic centers, including two all-carbon chiral quaternary centers and one tetrasubstituted chiral carbon center, were obtained with high diastereo- and enantioselectivities.Aufbaustrategien für Oxindol-funktionalisierte Spiro[4,5]decane und polycyclische Derivate wurden entwickelt. Eine formale (4+1)-Cycloaddition mit anschließender katalytischer asymmetrischer Michael-Henry-Reaktionskaskade liefert Produkte mit sieben Kohlenstoff-Stereozentren, darunter zwei vollständig kohlenstoffsubstituierte und ein tetrasubstituiertes, mit hohen Diastereo- und Enantioselektivitäten.
      PubDate: 2017-04-11T07:07:36.922245-05:
      DOI: 10.1002/ange.201701049
       
  • Optimierte Bindungsdauer am Zielenzym: Typ-I1/2 -Inhibitoren der
           p38α-MAP-Kinase mit verbesserter Bindungskinetik durch direkte
           Interaktion mit der R-Spine
    • Authors: Heike K. Wentsch; Niklas M. Walter, Mike Bührmann, Svenja Mayer-Wrangowski, Daniel Rauh, Guido J. R. Zaman, Nicole Willemsen-Seegers, Rogier C. Buijsman, Melanie Henning, Daniel Dauch, Lars Zender, Stefan Laufer
      Abstract: Vor kurzem wurde mit Skepinone-L ein p38α-MAP-Kinase-Inhibitor mit hoher Potenz und ausgezeichneter Selektivität in vitro und in vivo beschrieben. Der Bindemodus dieser Substanzklasse entspricht allerdings dem eines ATP-kompetitiven Typ-I-Inhibitors mit kurzer Verweildauer am Enzym. Nun wurde Skepinone-L zu den ersten Typ-I1/2-Inhibitoren der p38α-MAP-Kinase weiterentwickelt. Typ-I1/2-Inhibitoren stören den Aufbau der R-Spine, induzieren einen Glycin-Flip und besetzen beide hydrophobe Bindetaschen, die hydrophobe Region I und II. Dieses Konzept führte zu Inhibitoren mit verlängerter Verweildauer am Enzym, die sowohl die aktive als auch die inaktive Kinase binden. Des Weiteren kennzeichnet sie eine herausragende Selektivität gegenüber anderen Kinasen sowie eine ausgezeichnete Wirkung am isolierten Enzym. Darüber hinaus reicht ihre Hemmwirkung in einem humanen Vollblut-Assay bis tief in den nanomolaren Bereich. Dieser neue Bindemodus konnte röntgenkristallographisch belegt werden.Gekommen, um zu bleiben: Eine neue Klasse substituierter Dibenzosuberone kombiniert hohe Selektivität und Potenz in vitro mit einer verlängerten Enzymverweildauer dieser Typ-I1/2-Inhibitoren der p38α-MAP-Kinase. Das Konzept der zusätzlichen R-Spine-Wechselwirkung wurde auf das bereits sehr potente Skepinone-L-Grundgerüst übertragen.
      PubDate: 2017-04-11T03:35:53.714578-05:
      DOI: 10.1002/ange.201701185
       
  • Efficient Gene Transfection through Inhibition of β-Sheet (Amyloid Fiber)
           Formation of a Short Amphiphilic Peptide by Gold Nanoparticles
    • Authors: Poulami Jana; Krishnananda Samanta, Sandra Bäcker, Elio Zellermann, Shirley Knauer, Carsten Schmuck
      Abstract: The effect of citrate-stabilized gold nanoparticles (AuNPs) on the secondary structure of an artificial β-sheet-forming cationic peptide has been studied. The AuNPs inhibited β-sheet formation and led to fragmented fibrils and spherical oligomers with assembled AuNPs on their surface. Besides this structural change, the functional properties of the peptide are also different. Whereas the peptide was unable to act as a vector for gene delivery, formation of a complex with AuNPs allowed successful gene delivery into cells.Goldenes Händchen: Negativ geladene Goldnanopartikel (AuNPS) hemmen die Bildung von β-Faltblatt-Strukturen durch das kationische amphiphile Peptid 1 und brechen diese Aggregate auf. Ferner verändern sie die Funktion des Peptids dadurch, dass sie es durch Bildung eines Komplexes in einen effizienten Gentransfektionsvektor umwandeln.
      PubDate: 2017-04-10T08:56:41.057253-05:
      DOI: 10.1002/ange.201700713
       
  • Enhanced and Optically Switchable Proton Conductivity in a Melting
           Coordination Polymer Crystal
    • Authors: Sanjog S. Nagarkar; Satoshi Horike, Tomoya Itakura, Benjamin Le Ouay, Aude Demessence, Masahiko Tsujimoto, Susumu Kitagawa
      Abstract: The melting behavior of a coordination polymer (CP) crystal was utilized to achieve enhanced and optically switchable proton conductivity in the solid state. The strong acid molecules (triflic acid) were doped in one-dimensional (1D) CP, [Zn(HPO4)(H2PO4)2](ImH2)2 (ImH2=monoprotonated imidazole) in the melt state, and overall enhancement in the proton conductivity was obtained. The enhanced proton conductivity is assigned to increased number of mobile protons and defects created by acid doping. Optical control over proton conductivity in the CP is achieved by doping of the photo acid molecule pyranine into the melted CP. The pyranine reversibly generates the mobile acidic protons and local defects in the glassy state of CP resulting in the bulk switchable conductivity mediated by light irradiation. Utilization of CP crystal in liquid state enables to be a novel route to incorporate functional molecules and defects, and it provides a tool to control the bulk properties of the CP material.Ein Koordinationspolymer (CP) wurde durch Schmelzdotierung mit Trifluormethansulfonsäure oder der Photosäure Pyranin funktionalisiert. Damit gelangen eine Verstärkung und reversible optische Kontrolle der Protonenleitfähigkeit sowie das Einstellen einer asymmetrischen Protonenkonzentration im Festkörper.
      PubDate: 2017-04-10T04:07:26.997439-05:
      DOI: 10.1002/ange.201700962
       
  • Palladium in Chemical Protein Synthesis and Modifications
    • Authors: Ashraf Brik; Suman kumar Maity, Muhammad Jbara
      Abstract: The field of site-specific modification of proteins has drawn significant attentions in recent years owing to its high importance in various research areas such as the development of novel therapeutics and understanding the biochemical and cellular behaviors of proteins. The presence of a large number of reactive functional groups in the protein of interest and in the cellular environment renders the particular modification at a specific site a highly challenging task. However, with the development of sophisticated chemical methodologies it is now possible to target a specific site of a protein with a desired modification despite many challenges remain to be solved. In this context, transition metals in particular palladium mediated C-C bond forming and C-O bond cleavage reactions gained great interest owing to the unique catalytic properties of palladium. Palladium chemistry is being significantly explored for protein modifications in vitro, on cell surface and in cellular context. Very recently, palladium complexes have been also applied for the rapid deprotection of several widely utilized cysteine-protecting groups as well as in the removal of solubilizing tags to facilitate chemical protein synthesis. This minireview highlights these advances and how the accumulated knowledge of palladium chemistry in small molecules is being impressively transferred to the area of chemical protein synthesis and modification.
      PubDate: 2017-04-06T07:55:34.75814-05:0
      DOI: 10.1002/ange.201702370
       
  • New directions for mixed-matrix membranes
    • Authors: Janina Dechnik; Jorge Gascon, Christian Doonan, Christoph Janiak, Christopher James Sumby
      Abstract: Research into extended porous materials such as metal-organic frameworks (MOFs) and porous organic frameworks (POFs), and their molecular analogues, metal-organic polyhedra (MOPs) and porous organic cages (POCs), has blossomed over the last decade. Given their chemical and structural mutability and notable porosity, MOFs have been proposed as novel adsorbents for industrial gas separations. In this context they have also been identified as promising filler components for high-performance mixed matrix membranes (MMMs). Research in this area has focused on enhancing the chemical compatibility between the MOF and polymer phase by judiciously functionalising the organic linkers of the MOF, modifying the MOF surface chemistry and, more recently, exploring how particle size, morphology and distribution enhance separation performance. Other filler materials, including POFs, MOPs and POCs, are also being explored as additives for MMMs and have shown, unexpectedly, remarkable anti-aging performance and excellent chemical compatibility for commercially available polymers. This review briefly outlines the state-of-the-art in MOF-MMM fabrication, and the more recent use of porous organic frameworks and molecular additives for MMMs.
      PubDate: 2017-04-04T21:25:38.23184-05:0
      DOI: 10.1002/ange.201701109
       
  • Cyclic (alkyl)(amino)carbenes (CAACs): Recent Developments
    • Authors: Guy Bertrand; Michele Sioleilhavoup, Mohand Melaimi, Rodolphe Jazzar
      Abstract: Discovered in 2005, CAACs are among the most nucleophilic (σ-donating) and also electrophilic (π-accepting) stable carbenes known to date. These properties allow them to activate a variety of small molecules and enthalpically strong bonds, to stabilize highly reactive main group and transition metal diamagnetic and paramagnetic species, and to bind strongly to metal centers, which gives rise to very robust catalysts. The most important results published up to 2013 are briefly summarized, while the majority of this review focuses on findings reported within the last three years.
      PubDate: 2017-04-04T14:20:27.084288-05:
      DOI: 10.1002/ange.201702148
       
  • Annulative π-Extension (APEX): An Enabling Reaction for Rapid Access to
           Fused Aromatics, Heteroaromatics, and Nanographenes
    • Authors: Hideto Ito; Kyohei Ozaki, Kenichiro Itami
      Abstract: The annulative π-extension (APEX) reaction has the potential to impact tremendously on the fields of materials science and bioimaging, as well as the pharmaceutical/agrochemical industries, since it can access fused aromatic systems from relatively simple aromatic compounds in a single step. Typically, an APEX reaction facilitates a one-pot π-extension without the tedious need to pre-functionalize aromatic compounds. This advantageous feature is extremely useful for tuning and modifying molecular properties in the last step of a synthesis. In this review, the progress and applications of APEX reactions of unfunctionalized arenes and heteroarenes are described.
      PubDate: 2017-03-29T21:20:44.17974-05:0
      DOI: 10.1002/ange.201701058
       
