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Journal Cover Angewandte Chemie
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   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]
  • Tough Gel Electrolyte Using Double Polymer Network Design for the Safe,
           Stable Cycling of Lithium Metal Anode
    • Authors: Haiping Wu; Yue Cao, Haiping Su, Chao Wang
      Abstract: With high capacity, lithium (Li) metal is considered to enable at least two-times the energy density for lithium batteries. The growth of lithium dendrite and low columbic efficiency restrict the development of Li metal anode. Solid polymer electrolytes are expected to be promising candidates to solve the issue. But how to get polymer electrolyte which integrates high ionic conductivity and high mechanical strength is still challenging. Here, by introducing a double polymer network chemistry into electrolyte design to reshape, we have successfully developed a tough polymer electrolyte with high conductivity and further realized the stable operation of lithium metal anodes. The DNW gel electrolyte has high modulus of 44.3 MPa and high fracture energy of 8.2 kJ m-2. By using this gel electrolyte design, we can realize a stable cycling of lithium metal electrode for more than 400 cycles with a columbic efficiency (CE) as high as 96.3% with carbonates based electrolytes.
      PubDate: 2017-12-16T16:26:42.217926-05:
      DOI: 10.1002/ange.201709774
       
  • Pleading for a Dual Molecular-Orbital/Valence-Bond Culture
    • Authors: Philippe Charles Hiberty
      Abstract: The history of the two main theories of chemical bonding, Valence Bond and Molecular Orbital theories, with their respective localized and delocalized visions of the electron pairs, is briefly recalled with an emphasis on their equivalence at comparable computational levels. The delocalized/localized alternative also exists in the very framework of MO theory, since localized MOs can be obtained through unitary transformations which leave Slater determinants invariant. In particular, the use of hybrid orbitals in chemical interpretations is thus perfectly justified. It is argued that a dual knowledge of both theories and their interconnections is of great help to get a complete understanding of the nature of bonding in molecules. Other means of switching from the delocalized to localized representations are also shown to be quite insightful in, e.g., hydrogen-bonding around water molecules, or conformational analysis of propene and many other unsaturated acyclic systems. It is shown that playing with such equivalent readings of the same wave function of dicarbon provides a very clear bonding picture for this enigmatic molecule, whereas the original untransformed wave function is ambiguous. The localized orbital representations of water, ethylene and dicarbon are shown to basically provide the same picture as the analysis of electron density maps as provided by the Maximum Probability Domains method and by the Dynamic Voronoi Metropolis Sampling method. Some current misconceptions are falsified, like the supposed existence of some unique "real" set of orbitals for a molecule, or the belief that the localized lone pair orbitals of water, the famous "rabbit-ear" hybrid orbitals, are in conflict with photoelectron spectroscopy.
      PubDate: 2017-12-15T12:10:23.131484-05:
      DOI: 10.1002/ange.201710094
       
  • Synthesis of Phenols: Organophotoredox/Ni Dual Catalytic Hydroxylation of
           Aryl Halides with Water
    • Authors: Dong Xue; Liu Yang, Zhiyan Huang, Gang Li, Wei Zhang, Rui Cao, Chao Wang, Jianliang Xiao
      Abstract: A highly effective hydroxylation reaction of aryl halides with water under the synergistic merger of organophotoredox and nickel-catalysis is reported. The OH group of phenols originates from water following deprotonation facilitated by an intramolecular base group on the ligand. Significantly, aryl bromides as well as less reactive aryl chlorides can also serve as effective substrates, affording phenols with a wide range of functional groups. Using no strong inorganic bases and no expensive noble metal catalysts, this process can be applied to the efficient preparation of diverse phenols and enables the hydroxylation of several multifunctional pharmaceutical aryl halides.
      PubDate: 2017-12-15T09:40:42.198936-05:
      DOI: 10.1002/ange.201710698
       
  • First End-deck Cyclo-P4 Fe complex: Synthesis and Reactivity.
    • Authors: Anthony Cavaillé; Nathalie Saffon-Merceron, Noel Nebra, Marie Fustier-Boutignon, Nicolas Mézailles
      Abstract: Reduction of the FeII complex [(PhPP2Cy)FeCl2] (2) generates an electron rich and unsaturated Fe0 which is reacted with white phosphorus. The new complex obtained, [(PhPP2Cy)Fe(η4-P4)] (3), is the first iron cyclo-P4 complex and the only known stable end deck cyclo-P4 complex outside of group V. Complex 3 bears a FeII center as shown by Mössbauer spectroscopy, associated to a P42- fragment. Analysis of the molecular orbitals rationalizes the distinct reactivity of complex 3. Reaction of complex 3 with H+ affords the unstable complex [(PhPP2Cy)Fe(η4-P4)(H)]+ (4), whereas with CuCl and BCF the complexes [(PhPP2Cy)Fe(η4:η1-P4)(μ-CuCl)]2 (5) and [(PhPP2Cy)Fe(η4:η1-P4)B(C6F5)3] (6) are formed.
      PubDate: 2017-12-15T08:10:48.007901-05:
      DOI: 10.1002/ange.201711130
       
  • Catalytic Asymmetric Oxidative γ-Coupling of α,β-unsaturated Aldehydes
           with Air as the Terminal Oxidant
    • Authors: Karl Anker Jørgensen; Line Næsborg, Vasco Corti, Lars Astrup Leth, Pernille Hartveit Poulsen
      Abstract: : A novel concept for catalytic asymmetric coupling reactions is presented. Merging organocatalysis with singlet-electron oxidation using a catalytic amount of a copper(II) salt and air as the terminal oxidant, we have developed a highly stereose-lective carbon-carbon oxidative coupling reaction of α,β-unsaturated aldehydes. The concept relies on the generation of a dienamine intermediate, which is oxidized to an open-shell activated species that undergoes highly selective γ-homo- and γ-hetero-coupling reactions and in the majority of examples presented only a single stereoisomer is formed.
      PubDate: 2017-12-15T07:10:27.781579-05:
      DOI: 10.1002/ange.201711944
       
  • Two Distinct Substrate Binding Modes for the Normal and Reverse
           Prenylation of Hapalindoles by the Prenyltransferase AmbP3
    • Authors: Chin Piow Wong; Takayoshi Awakawa, Yu Nakashima, Takahiro Mori, Qin Zhu, Xinyu Liu, Ikuro Abe
      Abstract: The cyanobacterial prenyltransferase AmbP3 catalyzes the reverse prenylation of the tetracyclic indole alkaloid hapalindole U at its C-2 position. Interestingly, AmbP3 also accepts hapalindole A, a halogenated C-10 epimer of hapalindole U, and catalyzes normal prenylation at its C-2 position. The comparison of the two ternary crystal structures, AmbP3-DMSPP/hapalindole U and AmbP3-DMSPP/hapalindole A, at 1.65–2.00 Å resolution revealed two distinct orientations for the substrate binding that define reverse or normal prenylation. The tolerance of the enzyme for these altered orientations is attributed to the hydrophobicity of the substrate binding pocket and the plasticity of the amino acids surrounding the allyl group of the prenyl donor. This is the first study to provide the intimate structural basis for the normal and reverse prenylations catalyzed by a single enzyme, and it offers novel insight into the engineered biosynthesis of prenylated natural products.So oder so: AmbP3 ist eine Prenyltransferase, die, je nach Substrat, sowohl die reverse als auch die reguläre Prenylierung katalysieren kann. Eine Röntgenstrukturanalyse von AmbP3 im Komplex mit Substraten der reversen und regulären Prenylierung beleuchtet die strukturelle Basis der überraschenden Flexibilität des Enzyms.
      PubDate: 2017-12-15T05:51:47.113041-05:
      DOI: 10.1002/ange.201710682
       
  • In Situ Spatial Complementation of Aptamer-Mediated Recognition Enables
           Live-Cell Imaging of Native RNA Transcripts in Real Time
    • Authors: Zejun Wang; Yao Luo, Xiaodong Xie, Xingjie Hu, Haiyun Song, Yun Zhao, Jiye Shi, Lihua Wang, Gennadi Glinsky, Nan Chen, Ratnesh Lal, Chunhai Fan
      Abstract: Direct cellular imaging of the localization and dynamics of biomolecules helps to understand their function and reveals novel mechanisms at the single-cell resolution. In contrast to routine fluorescent-protein-based protein imaging, technology for RNA imaging remains less well explored because of the lack of enabling technology. Herein, we report the development of an aptamer-initiated fluorescence complementation (AiFC) method for RNA imaging by engineering a green fluorescence protein (GFP)-mimicking turn-on RNA aptamer, Broccoli, into two split fragments that could tandemly bind to target mRNA. When genetically encoded in cells, endogenous mRNA molecules recruited Split-Broccoli and brought the two fragments into spatial proximity, which formed a fluorophore-binding site in situ and turned on fluorescence. Significantly, we demonstrated the use of AiFC for high-contrast and real-time imaging of endogenous RNA molecules in living mammalian cells. We envision wide application and practical utility of this enabling technology to in vivo single-cell visualization and mechanistic analysis of macromolecular interactions.Geteilt und wiedervereint: Auf der Grundlage von aptamerinitiierter Fluoreszenzkomplementierung (AiFC) gelingt die RNA-Bildgebung. Zwei Teile eines RNA-Aptamers nach dem Vorbild von Grün fluoreszierendem Protein (GFP) binden dabei simultan an eine Ziel-mRNA. AiFC ermöglicht die nichtinvasive und kontraststarke Echtzeit-Visualisierung endogener RNA-Moleküle in lebenden Säugerzellen.
      PubDate: 2017-12-15T05:50:55.700853-05:
      DOI: 10.1002/ange.201707795
       
  • Ein gespanntes tricyclisches PC3-Phosphan – Koordinationschemie und
           Insertion von Chalkogenatomen in P-C-Bindungen
    • Authors: Anne Hentschel; Alexander Brand, Philipp Wegener, Werner Uhl
      Abstract: Das tricyclische Phosphan 4 hat ein starres Molekülgerüst. Ein großer Tolman-Winkel und hohes “Buried Volume” belegen die effektive sterische Abschirmung des P-Atoms, das ausschließlich an C(sp2)-Atome bindet. 4 ist ein interessanter neuer Ligand für die Koordinationschemie (Au-, Pd-Komplexe) und zeigt infolge der hohen Molekülspannung ungewöhnliche Insertionsreaktionen in endocyclische P-C-Bindungen.Eine Trilithiumverbindung reagiert mit PCl3 zu einem neuartigen tricyclischen und sterisch hoch abschirmenden Phosphan. Dieses hat einen großen Tolman-Winkel, und seine Ligandenbasizität entspricht derjenigen von PPh3. Ringspannung führt zu einer vielversprechenden Reaktivität, wie anhand der Insertion von S oder Se in P-C-Bindungen demonstriert wird.
      PubDate: 2017-12-15T05:46:09.541877-05:
      DOI: 10.1002/ange.201711373
       
  • Dynamic Covalent Chemistry within Biphenyl Scaffolds: Reversible Covalent
           Bonding, Control of Selectivity, and Chirality Sensing with One Single
           System
    • Authors: Cailing Ni; Daijun Zha, Hebo Ye, Yu Hai, Yuntao Zhou, Eric Anslyn, Lei You
      Abstract: Axial chirality is a prevalent and important phenomenon in chemistry. Herein we report a combination of dynamic covalent chemistry and axial chirality for the development of a universal platform toward binding and chirality sensing of multiple classes of mononucleophiles. An equilibrium between open aldehyde and its cyclic hemiaminal within biphenyl derivatives enables the dynamic incorporation of a broad range of alcohols, thiols, primary amines, and secondary amines with high efficiency. The selectivity toward different classes of nucleophiles was also achieved by regulating the distinct reactivity of the system with external stimuli. Through induced helicity as a result of central-to-axial chirality transfer the handedness and enantiomeric excess values of chiral monoalcohol and monoamine analytes can be reported via circular dichroism. The generality of the strategies introduced herein should find applications in many aspects, including assembly, sensing, and labeling.
      PubDate: 2017-12-15T05:25:32.794622-05:
      DOI: 10.1002/ange.201711602
       
  • Mesomeric effect of thiazolium to non-Kekulé diradicals in
           transketolase of Pichia stipitis
    • Authors: Tsung-Lin Li; Ning-Shian Hsu, Yung-Lin Wang, Kuan-Hung Lin, Chi-Fon Chang, Syue-Yi Lyu, Li-Jen Hsu, Yu-Chen Liu, Chin-Yuan Chang, Chang-Jer Wu
      Abstract: Given energetic carbene and uneven electronegativity, thiazolium that mesomerizes to congeners other than carbene in the low effective dielectric binding site is theoretically plausible but never reported. Here we report 9 subatomic-resolution crystal structures of TKps from Pichia stipitis, where thiazolium displays an extraordinary ring-bending effect. These bent thiazolium congeners are correlated to non-Kekulé diradicals due to no gain/loss of electrons. In conjunction with biophysical/biochemical analyses, we conclude that the ring bending is a result of tautomerization of thiazolium with its non-Kekulé diradicals exclusively in the binding site of TKps. The unique chemophysical properties of these thiazolium mesomers may account for the great variety of reactivities carried out by ThDP-containing enzymes. Additionally, the stability of ThDP in living systems may be regulated by the levels of both substrates and hydration/dehydration vs. diradical-mediated oxidative degradation.
      PubDate: 2017-12-15T05:24:54.690135-05:
      DOI: 10.1002/ange.201709799
       
  • Crystal-Field Tuning of Photoluminescence in Two-Dimensional Materials
           with Embedded Lanthanide Ions
    • Authors: Ding Xu; Weiyin Chen, Mengqi Zeng, Haifeng Xue, Yunxu Chen, Xiahan Sang, Yao Xiao, Tao Zhang, Raymond R. Unocic, Kai Xiao, Lei Fu
      Abstract: Lanthanide (Ln) group elements have been attracting considerable attention owing to the distinct optical properties. The crystal-field surroundings of Ln ions in the host materials can determine their energy level splitting, which is of vital importance to tailor their optical properties. 2D MoS2 single crystals were utilized as the host material to embed Eu3+ and energy-level splitting was achieved for tuning its photoluminescence (PL). The high anisotropy of the 2D host materials makes them distort the degenerate orbitals of the Ln ions more efficiently than the symmetrical bulk host materials. A significant red-shift of the PL peak for Eu3+ was observed. The strategy for tailoring the energy level splitting of Ln ions by the highly designable 2D material crystal field provides a new method to extend their optical properties.Feinjustierung im Kristall: Zweidimensionale MoS2-Einkristalle wurden als Wirtmaterial für Eu3+-Ionen verwendet, um deren Energieniveaus aufzuspalten. Eine signifikante Rotverschiebung der Photolumineszenz im Vergleich zur Situation mit einem Festkörper- oder Nanopartikel-Wirtmaterial wurde beobachtet.
      PubDate: 2017-12-15T04:49:26.219436-05:
      DOI: 10.1002/ange.201711071
       
  • Stereochemical Definition of the Natural Product (6R,10R,13R,
           14R,16R,17R,19S,20S,21R,24S,25S,28S,30S,32R,33R,34R,36S,37S,39R)-Azaspiracid-3
           by Total Synthesis and Comparative Analyses
    • Authors: Nathaniel T. Kenton; Daniel Adu-Ampratwum, Antony A. Okumu, Pearse McCarron, Jane Kilcoyne, Frode Rise, Alistair L. Wilkins, Christopher O. Miles, Craig J. Forsyth
      Abstract: The previously accepted structure of the marine toxin azaspiracid-3 is revised based upon an original convergent and stereoselective total synthesis of the natural product. The development of a structural revision hypothesis, its testing, and corroboration are reported. Synthetic (6R,10R,13R,14R,16R,17R,19S,20S,21R,24S,25S,28S,30S,32R, 33R,34R,36S,37S,39R)-azaspiracid-3 chromatographically and spectroscopically matched naturally occurring azaspiracid-3, whereas the previously assigned 20R epimer did not.Konvergent und stereochemisch definiert verläuft eine Totalsynthese des marinen Giftstoffs Azaspiracid-3 (AZA3). Ein direkter Vergleich mit dem Naturstoff führt zu einer Strukturrevision: Die Daten sprechen für eine stereochemische (19S*,20S*)-Relativkonfiguration für sowohl AZA1–AZA10 als auch AZA34.
      PubDate: 2017-12-15T04:48:34.872827-05:
      DOI: 10.1002/ange.201711008
       
  • Dreidimensionale Architekturen aus
           Übergangsmetall-Dichalkogenid-Nanomaterialien zur elektrochemischen
           Energiespeicherung und -umwandlung
    • Authors: Qinbai Yun; Qipeng Lu, Xiao Zhang, Chaoliang Tan, Hua Zhang
      Abstract: Übergangsmetall-Dichalkogenide (TMDs) finden seit einigen Jahren große Aufmerksamkeit wegen ihrer einzigartigen Eigenschaften und vielversprechenden Möglichkeiten für die elektrochemische Energiespeicherung und -umwandlung. Ungünstig wirkten sich bislang ihre geringe Zahl an aktiven Stellen und ein blockierter Ionen- und Massetransport aus. Diese Probleme lassen sich aber durch die Konstruktion von dreidimensionalen (3D) Architekturen aus TMD-Nanomaterialien effektiv lösen. 3D-TMD-Architekturen bieten eine wesentlich größere Oberfläche und deutlich kleinere Abstände für den Ionen- und Massetransport. Dieser Aufsatz fasst die gängigen Synthesewege für 3D-TMD-Architekturen zusammen und hebt deren Anwendungsmöglichkeiten in Akkumulatoren, Superkondensatoren und bei der elektrokatalytischen Wasserstoffproduktion hervor. Außerdem werden Herausforderungen und Zukunftsperspektiven dieses Forschungsgebiets aufgezeigt.Elektrochemie in 3D: Dreidimensionale Architekturen aus Übergangsmetall-Dichalkogeniden sind vielversprechende Materialien für Systeme zur elektrochemischen Energiespeicherung und -umwandlung. Dieser Aufsatz fasst gängige Strategien zur Herstellung solcher Architekturen zusammen und stellt ihre Anwendung in Akkumulatoren, Superkondensatoren und bei der elektrokatalytischen Wasserstoffproduktion vor.
      PubDate: 2017-12-15T04:48:12.653068-05:
      DOI: 10.1002/ange.201706426
       
  • Taking Photochromism Beyond Visible: Direct One-Photon NIR Photoswitches
           Operating in the Biological Window
    • Authors: Kristin Klaue; Yves Garmshausen, Stefan Hecht
      Abstract: The success of photopharmacology is inevitably tied to the availability of photoswitches, which can be operated within the biological window (650-1450 nm) to maximize penetration in tissue. We have devised a general design strategy and report here on a dihydropyrene derivative, which displays negative T-type photochromism allowing for efficient and nearly quantitative (95%) switching induced by NIR light > 800 nm. The thermal half-life of the decolored ring-open meta-cyclophanediene isomer ranges from minutes to hours, depending on the solvent polarity and hence serves as a probe of the local environment. Due to the rather subtle geometrical differences between the two isomers, suitably modified NIR photoswitches are potential candidates for switching when bound in the pocket of the biological target, in principle allowing for reversible light-induced inhibitor deactivation as an alternative approach to externally regulate biological functions.
      PubDate: 2017-12-15T04:44:34.434268-05:
      DOI: 10.1002/ange.201709554
       
  • Synthesis and Reactivity of the Phosphorus Analogues of Cyclopentadienone,
           Tricyclopentanone, and Housene
    • Authors: Chris Slootweg; Tania Krachko, Andreas W. Ehlers, Martin Nieger, Martin Lutz
      Abstract: The phosphorus analogues of cyclopentadienone, tricyclopentanone and housene were accessed from bis(cyclopropenyl)diphosphetanedione 3, that was prepared by mixing 1,2,3-tris-tert-butylcyclopropenium tetrafluoroborate (1) and sodium phosphaethynolate [Na(OCP)(dioxane)n]. While photolysis of 3 results in decarbonylation yielding bis(cyclopropenyl)diphosphene 4 and after rearrangement diphosphahousene 5, thermolysis of 3 leads to phosphatricyclo[2.1.0.0]pentanone 7. Metal-mediated valence isomerization of 7 and subsequent demetallation provides access to phosphacyclopentadienone 12.
      PubDate: 2017-12-15T04:30:22.817372-05:
      DOI: 10.1002/ange.201711838
       