  • A Challenging Pie to Splice: Drugging the Spliceosome.
    • Authors: Brian Leon; Manoj Kashyap, Warren Chan, Kelsey Krug, Januario Castro, James LaClair, Michael D. Burkart
      Abstract: Since its discovery in 1977, alternative RNA splicing has revealed a plethora of mechanisms undocumented in nature. Understanding these transitions and their outcome at the level of the cell and organism have become one of the great frontiers of modern chemical biology. Until 2007, this field remained in the hands of RNA biologists. However, recent identification of natural product and synthetic modulators of RNA splicing has opened new access to this field allowing for the first time a chemical-based interrogation of RNA splicing processes. Simultaneously, studies have begun to understand the vital importance of splicing in disease, therein offering a new platform for molecular discovery and human translation. As with many natural systems, gaining clear mechanistic detail at the molecular level is key towards understanding the operation of any biological machine. This minireview presents recent lessons learned in this emerging field of RNA splicing chemistry and chemical biology.
      PubDate: 2017-03-29T21:20:41.397867-05:
      DOI: 10.1002/ange.201701065
       
  • Importance of Inherent Substrate Reactivity in Enzyme Promoted Carbocation
           Cyclization/Rearrangements
    • Authors: Dean Tantillo
      Abstract: The importance of inherent substrate reactivity for terpene synthase enzymes is discussed, with a focus on recent experimental tests of predictions derived from computations on gas phase reactivity of carbocations.
      PubDate: 2017-03-27T22:25:47.338367-05:
      DOI: 10.1002/ange.201702363
       
  • Cr(0), Mo(0) and W(0) isocyanide complexes as luminophores and
           photosensitizers with long-lived excited states
    • Authors: Laura A. Büldt; Oliver S. Wenger
      Abstract: Group 6 d6 metal complexes with arylisocyanide ligands are earth-abundant alternatives to photoactive complexes made from precious metals such as Ru(II), Re(I), Os(II), or Ir(III). Some of them have long-lived 3MLCT excited states that exhibit luminescence with good quantum yields combined with nano- to microsecond lifetimes, and they are very strongly reducing. Recent studies have demonstrated that Cr(0), Mo(0), and W(0) arylisocyanides have great potential for application in luminescent devices, photoredox catalysis, and dye-sensitized solar cells.
      PubDate: 2017-03-20T02:16:22.373626-05:
      DOI: 10.1002/ange.201701210
       
  • Fervent Hype behind Magnesium Batteries: An Open Call to Synthetic
           Chemists - Electrolytes and Cathodes Needed
    • Authors: John Muldoon; Claudiu B Bucur, Thomas Gregory
      Abstract: Magnesium metal is an ideal anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of -2.37V vs. the standard hydrogen electrode. The major advantage of magnesium is the apparent lack of dendritic formation during charging which is one of the major concerns of using a lithium metal anode. In this review, we highlight the major research in the development of electrolytes and cathodes and discuss some of the major challenges which must be overcome in realizing a practical magnesium battery.
      PubDate: 2017-03-10T12:43:08.347148-05:
      DOI: 10.1002/ange.201700673
       
  • Cationic Polymerization: From Photoinitiation to Photocontrol
    • Authors: Quentin Michaudel; Veronika Kottisch, Brett P. Fors
      Abstract: During the last 40 years, researchers investigating photoinitiated cationic polymerizations have delivered tremendous success in both industrial and academic settings. A myriad of photoinitiating systems have been developed, allowing for the polymerization of a broad array of monomers (e.g., epoxides, vinyl ethers, alkenes, cyclic ethers, and lactones) under practical, inexpensive, and environmentally benign conditions. More recently, owing to progress in photoredox catalysis, photocontrolled cationic polymerization has emerged as a means to precisely regulate polymer chain growth. This review provides a concise historical perspective on cationic polymerization induced by light and discusses the latest advances in both photoinitiated and photocontrolled processes. The latter are exciting new directions for the field that will likely impact industries ranging from micropatterning to the synthesis of complex biomaterials and sequence-controlled polymers.
      PubDate: 2017-03-09T09:35:25.66218-05:0
      DOI: 10.1002/ange.201701425
       
  • Transition Metal-Catalyzed Utilization of Methanol as C1 Source in Organic
           Synthesis
    • Authors: Jagadeesh Rajenahally; Kishore Natte, Helfried Neumann, Matthias Beller
      Abstract: Methanol represents one of the privileged and widespread platform chemicals, which is used in many science sectors such as chemistry, biology, medicine and energy. This essential alcohol serves as common solvent, cost-effective reagent and sustainable feedstock for value-added chemicals, pharmaceuticals and materials. Among different applications, the utilization of methanol as C1 source for the formation of carbon-carbon, carbon-nitrogen and carbon-oxygen bonds continues to be important in organic synthesis and drug discovery. Particularly, the synthesis of C-methylated, N-methylated and O-methylated products is of central interest because these motifs are found in a large number of life science molecules as well as fine and bulk chemicals. In this Minireview, we summarize the utilization of methanol as C1 source in C-methylation, N-methylation, C-methoxylation, N-formylation, methoxycarbonylation and oxidative methyl esterification reactions for the synthesis of C-methylated products, N-methylamines, formamides, urea derivatives, ethers, esters and heterocycles.
      PubDate: 2017-03-09T06:36:03.049864-05:
      DOI: 10.1002/ange.201612520
       
  • Dynamic Macromolecular Material Design - The Versatility of Cyclodextrin
           Based Host/Guest Chemistry
    • Authors: Bernhard Schmidt; Christopher Barner-Kowollik
      Abstract: Dynamic and adaptive materials are powerful constructs in macromolecular and polymer chemistry with a wide array of applications in drug-delivery, bioactive systems or self-healing materials. Very frequently dynamic materials featuring non-covalent interactions driven by supramolecular chemistry are based on carefully tailored cyclodextrin (CD) host/guest interactions. The precise incorporation of these host and guest moieties into macromolecular building blocks allows for the formation of complex macromolecular structures that can be utilized to form higher level assemblies executing specific pre-defined functions. Thus, dynamic materials with extraordinary adaptive property profiles - responsive to thermal, chemical and photonic fields - become accessible. In the current critical review the hierarchical formation of dynamic materials and complex macromolecular structures is explored from the molecular to the macromolecular on to the colloidal and macroscopic level, with a specific emphasis on the functionality and outer field responsiveness of the assemblies, specifically in biological contexts.
      PubDate: 2017-02-28T08:45:49.050061-05:
      DOI: 10.1002/ange.201612150
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • Titelbild: Zinc Regulates Chemical-Transmitter Storage in Nanometer
           Vesicles and Exocytosis Dynamics as Measured by Amperometry (Angew. Chem.
           18/2017)
    • Authors: Lin Ren; Masoumeh Dowlatshahi Pour, Soodabeh Majdi, Xianchan Li, Per Malmberg, Andrew G. Ewing
      Pages: 4973 - 4973
      Abstract: Die Wirkung von Zink, einem wichtigen Element für Lern- und Erinnerungsprozesse, auf die Neurotransmission in einem Einzelzellmodell für die Botenstoff-Freisetzung wurde mit amperometrischen Methoden untersucht. In der Zuschrift auf S. 5052 belegen A. G. Ewing et al., dass Zink nicht nur den Vesikelgehalt von PC12-Zellen ändert, sondern auch die Dynamik einzelner Exozytoseprozesse, was eine längere und stabile Fusion bewirkt. Diese Beobachtung gibt Aufschluss darüber, wie Zink diesen zellulären Schlüsselprozess beeinflusst und so die Zell-Zell-Kommunikation modifiziert.
      PubDate: 2017-03-22T09:12:57.539221-05:
      DOI: 10.1002/ange.201702664
       
  • Innentitelbild: Hyperfine-Interaction-Driven Suppression of Quantum
           Tunneling at Zero Field in a Holmium(III) Single-Ion Magnet (Angew. Chem.
           18/2017)
    • Authors: Yan-Cong Chen; Jun-Liang Liu, Wolfgang Wernsdorfer, Dan Liu, Liviu F. Chibotaru, Xiao-Ming Chen, Ming-Liang Tong
      Pages: 4974 - 4974
      Abstract: Eine Unterdrückung des Quantentunnelns im Nullfeld und feldinduziertes Quantentunneln der Magnetisierung wurden in einem Holmium(III)-Einzelmolekülmagnet beobachtet und von J.-L. Liu, M.-L. Tong et al. in der Zuschrift auf S. 5078 beschrieben. Diese Dynamik wird auf die Kombination einer günstigen pentagonal-bipyramidalen Kristallfeldumgebung mit den Hyperfeinwechselwirkungen von 165Ho (I=7/2) mit einer natürlichen Häufigkeit von 100 % zurückgeführt.
      PubDate: 2017-03-29T08:20:45.570617-05:
      DOI: 10.1002/ange.201702921
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 18/2017
    • Pages: 4977 - 4988
      PubDate: 2017-04-18T03:15:49.183535-05:
      DOI: 10.1002/ange.201781811
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 18/2017
    • Pages: 4990 - 4993
      PubDate: 2017-04-18T03:15:38.791588-05:
      DOI: 10.1002/ange.201781813
       
  • The WSPC Reference on Organic Electronics: Organic Semiconductors.
           Materials and Energy Series. Band 1: Basic Concepts, Band 2: Fundamental
           Aspects of Materials and Applications. Herausgegeben von Jean-Luc Brédas
           und Seth R. Marder.
    • Authors: Enrico Da Como; Elizabeth von Hauff
      Pages: 4995 - 4996
      Abstract: World Scientific Publishing, Singapur 2016. 896 S., geb., 452.00 £.—ISBN 978-9814699228
      PubDate: 2017-03-22T09:37:30.151729-05:
      DOI: 10.1002/ange.201701913
       
  • Ein molekularer Knoten mit acht Überkreuzungen
    • Authors: Fabien B. L. Cougnon
      Pages: 4998 - 4999
      Abstract: Achtungserfolg: Die Synthese des Kleeblattknotens als einfachster Knoten gelang bereits 1989, dagegen blieb die Bildung komplexerer Knoten anspruchsvoll. Dementsprechend ist die Synthese des bislang komplexesten molekularen Knotens – 819 – mit acht Überkreuzungen durch Leigh et al. ein wesentlicher Schritt hin zum Aufbau topologisch komplexer Architekturen.
      PubDate: 2017-03-29T08:20:30.889846-05:
      DOI: 10.1002/ange.201701308
       
  • Fullerene im Weltraum
    • Authors: John P. Maier; Ewen K. Campbell
      Pages: 5000 - 5010
      Abstract: Im Jahr 1985 wurde für das Buckminsterfulleren, C60, eine Fußball-Struktur vorgeschlagen, die 1990 bestätigt wurde. Schon zu Beginn dieser Forschung beschäftigte man sich mit dem Vorkommen von C60 und C60+ im Weltraum, vor allem im Zusammenhang mit den rätselhaften diffusen interstellaren Banden. Diese stammen von Absorptionen, die man in den Spektren des Lichts roter Sterne findet. Das Absorptionsspektrum von C60+ wurde 1993 in einer Neonmatrix bei 5 K gemessen, und es enthielt zwei prominente Banden nahe 9583 Å und 9645 Å. Anhand dieser Datengrundlage wurde vorhergesagt, in welchem Wellenlängenbereich die Gasphasenabsorptionen von C60+ liegen sollten. In dieser Spektralregion wurden 1994 zwei diffuse interstellare Banden gefunden und C60+ zugeschrieben. Erst 20 Jahre später konnte man das Absorptionsspektrum von C60+ unter ähnlichen Bedingungen messen, wie sie in den diffusen Wolken vorherrschen. Komplexe Labormessungen bestätigten 2015, dass diese beiden interstellaren Banden tatsächlich von C60+ herrühren.Fußball von einem anderen Stern: Die Fullerene wurden 1985 durch Experimente entdeckt, mit denen man ursprünglich die Entstehung von Kohlenstoffketten im interstellaren Raum verstehen wollte. Dreißig Jahre später haben spektroskopische Experimente das Vorkommen von C60+ in diffusen Wolken aus Molekülen und Staub bestätigt und erste Antworten auf ein lange bestehendes astronomisches Rätsel geben können.
      PubDate: 2017-03-30T01:50:43.967618-05:
      DOI: 10.1002/ange.201612117
       
  • Ein achtkerniger metallosupramolekularer Würfel mit
           Spin-Crossover-Eigenschaften
    • Authors: Niklas Struch; Christoph Bannwarth, Tanya K. Ronson, Yvonne Lorenz, Bernd Mienert, Norbert Wagner, Marianne Engeser, Eckhard Bill, Rakesh Puttreddy, Kari Rissanen, Johannes Beck, Stefan Grimme, Jonathan R. Nitschke, Arne Lützen
      Pages: 5012 - 5017
      Abstract: Nach dem Ansatz der Subkomponenten-Selbstorganisation lassen sich aus 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin oder dessen Zink(II)-Komplex, 1H-4-Imidazol-carbaldehyd und Zink(II)- oder Eisen(II)-Salzen O-symmetrische Käfige mit einem abgeschlossenen Hohlraum von 1300 Å3 darstellen. Eisen(II)-Salze lieferten Käfigverbindungen, die bei Raumtemperatur im High-spin-Zustand vorliegen und beim Abkühlen in den Low-spin-Zustand übergehen, während die Verwendung von Zink(II)-Salzen die diamagnetischen Analoga liefert. Die Verbindungen wurden mit Synchrotron-Einkristallröntgenbeugung, hochauflösender Massenspektrometrie, NMR-, Mößbauer-, IR- und UV-Vis-Spektroskopie charakterisiert. Die Struktur der Käfigverbindungen und ihre UV-Vis-Spektren wurden unabhängig durch DFT-Rechnungen bestätigt. Ein besonderer Effekt ist die Stabilisierung des High-spin-Zustands durch Einschluss von C70 in den Käfigen. Im Fall des Wirt-Gast-Komplexes liegt die Übergangstemperatur T1/2 um 20 K tiefer als die des freien Wirts.Subkomponenten-Selbstorganisation liefert achtkernige metallosupramolekulare Käfige, die mit experimentellen und theoretischen Methoden charakterisiert wurden. Die Eisen(II)-Komplexe zeigen ein interessantes, gastabhängiges Spin-Crossover-Verhalten in Lösung. So führt der Einschluss von C70-Fulleren zu einer Stabilisierung des High-spin-Zustands und einer Verschiebung der Spinübergangstemperatur von 20 K.
      PubDate: 2017-03-30T08:36:58.583328-05:
      DOI: 10.1002/ange.201700832
       
  • Katalytisch-asymmetrische intramolekulare [4+2]-Cycloaddition von
           in situ generierten ortho-Chinonmethiden
    • Authors: Youwei Xie; Benjamin List
      Pages: 5018 - 5022
      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
       
  • Stabile Polyoxometallat-Nickelschaum-Elektroden für elektrochemische
           Sauerstoffentwicklung im alkalischen Milieu
    • Authors: Wenjing Luo; Jun Hu, Hongling Diao, Benjamin Schwarz, Carsten Streb, Yu-Fei Song
      Pages: 5023 - 5026
      Abstract: Die Entwicklung von technisch relevanten Elektroden für die elektrochemische Sauerstoffentwicklung (OER) ist eine der größten Herausforderungen der chemischen Energiewandlung. Nun gelang die hydrothermale Immobilisierung des Dexter-Silverton-Polyoxometallats, [Co6.8Ni1.2W12O42(OH)4(H2O)8], auf einer kommerziellen Nickelschaumelektrode. Im alkalischen Milieu (pH 13) zeigt das Elektrodenmaterial katalytische Sauerstoffentwicklung bei niedriger Überspannung (360 mV bei 10 mA cm−2 gegen RHE, Tafel-Steigung 126 mV dec−1, Faraday-Effizienz (96±5) %). Zudem ist keine Zersetzung oder Abtrennung der Polyoxometallat-Mikrokristalle von der Elektrode nach der Katalyse zu beobachten. Die vorgestellte Immobilisierungsroute kann also einen Zugang zu technisch relevanten Elektrodenmaterialien für die Sauerstoffentwicklung eröffnen.Die Immobilisierung eines Co2+/Ni2+-substituierten Dexter-Silverton-Polyoxometallats auf porösem Nickelschaum ermöglicht die elektrochemische Sauerstoffentwicklung im alkalischen Milieu. Das Elektrodenmaterial zeigt eine hohe Faraday-Effizienz (96 %) bei geringen Überspannungen (η=360 mV), wobei unter Betriebsbedingungen (>10 h) keine Zersetzung beobachtet wird. Diese Immobilisierungsmethode kann den Zugang zu technisch relevanten Elektrodenmaterialien für die Sauerstoffentwicklung eröffnen.
      PubDate: 2017-04-03T08:25:39.317749-05:
      DOI: 10.1002/ange.201612232
       
  • Struktur und Biosynthese der Isatropolone, bioaktiver und Amin-reaktiver
           fluoreszierender Naturstoffe aus Streptomyces Gö66
    • Authors: Xiaofeng Cai; Yi-Ming Shi, Nicole Pöhlmann, Ole Revermann, Isabel Bahner, Sacha J. Pidot, Frank Wesche, Helmut Lackner, Claudia Büchel, Marcel Kaiser, Christian Richter, Harald Schwalbe, Timothy P. Stinear, Axel Zeeck, Helge B. Bode
      Pages: 5027 - 5031
      Abstract: Die Naturstoffe Isatropolon A–C (1–3) wurden aus Streptomyces Gö66 reisoliert, und insbesondere 1 und 3 zeigen sehr gute Aktivität gegen Leishmania donovani. Sie tragen einen ungewöhnlichen Tropolonring, der über einen Typ-II-Polyketid-Biosyntheseweg aufgebaut wird. Ihre Biosynthese wurde mithilfe von Markierungsexperimenten, einer Analyse des Biosynthese-Genclusters, heterologer Expression des Hauptteils des Genclusters und strukturelle Charakterisierung verschiedener Intermediate aufgeklärt. Aufgrund eines 1,5-Diketon-Strukturelementes können die Isatropolone mit Ammoniak und Aminen und insbesondere Lysin sowie Lysin-tragenden Peptiden und Proteinen reagieren und einen Pyridinring bilden. Dabei ändern sich die Fluoreszenz-Eigenschaften so deutlich, dass die so markierten Peptide und Proteine sehr einfach sichtbar gemacht werden können.Ein guter grüner Fang! Die Struktur und Biosynthese der Isatropolon-Naturstoffe wurden aufgeklärt. Die Verbindungen zeigen einen deutlichen Wechsel der Fluoreszenz nach Reaktion mit Aminen sowie Amin-tragenden Peptiden und Proteinen.
      PubDate: 2017-03-30T08:36:35.048367-05:
      DOI: 10.1002/ange.201701223
       
  • Platin(II)-verknüpfte Einzelketten-Nanopartikel: ein Schritt in Richtung
           wiederverwendbarer Homogenkatalysatoren
    • Authors: Nicolai D. Knöfel; Hannah Rothfuss, Johannes Willenbacher, Christopher Barner-Kowollik, Peter W. Roesky
      Pages: 5032 - 5036
      Abstract: Platin(II)-verknüpfte Einzelketten-Nanopartikel (PtII-SCNPs) wurden synthetisiert, charakterisiert und als wiederverwendbare Homogenkatalysatoren eingesetzt. Als Vorstufe wurde ein lineares Copolymer aus Styrol und 4-(Diphenylphosphan)styrol mittels Nitroxid-vermittelter Polymerisation synthetisiert. Die Triarylphosphaneinheiten, die sich im Polymerrückgrad befinden, ermöglichen durch Zugabe von [Pt(1,5-cyclooctadien)Cl2] in verdünnter Lösung die intramolekulare Vernetzung einzelner Ketten. Die Bildung von PtII-SCNPs wurde durch Gelpermeationschromatographie, dynamische Lichtstreuung, NMR-Spektroskopie (1H, 31P{1H}, 195Pt) und DOSY-Messungen nachgewiesen. Die erfolgreiche Verwendung der PtII-SCNPs als wiederverwendbare Homogenkatalysatoren wurde am Beispiel der Aminierung von Allylalkohol veranschaulicht.Gut in Form: Wiederverwendbare metallhaltige Einzelketten-Nanopartikel (SCNPs) behalten ihre Form und Funktion in der homogenen Katalyse bei und ebnen damit den Weg für eine neue Klasse hochentwickelter katalytischer Systeme. Die neuartigen PtII-SCNP-Katalysatoren verbinden die Vorteile homogener Aktivität und heterogener Wiederverwendbarkeit.
      PubDate: 2017-04-03T08:25:28.26443-05:0
      DOI: 10.1002/ange.201700718
       