  • Synthesis and Stability of Lanthanum Superhydrides
    • Authors: Zachary M. Geballe; Hanyu Liu, Ajay K. Mishra, Muhtar Ahart, Maddury Somayazulu, Yue Meng, Maria Baldini, Russell J. Hemley
      Abstract: Recent theoretical calculations predict that megabar pressure stabilizes very hydrogen-rich simple compounds having new clathrate-like structures and remarkable electronic properties including room-temperature superconductivity. X-ray diffraction and optical studies demonstrate that superhydrides of lanthanum can be synthesized with La atoms in an fcc lattice at 170 GPa upon heating to about 1000 K. The results match the predicted cubic metallic phase of LaH10 having cages of thirty-two hydrogen atoms surrounding each La atom. Upon decompression, the fcc-based structure undergoes a rhombohedral distortion of the La sublattice. The superhydride phases consist of an atomic hydrogen sublattice with H−H distances of about 1.1 Å, which are close to predictions for solid atomic metallic hydrogen at these pressures. With stability below 200 GPa, the superhydride is thus the closest analogue to solid atomic metallic hydrogen yet to be synthesized and characterized.Lanthan-Superhydride mit kubisch flächenzentriertem La-Atom-Gitter wurden durch Erhitzen auf ca. 1000 K bei 170 GPa erhalten. Röntgenbeugungsmuster und optische Untersuchungen bestätigen die kubische metallische Phase für LaH10, in dem Käfige aus 32 H-Atomen jedes La-Atom einschließen. Das unterhalb 200 GPa stabile Superhydrid ist das beste bisher synthetisierte und charakterisierte Analogon für festen atomaren metallischen Wasserstoff.
      PubDate: 2017-12-15T04:30:11.59455-05:0
      DOI: 10.1002/ange.201709970
       
  • Achilles' Heel of Li-Air Batteries: Li2CO3
    • Authors: Zhiwei Zhao; Jun Huang, Zhangquan Peng
      Abstract: Lithium-air battery (LAB) is envisaged as an ultimate energy storage device because of its highest theoretical specific energy among all known battery chemistries. However, parasitic reactions bring about vexing issues on the efficiency and longevity of LAB, among which the formation and decomposition of lithium carbonate, Li_2 CO_3, is of paramount importance. The discovery of Li_2 CO_3 as the main discharge product in carbonate-based electrolytes once brought researchers to 'the end of the idyll' in the early 2010s. In the past few years, tremendous efforts have been made to understand the formation and decomposition mechanisms of Li_2 CO_3, as well as to conceive novel chemical/material strategies to suppress the Li_2 CO_3 formation and to facilitate the Li_2 CO_3 decomposition. Moreover, the study on Li_2 CO_3 in LABs is opening up a new research field of the Li-CO_2 battery. Considering the rapid development and innumerous emerging issues, it is timely to recapitulate the current understandings, define the ambiguities and scientific gaps, and discuss the topics of high priority for future research, which are the aims of this Minireview.
      PubDate: 2017-12-15T04:18:28.382087-05:
      DOI: 10.1002/ange.201710156
       
  • Evidence for Dynamic Chemical Kinetics at Individual Ruthenium Catalysts
    • Authors: Quinn T. Easter; Suzanne A. Blum
      Abstract: Catalytic cycles are typically depicted as possessing time-invariant steps with fixed rates. Yet the true behavior of individual catalysts with respect to time is unknown, hidden by the ensemble averaging inherent to bulk measurements. Herein, focused on a ring-opening metathesis polymerization reaction catalyzed by the second-generation Grubbs' ruthenium catalyst, we show evidence for variable chemical kinetics at individual catalysts with fluorescence microscopy possessing sufficient sensitivity for the detection of single chemical reactions. Insertion reactions in submicron regions likely occur at groups of many (not single) catalysts, yet not so many that their unique kinetic behavior is ensemble averaged.
      PubDate: 2017-12-14T15:10:57.402342-05:
      DOI: 10.1002/ange.201711314
       
  • Photoinduced Co-CF3 Bond Activation Enables Arene C-H Trifluoromethylation
    • Authors: Caleb F. Harris; Christopher S. Kuehner, John Bacsa, Jake D. Soper
      Abstract: Visible light capture activates a thermodynamically inert CoIII-CF3 bond for direct C-H trifluoromethylation of arenes and heteroarenes. New trifluoromethylcobalt(III) complexes supported by a redox-active [OCO] pincer ligand were prepared. Coordinating solvents, such as MeCN, afford quasi-octahedral [(SOCO)CoIII(CF3)(MeCN)2] (2), but in non-coordinating solvents the complex is square pyramidal [(SOCO)CoIII(CF3)(MeCN)] (3). Both are thermally stable, and 2 is stable in light. But exposure of 3 to low-energy light results in facile homolysis of the CoIII-CF3 bond, releasing ●CF3 radical, which is trapped by TEMPO● or (hetero)arenes. The homolytic aromatic substitution reactions do not require a sacrificial or substrate-derived oxidant because the CoII byproduct of CoIII-CF3 homolysis produces H2. The photophysical properties of 2 and 3 provide a rationale for the disparate light stability. Design principles for photoactivation of other strong M-CF3 complexes for catalysis are discussed.
      PubDate: 2017-12-14T13:11:23.008986-05:
      DOI: 10.1002/ange.201711693
       
  • A Breathing ATRP: Fully Oxygen Tolerant Polymerization Inspired by Aerobic
           Respiration of Cells
    • Authors: Krzysztof Matyjaszewski; Liye Fu Fu, Alan Russell Russell, Alan E. E. Enciso
      Abstract: The first well-controlled aqueous atom transfer radical polymerization (ATRP) conducted in the open air was enabled by the continuous conversion of oxygen to carbon dioxide catalyzed by glucose oxidase (GOx), with glucose and sodium pyruvate as sequential sacrificial substrates. Controlled initiators for continuous activator regeneration (ICAR) ATRP of oligo(ethylene oxide) methyl ether methacrylate (OEOMA, Mn=500), yielded polymers with low dispersity (1.09≤Đ ≤1.29) and molecular weights (MW) close to theoretical with pyruvate. Without pyruvate, lower MW were due to generation of new chains by H2O2 formed by reaction of O2 with GOx. Successful chain extension of POEOMA500 macroinitiator with OEOMA300 confirmed a well-controlled polymerization (Đ≤1.3). A "grafting from" polymerization from ATRP initiators covalently attached to Bovine Serum Albumin (BSA) was achieved with low amounts of catalyst (ppm vs. monomer) and short reaction time (≤ 2 hours).
      PubDate: 2017-12-14T13:10:34.177444-05:
      DOI: 10.1002/ange.201711105
       
  • Bioorthogonal cycloadditions with sub-millisecond intermediates
    • Authors: Yujia Qing; Gökçe Su Pulcu, Nicolas Bell, Hagan Bayley
      Abstract: Tetrazine- and sydnone-based click chemistries have emerged as important bioconjugation strategies with fast kinetics and N2 or CO2 as the only by-product. Mechanistic studies of these reactions have focused on the initial rate-determining cycloaddition steps. The subsequent N2 or CO2 release from the bicyclic intermediates has been approached mainly through computational studies, which have predicted lifetimes of femtoseconds. In the present study, bioorthogonal cycloadditions involving N2 or CO2 extrusion have been examined experimentally at the single-molecule level by using a protein nanoreactor. At the resolution of this approach, the reactions appeared to occur in a single step, which places an upper limit on the lifetimes of the intermediates of ~80 μs, consistent with the computational work.
      PubDate: 2017-12-14T10:35:23.056712-05:
      DOI: 10.1002/ange.201710262
       
  • Enantioselective Iridium Catalyzed Phthalide Formation via Internal Redox
           Allylation of Phthalaldehydes
    • Authors: Michael Joseph Krische; James M. Cabrera, Johannes Tauber
      Abstract: An Inside Job. Enantioselective phthalide synthesis is achieved through internal redox allylation of o-phthalaldehydes. Oxidative esterification is balanced by reductive carbonyl addition to achieve an overall redox neutral process. Using this method, formal syntheses of ent-spirolaxine methyl ether and CJ-12,954 are achieved.
      PubDate: 2017-12-14T10:12:22.056524-05:
      DOI: 10.1002/ange.201712015
       
  • Reductive Amination by Photoredox Catalysis via Polarity-Matched Hydrogen
           Atom Transfer
    • Authors: Xingwei Guo; Oliver S. Wenger
      Abstract: Excitation of a Ru(II) photosensitizer in presence of ascorbic acid leads to reduction of iminium ions to electron-rich alpha-aminoalkyl radical intermediates that are rapidly converted to reductive amination products via thiol-mediated hydrogen atom transfer (HAT). As a result, reductive amination of carbonyl compounds with amines via photoredox catalysis proceeds in good to excellent yields and with broad substrate scope, as illustrated by 16 different examples including detailed mechanistic studies. The three key novelties of this work are: (i) the rapid interception of electron-rich radical intermediates by polarity-matched HAT in a photoredox reaction, (ii) the method of reductive amination by photoredox catalysis itself, and (iii) the application of this new method for temporally and spatially controlled reactions on a solid support, as demonstrated by attachment of a fluorescent dye on an activated cellulose support via photoredox-catalyzed reductive amination.
      PubDate: 2017-12-14T10:12:03.699599-05:
      DOI: 10.1002/ange.201711467
       
  • Bis(perchlorocatecholato)silane - A neutral silicon Lewis super acid
    • Authors: Rezisha Maskey; Marcel Schädler, Claudia Legler, Lutz Greb
      Abstract: No neutral silicon Lewis super acids are known to date. We report on the synthesis of bis(perchlorocatecholato)silane and verify its Lewis super acidity by computation (DLPNO-CCSD(T)) and experiment (fluoride abstraction from SbF₆-). The exceptional affinity towards donors is further demonstrated by e.g. the characterization of an unprecedented SiO₄F₂ dianion and applied in the first hydrodefluorination reaction catalyzed by a neutral silicon Lewis acid. Given the strength and convenient access to this new Lewis acid, versatile applications might be foreseen.
      PubDate: 2017-12-14T09:06:01.686269-05:
      DOI: 10.1002/ange.201712155
       
  • The Otherwise Inactive Keggin Polyoxometalate becomes Active towards
           Electrocatalytic Water Oxidation in Neutral pH: POM@ZIF-8, an Efficient
           and Robust Electrocatalyst
    • Authors: Samar Kumar Das; Subhabrata Mukhopadhyay, Joyashish Debgupta, Chandani Singh, Aranya Kar
      Abstract: Keggin type of polyoxometalate anions, [XM12O40]n‒, are as versatile as their applications in interdisciplinary areas. We have shown that Keggin anion [CoW12O40]6‒ turns into an efficient and robust electrocatalyst upon its confinement in the well-defined void space of ZIF-8, a metal organic framework (MOF). We have demonstrated that [H6CoW12O40]@ZIF-8 is so stable to water oxidation, that it retains its initial activity even after 1000 catalytic cycles. The catalyst shows turnover frequency (TOF) of 10.8 mol O2(mol Co)-1s-1. To the best of our knowledge, this is one of the highest TOF for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoOx in the present electrocatalyic water oxidation.
      PubDate: 2017-12-14T09:05:55.975632-05:
      DOI: 10.1002/ange.201711920
       
  • Nagoya-Gold- und -Silbermedaillen/Prelog-Medaille und -Vorlesung:
           Stephen B. H. Kent/Kurz gemeldet
    • PubDate: 2017-12-14T08:45:28.921727-05:
      DOI: 10.1002/ange.201711956
       
  • FHBC, a Hexa-peri-hexabenzocoronene–Fluorene Hybrid: A Platform for
           Highly Soluble, Easily Functionalizable HBCs with an Expanded Graphitic
           Core
    • Authors: Tushar S. Navale; Maxim V. Ivanov, Mohammad M. Hossain, Rajendra Rathore
      Abstract: Materials based upon hexa-peri-hexabenzocoronenes (HBCs) show significant promise in a variety of photovoltaic applications. There remains the need, however, for a soluble, versatile, HBC-based platform, which can be tailored by incorporation of electroactive groups or groups that can prompt self-assembly. The synthesis of a HBC–fluorene hybrid is presented that contains an expanded graphitic core that is highly soluble, resists aggregation, and can be readily functionalized at its vertices. This new HBC platform can be tailored to incorporate six electroactive groups at its vertices, as exemplified by a facile synthesis of a representative hexaaryl derivative of FHBC. Synthesis of new FHBC derivatives, containing electroactive functional groups that can allow controlled self-assembly, may serve as potential long-range charge-transfer materials for photovoltaic applications.Ein Hybrid aus Fluoren- und Hexa-peri-hexabenzocoronen mit großem graphitischem Strukturkern wurde synthetisiert. Das Produkt erwies sich als gut löslich und konnte an seiner Peripherie leicht funktionalisiert werden.
      PubDate: 2017-12-14T08:25:40.594468-05:
      DOI: 10.1002/ange.201711739
       
  • A Hierarchical MFI Zeolite with a Two-Dimensional Square Mesostructure
    • Authors: Xuefeng Shen; Wenting Mao, Yanhang Ma, Dongdong Xu, Peng Wu, Osamu Terasaki, Lu Han, Shunai Che
      Abstract: A conceptual design and synthesis of ordered mesoporous zeolites is a challenging research subject in material science. Several seminal articles report that one-dimensional (1D) mesostructured lamellar zeolites are possibly directed by sheet-assembly of surfactants, which collapse after removal of intercalated surfactants. However, except for one example of two-dimensional (2D) hexagonal mesoporous zeolite, no other zeolites with ordered 2D or three-dimensional (3D) mesostructures have been reported. An ordered 2D mesoporous zeolite can be templated by a cylindrical assembly unit with specific interactions in the hydrophobic part. A template molecule with azobenzene in the hydrophobic tail and diquaternary ammonium in the hydrophilic head group directs hierarchical MFI zeolite with a 2D square mesostructure. The material has an elongated octahedral morphology, and quaternary, ordered, straight, square channels framed by MFI thin sheets expanded along the a–c planes and joined with 90° rotations. The structural matching between the cylindrical assembly unit and zeolite framework is crucial for mesostructure construction.Maßarbeit: Ein Tensid mit hydrophober Schwanzgruppe und ammoniumfunktionalisierter Kopfgruppe bildet zylindrische Motive, die für die Templatsynthese eines geordneten 2D- mesoporösen MFI-Zeoliths genutzt wurden. Das Produkt hat tetragonale Morphologie und enthält gerade Kanäle mit quadratischem Querschnitt.
      PubDate: 2017-12-14T08:16:27.630362-05:
      DOI: 10.1002/ange.201710748
       
  • Shape-Controllable and Fluorescent Supramolecular Organic Frameworks
           Through Aqueous Host–Guest Complexation
    • Authors: Yawen Li; Yunhong Dong, Xiaran Miao, Yulin Ren, Beilin Zhang, Pinpin Wang, Yang Yu, Bin Li, Lyle Isaacs, Liping Cao
      Abstract: Two kinds of shape-controllable and fluorescent supramolecular organic frameworks (cuboid or spheroid) are constructed hierarchically from CB[8] and tetraphenylethylene derivatives through host–guest interaction in water. These two fluorescent SOFs exhibit intriguing and varied photophysical properties, including large red-shifts (up to 82 nm) and stimuli-responsive behavior to competitive guest by binding with CB[8], the turn-on fluorescence of which is applied in cellular imaging.Bestimmte Formen: Supramolekulare organische Gerüste mit Würfel- oder Kugelform werden durch hierarchische Selbstorganisation aus CB[8] und Tetraphenylethen-Derivaten mit verschiedenen Linkern aufgebaut. Die Gerüste können zur Fluoreszenz angeregt werden, was Anwendungen bei der Zellbildgebung in Aussicht stellt.
      PubDate: 2017-12-14T08:16:06.799742-05:
      DOI: 10.1002/ange.201710553
       
  • Alkene 1,2-Difunctionalization by Radical Alkenyl Migration
    • Authors: Xinjun Tang; Armido Studer
      Abstract: Transition-metal-free radical α-perfluoroalkylation with the accompanying vicinal β-alkenylation of unactivated alkenes is presented. These radical cascades proceed by means of 1,4- or 1,5-alkenyl migration by electron catalysis on readily accessed allylic alcohols. The reactions comprise a regioselective perfluoroalkyl radical addition with subsequent alkenyl migration and concomitant deprotonation to generate a ketyl radical anion that sustains the chain as a single-electron-transfer reducing reagent.Die Elektronen-katalysierte, übergangsmetallfreie β-Alkenylierung/α-Perfluoralkylierung nichtaktivierter Alkene verläuft über eine radikalische 1,4- oder 1,5-Alkenylwanderung. Derartige Wanderungen sind nicht Teil der gängigen Synthesemethodik, und ihr Potenzial wird anhand von Beispielen aufgezeigt. DABCO=1,4-Diazabicyclo[2.2.2]octan, DCE=Dichlorethan.
      PubDate: 2017-12-14T08:15:56.030661-05:
      DOI: 10.1002/ange.201710397
       
  • Martin Pumera
    • PubDate: 2017-12-14T08:10:44.669357-05:
      DOI: 10.1002/ange.201710080
       
  • Quaternary β2,2-Amino Acids: Catalytic Asymmetric Synthesis and
           Incorporation into Peptides by Fmoc-Based Solid-Phase Peptide Synthesis
    • Authors: Jin-Sheng Yu; Hidetoshi Noda, Masakatsu Shibasaki
      Abstract: β-Amino acid incorporation has emerged as a promising approach to enhance the stability of parent peptides and to improve their biological activity. Owing to the lack of reliable access to β2,2-amino acids in a setting suitable for peptide synthesis, most contemporary research efforts focus on the use of β3- and certain β2,3-amino acids. Herein, we report the catalytic asymmetric synthesis of β2,2-amino acids and their incorporation into peptides by Fmoc-based solid-phase peptide synthesis (Fmoc-SPPS). A quaternary carbon center was constructed by the palladium-catalyzed decarboxylative allylation of 4-substituted isoxazolidin-5-ones. The N−O bond in the products not only acts as a traceless protecting group for β-amino acids but also undergoes amide formation with α-ketoacids derived from Fmoc-protected α-amino acids, thus providing expeditious access to α-β2,2-dipeptides ready for Fmoc-SPPS.Bessere Peptide: Der Einbau von β-Aminosäuren kann die Stabilität der Stammpeptide erhöhen und ihre biologische Aktivität verbessern. Eine Methode auf Basis einer katalytischen asymmetrischen Allylierung wurde für die Synthese von anderweitig unzugänglichen β2,2-Aminosäuren entwickelt. Die Produkte wurden zur Festphasensynthese von hybriden α/β-Peptiden genutzt (siehe Bild).
      PubDate: 2017-12-14T08:10:42.317541-05:
      DOI: 10.1002/ange.201711143
       
  • Uncatalyzed, Regioselective Oxidation of Saturated Hydrocarbons in an
           Ambient Corona Discharge
    • Authors: Stephen T. Ayrton; Rhys Jones, David S. Douce, Mike R. Morris, R. Graham Cooks
      Abstract: Atmospheric pressure chemical ionization (APCI) in air or in nitrogen with just traces of oxygen is shown to yield regioselective oxidation, dehydrogenation, and fragmentation of alkanes. Ozone is produced from ambient oxygen in situ and is responsible for the observed ion chemistry, which includes partial oxidation to ketones and C−C cleavage to give aldehydes. The mechanism of oxidation is explored and relationships between ionic species produced from individual alkanes are established. Unusually, dehydrogenation occurs by water loss. Competitive incorporation into the hydrocarbon chain of nitrogen versus oxygen as a mode of ionization is also demonstrated.Ionisation durch Koronaentladung bei Umgebungsdruck, in Luft oder in Gegenwart von Sauerstoffspuren führt zu regioselektiven Oxidationen, Dehydrierungen und Fragmentierungen. Die chemischen Prozesse werden untersucht, und Beziehungen zwischen den ionischen Spezies werden erschlossen. Ozon entsteht aus Sauerstoff in situ, und der Weg zu den beobachteten dehydrierten Ketonen führt über eine Dehydratisierung. HV=Hochvakuum.
      PubDate: 2017-12-14T08:05:31.049088-05:
      DOI: 10.1002/ange.201711190
       