  • Stereoelectronic Control in the Ozone-Free Synthesis of Ozonides
    • Authors: Gabriel dos Passos Gomes; Ivan A. Yaremenko, Peter S. Radulov, Roman A. Novikov, Vladimir V. Chernyshev, Alexander A. Korlyukov, Gennady I. Nikishin, Igor V. Alabugin, Alexander O. Terent'ev
      Pages: 5037 - 5041
      Abstract: The value of stereoelectronic guidelines is illustrated by the discovery of a convenient, ozone-free synthesis of bridged secondary ozonides from 1,5-dicarbonyl compounds and H2O2. The tetraoxane products generally formed in reactions of carbonyl and dicarbonyl compounds with H2O2 were not detected because the structural distortions imposed on the tetraoxacyclohexane subunit in [3.2.2]tetraoxanonanes by the three-carbon bridge leads to the partial deactivation of anomeric effects. The new procedure is readily scalable to produce gram quantities of the ozonides. This reaction enables the selective preparation of ozonides without the use of ozone.Ozonide ohne das Ozon: Eine Synthese von verbrückten sekundären Ozoniden aus 1,5-Dicarbonylverbindungen und H2O2 wurde auf der Grundlage stereoelektronischer Überlegungen entwickelt (siehe Schema). Die üblicherweise gebildeten Tetraoxan-Produkte wurden nicht gefunden; Ursache ist die teilweise Desaktivierung anomerer Effekte infolge der Verzerrung der Tetraoxacyclohexan-Untereinheit in den [3.2.2]Tetraoxanonan-Zwischenstufen durch die C3-Brücke.
      PubDate: 2017-04-05T02:25:49.080322-05:
      DOI: 10.1002/ange.201610699
       
  • From O2− to HO2−: Reducing By-Products and Overpotential in Li-O2
           Batteries by Water Addition
    • Authors: Yu Qiao; Shichao Wu, Jin Yi, Yang Sun, Shaohua Guo, Sixie Yang, Ping He, Haoshen Zhou
      Pages: 5042 - 5046
      Abstract: The development of aprotic Li-O2 batteries, which are promising candidates for high gravimetric energy storage devices, is severely limited by superoxide-related parasitic reactions and large voltage hysteresis. The fundamental reaction pathway of the aprotic Li-O2 battery can be altered by the addition of water, which changes the discharge intermediate from superoxide (O2−) to hydroperoxide (HO2−). The new mechanism involving HO2− intermediate realizes the two-electron transfer through a single step, which significantly suppresses the superoxide-related side reactions. Moreover, addition of water also triggers a solution-based pathway that effectively reduces the voltage hysteresis. These discoveries offer a possible solution for desirable Li-O2 batteries free of aggressive superoxide species, highlighting the design strategy of modifying the reaction pathway for Li-O2 electrochemistry.Die Zugabe von Wasser kontrolliert die Nebenreaktionen in der Sauerstoffreduktion, indem das aggressivere Superoxid (O2−) in das moderate Hydroperoxid überführt wird. Die reversible Sauerstoff-Peroxid-Redoxreaktion gewährleistet ein niedriges Überpotential und ist damit der Elektrochemie an der Kathode/Li2O2-Grenzfläche überlegen.
      PubDate: 2017-03-29T07:32:41.502434-05:
      DOI: 10.1002/ange.201611122
       
  • A Photocatalytically Active Lubricant-Impregnated Surface
    • Authors: Sanghyuk Wooh; Hans-Jürgen Butt
      Pages: 5047 - 5051
      Abstract: Lubricant impregnated surfaces (LISs) exhibit sliding angles below 5°. A LIS is presented that possesses photocatalytic activity as well as improved liquid repellency. In a single-step reaction, the surface of photocatalytic mesoporous TiO2 substrate is modified by grafting polydimethylsiloxane (PDMS) brush and the residual non-bound PDMS serves as lubricant. Since the lubricant and the hydrophobic layer are chemically identical, the grafting PDMS layer is stably swollen by the lubricant PDMS, which inhibits direct contact of liquid drops to the solid substrate. Liquid drops such as water, methanol, and even low-surface-tension fluorocarbons, slide on the surface with tilt angles below 1°. The surface exhibits long-term stable photocatalytic activity while retaining its liquid repellency. This photocatalytic activity allows photocatalytic chemistry, for example, decomposition of organics, on LIS to be carried out.Eine schmiermittelimprägnierte Oberfläche mit langanhaltender photokatalytischer Aktivität und verbesserter flüssigkeitsabweisender Wirkung wird vorgestellt. Im Aufbau der Oberfläche ist ein mesoporöses TiO2-Substrat durch Polydimethylsiloxan(PDMS)-Bürsten modifiziert. Verbleibendes ungebundenes PDMS dient als Schmiermittel. Tropfen von Wasser, Methanol und sogar Fluorkohlenstoffen gleiten schon beim Kippen um weniger als 1° von der Oberfläche ab.
      PubDate: 2017-03-28T05:11:22.398117-05:
      DOI: 10.1002/ange.201611277
       
  • Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and
           Exocytosis Dynamics as Measured by Amperometry
    • Authors: Lin Ren; Masoumeh Dowlatshahi Pour, Soodabeh Majdi, Xianchan Li, Per Malmberg, Andrew G. Ewing
      Pages: 5052 - 5057
      Abstract: We applied electrochemical techniques with nano-tip electrodes to show that micromolar concentrations of zinc not only trigger changes in the dynamics of exocytosis, but also vesicle content in a model cell line. The vesicle catecholamine content in PC12 cells is significantly decreased after 100 μm zinc treatment, but, catecholamine release during exocytosis remains nearly the same. This contrasts with the number of molecules stored in the exocytosis vesicles, which decreases, and we find that the amount of catecholamine released from zinc-treated cells reaches nearly 100 % content expelled. Further investigation shows that zinc slows down exocytotic release. Our results provide the missing link between zinc and the regulation of neurotransmitter release processes, which might be important in memory formation and storage.Zinkronisiert: Einzelzellamperometrie und intrazelluläre elektrochemische Vesikelstoßzytometrie belegen die Auswirkungen von Zink auf Exozytose und Vesikelgehalt von PC12-Zellen. Zink verändert nicht nur die Speicherung von Botenstoffen, sondern auch die Dynamik der Exozytose, indem es den Öffnungs- und Schließprozess von Fusionsporen stabilisiert.
      PubDate: 2017-03-20T10:10:51.169596-05:
      DOI: 10.1002/ange.201700095
       
  • Ionic Covalent Organic Frameworks: Design of a Charged Interface Aligned
           on 1D Channel Walls and Its Unusual Electrostatic Functions
    • Authors: Ning Huang; Ping Wang, Matthew A. Addicoat, Thomas Heine, Donglin Jiang
      Pages: 5064 - 5068
      Abstract: Covalent organic frameworks (COFs) have emerged as a tailor-made platform for designing layered two-dimensional polymers. However, most of them are obtained as neutral porous materials. Here, we report the construction of ionic crystalline porous COFs with positively charged walls that enable the creation of well aligned yet spatially confined ionic interface. The unconventional reversed AA-stacking mode alternately orientates the cationic centers to both sides of the walls; the ionic interface endows COFs with unusual electrostatic functions. Because all of the walls are decorated with electric dipoles, the uptake of CO2 is enhanced by three fold compared to the neutral analog. By virtue of sufficient open space between cations, the ionic interface exhibits exceptional accessibility, efficiency, and selectivity in ion exchange to trap anionic pollutants. These findings suggest that construction of the ionic interface of COFs offers a new way to structural and functional designs.Ein Gerüst für ionische Grenzflächen: Kovalente organische Gerüststrukturen mit gut ausgerichteten ionischen Grenzflächen (Benzimidazoliumkationen) an den eindimensionalen Kanalwänden wurden synthetisiert. Die ionischen Grenzflächen führen zu ungewöhnlichen elektrostatischen Funktionen, wie der CO2-Absorption und der selektiven Entfernung anionischer Schadstoffe.
      PubDate: 2017-03-29T07:50:34.986654-05:
      DOI: 10.1002/ange.201611542
       
  • Cyanobacterial ent-Sterol-Like Natural Products from a Deviated Ubiquinone
           Pathway
    • Authors: Philipp Moosmann; Reiko Ueoka, Laura Grauso, Alfonso Mangoni, Brandon I. Morinaka, Muriel Gugger, Jörn Piel
      Pages: 5069 - 5072
      Abstract: Natural products from marine animals show high potential for the development of new medicines, but drug development based on these compounds is commonly hampered by their low natural abundance. Since many of these metabolites are suspected or known to be produced by uncultivated bacterial symbionts, the rapidly growing diversity of sequenced prokaryotic genomes offers the opportunity to identify alternative, culturable sources of natural products computationally. In this work, we investigated the potential of using this sequenced resource to facilitate the production of meroterpenoid-like compounds related to those from marine sources. This genome-mining strategy revealed a biosynthetic gene cluster for highly modified cytotoxic meroterpenoids related to pelorol and other compounds isolated from sponges. Functional characterization of the terpene cyclase MstE showed that it generates an ent-sterol-like skeleton fused to an aryl moiety from an open-chain precursor and is therefore a promising tool for the chemoenzymatic preparation of synthetically challenging chemical scaffolds.Marine Meroterpenoid-artige Verbindungen sind aus pharmakologischer Sicht hoch interessant, über ihre Biosynthese ist jedoch nur wenig bekannt. Nun wurde ein sehr ähnliches Meroterpenoid in Cyanobakterien identifiziert. Die Biosynthese einer solchen Verbindung konnte erstmals einem Gencluster zugeordnet werden, der für eine Terpen-Cyclase (MstE) mit In-vitro-Aktivität codiert.
      PubDate: 2017-03-30T03:40:24.633744-05:
      DOI: 10.1002/ange.201611617
       
  • Low-Temperature Atomic Layer Deposition of MoS2 Films
    • Authors: Titel Jurca; Michael J. Moody, Alex Henning, Jonathan D. Emery, Binghao Wang, Jeffrey M. Tan, Tracy L. Lohr, Lincoln J. Lauhon, Tobin J. Marks
      Pages: 5073 - 5077
      Abstract: Wet chemical screening reveals the very high reactivity of Mo(NMe2)4 with H2S for the low-temperature synthesis of MoS2. This observation motivated an investigation of Mo(NMe2)4 as a volatile precursor for the atomic layer deposition (ALD) of MoS2 thin films. Herein we report that Mo(NMe2)4 enables MoS2 film growth at record low temperatures—as low as 60 °C. The as-deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift-off patterning for the straightforward fabrication of diverse device structures.60 °C genügen für die Abscheidung von dünnen MoS2-Filmen mit H2S und Mo(NMe2)4 als Vorstufen. Beim Tempern kristallisierten die abgeschiedenen Filme; sie erwiesen sich als kompatibel mit der Photolithographie und ermöglichten eine einfache großflächige Mustererzeugung. Die Methode lässt skalierbare Prozesse für Anwendungen von der Elektronik bis zur Katalyse möglich erscheinen.
      PubDate: 2017-04-07T02:56:49.854833-05:
      DOI: 10.1002/ange.201611838
       
  • Hyperfine-Interaction-Driven Suppression of Quantum Tunneling at Zero
           Field in a Holmium(III) Single-Ion Magnet
    • Authors: Yan-Cong Chen; Jun-Liang Liu, Wolfgang Wernsdorfer, Dan Liu, Liviu F. Chibotaru, Xiao-Ming Chen, Ming-Liang Tong
      Pages: 5078 - 5082
      Abstract: An extremely rare non-Kramers holmium(III) single-ion magnet (SIM) is reported to be stabilized in the pentagonal-bipyramidal geometry by a phosphine oxide with a high energy barrier of 237(4) cm−1. The suppression of the quantum tunneling of magnetization (QTM) at zero field and the hyperfine structures originating from field-induced QTMs can be observed even from the field-dependent alternating-current magnetic susceptibility in addition to single-crystal hysteresis loops. These dramatic dynamics were attributed to the combination of the favorable crystal-field environment and the hyperfine interactions arising from 165Ho (I=7/2) with a natural abundance of 100 %.Ein extrem seltener Holmium(III)-Einzelmolekülmagnet vom Nicht-Kramers-Typ wird beschrieben. Die Unterdrückung des Quantentunnelns der Magnetisierung im Nullfeld und die Hyperfeinstrukturen können sogar aus den feldunabhängigen Wechselstrom-Suszeptibilitäten abgelesen werden, was auf die Kombination der günstigen Kristallfeldumgebung und der Hyperfeinwechselwirkungen des 165Ho (I=7/2) mit einer natürlichen Häufigkeit von 100 % zurückgeführt wird.
      PubDate: 2017-03-15T03:25:54.246134-05:
      DOI: 10.1002/ange.201701480
       
  • Dynamic Gradient Directed Molecular Transport and Concentration in
           Hydrogel Films
    • Authors: Tsung-Han Tsai; Mohammad A. Ali, Zhelong Jiang, Paul V. Braun
      Pages: 5083 - 5088
      Abstract: Materials which selectively transport molecules along defined paths offer new opportunities for concentrating, processing and sensing chemical and biological agents. Here, we present the use of traveling ionic waves to drive molecular transport and concentration of hydrophilic molecules entrained within a hydrogel. The traveling ionic wave is triggered by the spatially localized introduction of ions, which through a dissipative ion exchange process, converts quaternary ammonium groups in the hydrogel from hydrophilic to hydrophobic. Through a reaction–diffusion process, the hydrophobic region expands with a sharp transition at the leading edge; it is this sharp gradient in hydrophilicity that drives the transport of hydrophilic molecules dispersed within the film. The traveling wave moved up to 450 μm within 30 min, while the gradient length remained 20 μm over this time. As an example of the potential of molecular concentration using this approach, a 70-fold concentration of a hydrophilic dye was demonstrated.Ionische Wanderwellen wurden genutzt, um den Transport hydrophiler Moleküle in einem Hydrogel anzutreiben. Die fortschreitende Welle wird durch räumlich lokalisierte Zugabe von Ionen ausgelöst, die hydrophile quartäre Ammoniumgruppen hydrophob machen, und legt bis zu 450 μm in 30 min zurück.
      PubDate: 2017-04-07T02:56:52.433228-05:
      DOI: 10.1002/ange.201700166
       
  • An Annulative Synthetic Strategy for Building Triphenylene Frameworks by
           Multiple C−H Bond Activations
    • Authors: Bijoy P. Mathew; Hyun Ji Yang, Joohee Kim, Jae Bin Lee, Yun-Tae Kim, Sungmin Lee, Chang Young Lee, Wonyoung Choe, Kyungjae Myung, Jang-Ung Park, Sung You Hong
      Pages: 5089 - 5093
      Abstract: C−H activation is a versatile tool for appending aryl groups to aromatic systems. However, heavy demands on multiple catalytic cycle operations and site-selectivity have limited its use for graphene segment synthesis. A Pd-catal- yzed one-step synthesis of functionalized triphenylene frameworks is disclosed, which proceeds by 2- or 4-fold C−H arylation of unactivated benzene derivatives. A Pd2(dibenzylideneacetone)3 catalytic system, using cyclic diaryliodonium salts as π-extending agents, leads to site-selective inter- and intramolecular tandem arylation sequences. Moreover, N-substituted triphenylenes are applied to a field-effect transistor sensor for rapid, sensitive, and reversible alcohol vapor detection.Her mit den Ringen: Eine palladiumkatalysierte zwei- oder vierfache C-H-Arylierung nichtaktivierter Arene öffnet einen Zugang zu substituierten Triphenylen-Gerüsten.
      PubDate: 2017-03-30T08:37:18.197981-05:
      DOI: 10.1002/ange.201700405
       
  • Toward Stable Superbenzoquinone Diradicaloids
    • Authors: Guangwu Li; Hoa Phan, Tun Seng Herng, Tullimilli Y. Gopalakrishna, Chunchen Liu, Wangdong Zeng, Jun Ding, Jishan Wu
      Pages: 5094 - 5098
      Abstract: Superbenzoquinone (SBQ) is a quinone derived from a classic polycyclic aromatic hydrocarbon (PAH), hexa-peri-hexabenzocoronene (so-called “superbenzene”), and is a challenging synthetic target. Herein we report the successful synthesis and characterization of its derivatives. We reveal that the high reactivity of SBQ is due to its intrinsic open-shell diradical character. Thus, two kinetically blocked SBQs, SBQ-Me and SBQ-Ph, were prepared by different synthetic strategies. 4-tert-Butylphenyl-substituted SBQ-Ph demonstrated good stability and could be isolated in crystalline form. Both compounds have an open-shell singlet ground state and show thermally populated paramagnetic activity. Our studies provide effective strategies toward stable quinone-based diradicaloids.So einnehmend wie ein Schmetterling: Verschiedene Strategien zur Synthese von Superbenzochinon(SBQ)-Derivaten wurden erforscht, und stabiles 4-tert-Phenyl-substituiertes SBQ-Ph wurde durch kinetische Blockierung erhalten. SBQ-Ph (siehe Struktur) weist einen offenschaligen Singulett-Grundzustand mit moderatem Diradikalcharakter auf und nimmt im Einkristall eine schmetterlingsartige Geometrie ein.
      PubDate: 2017-03-30T08:37:06.28692-05:0
      DOI: 10.1002/ange.201700441
       
  • Selective Enzymatic Demethylation of N2,N2-Dimethylguanosine in RNA and
           Its Application in High-Throughput tRNA Sequencing
    • Authors: Qing Dai; Guanqun Zheng, Michael H. Schwartz, Wesley C. Clark, Tao Pan
      Pages: 5099 - 5102
      Abstract: The abundant Watson–Crick face methylations in biological RNAs such as N1-methyladenosine (m1A), N1-methylguanosine (m1G), N3-methylcytosine (m3C), and N2,N2-dimethylguanosine (m22G) cause significant obstacles for high-throughput RNA sequencing by impairing cDNA synthesis. One strategy to overcome this obstacle is to remove the methyl group on these modified bases prior to cDNA synthesis using enzymes. The wild-type E. coli AlkB and its D135S mutant can remove most of m1A, m1G, m3C modifications in transfer RNA (tRNA), but they work poorly on m22G. Here we report the design and evaluation of a series of AlkB mutants against m22G-containing model RNA substrates that we synthesize using an improved synthetic method. We show that the AlkB D135S/L118V mutant efficiently and selectively converts m22G modification to N2-methylguanosine (m2G). We also show that this new enzyme improves the efficiency of tRNA sequencing.Eine AlkB-Mutation wurde identifiziert, die eine Methylgruppe von N2,N2-Dimethylguanosin (m22G) entfernt und N2-Methylguanosin (m2G) bildet. Im Unterschied zu m22G blockiert m2G nicht die reverse Transkriptionsreaktion unter Sequenzierungsbedingungen, was eine verbesserte tRNA-Sequenzierung ermöglicht.
      PubDate: 2017-03-30T01:50:45.82303-05:0
      DOI: 10.1002/ange.201700537
       
  • Self-Assembly of Magnesium Hydride Clusters Driven by Chameleon-Type
           Ligands
    • Authors: Jens Langer; Brant Maitland, Samuel Grams, Alexandra Ciucka, Jürgen Pahl, Holger Elsen, Sjoerd Harder
      Pages: 5103 - 5107
      Abstract: While magnesium hydride complexes are generally stabilized by hard, bulky N-donor ligands, softer ligands with a broad variety of coordination modes are shown to efficiently adapt themselves to the large variety of Mg2+ centers in a growing magnesium hydride cluster. A P,N-chelating ligand is introduced that displays coordination modes between that of enamide, aza-allyl, and phosphinomethanide. Slight changes in the ligand bite angle have dramatic consequences for the structure type. The hitherto largest neutral magnesium hydride clusters are isolated either in a nonanuclear sheet-structure (brucite-type) or a dodecanuclear ring structure.Kleine Änderung, große Wirkung: Ein weicher, Chamäleon-artiger Ligand kann seine Koordinationsweise an die große Bandbreite von Magnesium(II)-Zentren in einem wachsenden Magnesiumhydridcluster anpassen. Kleine Veränderungen in der Ringgröße und im Bisswinkel des Liganden haben drastische Auswirkungen auf den Strukturtyp.
      PubDate: 2017-03-29T07:52:56.418412-05:
      DOI: 10.1002/ange.201700719
       
  • Steering On-Surface Reactions by a Self-Assembly Approach
    • Authors: Qiwei Chen; Jacob R. Cramer, Jing Liu, Xin Jin, Peilin Liao, Xiang Shao, Kurt V. Gothelf, Kai Wu
      Pages: 5108 - 5112
      Abstract: 4,4′-Bis(2,6-difluoropyridin-4-yl)-1,1′:4′,1′′-terphenyl (BDFPTP) molecules underwent dehydrocyclization and covalent coupling reactions on Au(111) according to scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. Self-assembly of the reactants in well-defined molecular domains prior to reaction could greatly enhance the regioselectivity of the dehydrocyclization reaction and suppress defluorinated coupling, demonstrating that self-assembly can efficiently steer on-surface reactions. Such a strategy could be of great importance in surface chemistry and widely applied to control on-surface reactions.Oberflächenverstärkte Selektivität: Zufällig auf Au(111) verteiltes 4,4′-Bis(2,6-difluorpyridin-4-yl)-1,1′:4′,1′′-terphenyl (BDFPTP) geht sowohl Dehydrocyclisierungen (DHC) als auch Kupplungsreaktionen ein. Letztere werden komplett unterdrückt, und die DHC-Regioselektivität wird deutlich verstärkt, wenn vor der Reaktion eine BDFPTP-Selbstorganisation auf der Oberfläche stattfindet.
      PubDate: 2017-03-24T07:21:02.881732-05:
      DOI: 10.1002/ange.201700745
       