  • Molekulare Magnesiumhydride
    • Authors: Debabrata Mukherjee; Jun Okuda
      Abstract: Festes Magnesiumhydrid [MgH2]∞ wird als potenzieller Werkstoff für die Wasserstoffspeicherung untersucht. Seit Mitte des 20. Jahrhunderts interessieren sich Organiker für lösliche Magnesiumhydrid-Reagenzien. Erst in den letzten zwei Jahrzehnten haben Metallorganiker mit einer Reihe strukturell gut charakterisierter Magnesiumhydride für einen größeren Aufschwung bei dieser neuen Verbindungklasse gesorgt. Über vierzig solcher Vertreter sind nun isoliert, von einkernigen terminalen Hydriden bis hin zu großen Hydridclustern mit mehr als 10 Magnesiumatomen. Sie geben nicht nur einen Einblick in die Struktur und die Bindung von Mg-H-Einheiten, sondern dienen auch als Modell für Materialien zur Wasserstoffspeicherung. Bei einigen wurde auch deutlich, dass sie in katalytischen Umwandlungen wie der Hydroelementierung vorkommen. Dieser Aufsatz gibt einen Überblick über die molekularen Magnesiumhydride, wobei das Augenmerk auf deren Synthese und strukturellen Charakterisierung liegt.Die Suche nach der richtigen Größe: Molekulare Magnesiumhydride, einschließlich größerer Cluster, werden als potenzielle Materialien für die Wasserstoffspeicherung erforscht. Dieser Aufsatz gibt einen Überblick über diese Verbindungsklasse, mit einem Augenmerk auf ihrer Synthese und strukturellen Charakterisierung.
      PubDate: 2017-12-14T07:51:07.226571-05:
      DOI: 10.1002/ange.201708592
       
  • Mono- and Bis(imidazolidinium ethynyl) Cations and Reduction of the Latter
           To Give an Extended Bis-1,4-([3]Cumulene)-p-carboquinoid System
    • Authors: Brian M. Barry; R. Graeme Soper, Juha Hurmalainen, Akseli Mansikkamäki, Katherine N. Robertson, William L. McClennan, Alex J. Veinot, Tracey L. Roemmele, Ulrike Werner-Zwanziger, René T. Boeré, Heikki M. Tuononen, Jason A. C. Clyburne, Jason D. Masuda
      Abstract: An extended π-system containing two [3]cumulene fragments separated by a p-carboquinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carboquinoid as a result of the π-accepting properties of the capping NHCs.Die Zwei-Elektronen-Reduktion eines Bis(imidazolidiniumethinyl)-Dikations, das von einem N-heterocyclischen Carben (NHC) und 1,4-Bis(bromethinyl)benzol abgeleitet ist, führt zum erweiterten Bis-1,4-([3]cumulen)-p-carbochinoid 1 mit gleichbleibendem Abstand zwischen den NHC-Einheiten. Zyklovoltammetrie in Kombination mit Synthese- und Strukturstudien lässt auf eine Rolle der π-Akzeptoreigenschaften der abschirmenden NHCs bei der Reduktion des Dikations schließen.
      PubDate: 2017-12-14T07:50:51.490992-05:
      DOI: 10.1002/ange.201711031
       
  • General and Facile Route to Isomerically Pure Tricyclic Peptides Based on
           Templated Tandem CLIPS/CuAAC Cyclizations
    • Authors: Gaston J. J. Richelle; Sumeet Ori, Henk Hiemstra, Jan H. van Maarseveen, Peter Timmerman
      Abstract: We report a one-pot ligation/cyclization technology for the rapid and clean conversion of linear peptides into tricyclic peptides that is based on using tetravalent scaffolds containing two benzyl bromide and two alkyne moieties. These react via CLIPS/CuAAC reactions with cysteines and azides in the peptide. Flexibility in the scaffolds is key to the formation of isomerically pure products as the flexible scaffolds T41 and T42 mostly promote the formation of single isomeric tricycles while the rigid scaffolds T43 and T44 do not yield clean products. There seems to be no limitation to the number and types of amino acids present as 18 canonical amino acids were successfully implemented. We also observed that azides at the peptide termini and cysteine residues in the center gave better results than compounds with the functional groups placed the other way round.Drehbare tetravalente Gerüste mit zwei Brommethyl- und zwei Alkin-Einheiten ermöglichen durch Ligation/Cyclisierung im Eintopfverfahren das Verknüpfen linearer Peptide mit zwei Cystein- und zwei Azidohomoalanin(Aha)-Resten zu tricyclischen Systemen (CLIPS=chemical linkage of peptides onto scaffolds).
      PubDate: 2017-12-14T07:45:38.323316-05:
      DOI: 10.1002/ange.201709127
       
  • Synthesis of α-Chiral Ketones and Chiral Alkanes Using Radical Polar
           Crossover Reactions of Vinyl Boron Ate Complexes
    • Authors: Carolin Gerleve; Marvin Kischkewitz, Armido Studer
      Abstract: Vinyl boron ate complexes of enantioenriched secondary alkyl pinacolboronic esters undergo stereospecific radical induced 1,2-migration in radical polar crossover reactions. In this three component process various commercially available alkyl iodides act as radical precursors and light is used for chain initiation. A subsequent oxidation or protodeborylation leads to valuable α-chiral ketones and chiral alkanes with excellent enantiopurity.
      PubDate: 2017-12-14T07:36:05.465846-05:
      DOI: 10.1002/ange.201711390
       
  • Hierarchical Hollow Nanoprisms Based on Ultrathin Ni-Fe Layered Double
           Hydroxide Nanosheets with Enhanced Electrocatalytic Activity towards
           Oxygen Evolution
    • Authors: Le Yu; Jing Fan Yang, Bu Yuan Guan, Yan Lu, Xiong Wen (David) Lou
      Abstract: The oxygen evolution reaction (OER) is involved in various renewable energy systems, such as water-splitting cells and metal–air batteries. Ni-Fe layered double hydroxides (LDHs) have been reported as promising OER electrocatalysts in alkaline electrolytes. The rational design of advanced nanostructures for Ni-Fe LDHs is highly desirable to optimize their electrocatalytic performance. Herein, we report a facile self-templated strategy for the synthesis of novel hierarchical hollow nanoprisms composed of ultrathin Ni-Fe LDH nanosheets. Tetragonal nanoprisms of nickel precursors were first synthesized as the self-sacrificing template. Afterwards, these Ni precursors were consumed during the hydrolysis of iron(II) sulfate for the simultaneous growth of a layer of Ni-Fe LDH nanosheets on the surface. The resultant Ni-Fe LDH hollow prisms with large surface areas manifest high electrocatalytic activity towards the OER with low overpotential, small Tafel slope, and remarkable stability.Selbsttemplatisierung ermöglicht die Synthese hierarchischer hohler Nanoprismen basierend auf Nanoschichten aus Ni-Fe-Doppelschichthydroxiden (LDH). Bei der Hydrolyse von Eisen(II)sulfat lösen sich die prismenförmigen Ni-Vorstufen auf und werden in eine Ni-Fe-LDH-Oberflächenschale umgewandelt. Mit ihrer Struktur und Zusammensetzung eignen sich die Nanoprismen für die elektrochemische Sauerstoffentwicklung.
      PubDate: 2017-12-14T05:50:31.989631-05:
      DOI: 10.1002/ange.201710877
       
  • Europa und die Chemie voranbringen
    • Authors: Gilberte Chambaud
      Abstract: „… Für die Wissenschaftlerwelt sind die Reisemöglichkeiten, die den persönlichen Austausch zwischen Forschern begünstigen, von großer Bedeutung. Wesentliche Erfolge waren die Verschmelzung nationaler Zeitschriften zu erfolgreichen europäischen Journalen und die Schaffung der EuCheMS-Kongresse …” Lesen Sie mehr im Gast-Editorial von Gilberte Chambaud.
      PubDate: 2017-12-14T04:40:25.016843-05:
      DOI: 10.1002/ange.201709947
       
  • Bimetallic Ag-Pt sub-nanometer supported clusters as highly efficient and
           robust oxidation catalysts
    • Authors: Fabio R. Negreiros; Avik Halder, Chunrong Yin, Akansha Singh, Giovanni Barcaro, Luca Sementa, Eric C. Tyo, Michael J. Pellin, Stephan Bartling, Karl-Heinz Meiwes-Broer, Sönke Seifert, Prasenjiy Sen, Sandeep Nigam, Chiranjib Majumder, Nobuyuki Fukui, Hisato Yasumatsu, Stefan Vajda, Alessandro Fortunelli
      Abstract: A combined experimental and theoretical investigation of Ag-Pt sub-nanometer clusters as heterogeneous catalysts in the COCO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size-selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and via first-principles simulations at realistic coverage. In situ GISAXS/TPRx demonstrates that the clusters neither sinter nor deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano-aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species.
      PubDate: 2017-12-14T04:35:30.209064-05:
      DOI: 10.1002/ange.201709784
       
  • The molecular structure of gauche-1,3-butadiene: Experimental proof of
           non-planarity
    • Authors: Joshua Baraban; Marie-Aline Martin-Drumel, P. Bryan Changala, Sandra Eibenberger, Matthew Nava, David Patterson, John F Stanton, G. Barney Ellison, Michael C McCarthy
      Abstract: The planarity of the second stable conformer of 1,3-butadiene - the archetypal diene for the Diels- Alder reaction, in which a planar conjugated diene and a dienophile combine to form a ring - is not established. The most recent high level calculations predict the species to adopt a twisted, gauche structure due to steric interactions between the inner terminal hydrogens rather than a planar, cis structure favored by the conjugation of the doubled bonds. Here we unambiguously prove experimentally that the structure cis-1,3-butadiene is indeed gauche with a substantial dihedral angle of 34°, in excellent agreement with theory. Observation of two tunneling components indicates that the molecule undergoes facile interconversion between two equivalent enantiomeric forms. Comparison of experimentally determined structures for gauche-and trans-butadiene provides an opportunity to examine the effects of conjugation and steric interactions.
      PubDate: 2017-12-14T04:07:31.481723-05:
      DOI: 10.1002/ange.201709966
       
  • Smart Solid Electrolyte Interphase Layer for Long Life Lithium Metal
           Anodes
    • Authors: Nian-Wu Li; Yang Shi, Ya-Xia Yin, Xian-Xiang Zeng, Jin-Yi Li, Cong-Ju Li, Li-Jun Wan, Rui Wen, Yu-Guo Guo
      Abstract: Lithium (Li) metal is a promising anode material for high-energy density batteries. However, the unstable and static solid electrolyte interphase (SEI) can be destroyed by the dynamic Li plating/stripping behavior on the Li anode surface, leading to side reactions and Li dendrites growth. Herein, we design a smart Li polyacrylic acid (LiPAA) SEI layer with high stretchability to address the dynamic Li plating/stripping processes by the self-adapting interface regulation, which is demonstrated by in situ AFM process. With the high binding ability and excellent stability of LiPAA polymer, the smart SEI can significantly reduce the side reactions and improve the safety property markedly. The stable cycling of 700 h is achieved in the LiPAA-Li LiPAA-Li symmetrical cell. The innovative strategy of self-adapting SEI design is broadly applicable, conceptually providing admirable opportunities for Li metal anodes.
      PubDate: 2017-12-14T00:06:45.338592-05:
      DOI: 10.1002/ange.201710806
       
  • Controlling the polymer microstructure in anionic polymerization by
           compartmentalization
    • Authors: Elisabeth Rieger; Jan Blankenburg, Eduard Grune, Manfred Wagner, Katharin Landfester, Frederik Roman Wurm
      Abstract: An ideal random anionic copolymerization is forced to gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO-in-cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real-time 1H NMR kinetics, proving a change of the reactivity ratios of both monomers upon dilution of the continuous phase from ideal random to adjustable gradients by simple dilution. This model system will allow the preparation of copolymer libraries in the future in a one-pot, one-shot reaction, without any sequential monomer addition.
      PubDate: 2017-12-13T21:42:22.646626-05:
      DOI: 10.1002/ange.201710417
       
  • Artificial Cysteine S-Glycosylation Induced by Per-O-Acetylated Unnatural
           Monosacharides during Metabolic Glycan Labeling
    • Authors: Wei Qin; Ke Qin, Xinqi Fan, Linghang Peng, Weiyao Hong, Yuntao Zhu, Pinou Lv, Yifei Du, Rongbing Huang, Mengting Han, Bo Cheng, Yuan Liu, Wen Zhou, Chu Wang, Xing Chen
      Abstract: Here we report an unexpected, non-enzymatic cysteine S-glycosylation induced by per-O-acetylated monosaccharides and their clickable analogs on various proteins. This artificial S-glycosylation broadly compromises the specificity and validity of metabolic glycan labeling in living cells using per-O-acetylated azido and alkynyl sugars, which has been overlooked in the field for decades. We demonstrate that free unnatural sugars can avoid the artifacts and by using N-azidoactylgalactosamine, we provide a corrected list of O-GlcNAcylated proteins and O-GlcNAc sites in HeLa cells.
      PubDate: 2017-12-13T12:35:35.556466-05:
      DOI: 10.1002/ange.201711710
       
  • A New Mechanism for β-Lactamases: Class D Enzymes Degrade 1β-Methyl
           Carbapenems via Lactone Formation
    • Authors: Christopher T. Lohans; Emma van Groesen, Kiran Kumar, Catherine L. Tooke, James Spencer, Robert S. Paton, Jürgen Brem, Christopher Schofield
      Abstract: β-Lactamases threaten the clinical use of carbapenems, considered antibiotics of last resort. The classical mechanism of serine carbapenemase activity proceeds via hydrolysis of an acyl-enzyme intermediate. We show that class D β-lactamases also degrade clinically used 1β-methyl-substituted carbapenems via the unprecedented formation of a carbapenem-derived β-lactone. β-Lactone formation results from the nucleophilic attack of the carbapenem hydroxyethyl side chain onto the ester carbonyl of the acyl-enzyme intermediate. The carbapenem-derived lactone products inhibit both serine β-lactamases (particularly class D) and metallo-β-lactamases. These results define a new mechanism for the class D carbapenemases, in which a hydrolytic water molecule is not required.
      PubDate: 2017-12-13T11:42:39.252281-05:
      DOI: 10.1002/ange.201711308
       
  • Isolation of a Reactive Tricoordinate alpha-Oxo Gold Carbene Complex
    • Authors: Abdallah Zeineddine; Feriel Rekhroukh, E. Daiann Sosa Carrizo, Sonia Mallet-Ladeira, Karinne Miqueu, Abderrahmane Amgoune, Didier Bourissou
      Abstract: The [(P,P)Au=C(Ph)CO2Et]+ complex 3 [where (P,P) is an o-carboranyl diphosphine ligand] was prepared by diazo decomposition at -40°C. It is the first alpha-oxo gold carbene complex to be characterized. Its crystallographic structure was determined and DFT calculations have been performed, unraveling the key influence of the chelating (P,P) ligand. The gold center is tricoordinate and the electrophilicity of the carbene center is reduced. Complex 3 mimics transient alpha-oxo gold carbenes in a series of catalytic transformations, and enables to support the critical role of electrophilicity in the chemoselectivity of phenol functionalization (O-H vs C-H insertion).
      PubDate: 2017-12-13T09:35:25.900107-05:
      DOI: 10.1002/ange.201711647
       
  • Röhrenförmige Selbstorganisation kovalenter organischer
           Netzwerke
    • Authors: Bappaditya Gole; Vladimir Stepanenko, Sabrina Rager, Matthias Grüne, Dana D. Medina, Thomas Bein, Frank Würthner, Florian Beuerle
      Abstract: Trotz erheblicher Fortschritte bei der Synthese kovalenter organischer Netzwerke (COFs) wurde für diese Materialien bis jetzt nur sporadisch über den präzisen Aufbau von templatfreien Nano- und Mikrostrukturen berichtet. Auf der Suche nach farbstoffhaltigen porösen Materialien konnte ein neues konjugiertes Netzwerk, DPP-TAPP-COF, durch reversible Iminkondensationen zwischen 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin (TAPP) und einem Diketopyrrolopyrrol-Dialdehyd (DPP) synthetisiert werden, das eine verstärkte Absorption bis zu λ=800 nm aufweist. Überraschenderweise wurde für dieses COF eine spontane Aggregation zu hohlen Mikroröhren mit äußeren und inneren Durchmessern von d≈300 und 90 nm beobachtet. Detaillierte mechanistische Studien ergaben, dass sich zunächst schichtartige Agglomerate bilden, die mit der Zeit in röhrenförmige Mikrostrukturen transformiert werden.Zusammengerollte COFs: Tetraphenylporphyrine und Diketopyrrolopyrrole wurden als funktionale Farbstoffkomponenten über reversible Imin-Kondensationen in kovalente organische Netzwerke integriert. Nach ihrer Bildung aggregieren diese kristallinen Polymere spontan zu hohlen mikrotubularen Überstrukturen.
      PubDate: 2017-12-13T09:06:45.077325-05:
      DOI: 10.1002/ange.201708526
       
  • Near-Infrared Light-Driven Hydrogen Evolution from Water Using a
           Polypyridyl Triruthenium Photosensitizer
    • Authors: Yutaro Tsuji; Keiya Yamamoto, Kosei Yamauchi, Ken Sakai
      Abstract: Die Entwicklung von H2 durch Einstrahlung von Nahinfrarotlicht ist ein beispielloses Phänomen, das sich einen ausgedehnten Wellenlängenbereich des Sonnenspektrums zu Nutze macht. In ihrer Zuschrift (
      DOI : 10.1002/ange.201708996) berichten K. Sakai et al. über die photokatalytische H2-Entwicklung unter Verwendung eines Triruthenium-Polypyridyl-Photosensibilisators mit lichtsammelnden Eigenschaften. Der Photosensibilisator fördert die H2-Entwicklung unter Lichteinstrahlung im Bereich von 700-800 nm.
      PubDate: 2017-12-13T09:02:04.948585-05:
       
  • Jan C. M van Hest
    • PubDate: 2017-12-13T09:01:51.371213-05:
      DOI: 10.1002/ange.201712084
       
  • Integrated Transmission Electron and Single-Molecule Fluorescence
           Microscopy Correlates Reactivity with Ultrastructure in a Single Catalyst
           Particle
    • Authors: Frank C. Hendriks; Sajjad Mohammadian, Zoran Ristanović, Sam Kalirai, Florian Meirer, Eelco T. C. Vogt, Pieter C. A. Bruijnincx, Hans C. Gerritsen, Bert M. Weckhuysen
      Abstract: Zwei „Superhelden” der hochauflösenden Bildgebung, nämlich die Einzelmolekülfluoreszenzmikroskopie und die Rasterelektronenmikroskopie, wurden kombiniert, um korrelierende Analysen durchführen zu können. In ihrer Zuschrift (
      DOI : 10.1002/ange.201709723) zeigen H. C. Gerritsen, B. M. Weckhuysen et al. die Gültigkeit dieses Ansatzes, indem sie Struktur-Aktivitäts-Verhältnisse in einem einzigen Katalysatorpartikel untersuchen. Unterschiede in der Reaktivität existieren innerhalb der aktiven Komponenten mit identischen Strukturmerkmalen.
      PubDate: 2017-12-13T09:01:49.570519-05:
       
  • Solubility-Parameter-Guided Solvent Selection to Initiate Ostwald Ripening
           for Interior Space-Tunable Structures with Architecture-Dependent
           Electrochemical Performance
    • Authors: Baoguang Mao; Donglei Guo, Jinwen Qin, Tao Meng, Xin Wang, Minhua Cao
      Abstract: Despite significant advancement in preparing various hollow structures by Ostwald ripening, one common problem is the intractable uncontrollability of initiating Ostwald ripening due to the complexity of the reaction processes. Here, a new strategy on Hansen solubility parameter (HSP)-guided solvent selection to initiate Ostwald ripening is proposed. Based on this comprehensive principle for solvent optimization, N,N-dimethylformamide (DMF) was screened out, achieving accurate synthesis of interior space-tunable MoSe2 spherical structures (solid, core–shell, yolk-shell and hollow spheres). The resultant MoSe2 structures exhibit architecture-dependent electrochemical performances towards hydrogen evolution reaction and sodium-ion batteries. This pre-solvent selection strategy can effectively provide researchers great possibility in efficiently synthesizing various hollow structures. This work paves a new pathway for deeply understanding Ostwald ripening.Löslichkeitsparameter wurden herangezogen, um das optimale Lösungsmittel für die Initiierung der Ostwald-Reifung von MoSe2 auszuwählen. Basierend auf diesem Ansatz wurden hohle MoSe2-Strukturen mit kontrolliert modulierbarem Innenraum in N,N-Dimethylformamid synthetisiert. Das elektrochemische Verhalten der resultierenden MoSe2-Strukturen bei der H2-Entwicklung und in Natriumionenbatterien hängt von ihrer Architektur ab.
      PubDate: 2017-12-13T08:07:21.235741-05:
      DOI: 10.1002/ange.201710378
       