  • A Membrane-Intercalating Conjugated Oligoelectrolyte with High-Efficiency
           Photodynamic Antimicrobial Activity
    • Authors: Bing Wang; Ming Wang, Alexander Mikhailovsky, Shu Wang, Guillermo C. Bazan
      Pages: 5113 - 5116
      Abstract: A membrane-intercalating conjugated oligoelectrolyte (COE), PTTP, was designed and synthesized with the goal of providing red-shifted absorption spectra relative to previously synthesized COE analogs. Specifically, electron-rich and electron-poor subunits were introduced in the conjugated backbone to modulate the band gap. PTTP exhibits maxima of absorption at 507 nm and of emission at 725 nm. PTTP can also efficiently function to generate singlet oxygen in situ (ΦΔ≈20 %) and has appropriate topology and dimensions to interact with lipid membranes. The resulting rapid membrane insertion and sensitizing ability provide PTTP with a highly efficient antibacterial capability under a low light dose (0.6 J cm−2) toward Gram-negative bacteria E. coli, making it a remarkably efficient optically mediated antimicrobial agent.Licht an, Bazillen raus: Ein membraninterkalierender konjugierter Oligoelektrolyt (COE), PTTP, wurde gezielt so entworfen, dass er ein rotverschobenes Spektrum in Bezug auf bekannte COEs aufweist. PTTP akkumuliert in der Membran von E. coli und bewirkt die Photogeneration von Singulett-Sauerstoff. Diese Kombination von Eigenschaften resultiert in einer exzellenten optisch vermittelten antibakteriellen Kapazität unter niedrigen Lichtdosen.
      PubDate: 2017-03-28T06:05:49.787449-05:
      DOI: 10.1002/ange.201701146
       
  • Gold-Catalyzed Oxidative [2+2+1] Annulations of Aryldiazo Nitriles with
           Imines To Yield Polyarylated Imidazolium Salts
    • Authors: Samir Kundlik Pawar; Ming-Chung Yang, Ming-Der Su, Rai-Shung Liu
      Pages: 5117 - 5121
      Abstract: Gold-catalyzed oxidative [2+2+1] annulations between two imines and one α-cyano arylgold carbene afforded polyarylated imidazolium salts and molecular hydrogen efficiently. Control experiments suggest that the gold catalyst alone facilitates the main annulation, whereas Ag+ avoids the formation of inactive LAuCN. DFT calculations suggest that the success of this annulation relies on a 6 π-electrocyclization of cyano-free intermediates with cis-configured imines as initial reagents.Fünf Ringe für Fünfringe: Die Titelreaktionen zwischen zwei Iminen und einem α-Cyan(aryl)goldcarben führen unter Freisetzung von molekularem Wasserstoff effizient zu polyarylierten Imidazoliumsalzen. Dichtefunktionalrechnungen führen die erfolgreichen Ringschlüsse auf eine 6 π-Elektrocyclisierung Cyangruppen-freier Zwischenstufen und cis-konfigurierte Imine als Ausgangspunkt zurück.
      PubDate: 2017-03-30T08:36:49.005419-05:
      DOI: 10.1002/ange.201701157
       
  • Synthesis of Responsive Two-Dimensional Polymers via Self-Assembled DNA
           Networks
    • Authors: Hao Yu; Duncan T. L. Alexander, Ulrich Aschauer, Robert Häner
      Pages: 5122 - 5126
      Abstract: Despite a growing interest in two-dimensional polymers, their rational synthesis remains a challenge. The solution-phase synthesis of a two-dimensional polymer is reported. A DNA-based monomer self-assembles into a supramolecular network, which is further converted into the covalently linked two-dimensional polymer by anthracene dimerization. The polymers appear as uniform monolayers, as shown by AFM and TEM imaging. Furthermore, they exhibit a pronounced solvent responsivity. The results demonstrate the value of DNA-controlled self-assembly for the formation of two-dimensional polymers in solution.Verzweigte Oligonukleotid-Monomere bilden durch Selbstorganisation und anschließende interne Vernetzung ausgedehnte dünne Schichten in Wasser. Beim Wechsel des Lösungsmittels zieht sich die ausgedehnte Struktur zusammen, und es entstehen dicke Scheiben.
      PubDate: 2017-03-30T08:36:28.474077-05:
      DOI: 10.1002/ange.201701342
       
  • Osmolyte Effects on the Conformational Dynamics of a DNA Hairpin at
           Ambient and Extreme Environmental Conditions
    • Authors: Satyajit Patra; Christian Anders, Nelli Erwin, Roland Winter
      Pages: 5127 - 5131
      Abstract: The structural dynamics of a DNA hairpin (Hp) are studied in the absence and presence of the two natural osmolytes trimethylamine-N-oxide (TMAO) and urea at ambient and extreme environmental conditions, including high pressures and high temperatures, by using single-molecule Förster resonance energy transfer and fluorescence correlation spectroscopy. The effect of pressure on the conformational dynamics of the DNA Hp is investigated on a single-molecule level, providing novel mechanistic insights into its conformational conversions. Different from canonical DNA duplex structures of similar melting points, the DNA Hp is found to be rather pressure sensitive. The combined temperature and pressure dependent data allow dissection of the folding free energy into its enthalpic, entropic, and volumetric contributions. The folded conformation is effectively stabilized by the compatible osmolyte TMAO not only at high temperatures, but also at high pressures and in the presence of the destabilizing co-solute urea.smFRET unter Druck: Die Konformationsdynamik eines DNA-Hairpins wurde mit Einzelmolekül-FRET und Fluoreszenzkorrelationsspektroskopie bei hohen Temperaturen und Drücken in Ab- und Anwesenheit von Osmolyten untersucht. Die Ergebnisse liefern reichhaltige Informationen über die freie Energie des DNA-Hairpins.
      PubDate: 2017-04-05T02:35:31.27233-05:0
      DOI: 10.1002/ange.201701420
       
  • Palladium-Catalyzed Asymmetric Construction of Vicinal Tertiary and
           All-Carbon Quaternary Stereocenters by Allylation of β-Ketocarbonyls with
           Morita–Baylis–Hillman Adducts
    • Authors: Jiawang Liu; Zhaobin Han, Xiaoming Wang, Fanye Meng, Zheng Wang, Kuiling Ding
      Pages: 5132 - 5136
      Abstract: Palladium-catalyzed regio-, diastereo-, and enantioselective allylic alkylation of β-ketocarbonyls with Morita–Baylis–Hillman adducts has been developed using a spiroketal-based diphosphine (SKP) as the ligand, thus affording a range of densely functionalized products bearing vicinal tertiary and all-carbon quaternary stereodyad in high selectivities. The utility of the protocol was demonstrated by the facile synthesis of some complex molecules by simple product transformations.Ein SKP/Pd-System überzeugt beim katalytischen Aufbau von Stereodiaden aus benachbarten tertiären und komplett kohlenstoffsubstituierten quartären Zentren durch die allylische Alkylierung von β-Ketocarbonylverbindungen mit Morita-Baylis-Hillman-Addukten. Die stark funktionalisierten Produkte werden hoch regio-, diastereo- und enantioselektiv erhalten.
      PubDate: 2017-04-05T02:40:44.667662-05:
      DOI: 10.1002/ange.201701455
       
  • Gold Nanowire Chiral Ultrathin Films with Ultrastrong and Broadband
           Optical Activity
    • Authors: Jiawei Lv; Ke Hou, Defang Ding, Dawei Wang, Bing Han, Xiaoqing Gao, Man Zhao, Lin Shi, Jun Guo, Yonglong Zheng, Xi Zhang, Chenguang Lu, Ling Huang, Wei Huang, Zhiyong Tang
      Pages: 5137 - 5142
      Abstract: An ultrastrong and broadband chiroptical response is key but remains challenging for many device applications. A simple and cost-effective bottom-up method is introduced to fabricate large-area long-range ordered chiral ultrathin films with the Langmuir–Schaeffer technique using gold nanowires as building blocks. Significantly, as-prepared ultrathin films display giant optical activity across a broad wavelength range covering visible and near infrared regions with an anisotropic factor of up to 0.285, which is the record value for bottom-up techniques. Detailed experimental result and theoretical analysis disclose that such remarkable optical activity originates from birefringence and dichroism of the well-aligned Au nanowire layers in the ultrathin films. The universality of this facile strategy for constructing chiral ultrathin films is further demonstrated with many other one-dimensional nanomaterials.Kontrolliert chiral: Ein allgemeines Herstellungsverfahren für chirale Filme nutzt die Langmuir-Blodgett-Technik sowie Nanodrähte als Bausteine. Die kontrolliert aufgebauten Strukturen verfügen über eine außergewöhnlich starke optische Aktivität und sind über eine große Bandbreite responsiv.
      PubDate: 2017-04-07T02:46:57.948433-05:
      DOI: 10.1002/ange.201701512
       
  • Boosting the Performance of the Nickel Anode in the Oxygen Evolution
           Reaction by Simple Electrochemical Activation
    • Authors: Tatsuya Shinagawa; Marcus Tze-Kiat Ng, Kazuhiro Takanabe
      Pages: 5143 - 5147
      Abstract: The development of cost-effective and active water-splitting electrocatalysts that work at mild pH is an essential step towards the realization of sustainable energy and material circulation in our society. Its success requires a drastic improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. A simple electrochemical protocol has been developed to activate Ni electrodes, by which a stable NiOOH phase was formed, which could weakly bind to alkali-metal cations. The electrochemically activated (ECA) Ni electrode reached a current of 10 mA at 75 °C) and a mild pH of ca. 10 with excellent stability (>24 h), greatly surpassing that of the state-of-the-art NiFeOx electrodes under analogous conditions. Water electrolysis was demonstrated with ECA-Ni and NiMo, which required an iR-free overall voltage of only 1.44 V to reach 10 mA cmgeo−2.Nickel legt nach: Eine elektrochemische Aktivierung steigert die Leistungsfähigkeit eines Nickel-Elektrokatalysators in der Sauerstoffentwicklung. Das neue Material übertrifft die etablierte NiFeOx-Elektrode bei Betriebstemperaturen und einem mittleren pH-Wert von 10.5.
      PubDate: 2017-03-27T03:00:49.408904-05:
      DOI: 10.1002/ange.201701642
       