  • A π-Conjugation Extended Viologen as a Two-Electron Storage Anolyte for
           Total Organic Aqueous Redox Flow Batteries
    • Authors: Jian Luo; Bo Hu, Camden Debruler, Tianbiao Leo Liu
      Abstract: Extending the conjugation of viologen by a planar thiazolo[5,4-d]thiazole (TTz) framework and functionalizing the pyridinium with hydrophilic ammonium groups yielded a highly water-soluble π-conjugation extended viologen, 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(1-(3-(trimethylammonio)propyl)pyridin-1-ium) tetrachloride, [(NPr)2TTz]Cl4 , as a novel two-electron storage anolyte for aqueous organic redox flow battery (AORFB) applications. Its physical and electrochemical properties were systematically investigated. Paired with 4-trimethylammonium-TEMPO (NMe-TEMPO) as catholyte, [(NPr)2TTz]Cl4 enables a 1.44 V AORFB with a theoretical energy density of 53.7 Wh L−1. A demonstrated [(NPr)2TTz]Cl4/NMe-TEMPO AORFB delivered an energy efficiency of 70 % and 99.97 % capacity retention per cycle.Auf der Überholspur: Ein hoch wasserlösliches Viologen mit erweiterter π-Konjugation wurde als Anolyt mit 2-Elektronen-Speicherung entwickelt und in einer vollständig organischen, neutralen wässrigen Redox-Flow-Batterie mit 1.44 V Batteriespannung eingesetzt.
      PubDate: 2017-12-13T08:06:54.193379-05:
      DOI: 10.1002/ange.201710517
       
  • Electrobiorefineries: Unlocking the synergy of electrochemical and
           microbial conversions
    • Authors: Falk Harnisch; Carolin Urban
      Abstract: Lead-in: An integrated biobased economy urges an alliance of the two realms "chemical production" and "electric power". The concept of electrobiorefineries provides a blueprint for such an alliance agreement. Joining the forces of microbial and electrochemical conversions in electrobiorefineries allows interfacing the production, storage, and exploitation of electricity as well as biobased chemicals. Electrobiorefineries are a technological evolution of biorefineries by means of the addition of (bio)electrochemical transformations. This interfacing of microbial and electrochemical conversions will result in synergies affecting the whole process line, like enlarging the product portfolio, increasing the productivity, or exploiting new feedstock. A special emphasis is given to the utilization of oxidative and reductive electroorganic reactions of microbially produced intermediates that may serve as privileged building blocks.
      PubDate: 2017-12-13T08:06:41.969659-05:
      DOI: 10.1002/ange.201711727
       
  • Martin D. Smith
    • PubDate: 2017-12-13T08:00:32.024224-05:
      DOI: 10.1002/ange.201712087
       
  • The Narrowest Band Gap Ever Observed in Molecular Ferroelectrics:
           Hexane-1,6-diammonium Pentaiodobismuth(III)
    • Authors: Han-Yue Zhang; Zhenhong Wei, Peng-Fei Li, Yuan-Yuan Tang, Wei-Qiang Liao, Heng-Yun Ye, Hu Cai, Ren-Gen Xiong
      Abstract: Narrow band gaps and excellent ferroelectricity are intrinsically paradoxical in ferroelectrics as the leakage current caused by an increase in the number of thermally excited carriers will lead to a deterioration of ferroelectricity. A new molecular ferroelectric, hexane-1,6-diammonium pentaiodobismuth (HDA-BiI5), was now developed through band gap engineering of organic–inorganic hybrid materials. It features an intrinsic band gap of 1.89 eV, and thus represents the first molecular ferroelectric with a band gap of less than 2.0 eV. Simultaneously, low-temperature solution processing was successfully applied to fabricate high-quality ferroelectric thin films based on HDA-BiI5, for which high-precision controllable domain flips were realized. Owing to its narrow band gap and excellent ferroelectricity, HDA-BiI5 can be considered as a milestone in the exploitation of molecular ferroelectrics, with promising applications in high-density data storage and photovoltaic conversion.Das molekulare Ferroelektrikum Hexan-1,6-diammoniumpentaiodbismut ist durch eine schmale Bandlücke von 1.89 eV charakterisiert. Hochqualitative flexible dünne Filme aus diesem ferroelektrischen Material wurden bei niedriger Temperatur aus der Lösung abgeschieden.
      PubDate: 2017-12-13T08:00:30.35617-05:0
      DOI: 10.1002/ange.201709588
       
  • Abderrahmane Amgoune
    • PubDate: 2017-12-13T08:00:19.663756-05:
      DOI: 10.1002/ange.201712422
       
  • Nanoscale Trimetallic Metal–Organic Frameworks Enable Efficient Oxygen
           Evolution Electrocatalysis
    • Authors: Fei-Long Li; Qi Shao, Xiaoqing Huang, Jian-Ping Lang
      Abstract: Metal–organic frameworks (MOFs) are a class of promising materials for diverse heterogeneous catalysis, but they are usually not directly employed for oxygen evolution electrocatalysis. Most reports focus on using MOFs as templates to in situ create efficient electrocatalysts through annealing. Herein, we prepared a series of Fe/Ni-based trimetallic MOFs (Fe/Ni/Co(Mn)-MIL-53 accordingly to the Material of Institute Lavoisier) by solvothermal synthesis, which can be directly adopted as highly efficient electrocatalysts. The Fe/Ni/Co(Mn)-MIL-53 shows a volcano-type oxygen evolution reaction (OER) activity as a function of compositions. The optimized Fe/Ni2.4/Co0.4-MIL-53 can reach a current density of 20 mA cm−2 at low overpotential of 236 mV with a small Tafel slope of 52.2 mV dec−1. In addition, the OER performance of these MOFs can be further enhanced by directly being grown on nickel foam (NF).Multimetallische MOFs unterschiedlicher Zusammensetzungen wurden synthetisiert und als Elektrokatalysatoren für die Sauerstoffentwicklung (OER) verwendet (MOFs=Metall-organische Gerüste). Der Fe/Ni/Co/(Mn)-MIL-53-Katalysator zeigt eine Vulkankurve der OER-Aktivität als Funktion der Zusammensetzung. Der optimierte Fe/Ni/Mn0.4-MIL-53/NF-Katalysator ist hochaktiv und ultrastabil in der OER-Katalyse.
      PubDate: 2017-12-13T07:21:08.054917-05:
      DOI: 10.1002/ange.201711376
       
  • Hinweise auf eine Triplett-Sensibilisierung in der
           [2+2]-Photocycloaddition von Eniminiumionen mit sichtbarem Licht
    • Authors: Fabian M. Hörmann; Tim S. Chung, Elsa Rodriguez, Matthias Jakob, Thorsten Bach
      Abstract: Eniminiumionen, die aus den entsprechenden Carbonylverbindungen (Enonen und Enalen) hergestellt wurden, konnten durch Energietransfer in ihren Triplett-Zustand angeregt werden. Die Intermediate unterzogen sich bei einer Anregungswellenlänge von λ=433 nm oder λ=457 nm in guten Ausbeuten (50–78 %) einer intra- oder intermolekularen [2+2]-Photocycloaddition. Für die Reaktion wurden Iridium- oder Rutheniumkatalysatoren (2.5 Mol-%) mit einer ausreichend hohen Triplett-Energie verwendet. Ausgehend von einem chiralen sekundären Amin wurde ein Eniminiumion synthetisiert, das mit hoher Enantioselektivität (88 % ee) in einer intermolekularen [2+2]-Photocycloaddition umgesetzt werden konnte.Die Energie als Grenze: Die [2+2]-Photocycloaddition der Iminiumionen 1 wird von Iridium- oder Rutheniumkomplexen mittels Triplett-Energietransfer katalysiert. Die intermediären Iminiumionen 2 werden zu den entsprechenden Carbonylverbindungen hydrolysiert, beispielsweise zu Aldehyd 3, der ausgehend von einem chiralen Eniminiumion gebildet wurde (78 % Ausbeute).
      PubDate: 2017-12-13T07:20:57.809688-05:
      DOI: 10.1002/ange.201710441
       
  • Ronald Breslow (1931–2017)
    • Authors: Alanna Schepartz; Robert Bergman, Robert H. Grubbs
      Abstract: Ronald Breslow, Samuel Latham Mitchill Professor of Chemistry an der Columbia University, ist am 25. Oktober 2017 im Alter von 86 Jahren verstorben. Von ihm kamen bemerkenswerte Beiträge zur physikalisch-organischen und bioorganischen Chemie, darunter zu biologischen und biomimetischen Umsetzungen und zum Einsatz der molekularen Erkennung zur Steuerung der Selektivität einer Reaktion.
      PubDate: 2017-12-13T07:20:44.171946-05:
      DOI: 10.1002/ange.201711641
       
  • Total Synthesis of (+)-Sarcophytin
    • Authors: Leonardo J. Nannini; Suren J. Nemat, Erick M. Carreira
      Abstract: A total synthesis of the cembranoid (+)-sarcophytin is presented, featuring a Diels–Alder cycloaddition of an enone as the dienophile with an ester-derived dienoate. The study highlights a peculiar geometric preference for the Z dienoate to furnish the cycloadduct. The endgame involves a reaction cascade, including lactone opening, alcohol oxidation, and ketone epimerization to complete an efficient synthesis. A salient feature of the synthesis is the resulting reassignment of the absolute configuration, which corrects the previously reported nominal structure.So ist's richtig: Eine Totalsynthese des Cembranoids (+)-Sarcophytin über die Diels-Alder-Cycloaddition eines Enons mit einem Z-Dienoat wird vorgestellt. Eine Reaktionskaskade mit Lactonringöffnung, Alkoholoxidation und Ketonepimerisierung beschließt die effiziente Synthese. Die zuvor angegebene Struktur des Naturstoffs konnte auf dieser Grundlage bezüglich der absoluten Konfiguration korrigiert werden.
      PubDate: 2017-12-13T07:17:38.687444-05:
      DOI: 10.1002/ange.201711372
       
  • Total Synthesis of (6R,10R,13R,14R,16R,17R,19S,20R,21R,24S,
           25S,28S,30S,32R,33R,34R,36S,37S,39R)-Azaspiracid-3 Reveals Non-Identity
           with the Natural Product
    • Authors: Nathaniel T. Kenton; Daniel Adu-Ampratwum, Antony A. Okumu, Zhigao Zhang, Yong Chen, Son Nguyen, Jianyan Xu, Yue Ding, Pearse McCarron, Jane Kilcoyne, Frode Rise, Alistair L. Wilkins, Christopher O. Miles, Craig J. Forsyth
      Abstract: A convergent and stereoselective total synthesis of the previously assigned structure of azaspiracid-3 has been achieved by a late-stage Nozaki–Hiyama–Kishi coupling to form the C21−C22 bond with the C20 configuration unambiguously established from l-(+)-tartaric acid. Postcoupling steps involved oxidation to an ynone, modified Stryker reduction of the alkyne, global deprotection, and oxidation of the resulting C1 primary alcohol to the carboxylic acid. The synthetic product matched naturally occurring azaspiracid-3 by mass spectrometry, but differed both chromatographically and spectroscopically.Eine konvergente und stereospezifische Totalsynthese der vormals zugewiesenen Struktur des marinen Neurotoxins Azaspiracid-3 offenbart, dass sie nicht identisch mit dem Naturstoff ist. Eine Strukturrevision der primären Azaspiracide ist daher notwendig.
      PubDate: 2017-12-13T07:17:31.709162-05:
      DOI: 10.1002/ange.201711006
       
  • The Ideal Ionic Liquid Salt Bridge for the Direct Determination of Gibbs
           Energies of Transfer of Single Ions, Part I: The Concept
    • Authors: Valentin Radtke; Andreas Ermantraut, Daniel Himmel, Thorsten Koslowski, Ivo Leito, Ingo Krossing
      Abstract: We describe a procedure for the thermodynamicallyrigorous, experimental determination of the Gibbs Energy of Transferof single ions between solvents. The method is based on potentialdifference measurements between two electrochemical half cells withdifferent solvents connected by an ideal Ionic Liquid Salt Bridge(ILSB). We discuss the specific requirements for the IL with regard tothe procedure, ensuring that the Liquid Junction Potentials (LJP) atboth ends of the ILSB cancel largely. The remaining parts of the LJPscan be determined by separate emf measurements. No extrathermodynamicassumptions are necessary for this procedure. Theaccuracy of the measurements depends amongst others on the"ideality" of the used IL, as shown in our companion paper Part II.
      PubDate: 2017-12-13T05:13:49.685964-05:
      DOI: 10.1002/ange.201707333
       
  • The Ideal Ionic Liquid Salt Bridge for the Direct Determination of Gibbs
           Energies of Transfer of Single Ions, Part II: Evaluation of the Role of
           Ion Solvation and Ion Mobilities
    • Authors: Andreas Ermantraut; Valentin Radtke, Niklas Gebel, Daniel Himmel, Thorsten Koslowski, Ivo Leito, Ingo Krossing
      Abstract: An important intermediate goal to evaluate our concept for the assumption-free determination of single ion Gibbs transfer energies ΔtrG°(i, S1> S2) is presented: We executed the crucial steps a) and b) of the methodology, described in Part I of this treatise, exemplarily for Ag+ and Cl− with S1 being water and S2 being acetonitrile. The experiments showed that virtually all parts of the liquid junction potentials (LJPs) at both ends of a salt bridge cancel, if the bridge electrolyte is an "ideal" ionic liquid - one with nearly identical diffusion of anion and cation. This holds for [N2225]+[NTf2]- in the pure IL, but also in water and acetonitrile solution. Emf measurements of solvate cells between S1 and S2 gave Nernstian behavior for Ag+-concentration cells and constant like cell potentials for solutions with five tested Ag+-counterions.
      PubDate: 2017-12-13T05:13:47.16695-05:0
      DOI: 10.1002/ange.201707334
       
  • Direct asymmetric Michael reaction of α,β-unsaturated aldehydes and
           ketones catalyzed by two secondary amine catalysts
    • Authors: Yujiro Hayashi; Nariyoshi Umekubo
      Abstract: Direct asymmetric Michael reaction of α,β-unsaturated aldehydes and ketones proceeds in the presence of two pyrrolidine-type catalysts, such as diphenylprolinol silyl ether and hydroxyproline, to afford synthetically useful δ-keto aldehydes with excellent diastereo- and enantioselectivities. Although there are several iminium ions and enamines in the reaction mixture, an iminium ion generated from the former catalyst reacts preferentially with an enamine generated from the latter catalyst.
      PubDate: 2017-12-13T05:13:25.569212-05:
      DOI: 10.1002/ange.201710085
       
  • CO Hydrogenation on Cobalt-Based Catalysts: Tin Poisoning Unravels CO in
           Hollow Sites as a Main Surface Intermediate
    • Authors: Anaëlle Paredes-Nunez; Davide Lorito, Laurence Burel, Debora Motta-Meira, Giovanni Agostini, Nolven Guilhaume, Yves Schuurman, Frederic Meunier
      Abstract: Site poisoning is a powerful method to unravel the nature of active sites or reaction intermediates. The nature of the intermediates involved in the hydrogenation of CO was unraveled by poisoning alumina-supported cobalt catalysts with various concentrations of tin. The rate of formation of the main reaction products (methane and propylene) was found to be proportional to the concentration of multi-bonded CO, likely located in hollow sites. The specific rate of decomposition of these species was sufficient to account for the formation of the main products. These hollow-CO are proposed to be main reaction intermediates in the hydrogenation of CO under the reaction conditions used here, while linear CO are mostly spectators.Eine Zinnvergiftung aktiver Zentren von Co/Al2O3-Katalysatoren hilft beim Studium der Zwischenstufen in der CO-Hydrierung. Die Bildungsrate von Methan und Propen ist proportional zur Konzentration an mehrfach gebundenem CO, das sich vermutlich über Mulden befindet. Derartiges CO wird als wichtigste Zwischenstufe der untersuchten CO-Hydrierung vorgeschlagen, linear gebundenes CO ist hingegen weitgehend unbeteiligt.
      PubDate: 2017-12-13T04:41:12.529559-05:
      DOI: 10.1002/ange.201710301
       
  • Live-Cell Protein Sulfonylation Based on Proximity-driven N-Sulfonyl
           Pyridone Chemistry
    • Authors: Kazuya Matsuo; Yuki Nishikawa, Marie Masuda, Itaru Hamachi
      Abstract: The development of bioorthogonal approaches for labeling of endogenous proteins under the multimolecular crowding conditions of live cells is highly desirable for the analysis and engineering of proteins without using genetic manipulation. N-Sulfonyl pyridone (SP) is reported as a new reactive group for protein sulfonylation. The ligand-directed SP chemistry was able to modify not only purified proteins in vitro, but also endogenous ones on the surface of and inside live cells selectively and rapidly, which allowed to convert endogenous proteins to FRET-based biosensors in situ.Ligand-gesteuerte Umsetzungen mit N-Sulfonylpyridonen ermöglichen die spezifische Sulfonylierung endogener Proteine ohne Beeinträchtigung ihrer natürlichen Eigenschaften. Auf diese Weise können endogene Proteine in lebenden Zellen in halbsynthetische FRET-Biosensoren für die Analyse dynamischer Wechselwirkungen zwischen Proteinen und (niedermolekularen) Liganden umgewandelt werden .
      PubDate: 2017-12-13T04:41:03.88813-05:0
      DOI: 10.1002/ange.201707972
       
  • Photoactivated N-Acyliminoiodinanes Applied to Amination: an
           ortho-Methoxymethyl Group Stabilizes Reactive Precursors
    • Authors: Yusuke Kobayashi; Sota Masakado, Yoshiji Takemoto
      Abstract: N-Acyliminoiodinanes were characterized for the first time by X-ray structural analysis. The ortho-methoxymethyl group and the carbonyl oxygen coordinate to the iodine atom of the iminoiodinane. Activation of the N-acyliminoiodinane was achieved by photoirradiation at 370 nm, thereby enabling reaction with various silyl enol ethers to give α-aminoketone derivatives in good to high yield. N-sulfonyliminoiodinanes bearing ortho substituents were used in photoinduced amination.N-Acyliminoiodinane, die durch eine ortho-Methoxymethyl-Gruppe stabilisiert sind, werden durch Bestrahlung mit 370-nm-Licht für eine Reaktivität gegenüber verschiedenen Silylenolethern aktiviert. Hierbei entstehen α-Aminoketone in guten bis hohen Ausbeuten. Die photoinduzierte Aminierung gelingt auch für N-Sulfonyliminoiodinane mit ortho-Substituenten. PG=Schutzgruppe.
      PubDate: 2017-12-13T04:35:36.326831-05:
      DOI: 10.1002/ange.201710277
       
  • Hierarchical Hollow Nanoprisms Based on Ultrathin Ni-Fe Layered Double
           Hydroxide Nanosheets with Enhanced Electrocatalytic Activity towards
           Oxygen Evolution
    • Authors: Le Yu; Jing Fan Yang, Bu Yuan Guan, Yan Lu, Xiong Wen (David) Lou
      Abstract: Ni-Fe-Doppelschichthydroxide (LDH) sind vielversprechende Elektrokatalysatoren der Sauerstoffentwicklung (OER) in alkalischen Elektrolyten. In ihrer Zuschrift (
      DOI : 10.1002/ange.201710877) beschreiben X. W. Lou et al. die Synthese hierarchischer hohler Nanoprismen aus Ni-Fe-LDH-Nanoschichten durch Selbsttemplatisierung. Diese Nanoprismen zeichnen sich durch große Oberflächen und hohe elektrokatalytische Aktivität in der OER aus, bei niedriger Überspannung, einer geringen Tafel-Steigung und guter Stabilität.
      PubDate: 2017-12-13T04:32:58.989323-05:
       
  • Ultrathin Graphdiyne Nanosheets Grown In Situ on Copper Nanowires and
           Their Performance as Lithium-Ion Battery Anodes
    • Authors: Hong Shang; Zicheng Zuo, Liang Li, Fan Wang, Huibiao Liu, Yongjun Li, Yuliang Li
      Abstract: A method is presented for the scalable preparation of high-quality graphdiyne nanotubes and ultrathin graphdiyne nanosheets (average thickness: ca. 1.9 nm) using Cu nanowires as a catalyst. For the storage of Li+ ions, the graphdiyne nanostructures show a high capacity of 1388 mAh g−1 and high rate performance (870 mA h g−1 at 10 A g−1, and 449.8 mA h g−1 at 20 A g−1) with robust stability, demonstrating outstanding overall potential for its applications.Ein Kupfer-Nanodraht wurde für die Herstellung von 1.9 nm dünnen Graphdiin-Nanoblätter verwendet, und der Wachstumsprozess wurde untersucht. Die Graphdiin-Nanoblätter speichern große Mengen an Lithiumionen und ergaben eine Kapazität von 1380 mAh g−1. Das Bild zeigt die Diffusion innerhalb der Ebenen (blauer Pfeil) und senkrecht zu diesen (roter Pfeil).
      PubDate: 2017-12-13T04:31:58.68191-05:0
      DOI: 10.1002/ange.201711366
       
  • para-Xylene Ultra-selective Zeolite MFI Membranes Fabricated from
           Nanosheet Monolayers at the Air–Water Interface
    • Authors: Donghun Kim; Mi Young Jeon, Benjamin L. Stottrup, Michael Tsapatsis
      Abstract: The control of membrane morphology and microstructure is crucial to improve the separation performance of molecular-sieve membranes. This can be enabled by making thin, dense, and uniform seed-crystal coatings, which are then intergrown into continuous membranes. Herein, we show a novel and simple floating particle coating method can give closely packed monolayers of zeolite nanosheets on nonporous or porous supports. The zeolite nanosheet monolayer is formed at the air–water interface in a conical Teflon trough. As the water in the trough is drained, the monolayer is deposited on a support placed below. Membranes prepared by gel-free secondary growth of the nanosheets deposited by this method show unprecedented ultra-selective performance for separation of para- from ortho-xylene (separation factor>10 000).Drum trenne, was sich ewig bindet: Eine neue Abscheidungsmethode für Monolagen, bei der eine konische, ablaufende Mulde zum Einsatz kommt, ermöglicht die Übertragung einer MFI-Nanoschicht von der Luft-Wasser-Grenzfläche auf einen porösen Träger. Die dichte Bedeckung mit Nanoschichtkeimen und anschließende Verwachsung ergeben eine dünne, ausgerichtete und defektarme Membran mit hoch selektiven Trenneigenschaften für Xylolisomere.
      PubDate: 2017-12-13T04:01:47.854241-05:
      DOI: 10.1002/ange.201708835
       
  • A Metal–Organic Framework with Exceptional Activity for C−H
           Bond Amination
    • Authors: Le Wang; Douglas W. Agnew, Xiao Yu, Joshua S. Figueroa, Seth M. Cohen
      Abstract: The development of catalysts capable of fast, robust C−H bond amination under mild conditions is an unrealized goal despite substantial progress in the field of C−H activation in recent years. A Mn-based metal–organic framework (CPF-5) is described that promotes the direct amination of C−H bonds with exceptional activity. CPF-5 is capable of functionalizing C−H bonds in an intermolecular fashion with unrivaled catalytic stability producing>105 turnovers.Ein Mn-basiertes MOF mit einem einzigartigen aktiven Zentrum katalysiert C-H-Aminierungen unter milden Reaktionsbedingungen. Der Katalysator zeigt eine außergewöhnliche Umsatzzahl von>120 000, knapp 4 Größenordnungen mehr als andere moderne C-H-Aminierungskatalysatoren.
      PubDate: 2017-12-13T04:01:33.058495-05:
      DOI: 10.1002/ange.201709420
       
  • Stephan Irle
    • PubDate: 2017-12-13T04:00:48.801628-05:
      DOI: 10.1002/ange.201712472
       
  • Frontispiz: Facile Supramolecular Processing of Carbon Nanotubes and
           Polymers for Electromechanical Sensors
    • Authors: Chae Bin Kim; Ki Beom Jeong, Beom Joo Yang, Jong-Won Song, Bon-Cheol Ku, Seunghyun Lee, Seoung-Ki Lee, Chiyoung Park
      Abstract: Supramolekulare Gele Ein supramolekulares nichtflüchtiges flüssiges Eutektikum bildet Gele beim Vermahlen mit Kohlenstoffnanoröhren. Dabei entstehen viskoelastische leitfähige Medien, die, wie S. Lee, S.-K. Lee und C. Park in ihrer Zuschrift auf S. 16398 zeigen, als selbstheilender elektromechanischer Sensor wirken können.
      PubDate: 2017-12-13T03:20:52.921769-05:
      DOI: 10.1002/ange.201785161
       
  • Dichotomy of Manganese Catalysis via Organometallic or Radical Mechanism:
           Stereodivergent Hydrosilylation of Alkynes
    • Authors: Congyang Wang; Xiaoxu Yang
      Abstract: Herein, we disclose the first manganese-catalyzed hydrosilylation of alkynes featuring diverse selectivities. The highly selective formation of E-products was achieved by using mononuclear MnBr(CO)5 with the arsenic ligand, AsPh3. On the contrary, the dinuclear catalyst Mn2(CO)10 together with LPO (dilauroyl peroxide) enabled the reversed generation of Z-products in good to excellent stereo- and regioselectivity. Such a way of controlling the reaction stereoselectivity is unprecedented and unique. Mechanistic experiments revealed the dichotomy of manganese catalysis via organometallic and radical pathways operating in the E- and Z-selective protocols respectively.
      PubDate: 2017-12-13T02:06:24.080988-05:
      DOI: 10.1002/ange.201710206
       
  • Co(II)-Based Metalloradical Activation of 2-(Diazomethyl)pyridines for
           Radical Transannulation and Cyclopropanation
    • Authors: Buddhadeb Chattopadhyay; Satyajit Roy, Sandip Kumar Das
      Abstract: A new catalytic method for the denitrogenative transannulation/cyclopropanation of in-situ generated 2-(diazomethyl)pyridines is described via a cobalt-catalyzed radical activation mechanism. The method has been developed by taking advantage of the inherent property of Co(III)-carbene radical intermediate. This is the first report for the denitrogenative transannulation/cyclopropanation via radical activation mechanism, which is supported by various control experiments. For synthetic application of this metalloradical approach, it has been showcased by the short total synthesis of ()-monomorine.
      PubDate: 2017-12-13T01:38:09.374727-05:
      DOI: 10.1002/ange.201711209
       
  • Surface Molding of Microscale Hydrogels with Microactuation Functionality
    • Authors: John J. Bowen; Mark A. Rose, Abhiteja Konda, Stephen A. Morin
      Abstract: This work describes the fabrication of numerous hydrogel microstructures, μ-gels, via a process called "surface molding"—chemically patterned elastomeric assembly substrates were used to organize and manipulate the geometry of liquid prepolymer microdroplets, which, following photo-initiated crosslinking, maintained the desired morphology. By adjusting the state of strain during the crosslinking process, a continua of structures could be created using one pattern. These arrays of μ-gels have stimuli-responsive properties that are directly applicable to actuation where the basis shape and array geometry of the μ-gels can be used to rationally generate microactuators with programmed motions. As a method, "surface molding," represents a powerful addition to the soft lithographic toolset that can be readily applied to the simultaneous synthesis of large numbers of geometrically and functionally distinct polymeric microstructures.
      PubDate: 2017-12-12T22:11:33.269068-05:
      DOI: 10.1002/ange.201710612
       
  • Selective C-H Halogenations with a Highly Fluorinated Manganese Porphyrin
    • Authors: Gang Li; Andrew Dilger, Peter Cheng, William Ewing, John T. Groves
      Abstract: Selective C-H functionalizations of aliphatic molecules remain a challenge in organic synthesis. While radical chain halogenations provide an efficient way to access many halogenated molecules, application of typical protocols to selectively halogenate electron-deficient and strained aliphatic molecules are rare. Herein, we report selective C-H chlorinations and fluorinations that use an electron-deficient manganese pentafluorophenyl porphyrin catalyst, Mn(TPFPP)Cl. This catalyst displays superior properties for aliphatic halogenations of recalcitrant, electron-deficient and strained substrates with unique regio- and stereoselectivity. In operando UV-vis analyses indicate that an oxoMn(V) species is responsible for hydrogen atom abstraction. The observed stereoselectivity results from steric interactions between the bulky porphyrin ligand and the intermediate substrate radical in the halogen rebound step.
      PubDate: 2017-12-12T22:08:02.549848-05:
      DOI: 10.1002/ange.201710676
       
  • Kinetic Dearomatization Strategy for an Expedient Biomimetic Route to the
           Bielschowskysin Skeleton.
    • Authors: Stephane Roche; Paul Scesa, Medhi Wangpaichitr, Niramol Savaraj, Lyndon West
      Abstract: Bielschowskysin (1), the flagship of the furanocembranoid-derived diterpene family has attracted attention from chemists owing to its intriguing and daunting polycyclic architecture and medicinal potential against lung cancer. The high level of functionalization of 1 poses a considerable challenge to synthesis. Herein a stereoselective furan dearomatization strategy of furanocembranoids was achieved via the intermediacy of chlorohydrins. The stereochemical course of the kinetic dearomatization was established and the C-3 configuration of the resulting exo-enol ether intermediates proved to be essential to complete the late-stage transannular [2+2] photocycloaddition. Overall, this biomimetic strategy starting from the natural product acerosolide (9) featured an unprecedented regio- and highly stereoselective furan dearomatization which enabled a rapid access to the pivotal exo-enol ethers en route to the intricate bielschowskyane skeleton.
      PubDate: 2017-12-12T15:05:52.660305-05:
      DOI: 10.1002/ange.201711780
       
  • Catalytic Asymmetric Synthesis of Trifluoromethylated γ-Amino Acids via
           Umpolung Addition of Trifluoromethyl Imines to Carboxylic Acid Derivatives
           
    • Authors: Bin Hu; Li Deng
      Abstract: Enabled by the discovery of novel cinchona alkaloid-derived chiral phase-transfer catalysts, highly chemo-, regio-, diastereo- and enantioselective umpolung additions of trifluoromethyl imines to α, β-unsaturated N-acylpyrroles were realized. With a catalyst loading ranging from 0.2 to 5.0 mol%, this new catalytic asymmetric transformation provides facile and high-yield access to highly enantiomerically enriched chiral trifluoromethylated γ-amino acids and γ-lactams.
      PubDate: 2017-12-12T14:07:00.245929-05:
      DOI: 10.1002/ange.201710915
       
  • Electron-Precise Actinide-Pnictide (An-Pn) Bonds Spanning Non-Metal,
           Metalloid, and Metal Combinations (An = U, Th; Pn = P, As, Sb, Bi)
    • Authors: Stephen Liddle; Thomas Rookes, Elizabeth Wildman, Gabor Balazs, Benedict Gardner, Ashley Wooles, Matthew Gregson, Floriana Tuna, Manfred Scheer
      Abstract: We report the synthesis and characterisation of the compounds [An(TrenDMBS){Pn(SiMe3)2}] and [An(TrenTIPS){Pn(SiMe3)2}] [TrenDMBS = N(CH2CH2NSiMe2But)3, An = U, Pn = P, As, Sb, Bi; An = Th, Pn = P, As; TrenTIPS = N(CH2CH2NSiPri3)3, An = U, Pn = P, As, Sb; An = Th, Pn = P, As, Sb]. The U-Sb and Th-Sb moieties are unprecedented examples of any kind of An-Sb molecular bond, and the U-Bi bond is the first electron-precise one. The Th-Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U-Bi complex is the heaviest electron-precise pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An-An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U-Pn bonds degrade by hemolytic bond cleavage, whereas the more redox robust thorium compounds engage in an acid-base/dehydrocoupling route.
      PubDate: 2017-12-12T13:36:07.510943-05:
      DOI: 10.1002/ange.201711824
       
  • Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using
           Diffusion-Limited Atomic Layer Deposition
    • Authors: Shufang Zhang; Bin Zhang, Haojie Liang, Yequn Liu, Yan Qiao, Yong Qin
      Abstract: The heterogenization of homogeneous metal complex catalysts has attracted great attention. Herein, we report the encapsulation of metal complexes into nanochannels of mesoporous materials by coating metal oxides at/near the pore entrance via diffusion-limited atomic layer deposition (ALD) to produce a "hollow plug". The pore size of the hollow plug is precisely controlled on the sub-nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA-15, SBA-16 and MCM-41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD-assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.
      PubDate: 2017-12-12T13:00:24.429821-05:
      DOI: 10.1002/ange.201712010
       
  • CO2 to terpenes - autotrophic and electroautotrophic α-humulene
           production with Cupriavidus necator
    • Authors: Thomas Krieg; Anne Sydow, Sonja Faust, Ina Huth, Dirk Holtmann
      Abstract: Herein, we demonstrate that CO2 can be converted by an engineered "Knallgas" bacterium (Cupriavidus necator) to the terpene α-humulene. Heterologous expression of the mevalonate pathway and α-humulene synthase resulted in a production of approx. 10 mg α-humulene per gram cell dry mass (CDM) under heterotrophic conditions. This first example of chemolithoautotrophic production of a terpene from carbon dioxide, hydrogen and oxygen is a promising starting point for the production of different high value terpene compounds from abundant and simple raw materials. Furthermore, the production system was used to produce 17 mg α-humulene per gram CDM from CO2 and electrical energy in microbial electrosynthesis (MES) mode. Due to the fact that the system can convert CO2 by using electrical energy from solar energy it opens a new route to artificial photosynthetic systems.
      PubDate: 2017-12-12T12:06:45.57524-05:0
      DOI: 10.1002/ange.201711302
       
  • pH resistant monodispersed polymer-lipid nanodiscs
    • Authors: Thirupathi Ravula; Nathaniel Z Hardin, Sudheer Ramadugu, Sarah J Cox, Ayyalusamy Ramamoorthy
      Abstract: Polymer lipid nanodiscs have provided an invaluable system for structural and functional studies of membrane proteins in their near-native environment. In spite of the recent advances in the development and usage of polymer lipid nanodisc systems, lack of control over size and poor tolerance to pH and divalent metal ions are major limitations for further applications. Here we report a facile modification of a low molecular weight styrene maleic acid copolymer to form monodispersed lipid bilayer nanodiscs that show ultra-stability towards a pH range of 2.5 to 10 and divalent metal ion concentration. The macro-nanodiscs (>20 nm diameter) show magnetic-alignment properties that can be exploited for high-resolution structural studies of membrane proteins using well-established solid-state NMR techniques. As demonstrated in this study, the new polymer, SMA-QA, is a robust membrane mimetic tool that offers significant advantages over currently reported nanodisc systems.
      PubDate: 2017-12-12T11:36:11.615612-05:
      DOI: 10.1002/ange.201712017
       
  • Distal Weak Coordination of Acetamides in Ruthenium(II)-Catalyzed
           C−H Activation Processes
    • Authors: Qingqing Bu; Torben Rogge, Vladislav Kotek, Lutz Ackermann
      Abstract: C−H activations with challenging arylacetamides were accomplished by versatile ruthenium(II) biscarboxylate catalysis. The distal C−H functionalization offers ample scope—including twofold oxidative C−H functionalizations and alkyne hydroarylations—through facile base-assisted internal electrophilic-type substitution (BIES) C−H ruthenation by weak O-coordination.Auf Distanz: Eine vielseitige RuII-katalysierte Methode für die distale C-H-Aktivierung schwach O-koordinierender Arylacetamide über einen sechsgliedrigen Ruthenacyclus wird vorgestellt. Die Reaktion ist für primäre, sekundäre und tertiäre Amide geeignet.
      PubDate: 2017-12-12T09:00:07.235472-05:
      DOI: 10.1002/ange.201711108
       
  • Ion–Solvent Complexes Promote Gas Evolution from Electrolytes on a
           Sodium Metal Anode
    • Authors: Xiang Chen; Xin Shen, Bo Li, Hong-Jie Peng, Xin-Bing Cheng, Bo-Quan Li, Xue-Qiang Zhang, Jia-Qi Huang, Qiang Zhang
      Abstract: Lithium and sodium metal batteries are considered as promising next-generation energy storage devices due to their ultrahigh energy densities. The high reactivity of alkali metal toward organic solvents and salts results in side reactions, which further lead to undesirable electrolyte depletion, cell failure, and evolution of flammable gas. Herein, first-principles calculations and in situ optical microscopy are used to study the mechanism of organic electrolyte decomposition and gas evolution on a sodium metal anode. Once complexed with sodium ions, solvent molecules show a reduced LUMO, which facilitates the electrolyte decomposition and gas evolution. Such a general mechanism is also applicable to lithium and other metal anodes. We uncover the critical role of ion–solvent complexation for the stability of alkali metal anodes, reveal the mechanism of electrolyte gassing, and provide a mechanistic guidance to electrolyte and lithium/sodium anode design for safe rechargeable batteries.Sicher wiederaufladbare Batterien: Ion-Solvens-Komplexe in Alkalimetallbatterien wurden durch First-Principles-Rechnungen und optische In-situ-Mikroskopie untersucht. Die Komplexe weisen niedrige LUMOs auf und können an einer Alkalimetallanode leicht reduziert werden. Ein allgemeiner Mechanismus für die Zersetzung von organischen Elektrolyten und die Gasentwicklung wurde entdeckt.
      PubDate: 2017-12-12T08:59:40.929886-05:
      DOI: 10.1002/ange.201711552
       
  • A General Synthesis of Porous Carbon Nitride Films with Tunable Surface
           Area and Photophysical Properties
    • Authors: Guiming Peng; Lidan Xing, Jesús Barrio, Michael Volokh, Menny Shalom
      Abstract: Graphitic carbon nitride (g-CN) has emerged as a promising material for energy-related applications. However, exploitation of g-CN in practical devices is still limited owing to difficulties in fabricating g-CN films with adjustable properties and high surface area. A general and simple pathway is reported to grow highly porous and large-scale g-CN films with controllable chemical and photophysical properties on various substrates using the doctor blade technique. The growth of g-CN films, ascribed to the formation of a supramolecular paste, comprises g-CN monomers in ethylene glycol, which can be cast on different substrates. The g-CN composition, porosity, and optical properties can be tuned by the design of the supramolecular paste, which upon calcination results in a continuous porous g-CN network. The strength of the porous structure is demonstrated by high electrochemically active surface area, excellent dye adsorption and photoelectrochemical and photodegradation properties.Auf einfache Weise zu hoch porösen ausgedehnten Kohlenstoffnitrid(g-CN)-Gerüsten auf verschiedenen Substraten mithilfe einer Rakel-Technik: g-CN-Filme mit großer elektrochemisch aktiver Oberfläche, ausgezeichneter Farbstoffadsorption sowie guten photoelektrochemischen Eigenschaften und guter Photobeständigkeit werden erhalten, die Perspektiven für (photo)elektronische Anwendungen eröffnen.
      PubDate: 2017-12-12T08:59:09.39454-05:0
      DOI: 10.1002/ange.201711669
       
  • The Chemical Record Lectureship für Michael Grätzel / Baizer-Preis für
           Flavio Maran / Kurz gemeldet
    • PubDate: 2017-12-12T08:58:04.595073-05:
      DOI: 10.1002/ange.201712406
       
  • Three-Component Enantioselective Cyclization Reaction Catalyzed by an
           Unnatural Amino Acid Derivative
    • Authors: María de Gracia Retamosa; Andrea Ruiz-Olalla, Tamara Bello, Abel de Cózar, Fernando P. Cossío
      Abstract: A new diastereo- and enantioselective three-component cyclization reaction is described. The reaction takes place between a ketone, a carboxylic acid, and a nitroalkene to yield a bicyclic octahydro-2H-indol-2-one scaffold possessing three chiral centers. This reaction involves a rearrangement of the nitro group under simple thermal conditions. A plausible mechanism is proposed for this new reaction based on DFT calculations and isotope-labeling experiments. A new concise enantioselective synthesis of the alkaloid (+)-pancracine is presented as an example of the potential of this novel organocatalytic cyclization reaction in the synthesis of natural products.Bicyclische γ-Lactame mit drei neuen Chiralitätszentren werden mit dem hochfunktionalisierten nichtnatürlichen l-Prolin-Ester XL als Katalysator aufgebaut. Die beschriebene Reaktion ist ohne Vorbild in der Organokatalyse, Enzym- oder Organometallchemie und bietet sich für die Synthese komplexer Naturstoffe an.
      PubDate: 2017-12-12T08:53:56.422155-05:
      DOI: 10.1002/ange.201708952
       