  • A Structurally Characterized Organometallic Plutonium(IV) Complex
    • Authors: Christos Apostolidis; Olaf Walter, Jochen Vogt, Phil Liebing, Laurent Maron, Frank T. Edelmann
      Pages: 5148 - 5152
      Abstract: The blood-red plutonocene complex Pu(1,3-COT′′)(1,4-COT′′) (4; COT′′=η8-bis(trimethylsilyl)cyclooctatetraenyl) has been synthesized by oxidation of the anionic sandwich complex Li[Pu(1,4-COT′′)2] (3) with anhydrous cobalt(II) chloride. The first crystal structure determination of an organoplutonium(IV) complex revealed an asymmetric sandwich structure for 4 where one COT′′ ring is 1,3-substituted while the other retains the original 1,4-substitution pattern. The electronic structure of 4 has been elucidated by a computational study, revealing a probable cause for the unexpected silyl group migration.Der neutrale Plutonium(IV)-Sandwichkomplex Pu(1,3-COT′′)(1,4-COT′′) (COT′′=η8-Bis(trimethylsilyl)cyclooctatetraenyl) wurde synthetisiert und durch Einkristall-Röntgenstrukturanalyse charakterisiert. Die asymmetrische Sandwichstruktur enthält 1,3- und 1,4-substituierte COT′′-Ringe. Die elektronische Struktur der Verbindung wurde mit quantenchemischen Methoden aufgeklärt, wobei ein wahrscheinlicher Grund für die Silylgruppenwanderung ermittelt wurde.
      PubDate: 2017-03-30T03:40:45.173426-05:
      DOI: 10.1002/ange.201701858
       
  • Template-Directed Approach Towards the Realization of Ordered
           Heterogeneity in Bimetallic Metal–Organic Frameworks
    • Authors: Daeok Kim; Ali Coskun
      Pages: 5153 - 5158
      Abstract: Controlling the arrangement of different metal ions to achieve ordered heterogeneity in metal–organic frameworks (MOFs) has been a great challenge. Herein, we introduce a template-directed approach, in which a 1D metal–organic polymer incorporating well-defined binding pockets for the secondary metal ions used as a structural template and starting material for the preparation of well-ordered bimetallic MOF-74s under heterogeneous-phase hydrothermal reaction conditions in the presence of secondary metal ions such as Ni2+ and Mg2+ in 3 h. The resulting bimetallic MOF-74s were found to possess a nearly 1:1 metal ratio regardless of their initial stoichiometry in the reaction mixture, thus demonstrating the possibility of controlling the arrangement of metal ions within the secondary building blocks in MOFs to tune their intrinsic properties such as gas affinity.Geordnete Heterogenität in MOFs: Durch Einsatz eindimensionaler Metall-organischer Polymere mit gut definierten Bindetaschen für sekundäre Metallionen als Strukturtemplate sowie ihre nachfolgende Umwandlung in dreidimensionale Metall-organische Gerüste (MOFs) konnte auf einfache Weise ein wohlgeordnetes bimetallisches MOF-74 hergestellt werden.
      PubDate: 2017-03-29T08:21:02.590588-05:
      DOI: 10.1002/ange.201702501
       
  • Structural Transformation and Stabilization of Metal–Organic Motifs
           Induced by Halogen Doping
    • Authors: Lei Xie; Chi Zhang, Yuanqi Ding, Wei Xu
      Pages: 5159 - 5163
      Abstract: The structural transformation of supramolecular nanostructures with constitutional diversity and adaptability by dynamic coordination chemistry would be of fundamental importance for potential applications in molecular switching devices. The role of halogen doping in the formation of elementary metal–organic motifs on surfaces has not been reported. Now, the 9-ethylguanine molecule (G) and Ni atom, as a model system, are used for the structural transformation and stabilization of metal–organic motifs induced by iodine doping on Au(111). The iodine atoms are homogeneously located at particular hydrogen-rich locations enclosed by G molecules by electrostatic interactions, which would be the key for such an unexpected stabilizing effect. The generality and robustness of this approach are demonstrated in different metal–organic systems (G/Fe) and also by chlorine and bromine.I gibt den Ton an: 9-Ethylguanin-Moleküle (G) und Ni-Atome bilden Metall-organische Motive auf Au(111)-Oberflächen, die durch Ioddotierung strukturell verändert und stabilisiert werden. Die Iodatome befinden sich an besonders wasserstoffreichen Positionen der G-Moleküle, mit denen sie elektrostatisch wechselwirken. C grau, H weiß, O rot, N blau, I violett, Ni dunkelblau.
      PubDate: 2017-04-18T03:15:45.050985-05:
      DOI: 10.1002/ange.201702589
       
  • Unsymmetric Twofold Scholl Cyclization of a 5,11-Dinaphthyltetracene:
           Selective Formation of Pentagonal and Hexagonal Rings via Dicationic
           Intermediates
    • Authors: Chaolumen; Michihisa Murata, Atsushi Wakamiya, Yasujiro Murata
      Pages: 5164 - 5168
      Abstract: Even though the Scholl reaction is one of the most powerful processes for the synthesis of polycyclic aromatic hydrocarbons (PAHs), its mechanism still remains a subject of discussion. Herein, we report a unique twofold Scholl cyclization of a 5,11-dinaphthyltetracene. Single-crystal X-ray diffraction analysis of the cyclization product revealed that unsymmetric cyclizations of the two naphthyl groups resulted in the formation of fully unsaturated pentagonal and hexagonal rings. The thus obtained product exhibits a twisted π-surface and an absorption band that reaches up to 950 nm. A combined experimental and theoretical study showed that such unsymmetric Scholl cyclizations can be rationalized in terms of a mechanism that involves dicationic intermediates, which stands in contrast to previously reported pathways based on radical cations and arenium ions.Doppelt positiv: Die zweifache Scholl-Cyclisierung eines 5,11-Dinaphthyltetracens führt zu einem unsymmetrisch cyclisierten Produkt mit einer verdrillten π-Oberfläche und einer Absorptionsbande bis 950 nm. Experimentelle und theoretische Studien zeigen, dass solche unsymmetrischen Scholl-Cyclisierungen durch einen Mechanismus mit dikationischen Intermediaten erklärt werden können.
      PubDate: 2017-03-30T01:45:41.828937-05:
      DOI: 10.1002/ange.201701054
       
  • Divergent Synthesis of Heteroatom-Centered 4,8,12-Triazatriangulenes
    • Authors: Soichiro Nakatsuka; Hajime Gotoh, Keisuke Kinoshita, Nobuhiro Yasuda, Takuji Hatakeyama
      Pages: 5169 - 5172
      Abstract: The increasing attention devoted to triangulenes and their heteroatom derivatives inspired us to explore a divergent synthesis of heteroatom-centered 4,8,12-triazatriangulenes, which involved the preparation of a nitrogen-containing macrocyclic precursor and subsequent central heteroatom introduction by electrophilic C−Li and C−H substitution. The boron-centered triangulene has a planar structure unlike the bowl-shaped phosphorus- and silicon-centered triangulenes. The described synthetic procedure can be used to fabricate a broad range of attractive functional materials, for example, for organic light-emitting diodes, based on heteroatom-centered triangulenes.Qual der Wahl: Bor-, Phosphor- und Silicium-zentrierte 4,8,12-Triazatriangulene wurden synthetisiert. Die effiziente Einbindung des Heteroatoms in eine stickstoffhaltige makrocyclische Vorstufe durch elektrophile C-Li- und C-H-Substitution (siehe Schema) ist ein Schlüsselschritt der Synthese.
      PubDate: 2017-03-29T08:20:37.109928-05:
      DOI: 10.1002/ange.201701246
       
  • Chelation versus Non-Chelation Control in the Stereoselective Alkenyl sp2
           C−H Bond Functionalization Reaction
    • Authors: Qiu-Ju Liang; Chao Yang, Fei-Fan Meng, Bing Jiang, Yun-He Xu, Teck-Peng Loh
      Pages: 5173 - 5177
      Abstract: A hydroxy group chelation-assisted stereospecific oxidative cross-coupling reaction between alkenes was developed under mild reaction conditions. In the presence of palladium catalyst, the alkenes tethered with hydroxy functionality can couple efficiently with electron-deficient alkenes to form the corresponding multi-substituted olefin products. The hydroxy group on the substrate could play dual roles in reaction, acting as the directing group for alkenyl C−H bond activation and controlling the stereoselectivity of the products.Stereospezifische oxidative Kreuzkupplungen zwischen Alkenen nutzen eine chelatisierend bindende Hydroxygruppe. In Gegenwart eines Palladiumkatalysators vereinen sich Alkene mit Hydroxyfunktion mit elektronenarmen Alkenen zu olefinischen Produkten. Die Hydroxygruppe kontrolliert dabei sowohl die Alkenyl-C-H-Aktivierung als auch die Stereoselektivität.
      PubDate: 2017-03-30T08:49:35.000499-05:
      DOI: 10.1002/ange.201700559
       
  • Protein Crosslinking by Genetically Encoded Noncanonical Amino Acids with
           Reactive Aryl Carbamate Side Chains
    • Authors: Weimin Xuan; Sida Shao, Peter G. Schultz
      Pages: 5178 - 5182
      Abstract: The use of genetically encoded noncanonical amino acids (ncAAs) to construct crosslinks within or between proteins has emerged as a useful method to enhance protein stability, investigate protein–protein interactions, and improve the pharmacological properties of proteins. We report ncAAs with aryl carbamate side chains (PheK and FPheK) that can react with proximal nucleophilic residues to form intra- or intermolecular protein crosslinks. We evolved a pyrrolysyl-tRNA synthetase that incorporates site-specifically PheK and FPheK into proteins in both E. coli and mammalian cells. PheK and FPheK when incorporated into proteins showed good stability during protein expression and purification. FPheK reacted with adjacent Lys, Cys, and Tyr residues in thioredoxin in high yields. In addition, crosslinks could be formed between FPheK and Lys residue of two interacting proteins, including the heavy chain and light chain of an antibody Fab.Nichtkanonische Aminosäure (ncAA): Eine reaktive Carbamat-haltige ncAA (FPheK) wurden genetisch in rekombinante Proteine eingebaut. FPheK zeigt unter schwach basischen Bedingungen eine hohe Reaktivität gegenüber proximalen nukleophilen Resten, einschließlich Lys, Cys und Tyr. Hocheffiziente und ortsspezifische intra- und intermolekulare Querverbindungen ließen sich mit FPheK erhalten.
      PubDate: 2017-04-03T02:40:42.615742-05:
      DOI: 10.1002/ange.201611841
       