  • Can Coordination-Driven Supramolecular Self-Assembly Reactions Be
           Conducted from Fully Aliphatic Linkers'
    • Authors: Mehdi Elsayed Moussa; Sloane Evariste, Barbara Krämer, Régis Réau, Manfred Scheer, Christophe Lescop
      Abstract: The reaction between a preassembled CuI bimetallic molecular clip with a short intermetallic distance and a series of fully aliphatic cyano-capped ditopic linkers with increasing lengths was investigated. It is shown that, depending on the length of the ditopic linkers, the rational design of unprecedented supramolecular compact metallacycles containing fully aliphatic walls is possible. The specific preorganized molecular arrangement of the molecular clip used favors stabilizing interlinker London dispersion interactions, which allow, as the length of the linkers increases, the selective formation of discrete compact metallacycles at the expense of 1D coordination polymers. The generalizability of this approach was demonstrated by the reaction of fully aliphatic cyano-capped linkers with two other types of preassembled CuI bimetallic molecular clips that also had short intermetallic distances.CN-terminierte aliphatische Linker bilden supramolekulare Anordnungen mit vororganisierten CuI-Dimeren mit kleinen intermetallischen Abständen. Unterschiedliche Arten von Metallacyclen und 1D-Koordinationspolymeren werden abhängig von der Länge der Linker erhalten. London-Dispersionswechselwirkungen zwischen den Methyleneinheiten ermöglichen die selektive Selbstorganisation solcher Linker mit ungerichteten Rückgratstrukturen.
      PubDate: 2017-12-12T08:53:26.909918-05:
      DOI: 10.1002/ange.201709119
       
  • Asymmetric Synthesis of 2H-Azirines with a Tetrasubstituted Stereocenter
           by Enantioselective Ring Contraction of Isoxazoles
    • Authors: Kazuhiro Okamoto; Atsushi Nanya, Akira Eguchi, Kouichi Ohe
      Abstract: Highly strained 2H-azirines with a tetrasubstituted stereocenter were synthesized by the enantioselective isomerization of isoxazoles with a chiral diene–rhodium catalyst system. The effect of ligands and the coordination behavior support the proposed catalytic cycle in which the coordination site is fixed in favor of efficient enantiodiscrimination by a bulky substituent of the ligand. In silico studies also support the existence of a rhodium–imido complex as a key intermediate for enantiodiscrimination.Mit Spannung erwartet: Hoch gespannte 2H-Azirine mit tetrasubstituierten Stereozentren wurden mit hoher Enantioselektivität durch die N-O-bindungsspaltende Isomerisierung von Isoxazolen in Gegenwart eines chiralen Dien-Rhodium-Katalysators synthetisiert (siehe Schema). Die asymmetrische Ringverengung läuft unter milden Bedingungen ab und liefert 2-Alkoxycarbonyl-2H-azirine mit diversen Substituenten, einschließlich Halogengruppen.
      PubDate: 2017-12-12T08:48:17.687246-05:
      DOI: 10.1002/ange.201710920
       
  • A Six-Oxidase Cascade for Tandem C−H Bond Activation Revealed by
           Reconstitution of Bicyclomycin Biosynthesis
    • Authors: Song Meng; Wei Han, Juan Zhao, Xiao-Hong Jian, Hai-Xue Pan, Gong-Li Tang
      Abstract: As a commercial antibiotic, bicyclomycin (BCM) is currently the only known natural product targeting the transcription termination factor rho. It belongs to a family of highly functionalized diketopiperazine (DKP) alkaloids and bears a unique O-bridged bicyclo[4.2.2]piperazinedione ring system, a C1 triol, and terminal exo-methylene groups. We have identified and characterized the BCM biosynthetic pathway by heterologous biotransformations, in vitro biochemical assays, and one-pot enzymatic synthesis. A tRNA-dependent cyclodipeptide synthase guides the heterodimerization of leucine and isoleucine to afford the DKP precursor; subsequently, six redox enzymes, including five α-ketoglutarate/Fe2+-dependent dioxygenases and one cytochrome P450 monooxygenase, regio- and stereoselectively install four hydroxy groups (primary, secondary, and two tertiary), an exo-methylene moiety, and a medium-sized bridged ring through the functionalization of eight unactivated C−H bonds.Eine enzymatische Analyse der Biosynthese des Antibiotikums Bicyclomycin ergab, dass die Reaktion von Leu und Ile zu einer Diketopiperazin-Vorstufe von einer tRNA-abhängigen Cyclodipeptidsynthase katalysiert wird. Daraufhin aktivieren sechs Redox-Enzyme acht nicht-aktivierte C-H-Bindungen durch regio- und stereoselektive Hydroxylierung, Alkenylierung, Heterocyclisierung und Entsättigung/Epoxidierung.
      PubDate: 2017-12-12T08:46:45.211828-05:
      DOI: 10.1002/ange.201710529
       
  • The Catalytic Asymmetric Mukaiyama-Michael Reaction of Silyl Ketene
           Acetals with α,β-Unsaturated Methyl Esters
    • Authors: Benjamin List; Tim Gatzenmeier, Philip S. J. Kaib, Julia B. Lingnau, Richard Goddard
      Abstract: α,β-Unsaturated esters are readily available but challenging substrates to activate in asymmetric catalysis. We now describe an efficient, general, and highly enantioselective Mukaiyama-Michael reaction of silyl ketene acetals with α,β-unsaturated methyl esters, catalyzed by a silylium imidodiphosphorimidate (IDPi) Lewis acid.
      PubDate: 2017-12-12T08:37:56.117933-05:
      DOI: 10.1002/ange.201712088
       
  • Introducing Chiral Bifunctional Phosphine-Carboxylate Ligands for
           Palladium(0)-Catalyzed Enantioselective C-H Arylation
    • Authors: Lei Yang; Markus Neuburger, Olivier Baudoin
      Abstract: Previous enantioselective Pd0-catalyzed C-H activation reactions proceeding via the concerted metalation-deprotonation mechanism employed either a chiral ancillary ligand, a chiral base, or a bimolecular mixture thereof. This study describes the development of new chiral bifunctional ligands based on a binaphthyl scaffold and incorporating both a phosphine and a carboxylic acid moiety. The optimal ligand provided high yields and enantioselectivities for the desymmetrizing C(sp2)-H arylation leading to 5,6-dihydrophenanthridines, whereas the corresponding monofunctional ligands showed low enantioselectivities. The bifunctional system proved applicable to a range of substituted dihydrophenanthridines, and allowed the parallel kinetic resolution of racemic substrates.
      PubDate: 2017-12-12T06:03:46.524712-05:
      DOI: 10.1002/ange.201712061
       
  • Enantioselective Synthesis of N,S-Acetals by an Oxidative Pummerer-Type
           Transformation using Phase-Transfer Catalysis
    • Authors: Souvagya Biswas; Koji Kubota, Manuel Orlandi, Mathias Turberg, Dillon H. Miles, Matthew S. Sigman, F. Dean Toste
      Abstract: Reported is the first enantioselective oxidative Pummerer-type transformation using phase-transfer catalysis to deliver enantioenriched sulfur-bearing heterocycles. This reaction includes the direct oxidation of sulfides to a thionium intermediate, followed by an asymmetric intramolecular nucleophilic addition to form chiral cyclic N,S-acetals with moderate to high enantioselectivites. Deuterium-labelling experiments were performed to identify the stereodiscrimination step of this process. Further analysis of the reaction transition states, by means of multidimensional correlations and DFT calculations, highlight the existence of a set of weak noncovalent interactions between the catalyst and substrate that govern the enantioselectivity of the reaction.CAPiTaler Fortschritt: Eine katalytische enantioselektive Pummerer-Umwandlung setzt auf Phasentransferkatalyse mit einem chiralen Anion („chiral-anion phase-transfer catalysis”, CAPT). Auf diese Weise wurden vielfältige enantiomerenangereicherte cyclische N,S-Acetale aufgebaut, die zuvor nur schwer zugänglich waren.
      PubDate: 2017-12-12T04:32:48.399232-05:
      DOI: 10.1002/ange.201711277
       
  • Highly Branched Polymers with Layered Structures that Mimic
           Light-Harvesting Processes
    • Authors: Yi Shi; Xiaosong Cao, Daqiao Hu, Haifeng Gao
      Abstract: Hyperbranched polymers (HBPs) with decorated donor and acceptor chromophores in different domains were constructed to demonstrate the function of light harvesting in a polymeric nanostructure. Taking advantage of our recently developed chain-growth copper-catalyzed azide–alkyne cycloaddition polymerization, two structural parameters in the HBPs, for example, the molar ratio of the acceptor Coumarin 343 in the core to the donor Coumarin 2 on the periphery, and the average distance between these two layers, could be independently varied in a one-pot synthesis. The results demonstrated an efficient energy transfer from the excited Coumarin 2 to the ground-state Coumarin 343 in the core, with the efficiency of the energy transfer reaching as high as 98 %. The excited Coumarin 343, after receiving energy from donor Coumarin 2 emitted higher fluorescence intensity than when directly excited, indicating an observed light concentration effect from the periphery dye to the central dye in one polymer structure.Hochverzweigte Polymere (HBPs) mit Donor- (Cumarin 2, C2) und Akzeptor-Chromophoren (Cumarin 343, C343) in verschiedenen Domänen wurden durch Kettenwachstumspolymerisation über kupferkatalysierte Azid-Alkin-Cycloaddition (CuAACP) aufgebaut, um Lichtsammelverhalten für eine Polymernanostruktur zu demonstrieren. Der Energietransfer erreichte Effizienzen bis 98 %.
      PubDate: 2017-12-12T04:31:53.581901-05:
      DOI: 10.1002/ange.201709492
       
  • NMR mit Tischgeräten und deren Anwendungen von der Materialwissenschaft
           bis zur organischen Chemie
    • Authors: Bernhard Blümich; Kawarpal Singh
      Abstract: Die NMR-Spektroskopie ist eine unverzichtbare Analysemethode. Bis vor kurzem erforderten die Geräte viel Platz, waren teuer und schwer zu bedienen. Dies hat sich mit der Einführung kompakter NMR-Spektrometer geändert, die sich für die Analyse kleiner Moleküle auf der Laborbank eignen. Solche Spektrometer sind mit Permanentmagneten für 1H-NMR-Frequenzen zwischen 40 und 80 MHz ausgestattet. Erst seit wenigen Jahren gibt es kleine Permanentmagnete mit homogenen Magnetfeldern für hochaufgelöste Spektroskopie. Tischgeräte mit inhomogenen Feldern werden schon seit 40 Jahren zur Charakterisierung von Lebensmitteln und Materialien über Relaxations- und Diffusionsmessungen genutzt. Ähnliche NMR-Geräte messen diese Parameter im Streufeld außerhalb des Magneten. Sie werden zur Untersuchung von Bohrlochwänden in Ölquellen sowie für zerstörungsfreie Analysenverwendet. Der gegenwärtige Stand von NMR-Spektroskopie, -Bildgebung und -Relaxometrie wird hier anhand repräsentativer Beispiele beschrieben.Als leistungsfähiges Analyseverfahren wird die NMR geschätzt, weniger aber für die Größe und Kosten der benötigten Spektrometer mit ihren sperrigen supraleitenden Magneten. In den vergangenen Jahren wurden kompakte Tischgeräte und sogar tragbare NMR-Instrumente für die Analyse kleiner Moleküle und zerstörungsfreie Materialtests entwickelt. Der Stand der Dinge bei kompakter NMR wird anhand von ausgewählten Beispielen veranschaulicht.
      PubDate: 2017-12-12T04:21:45.688854-05:
      DOI: 10.1002/ange.201707084
       
  • Computerchemie: das Schicksal aktueller Methoden und zukünftige
           Herausforderungen
    • Authors: Stefan Grimme; Peter R. Schreiner
      Abstract: „Wohin des Weges'” ist die zugrundeliegende Frage zu den vielleicht vorhersehbaren Entwicklungen in der Computerchemie. Während diese noch junge Disziplin praktisch die Chemie schon in Gänze durchdrungen hat, werden die schnellen Entwicklungen und Hard- und Software diesen Trend noch verstärken.
      PubDate: 2017-12-12T04:21:33.9469-05:00
      DOI: 10.1002/ange.201709943
       
  • Zur Nutzung von Polyelektrolyten und Polymediatoren in der organischen
           Elektrosynthese
    • Authors: Benjamin Schille; Niels Ole Giltzau, Robert Francke
      Abstract: Obwohl die organische Elektrosynthese im Allgemeinen als nachhaltige Methode anerkannt ist, stellt hier die Notwendigkeit zur Verwendung von Leitsalzen einen großen Nachteil dar. Zudem verursachen die vielfach eingesetzten Mediatoren ein weiteres Trennproblem. Vor diesem Hintergrund haben wir die Möglichkeit zur Verwendung von löslichen Polyelektrolyten und Polymediatoren untersucht, wobei uns die TEMPO-vermittelte Alkoholoxidation als Modellreaktion diente. Unsere Zyklovoltammetriestudien belegen, dass TEMPO-modifizierte Polymere bezüglich der Reaktionskinetik durchaus gegenüber dem molekular-definierten TEMPO konkurrenzfähig sind. Auch im präparativen Maßstab zeigt sich unser polymerbasierter Ansatz als verlässlich und effizient, wobei die Abtrennung des Mediators und des Leitsalzes in einem einzigen Schritt mittels Membranfiltration gelingt. Zudem konnten wir zeigen, dass beide Komponenten recyclingfähig sind.Kopplung von Elektrosynthese und Membranfiltration: Die Verknüpfung von TEMPO-Mediator und Leitsalz mit löslichen Polymeren ermöglicht eine selektive Umsetzung von Alkoholen zu Carbonylverbindungen und erlaubt die Rückgewinnung des Mediators und des Salzes über Membranverfahren.
      PubDate: 2017-12-12T04:16:57.751343-05:
      DOI: 10.1002/ange.201710659
       
  • Macrolide Synthesis trough Intramolecular Oxidative Cross-Coupling of
           Alkenes
    • Authors: Bing Jiang; Meng Zhao, Shu-Sen Li, Yun-He Xu, Teck-Peng Loh
      Abstract: A RhIII-catalyzed intramolecular oxidative cross-coupling between double bonds for the synthesis of macrolides is described. Under the optimized reaction conditions, macrocycles containing a diene moiety can be formed in reasonable yields and with excellent chemo- and stereoselectivity. This method provides an efficient approach to synthesize macrocyclic compounds containing a 1,3-conjugated diene structure.Doppelpack: Eine RhIII-katalysierte intramolekulare oxidative Kreuzkupplung zwischen zwei Doppelbindungen kam in der Makrolid-Synthese zum Einsatz. Unter den optimierten Bedingungen wurden Makrocyclen mit konjugiertem 1,3-Dienmotiv in befriedigenden Ausbeuten mit ausgezeichneter Chemo- und Stereoselektivität erhalten.
      PubDate: 2017-12-12T04:16:52.068578-05:
      DOI: 10.1002/ange.201710601
       
  • Visualization of Heterogeneous Oxygen Storage Behavior in Three-Way
           Catalyst Pt/Ce2Zr2Ox Particles by Hard X-ray Spectro-Ptychography
    • Authors: Makoto Hirose; Nozomu Ishiguro, Kei Shimomura, Nicolas Burdet, Hirosuke Matsui, Mizuki Tada, Yukio Takahashi
      Abstract: The cerium density and valence in micrometer-size Pt/Ce2Zr2Ox (x=7-8) three-way catalyst particles were successfully mapped by hard X-ray spectro-ptychography (ptychographic-XAFS). The analysis of correlation between the Ce density and valence in ptychographic-XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce2Zr2Ox particles. Ptychographic-XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts.
      PubDate: 2017-12-11T23:51:52.3027-05:00
      DOI: 10.1002/ange.201710798
       
  • Interfacial nanoprecipitation toward stable and responsive microbubbles
           and their use as a resuscitative fluid
    • Authors: Yifeng Peng; Raymond Seekell, Alexis Cole, Jemima Lamothe, Andrew Lock, Sarah van den Bosch, Xiaoqi Tang, John Kheir, Brian Polizzotti
      Abstract: : We report a new approach to prepare stable microbubbles (MBs) via interfacial nanoprecipitation of bioabsorbable polymers at air/liquid interface. This facile method offers robust control over MBs morphology and chemo-physical properties by simple chemical modifications. This approach is amenable to large-scale manufacturing, and is useful to develop functional MBs for advanced biomedical applications. To demonstrate this, we created a MB-based intravenous oxygen carrier that undergoes pH-triggered self-elimination. Intravenous injection of past MBs increase the risk of pulmonary vascular obstruction. However, we show, for the first time, that our current design supersedes previous MBs, as they 1) yielded no evidence of acute risks in rodents, and 2) improved the survival in a disease model of asphyxial cardiac arrest (from 0 to 100%), a condition that affects more than 100,000 in-hospital patients, carrying a ~90% mortality.
      PubDate: 2017-12-11T21:50:37.613479-05:
      DOI: 10.1002/ange.201711839
       
  • Emissive synthetic cofactors: enzymatic interconversions of tzA analogues
           of ATP, NAD+, NADH, NADP+ and NADPH
    • Authors: Yitzhak Tor; François Hallé, Andrea Fin, Alexander R Rovira
      Abstract: A series of enzymatic transformations, which generate visibly emissive isofunctional cofactors based on an isothiazolo[4,3-d]pyrimidine analogue of adenosine (tzA), is described. Nicotinamide adenylyl transferase condenses nicotinamide mononucleotide and tzATP to yield NtzAD+, which can be enzymatically phosphorylated by NAD+ kinase and ATP or tzATP to the corresponding NtzADP+. The latter can be engaged in NADP-specific coupled enzymatic transformations involving conversion to NtzADPH by glucose-6-phosphate dehydrogenase and reoxidation to NtzADP+ by glutathione reductase. The NtzADP+/NtzADPH cycle can be monitored in real time by fluorescence spectroscopy.
      PubDate: 2017-12-11T12:51:17.567007-05:
      DOI: 10.1002/ange.201711935
       
  • Transition-Metal-Catalyzed Selective Functionalization of C(sp3)-H Bonds
           in Natural Products
    • Authors: Rashad R Karimov; John F. Hartwig
      Abstract: Direct functionalization of natural products is important for studying structure-activity and structure-property relationships of these molecules. Recent advances in transition-metal-catalyzed functionalizations of C(sp3)-H bonds, the most abundant yet inert bonds in natural products, have been shown to create natural product derivatives selectively. Strategies to achieve such transformation are reviewed.
      PubDate: 2017-12-11T12:50:46.201822-05:
      DOI: 10.1002/ange.201710330
       
  • A bioresistant nitroxide spin label for in-cell EPR spectroscopy: in vitro
           and in oocytes protein structural dynamics studies.
    • Authors: Ganesan Karthikeyan; Alessio Bonucci, Gilles Casano, Guillaume Gerbaud, Sébastien Abel, Virginie Thomé, Laurent Kodjabachian, Axel Magalon, Bruno Guigliarelli, Valérie Belle, Olivier Ouari, Elisabetta Mileo
      Abstract: Approaching proteins structural dynamics and protein-protein interactions in the cellular environment is a fundamental challenge. Due to its absolute sensitivity and to its selectivity to paramagnetic species, Site-Directed Spin Labeling (SDSL) combined with Electron Paramagnetic Resonance (EPR) has the potential to evolve into an efficient method to follow conformational changes in proteins directly inside cells. Until now, the use of nitroxyde-based spin labels for in-cell studies has represented a major hurdle because of their short persistence in the cellular context. In this work we present the design and synthesis of the first maleimido-proxyl-based spin label (M-TETPO) resistant towards reduction and being efficient to probe protein dynamics by continuous wave and pulsed EPR. In particular, the extended lifetime of M-TETPO enabled the study of structural features of a chaperone in the absence and presence of its binding partner at endogenous concentration directly inside cells.
      PubDate: 2017-12-11T11:20:37.524643-05:
      DOI: 10.1002/ange.201710184
       
  • Building Organic/Inorganic Hybrid Interphases for Fast Interfacial
           Transport in Rechargeable Metal Batteries
    • Authors: Qing Zhao; Zhengyuan Tu, Shuya Wei, Kaihang Zhang, Snehashis Choudhury, Xiaotun Liu, Lynden Archer
      Abstract: We report a facile, in-situ synthesis to create durable, hybrid Solid-electrolyte interphases (SEI) on metal anodes. Composed of Si-interlinked molecules that host LiCl salt, the hybrid SEI exhibit fast charge-transfer kinetics and high exchange current densities. By means of electrochemical analysis and direct optical visualization of Li and Na deposition in symmetric Li/Li and Na/Na cells, it is further shown that the hybrid SEI enables excellent morphological control at relatively high current densities (3-5 mA/cm2) and even for notoriously unstable Na metal anodes. We investigate benefits of the fast interfacial transport attributes of the SEI in Li-S cells. It is found that stable electrochemical cycling is achieved in galvanostatic studies at rates as high as 2 C. Our work provides a promising path towards rational design of multi-functional, elastic SEI that overcomes the most serious limitations of spontaneously formed interphases on high-capacity metal anodes.
      PubDate: 2017-12-11T10:21:20.908373-05:
      DOI: 10.1002/ange.201711598
       
  • Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3−
           (A=As, Sb, Bi) Complexes
    • Authors: Jia-Qi Wang; Chaoxian Chi, Han-Shi Hu, Luyan Meng, Mingbiao Luo, Jun Li, Mingfei Zhou
      Abstract: Heteronuclear transition-metal–main-group-element carbonyl complexes of AsFe(CO)3−, SbFe(CO)3−, and BiFe(CO)3− were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass-selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)3−. Chemical bonding analyses on the whole series of AFe(CO)3− (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp–p) type of transition-metal–main-group-element multiple bonding. The σ-type three-orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)3− (A=As, Sb, Bi) complexes.Aller guten Bindungen sind drei: IR-Photodissoziationsspektroskopie und quantenchemische Rechnungen zu den Komplexen AFe(CO)3− (A=As, Sb, Bi) deuten auf das Vorliegen einer A-Fe-Dreifachbindung vom (dp–p)-Typ hin.
      PubDate: 2017-12-11T09:30:49.214425-05:
      DOI: 10.1002/ange.201709875
       
  • Magnetic Actuation of Drops and Liquid Marbles Using a Deformable
           Paramagnetic Liquid Substrate
    • Authors: Jacopo Vialetto; Masayuki Hayakawa, Nikita Kavokine, Masahiro Takinoue, Subramanyan Namboodiri Varanakkottu, Sergii Rudiuk, Manos Anyfantakis, Mathieu Morel, Damien Baigl
      Abstract: The magnetic actuation of deposited drops has mainly relied on volume forces exerted on the liquid to be transported, which is poorly efficient with conventional diamagnetic liquids such as water and oil, unless magnetosensitive particles are added. Herein, we describe a new and additive-free way to magnetically control the motion of discrete liquid entities. Our strategy consists of using a paramagnetic liquid as a deformable substrate to direct, using a magnet, the motion of various floating liquid entities, ranging from naked drops to liquid marbles. A broad variety of liquids, including diamagnetic (water, oil) and nonmagnetic ones, can be efficiently transported using the moderate magnetic field (ca. 50 mT) produced by a small permanent magnet. Complex trajectories can be achieved in a reliable manner and multiplexing potential is demonstrated through on-demand drop fusion. Our paramagnetofluidic method advantageously works without any complex equipment or electric power, in phase with the necessary development of robust and low-cost analytical and diagnostic fluidic devices.Murmelspiel: Kleine Magnete treiben die Bewegung schwimmender Tröpfchen und Flüssigkeitsmurmeln aus Wasser, Öl oder nichtmagnetischen Fluiden an, ohne dass magnetisch responsive Partikel erforderlich sind. Digitale Mikrofluidikoperationen wie der Transport entlang komplizierter Trajektorien und die programmierte Verschmelzung von Tröpfchen werden demonstriert.
      PubDate: 2017-12-11T09:27:48.777002-05:
      DOI: 10.1002/ange.201710668
       
  • Light-driven C-H Oxygenation of Methane into Methanol and Formic Acid by
           Molecular Oxygen Using Perfluorinated Solvent
    • Authors: Kei Ohkubo; Kensaku Hirose
      Abstract: Chlorine dioxide radical (ClO2*) was found to act as an efficient oxidizing agent in the aerobic oxygenation of methane to methanol and formic acid under photoirradiation. Photochemical oxygenation of methane occurred in a two-phase system comprising perfluorohexane and water under ambient conditions (298 K, 1 atm). The yields of methanol and formic acid were 14% and 85%, respectively, with a methane conversion of 99% without formation of the further oxygenated products such as CO2 and CO. Ethane was also photochemically converted into ethanol (19%) and acetic acid (78%). The methane oxygenation is initiated by the photochemical Cl-O bond cleavage of ClO2* to generate Cl* and O2. The produced Cl* reacts with CH4 to form a methyl radical (CH3*). Finally, the oxygenated products such as methanol and formic acid were given by the radical chain reaction. A fluorous solvent plays an important role of inhibiting the deactivation of reactive radical species such as Cl* and CH3*.
      PubDate: 2017-12-11T08:22:15.627843-05:
      DOI: 10.1002/ange.201710945
       
  • Copper-Catalyzed Enantioselective Markovnikov Protoboration of α-Olefins
           Enabled by a Buttressed NHC Ligand
    • Authors: Yuan Cai; Xin-Tuo Yang, Shuo-Qing Zhang, Feng Li, Yu-Qing Li, Lin-Xin Ruan, Xin Hong, Shi-Liang Shi
      Abstract: We report herein a highly enantioselective copper-catalyzed Markovnikov protoboration of unactivated terminal alkenes. A variety of simple and abundant feedstock α-olefins bearing a diverse array of functional groups and heterocyclic substituents can be applied in this process, which proceeds under mild conditions at ambient temperature to provide expedient access to enantioenriched alkylboronic esters in good regioselectivity and with excellent enantiocontrol. Critical to the success of the protocol was the development and application of a novel, sterically hindered N-heterocyclic carbene, (R,R,R,R)-ANIPE, as the ligand for copper.
      PubDate: 2017-12-11T07:53:08.99635-05:0
      DOI: 10.1002/ange.201711229
       
  • ortho-Directing Chromium Arene Complexes as Efficient Mediators for
           Enantiospecific sp2-sp3 Cross-Coupling Reactions
    • Authors: Raphael Bigler; Varinder Kumar Aggarwal
      Abstract: A new strategy for the coupling of a broad scope of electronically diverse aromatics to boronic esters is reported. The coupling sequence, which relies on the directed ortho-lithiation of chromium arene complexes followed by boronate formation and oxidation, occurs with complete ortho-selectivity and enantiospecificity to give the coupling products in excellent yields and with high functional group tolerance. An intermediate chromium arene boronate complex was characterized by X-ray, NMR and IR to elucidate the reaction mechanism.
      PubDate: 2017-12-11T05:27:09.901896-05:
      DOI: 10.1002/ange.201711816
       
  • Magnetic Actuation of Drops and Liquid Marbles Using a Deformable
           Paramagnetic Liquid Substrate
    • Authors: Jacopo Vialetto; Masayuki Hayakawa, Nikita Kavokine, Masahiro Takinoue, Subramanyan Namboodiri Varanakkottu, Sergii Rudiuk, Manos Anyfantakis, Mathieu Morel, Damien Baigl
      Abstract: Wie ein Brunnen, aus dem Wasser abfließt, so ermöglicht auch die lokale Deformation eines paramagnetischen Substrats mit einem Magneten einen gravitationsgetriebenen Flüssigkeitstransport. Dieses Phänomen beschreiben D. Baigl et al. in ihrer Zuschrift (
      DOI : 10.1002/ange.201710668) und auf dem Titelbild schematisch anhand der Deformation des Texts, wobei die „i”-Punkte für manipulierte Tröpfchen und Flüssigkeitsmurmeln stehen. Die Methode erfordert keinerlei magnetisch responsiven Partikeln und ist für die meisten Flüssigkeiten geeignet, etwa für Wasser und Öl.
      PubDate: 2017-12-11T05:02:48.05414-05:0
       
  • CO oxidation on metal-supported monolayer oxide films: Do we know which
           phase (interface) is active'
    • Authors: Ke Zhang; Linfei Li, Shamil Shaikhutdinov, Hans-Joachim Freund
      Abstract: Ultrathin ("monolayer") films of transition metal oxides grown on metal substrates have recently received considerable attention as promising catalytic materials, in particular for low-temperature CO oxidation. The reaction rate on such systems often increases when the film only partially covers the support, and the effect is commonly attributed to the formation of active sites at the metal/oxide boundary. By studying the structure and reactivity of FeO(111) films on Pt(111), here we show that, independently of the film coverage, CO oxidation takes place at the interface between reduced and oxidized phases in the oxide film formed under reaction conditions. The promotional role of a metal support is to ease formation of the reduced phase via reaction between CO adsorbed on metal and oxygen at the oxide island edge.
      PubDate: 2017-12-11T04:57:26.577795-05:
      DOI: 10.1002/ange.201710934
       
  • Enantio- and Diastereoselective Cyclopropanation of 1-Alkenylboronates:
           Synthesis of 1-boryl-2,3-disubstituted Cyclopropanes
    • Authors: Pedro J. Pérez; Javier Carreras, Ana Caballero
      Abstract: A novel, highly enantio- and diastereoselective synthesis of 1-boryl-2,3-disubstituted cyclopropanes has been developed by means of the cyclopropanation of alkenylboronates with ethyl diazoacetate in the presence of catalytic amounts of a chiral copper-(I) complex. The products can also be directly accessed from alkynes through an operationally simple sequential hydroboration-cyclopropanation protocol. The resulting enantioenriched 1-boryl-2,3-disubstituted-cyclopropanes are versatile synthetic intermediates through further transformations at the carbon-boron bonds
      PubDate: 2017-12-11T03:51:15.2264-05:00
      DOI: 10.1002/ange.201710415
       
  • Thioketone Directed Palladium(II)-Catalyzed C-H Arylation of Ferrocenes
           with Aryl Boronic Acids
    • Authors: Shuli You; Zhong-Jian Cai, Chen-Xu Liu, Qing Gu
      Abstract: A palladium(II)-catalyzed thioketone-chelation-assisted C-H direct arylation of ferrocenes is described. With thioketone as an efficient directing group, various mono- and di-aryl-substituted thiocarbonylferrocenes were obtained via Pd-catalyzed C-H direct functionalization reaction in high yields under mild and base-free conditions. Furthermore, the arylated thiocarbonylferrocene could undergo diverse transformations.
      PubDate: 2017-12-11T03:21:39.809759-05:
      DOI: 10.1002/ange.201711451
       
  • Dicarboxylic Acid Separation by Dynamic and Size-Matched Recognition in
           Solution and in the Solid State
    • Authors: Pierangelo Metrangolo; giancarlo terraneo, giuseppe resnati, tullio pilati, vijith kumar, alceo macchioni, gianluca ciancaleoni
      Abstract: Bis(trimethylammonium) alkane diiodides dynamically encapsulate dicarboxylic acids through intermolecular hydrogen bonds between the hosts' I- anions and the guests' carboxylic OH groups. A selective recognition is realized when the size of the I-∙∙∙HOOC-(CH2/CF2)n-COOH∙∙∙I- superanion matches the dication alkyl chain length. Dynamic recognition is demonstrated also in solution, where the presence of the size-matching organic salt boosts acid solubility profile thus allowing efficient mixture separation.
      PubDate: 2017-12-10T21:51:54.26273-05:0
      DOI: 10.1002/ange.201711822
       
  • Photocatalytic Aerobic Phosphatation of Alkenes
    • Authors: Alexander Breder; Christian Depken, Felix Krätzschmar, Rene Rieger, Katharina Rode
      Abstract: A catalytic regime for the direct phosphatation of simple, non-polarized alkenes, using ordinary, non-activated phosphoric acid diesters as the phosphate source and O2 as the terminal oxidant, has been devised. The title method allows for the direct and highly econo-mic construction of a diverse range of allylic phosphate esters. From a conceptual viewpoint, the aerobic phosphatation is entirely complementary to traditional protocols for phosphate ester formation, which predominantly rely on the use of pre-functionalized or pre-activated reactants, such as alcohols and phosphoryl halides. The title transformation is enabled by the dual interplay of a photoredox- and a selenium-π-acid catalyst involving a sequence of single-electron-transfer processes.
      PubDate: 2017-12-08T08:55:59.737351-05:
      DOI: 10.1002/ange.201711599
       
  • Nanosheet Catalysis of Carbon Dioxide Photoreduction: Fundamentals and
           Challenges
    • Authors: Zhenyu Sun; Neetu Talreja, Hengcong Tao, John Texter, Jennifer Strunk, Martin Muhler, Jianfeng Chen
      Abstract: Transformation of CO2 into fuels and chemicals by using photocatalysis is a promising strategy to provide a long-term solution to mitigating global warming and energy supply problems. Achievements in photocatalysis during the last decade have sparked increased interest in using sunlight to reduce CO2. Traditional semiconductors used in photocatalysis (e.g. TiO2), are not suitable for the use in natural sunlight, and even under UV irradiation their performance is not sufficient. Some two-dimensional (2D) materials have recently been designed for catalytic reduction of CO2. These materials still require significant modification, which remains a challenge for photocatalytic process design. An overarching aim of this article is to summarize the literature reported on photocatalytic conversion of CO2 by various 2D materials in the liquid phase, with special attention given to development of novel 2D photocatalyst materials, to provide a basis to suggest improved materials.
      PubDate: 2017-12-08T07:26:19.537577-05:
      DOI: 10.1002/ange.201710509
       
  • The common Intermediates of Oxygen Evolution and Dissolution Reactions
           during Water Electrolysis on Iridium
    • Authors: Olga Kasian; Jan-Philipp Grote, Simon Geiger, Serhiy Cherevko, Karl J.J. Mayrhofer
      Abstract: Understanding the pathways of catalyst degradation during the oxygen evolution reaction is a cornerstone in development of efficient and stable electrolyzers, since even for most promising Ir based anodes the destined harsh conditions are detrimental. The dissolution mechanism has a complex nature and the correlation to the oxygen evolution reaction itself is still poorly understood. Here, hyphening a scanning flow cell with inductively coupled plasma and online electrochemical mass spectrometers, we in-situ monitor the oxygen evolution and degradation products of Ir and Ir-oxides. We show that at high anodic potentials several dissolution routes become possible, including formation of gaseous IrO3. On the basis of our experimental data possible pathways of oxygen evolution triggered dissolution of Ir are proposed, and the role of common intermediates for these reactions is discussed.
      PubDate: 2017-12-08T07:26:03.983751-05:
      DOI: 10.1002/ange.201709652
       
  • Hochselektive Mangan(I)/Lewis-Säure-cokatalysierte direkte
           C-H-Propargylierung unter Verwendung von Bromallenen
    • Authors: Can Zhu; Jonas Luca Schwarz, Sara Cembellín, Steffen Greßies, Frank Glorius
      Abstract: Eine Mangan(I)/Lewis-Säure-cokatalysierte direkte hochselektive C-H-Propargylierung wurde entwickelt. BPh3 erhöht bei dieser Propargylierung nicht nur die Reaktivität, sondern auch die Selektivität. Sekundäre, tertiäre und sogar quartäre Kohlenstoffzentren konnten in der propargylischen Position direkt aufgebaut werden. Sowohl interne als auch terminale Alkine können leicht gebildet werden. Die Chiralität konnte erfolgreich von einem axial-chiralen Allen zu einem Chiralitätszentrum transferiert werden. Die Reaktivität des Mangan-Katalysators in dieser Umsetzung ist im Vergleich zu anderen Übergangsmetallkatalysatoren einzigartig.Robuste Propargylierung: Bei einer hoch selektiven Mangan(I)/Lewis-Säure-cokatalysierten direkten C-H-Propargylierung erhöht BPh3 nicht nur die Reaktivität, sondern auch die Selektivität. Sekundäre, tertiäre und sogar quartäre Kohlenstoffzentren konnten in der propargylischen Position direkt aufgebaut werden. Die Reaktivität des Mangan-Katalysators in dieser Umsetzung ist im Vergleich zu anderen Übergangsmetallkatalysatoren einzigartig.
      PubDate: 2017-12-08T07:07:58.138791-05:
      DOI: 10.1002/ange.201710835
       
  • Palladium-Catalyzed Intramolecular Trost-Oppolzer-Type Alder-Ene Reaction
           of Dienyl Acetates to Cyclopentadienes
    • Authors: Siddheshwar K. Bankar; Bara Singh, Pinku Tung, S. S. V. Ramasastry
      Abstract: A new approach for the synthesis of highly substituted cyclopentadienes, indenes and cyclopentene-fused heteroarenes via the Pd-catalyzed Trost-Oppolzer-type intramolecular Alder-ene reaction of 2,4-pentadienyl acetates is described. This unprecedented transformation combines the electrophilic features of the Tsuji-Trost reaction with the nucleophilic features of the Alder-ene reaction. The overall outcome can be perceived as a hitherto unknown 'acid-free' iso-Nazarov-type cyclization. The versatility of this strategy was further demonstrated via the formal synthesis of paucifloral F, a resveratrol-based natural product.
      PubDate: 2017-12-08T05:12:41.431239-05:
      DOI: 10.1002/ange.201711797
       
  • Solar hydrogen generation from lignocellulose
    • Authors: Moritz Kuehnel; Erwin Reisner
      Abstract: Photocatalytic reforming of lignocellulosic biomass is an emerging approach to produce renewable H2. This process combines photo-oxidation of aqueous biomass with photocatalytic hydrogen evolution at ambient temperature and pressure. Biomass conversion is less energy demanding than water splitting and generates high-purity H2 without O2 production. Direct photoreforming of raw, unprocessed biomass has the potential to provide affordable, clean energy across the globe from locally sourced materials.
      PubDate: 2017-12-08T02:42:00.79568-05:0
      DOI: 10.1002/ange.201710133
       
  • Titelbild: Efficient Encapsulation of Fluorinated Drugs in the Confined
           
    • Authors: Claudia Pigliacelli; Daniele Maiolo, Nonappa, Johannes S. Haataja, Heinz Amenitsch, Claire Michelet, Paola Sánchez Moreno, Ilaria Tirotta, Pierangelo Metrangolo, Francesca Baldelli Bombelli
      Pages: 16309 - 16309
      Abstract: Der Transport fluorierter Wirkstoffe … … in wässrigen Medien erfordert stabile und in Wasser dispergierbare Träger. In ihrer Zuschrift auf S. 16404 beschreiben P. Metrangolo und F. Baldelli Bombelli et al. mit fluorierten Goldnanopartikeln gefüllte Suprapartikel, die mit dem pflanzlichen Protein Hydrophobin II überzogen sind und vom Aufbau her einer Passionsfrucht ähneln. Der fluorreiche Innenraum der Suprapartikel fasst Millionen fluorierter Wirkstoffmoleküle.
      PubDate: 2017-12-05T07:37:59.824592-05:
      DOI: 10.1002/ange.201712048
       
  • Innentitelbild: Sorting of C4 Olefins with Interpenetrated Hybrid
           Ultramicroporous Materials by Combining Molecular Recognition and
           Size-Sieving (Angew. Chem. 51/2017)
    • Authors: Zhaoqiang Zhang; Qiwei Yang, Xili Cui, Lifeng Yang, Zongbi Bao, Qilong Ren, Huabin Xing
      Pages: 16310 - 16310
      Abstract: Das Sortieren von C4-Olefinen gelingt mithilfe einer Kombination aus molekularer Erkennung und Größensiebeffekt. In ihrer Zuschrift auf S. 16500 berichten H. B. Xing und Mitarbeiter über verzahnte poröse Hybridmaterialien mit anionischen Säulen, funktionellen Zentren (die Seerosen) und Hohlräumen (die Durchfahrt unter der Brücke), deren Größe in 0.2-Å-Schritten fein einstellbar ist. Die Materialien ermöglichen eine hervorragende Trennung von C4-Olefinen.
      PubDate: 2017-11-29T02:26:05.557572-05:
      DOI: 10.1002/ange.201711715
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 51/2017
    • Pages: 16313 - 16327
      PubDate: 2017-12-13T03:20:58.751733-05:
      DOI: 10.1002/ange.201785111
       