  • Multicomponent Reactions with Cyclic Tertiary Amines Enabled by Facile
           C−N Bond Cleavage
    • Authors: Qiming Zhu; Qinghe Yuan, Mingwei Chen, Mengping Guo, Hanmin Huang
      Pages: 5183 - 5187
      Abstract: A novel and catalyst-free multicomponent reaction with cyclic tertiary amines, electron-deficient aryl halides or heteroaromatic halides, and Na2S enabled by facile C−N bond cleavage of the cyclic tertiary amines was developed. This direct and operationally simple method can be applied with a wide range of functional groups and provides an efficient and rapid approach to potentially drug-like products containing amine, azaarene, thioether, or phenol ether functionalities in good to excellent yields. The utility of this method was demonstrated by the rapid synthesis of the analgesic ruzadolane.Eine katalysatorfreie Mehrkomponentenreaktion verknüpft cyclische tertiäre Amine, elektronenarme (Hetero-)Arylhalogenide und Na2S unter C-N-Bindungsspaltung. Die einfach durchführbare Methode ist gut mit funktionellen Gruppen verträglich und liefert direkt Wirkstoff-artige Produkte mit Amin-, Azaaren-, Thioether- oder Phenolether-Funktionalitäten.
      PubDate: 2017-04-07T02:56:42.000511-05:
      DOI: 10.1002/ange.201612017
       
  • Four-Component Synthesis of Phosphonium Salts: Application Toward an
           Alternative Approach to Cross-Coupling for the Synthesis of
           Bis-Heteroarenes
    • Authors: Yi-Ru Chen; Ganapuram Madhusudhan Reddy, Shao-Hao Hong, Ying-Zheng Wang, Jhen-Kuei Yu, Wenwei Lin
      Pages: 5188 - 5192
      Abstract: A series of stable phosphonium salts have been synthesized via a novel four-component reaction of an arene nucleophile, 2-heteroatom substituted aryl aldehyde, and phosphine in presence of an acid. The phosphonium salts thus obtained were utilized for the synthesis of a variety of bis-heteroarenes, providing an efficient alternative method to the classical cross-coupling strategies.Vier gewinnt: Eine Vierkomponentenreaktion zur Herstellung einer Serie von Phosphoniumsalzen wurde entwickelt. Die erzeugten Salze wurden in der Synthese von Bisheteroarenen eingesetzt; die Methode ist eine vielversprechende Alternative zu klassischen Kreuzkupplungsstrategien.
      PubDate: 2017-04-03T08:25:45.828109-05:
      DOI: 10.1002/ange.201700945
       
  • Substrate-Assisted, Transition-Metal-Free Diboration of Alkynamides with
           Mixed Diboron: Regio- and Stereoselective Access to
           trans-1,2-Vinyldiboronates
    • Authors: Astha Verma; Russell F. Snead, Yumin Dai, Carla Slebodnick, Yinuo Yang, Haizhu Yu, Fu Yao, Webster L. Santos
      Pages: 5193 - 5197
      Abstract: A substrate-assisted diboration of alkynamides using the unsymmetrical pinacolato-1,8-diaminonaphthalenato diboron (pinBBdan) is described. The transition-metal-free reaction proceeds in a regio- and stereoselective fashion to exclusively afford trans-vinyldiboronates in good to excellent yields. Notably, Bdan and Bpin are installed on the α- and β-carbon atoms, respectively.Wer braucht schon Metalle? Die übergangsmetallfreie Aktivierung von Alkinamiden mit einem Dibor-Reagens ermöglicht die intramolekulare Bildung von verschiedenartigen geschützten trans-Vinyldiboronaten. Die Reaktion verläuft regio- und stereoselektiv mit Bdan- und Bpin-Schutzgruppen an den α- und β-Kohlenstoffatomen. dan=1,8-Diaminonaphthalin, pin=Pinakol.
      PubDate: 2017-03-29T07:50:26.635874-05:
      DOI: 10.1002/ange.201700946
       
  • Organocatalytic Redox Deracemization of Cyclic Benzylic Ethers Enabled by
           An Acetal Pool Strategy
    • Authors: Miao Wan; Shutao Sun, Yangshan Li, Lei Liu
      Pages: 5198 - 5202
      Abstract: The first redox deracemization of a series of cyclic benzylic ethers, including 6H-benzo[c]chromenes, isochromans, and 1H-isochromenes, is described. An “acetal pool” strategy was adopted to harmonize the complete oxidation of secondary ethers with imidodiphosphoric acid catalyzed asymmetric transfer hydrogenation. The synthetic utility of the process was demonstrated by the effective deracemization of biologically active molecules of interest that are difficult to prepare by other methods.Ein Pool von Möglichkeiten: Die Redox-Deracemisierung einer Serie von cyclischen Benzylethern wurde mithilfe einer „Acetal-Pool”-Strategie realisiert (siehe Schema). Die vollständige Oxidation der racemischen sekundären Ether wird durch die schnelle Bildung von Acetalen vermittelt, die eine asymmetrische Transferhydrierung unter Imidodiphosphorsäurekatalyse eingehen. Die Methode eignet sich auch für die direkte Deracemisierung biologisch aktiver Moleküle.
      PubDate: 2017-03-31T06:05:34.041704-05:
      DOI: 10.1002/ange.201701439
       
  • Synthesis of Functionalized Cyclopentene Derivatives from Vinyldiazo
           Compounds and Vinylazides through Sequential Copper-Promoted [3+2]
           Cycloaddition/Azide Rearrangement
    • Authors: Enol López; Luis A. López
      Pages: 5203 - 5206
      Abstract: The reaction of vinylazides with alkenyldiazo compounds in the presence of [Cu(CH3CN)4][BF4] provided cyclopentene derivatives with retention of the azide functionality. This process likely involves a sequence comprising: 1) decomposition of the diazo component with generation of a copper alkenylcarbene species; 2) stepwise regioselective [3+2] cycloaddition; 3) allylic azide rearrangement. This method is compatible with a broad range of substrates. We also show that the azide-containing cycloadducts can be efficiently converted into the corresponding amine and triazole derivatives.2×(Vinyl)=[3+2]: Die Titelreaktion führt in bequemer Weise zu azidfunktionalisierten Cyclopent-1-encarbonsäure-Derivaten. Dabei entsteht zunächst eine Kupferalkenylcarben-Spezies, die dann eine Sequenz aus [3+2]-Cycloaddition und Allylazid-Umlagerung durchläuft. Durch Modifizierung der Azidfunktion sind weitere Carbocyclen mit Stickstoffsubstituenten zugänglich.
      PubDate: 2017-03-28T06:05:52.505618-05:
      DOI: 10.1002/ange.201701572
       
  • Ligand-Promoted meta-C−H Functionalization of Benzylamines
    • Authors: Peng Wang; Marcus E. Farmer, Jin-Quan Yu
      Pages: 5207 - 5211
      Abstract: Meta-C−H functionalization of benzylamines has been developed using a PdII/transient mediator strategy. Using 2-pyridone ligands and 2-carbomethoxynorbornene (NBE-CO2Me) as the mediator, arylation, amination, and chlorination of benzylamines are realized. This protocol features a broad substrate scope and is compatible with heterocylic coupling partners. Moreover, the loading of the Pd can be lowered to 2.5 mol % by using the optimal ligand.Ein Palladium(II)-2-Pyridon-Katalysatorsystem und 2-Carbomethoxynorbornen als transienter Mediator aktivieren die meta-C-H-Bindung von Benzylaminen für die Arylierung, Aminierung und Chlorierung (siehe Schema; DG=dirigierende Gruppe). Das Protokoll zeichnet sich durch einen breiten Substratbereich aus und ist mit heterocyclischen Kupplungspartnern kompatibel. Mit dem richtigen Liganden kann die Pd-Menge auf 2.5 Mol-% gesenkt werden.
      PubDate: 2017-03-30T03:40:36.567161-05:
      DOI: 10.1002/ange.201701803
       
  • Innenrücktitelbild: Platin(II)-verknüpfte Einzelketten-Nanopartikel: ein
           Schritt in Richtung wiederverwendbarer Homogenkatalysatoren (Angew. Chem.
           18/2017)
    • Authors: Nicolai D. Knöfel; Hannah Rothfuss, Johannes Willenbacher, Christopher Barner-Kowollik, Peter W. Roesky
      Pages: 5213 - 5213
      Abstract: Wiederverwendbare platinhaltige Einzelketten-Nanopartikel (SCNPs), die ihre Form und Funktion bei Platin-Homogenkatalysen beibehalten, weisen den Weg zu neuartigen Katalysesystemen. In ihrer Zuschrift auf S. 5032 zeigen C. Barner-Kowollik, P. W. Roesky und Mitarbeiter anhand der Aminierung von Allylalkohol, dass die Platin(II)-SCNPs die höhere Aktivität von Homogenkatalysatoren mit der leichteren Zurückgewinnung von Heterogenkatalysatoren vereinen.
      PubDate: 2017-03-24T05:17:01.237395-05:
      DOI: 10.1002/ange.201702519
       
  • Rücktitelbild: Divergent Synthesis of Heteroatom-Centered
           4,8,12-Triazatriangulenes (Angew. Chem. 18/2017)
    • Authors: Soichiro Nakatsuka; Hajime Gotoh, Keisuke Kinoshita, Nobuhiro Yasuda, Takuji Hatakeyama
      Pages: 5214 - 5214
      Abstract: Die divergente Synthese …… von Heteroatom-zentrierten Triangulenen wird von T. Hatakeyama et al. in der Zuschrift auf S. 5169 ff. beschrieben. Die effiziente Einbindung des Bor-, Phosphor- oder Siliciumatoms in eine makrocyclische Vorstufe durch elektrophile C-Li- und C-H-Substitution ist ein Schlüsselschritt der Synthese.
      PubDate: 2017-03-29T08:20:43.519197-05:
      DOI: 10.1002/ange.201702884
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • Troels Skrydstrup
    • Pages: 4994 - 4994
      Abstract: „Mein Lieblingsort auf der Welt ist mein Zuhause, vor allem nach einer Reise. Ich bin Chemiker geworden – wegen eines motivierenden Chemielehrers an der Queen's University ...“ Dies und mehr von und über Troels Skrydstrup finden Sie auf Seite 4994.
      PubDate: 2016-10-28T06:36:35.02147-05:0
      DOI: 10.1002/ange.201610024
       
 
 
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