  • Berichtigung: Copper-Catalyzed Synthesis of γ-Amino Acids Featuring
           Quaternary Stereocenters
    • Authors: José Enrique Gómez; Wusheng Guo, Silvia Gaspa, Arjan W. Kleij
      Pages: 16327 - 16327
      PubDate: 2017-12-13T03:21:02.350395-05:
      DOI: 10.1002/ange.201711781
       
  • Berichtigung: Trace H2O2-Assisted High-Capacity Tungsten Oxide
           Electrochromic Batteries with Ultrafast Charging in Seconds
    • Authors: Jinxiong Zhao; Yuyu Tian, Zhen Wang, Shan Cong, Di Zhou, Qingzhu Zhang, Mei Yang, Weikun Zhang, Fengxia Geng, Zhigang Zhao
      Pages: 16327 - 16327
      PubDate: 2017-12-13T03:20:54.158443-05:
      DOI: 10.1002/ange.201711618
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 51/2017
    • Pages: 16330 - 16333
      PubDate: 2017-12-13T03:20:47.759764-05:
      DOI: 10.1002/ange.201785113
       
  • Sensuke Ogoshi
    • Pages: 16334 - 16334
      Abstract: „Wenn ich kein Wissenschaftler wäre, wäre ich Rechtsanwalt. Mein Lieblingsort auf der Welt ist auf dem Parker-Ridge-Wanderweg in den Rocky Mountains ...“ Dies und mehr von und über Sensuke Ogoshi finden Sie auf Seite 16334.
      PubDate: 2017-09-18T11:31:19.737387-05:
      DOI: 10.1002/ange.201708270
       
  • Fellows der Electrochemical Society: C. Amatore, K. Amine, P. Atanassov,
           C. P. Grey, Y. Shao-Horn und N. Wu / Priestley-Medaille: G. Richmond /
           Förderungspreis der Stadt Wien: N. Maulide
    • Pages: 16335 - 16336
      PubDate: 2017-11-28T09:26:18.94142-05:0
      DOI: 10.1002/ange.201711427
       
  • Chirale Prägung in der Gasphase
    • Authors: David W. Pratt; Brooks H. Pate
      Pages: 16338 - 16340
      Abstract: Prägende Ereignisse: In einer jüngsten Studie ist es gelungen, die relativen Populationen zweier ansonsten identischer Enantiomere eines großen Gasphasenmoleküls mithilfe resonanter Mikrowellenfelder zu manipulieren. Durch die Anwendung einer phasen- und polarisationskontrollierten Sequenz von Mikrowellenpulsen wurde die Population eines spezifischen Enantiomers eines chiralen Terpens im Verhältnis zum anderen Enantiomer verstärkt.
      PubDate: 2017-11-08T10:20:26.29492-05:0
      DOI: 10.1002/ange.201709438
       
  • Die Suche nach einkernigem Gold(II) und seine mögliche Rolle in
           Photokatalyse und Medizinalchemie
    • Authors: Katja Heinze
      Pages: 16342 - 16350
      Abstract: Die Chemie des Goldes wird von den allgegenwärtigen Oxidationsstufen +I und +III beherrscht. In einkernigen Goldverbindungen wird die Oxidationsstufe +II im Allgemeinen vermieden. In den letzten Jahren wurde Gold(II) wiederholt als Schlüsselintermediat in künstlichen Photosynthese-Systemen mit Gold(III)-Einheiten als Elektronenakzeptoren, in Gold-katalysierten Photoredoxreaktionen und in der Radikalchemie vorgeschlagen. Dieser Kurzaufsatz fasst alle bestätigten und charakterisierten offenschaligen Gold(II)-Komplexe zusammen. Aktuelle Erkenntnisse über Strukturmotive und Reaktivitätsmuster werden diskutiert. Spannende Entwicklungen auf den Gebieten der Photosynthese, der Photokatalyse und der Medizinalchemie werden umrissen.Gold(II) spielt in künstlichen Photosynthesesystemen mit Gold(III)-Einheiten als Elektronenakzeptoren, in der Gold-Photoredoxchemie und in der Gold-Radikalchemie eine Schlüsselrolle. Dieser Kurzaufsatz fasst die zweifelsfrei charakterisierten Gold(II)-Komplexe sowie sich abzeichnende Strukturmotive und Reaktivitätsmuster zusammen. Entwicklungen auf den Gebieten der Photosynthese, der Photokatalyse und der möglichen Wirkungsweise von Krebsmedikamenten werden umrissen.
      PubDate: 2017-11-22T03:11:05.090041-05:
      DOI: 10.1002/ange.201708349
       
  • Ausgewählte Kupfer-katalysierte Reaktionen für die Bildung von C-N-,
           C-O-, C-S- und C-C-Bindungen
    • Authors: Subhajit Bhunia; Govind Goroba Pawar, S. Vijay Kumar, Yongwen Jiang, Dawei Ma
      Pages: 16352 - 16397
      Abstract: Die metallkatalysierte Kreuzkupplung ist eine der wichtigsten Umwandlungen der organischen Synthese. Aufgrund der geringen Toxizität und des günstigen Preises von Kupfer hat die Kupferkatalyse viel Interesse geweckt. Die traditionelle Ullmann-Kupplung hat jedoch eine geringe Substratbreite und erfordert harsche Reaktionsbedingungen. In den vergangenen zwei Jahrzehnten wurden zweizähnige Liganden, z. B. Aminosäuren, Diamine, 1,3-Diketone und Oxalsäurediamide, eingeführt, die Cu-katalysierte Kupplungen von Arylhalogeniden und Nucleophilen sowohl bei niedrigen Temperaturen als auch in katalytischer Weise ermöglichen. Dadurch ist die Cu-vermittelte Kreuzkupplung zu einer attraktiven Reaktion für die akademische Forschung und die Industrie geworden. Dieser Aufsatz fasst Fortschritte bei Kupplungen von (Hetero)Arylhalogeniden mit verschiedenen Nucleophilen zusammen und stellt Entwicklungen bei Cu-katalysierten Kupplungen mit Arylboronaten und Cu-vermittelten Trifluormethylierungen von aromatischen Elektrophilen vor.Aktuelle Fortschritte bei Cu/Ligand-katalysierten Kupplungen von (Hetero)Arylhalogeniden und Nucleophilen, Cu-katalysierten Kupplungen mit Arylboronaten und Cu-vermittelten Trifluormethylierungen von aromatischen Elektrophilen werden in diesem Aufsatz zusammengefasst.
      PubDate: 2017-11-14T12:50:46.206255-05:
      DOI: 10.1002/ange.201701690
       
  • Facile Supramolecular Processing of Carbon Nanotubes and Polymers for
           Electromechanical Sensors
    • Authors: Chae Bin Kim; Ki Beom Jeong, Beom Joo Yang, Jong-Won Song, Bon-Cheol Ku, Seunghyun Lee, Seoung-Ki Lee, Chiyoung Park
      Pages: 16398 - 16403
      Abstract: We herein report a facile, cost-competitive, and scalable method for producing viscoelastic conductors via one-pot melt-blending using polymers and supramolecular gels composed of carbon nanotubes (CNTs), diphenylamine (DP), and benzophenone (BP). When mixed, a non-volatile eutectic liquid (EL) produced by simply blending DP with BP (1:1 molar ratio) enabled not only the gelation of CNTs (EL-CNTs) but also the dissolution of a number of commodity polymers. To make use of these advantages, viscoelastic conductors were produced via one-pot melt-blending the EL and CNTs with a model thermoplastic elastomer, poly(styrene-b-butadiene-b-styrene) (SBS, styrene 30 wt %). The resulting composites displayed an excellent electromechanical sensory along with re-mendable properties. This simple method using cost-competitive EL components is expected to provide an alternative to the use of expensive ionic liquids as well as to facilitate the fabrication of novel composites for various purposes.Sensibles Gel: Eine supramolekulare nichtflüchtige eutektische Flüssigkeit (EL) aus Diphenylamin und Benzophenon löst nicht nur viele Gebrauchspolymere, sondern bildet beim Vermahlen auch Bucky-Gele mit Kohlenstoff-Nanoröhren (CNTs). Ein viskoelastischer Leiter aus der EL, CNTs und Polymeren, hergestellt durch gemeinsames Schmelzen, ist ein hoch empfindlicher elektromechanischer Sensor mit Selbstheilungsfähigkeit.
      PubDate: 2017-11-09T12:21:27.205137-05:
      DOI: 10.1002/ange.201708111
       
  • Efficient Encapsulation of Fluorinated Drugs in the Confined Space of
           Water-Dispersible Fluorous Supraparticles
    • Authors: Claudia Pigliacelli; Daniele Maiolo, Nonappa, Johannes S. Haataja, Heinz Amenitsch, Claire Michelet, Paola Sánchez Moreno, Ilaria Tirotta, Pierangelo Metrangolo, Francesca Baldelli Bombelli
      Pages: 16404 - 16408
      Abstract: Fluorophobic-driven assemblies of gold nanomaterials were stabilized into water-dispersible fluorous supraparticles by the film-forming protein hydrophobin II. The strategy makes use of fluorous nanomaterials of different dimensions to engineer size and inner functionalization of the resulting confined space. The inner fluorous compartments allow efficient encapsulation and transport of high loadings of partially fluorinated drug molecules in water.Fluorierte Suprapartikel: Das filmbildende Protein Hydrophobin II stabilisiert die fluorophobiegetriebene Anordnung fluorierter Goldnanopartikel in Wasser. Durch Verwendung von Nanomaterialien unterschiedlicher Abmessungen lassen sich die Größe und innere Funktionalisierung des resultierenden beschränkten Raums einstellen. Teilweise fluorierte Wirkstoffmoleküle werden effizient verkapselt und können in Wasser transportiert werden.
      PubDate: 2017-11-23T09:17:59.319354-05:
      DOI: 10.1002/ange.201710230
       
  • Transition-Metal-Free Catalytic Hydrodefluorination of Polyfluoroarenes by
           Concerted Nucleophilic Aromatic Substitution with a Hydrosilicate
    • Authors: Kotaro Kikushima; Mary Grellier, Masato Ohashi, Sensuke Ogoshi
      Pages: 16409 - 16414
      Abstract: A transition-metal-free catalytic hydrodefluorination (HDF) reaction of polyfluoroarenes is described. The reaction involves direct hydride transfer from a hydrosilicate as the key intermediate, which is generated from a hydrosilane and a fluoride salt. The eliminated fluoride regenerates the hydrosilicate to complete the catalytic cycle. Dispersion-corrected DFT calculations indicated that the HDF reaction proceeds through a concerted nucleophilic aromatic substitution (CSNAr) process.Eine clevere Kombination: Die übergangsmetallfreie katalytische Hydrodefluorierung (HDF) von Polyfluorarenen gelingt mit einem Hydrosilicat-Katalysator, der in situ aus einem Hydrosilan und einem Fluoridion gebildet wird. Die Reaktion umfasst einen direkten Hydridtransfer aus dem Hydrosilicat durch konzertierte nukleophile aromatische Substitution (CSNAr; siehe Schema).
      PubDate: 2017-11-22T03:10:58.286595-05:
      DOI: 10.1002/ange.201708003
       
  • One-Pot Synthesis of Cyclopropane-Fused Cyclic Amidines: An Oxidative
           Carbanion Cyclization
    • Authors: Kirana Devarahosahalli Veeranna; Kanak Kanti Das, Sundarababu Baskaran
      Pages: 16415 - 16419
      Abstract: A novel and efficient one-pot method has been developed for the synthesis of cyclopropane-fused bicyclic amidines on the basis of a CuBr2-mediated oxidative cyclization of carbanions. The usefulness of this unique multicomponent strategy has been demonstrated by the use of a wide variety of substrates to furnish novel cyclopropane-containing amidines with a quaternary center in very good yields. This ketenimine-based approach provides straightforward access to biologically active and pharmaceutically important 3-azabicyclo[n.1.0]alkane frameworks under mild conditions. The synthetic power of this methodology is exemplified in the concise synthesis of the pharmaceutically important antidepressant drug candidate GSK1360707 and key intermediates for the synthesis of amitifadine, bicifadine, and narlaprevir.Ohne Zwischenstopp: Ein effizienter mehrstufiger Ein-Topf-Prozess ermöglichte die Synthese von neuartigen cyclischen Cyclopropanamidinen mit quartärem Stereozentrum (siehe Schema). Diese CuBr2-vermittelte oxidative Cyclisierung bietet raschen Zugang zum 3-Azabicyclo[n.1.0]alkan-Grundgerüst und wurde für eine vierstufige Synthese des Wirkstoffkandidaten GSK1360707 genutzt.
      PubDate: 2017-11-27T08:08:34.562855-05:
      DOI: 10.1002/ange.201708138
       
  • High-Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under
           Ambient Conditions
    • Authors: Pao-Tao Yu; Chieh Tsao, Chun-Chieh Wang, Chun-Yu Chang, Chia-Hsin Wang, Jerry Chun Chung Chan
      Pages: 16420 - 16424
      Abstract: Mesocrystals of high-magnesian calcites are commonly found in biogenic calcites. Under ambient conditions, it remains challenging to prepare mesocrystals of high-magnesian calcite in aqueous solution. We report that mesocrystals of calcite with magnesium content of about 20 mol % can be obtained from the phase transformation of magnesian amorphous calcium carbonate (Mg-ACC) in lipid solution. The limited water content on the Mg-ACC surface would reduce the extent of the dissolution–reprecipitation process and bias the phase transformation pathway toward solid-state reaction. We infer from the selected area electron diffraction patterns and the dark-field transmission electron microscopic images that the formation of Mg-calcite mesocrystals occurs through solid-state secondary nucleation, for which the phase transformation is initiated near the mineral surface and the crystalline phase propagates gradually toward the interior part of the microspheres of Mg-ACC.Mesokristalle von Calcit mit hohem Mg-Gehalt wurden in wässriger Lösung unter Verwendung von Phospholipid-Additiven hergestellt. Die Dunkelfeldbilder mit dem Ursprung im (104)-Beugungspunkt legen nahe, dass zahlreiche Mg-Calcit-Nanokristallite die gleiche Orientierung haben.
      PubDate: 2017-11-23T04:56:39.576082-05:
      DOI: 10.1002/ange.201708507
       
  • Room-Temperature-Phosphorescence-Based Dissolved Oxygen Detection by
           Core-Shell Polymer Nanoparticles Containing Metal-Free Organic Phosphors
    • Authors: Youngchang Yu; Min Sang Kwon, Jaehun Jung, Yingying Zeng, Mounggon Kim, Kyeongwoon Chung, Johannes Gierschner, Ji Ho Youk, Sergey M. Borisov, Jinsang Kim
      Pages: 16425 - 16429
      Abstract: The highly sensitive optical detection of oxygen including dissolved oxygen (DO) is of great interest in various applications. We devised a novel room-temperature-phosphorescence (RTP)-based oxygen detection platform by constructing core–shell nanoparticles with water-soluble polymethyloxazoline shells and oxygen-permeable polystyrene cores crosslinked with metal-free purely organic phosphors. The resulting nanoparticles show a very high sensitivity for DO with a limit of detection (LOD) of 60 nm and can be readily used for oxygen quantification in aqueous environments as well as the gaseous phase.O2 als Leuchtmittel: Ein Nachweissystem für gelösten Sauerstoff beruht auf Nanopartikeln mit wasserlöslicher Polymethyloxazolin-Schale und sauerstoffdurchlässigem Polystyrolkern, vernetzt über metallfreie, rein organische Phosphore. Die Kern-Schale-Nanopartikel eignen sich für die hoch empfindliche Sauerstoffquantifizierung in zahlreichen Umgebungen.
      PubDate: 2017-11-22T03:37:51.634962-05:
      DOI: 10.1002/ange.201708606
       
  • Breaking Bonds and Forming Nanographene Diradicals with Pressure
    • Authors: Maude Desroches; Paula Mayorga Burrezo, Joël Boismenu-Lavoie, Miriam Peña Álvarez, Carlos J. Gómez-García, Jon M. Matxain, David Casanova, Jean-François Morin, Juan Casado
      Pages: 16430 - 16435
      Abstract: New anthanthrone-based polycyclic scaffolds possessing peripheral crowded quinodimethanes have been prepared. While the compounds adopt a closed-shell butterfly-shaped structure in the ground state, a curved-to-planar fluxional inversion is accessible with a low energy barrier through a biradicaloid transition state. Inversion is primarily driven by the release of strain associated with steric hindrance at the peri position of the anthanthrone core; a low-lying diradical state is accessible through planarization of the core, which is attained in solution at moderate temperatures. The most significant aspect of this transformation is that planarization is also achieved by application of mild pressure in the solid state, wherein the diradical remains kinetically trapped. Complementary information from quantum chemistry, 1H NMR, and Raman spectroscopies, together with magnetic experiments, is consistent with the formation of a nanographene-like structure that possesses radical centers localized at the exo-anthanthrone carbons bearing phenyl substituents.π-Bindungsbruch mit bloßen Händen: Geschlossenschalige Chinodimethan-Nanographene passieren beim fluxionalen Übergang zwischen ihren gewölbten Strukturen ein planares Diradikal-Intermediat, das abgefangen werden kann. Das Diradikal ist durch einen energiearmen Triplettzustand charakterisiert. P=Druck, S=Lösungsmittel.
      PubDate: 2017-11-28T07:55:53.689935-05:
      DOI: 10.1002/ange.201708740
       
  • Liver-Targeted Small-Molecule Inhibitors of Proprotein Convertase
           Subtilisin/Kexin Type 9 Synthesis
    • Authors: Kim F. McClure; David W. Piotrowski, Donna Petersen, Liuqing Wei, Jun Xiao, Allyn T. Londregan, Adam S. Kamlet, Anne-Marie Dechert-Schmitt, Brian Raymer, Roger B. Ruggeri, Daniel Canterbury, Chris Limberakis, Spiros Liras, Paul DaSilva-Jardine, Robert G. Dullea, Paula M. Loria, Benjamin Reidich, Christopher T. Salatto, Heather Eng, Emi Kimoto, Karen Atkinson, Amanda King-Ahmad, Dennis Scott, Kevin Beaumont, Jeffrey R. Chabot, Michael W. Bolt, Kevin Maresca, Kenneth Dahl, Ryosuke Arakawa, Akihiro Takano, Christer Halldin
      Pages: 16436 - 16440
      Abstract: Targeting of the human ribosome is an unprecedented therapeutic modality with a genome-wide selectivity challenge. A liver-targeted drug candidate is described that inhibits ribosomal synthesis of PCSK9, a lipid regulator considered undruggable by small molecules. Key to the concept was the identification of pharmacologically active zwitterions designed to be retained in the liver. Oral delivery of the poorly permeable zwitterions was achieved by prodrugs susceptible to cleavage by carboxylesterase 1. The synthesis of select tetrazole prodrugs was crucial. A cell-free in vitro translation assay containing human cell lysate and purified target mRNA fused to a reporter was used to identify active zwitterions. In vivo PCSK9 lowering by oral dosing of the candidate prodrug and quantification of the drug fraction delivered to the liver utilizing an oral positron emission tomography 18F-isotopologue validated our liver-targeting approach.Auf die Leber zielt ein niedermolekularer Wirkstoffkandidat, der die PCSK9-Synthese am humanen Ribosom hemmt. Chemische Syntheseverfahren für N1-Tetrazol-Prodrugs und ein begleitender PET-Tracer waren für diesen Ansatz von entscheidender Bedeutung.
      PubDate: 2017-11-24T05:55:59.605273-05:
      DOI: 10.1002/ange.201708744
       
  • A Supramolecular Capsule for Reversible Polysulfide Storage/Delivery in
           Lithium-Sulfur Batteries
    • Authors: Jin Xie; Hong-Jie Peng, Jia-Qi Huang, Wen-Tao Xu, Xiang Chen, Qiang Zhang
      Pages: 16441 - 16445
      Abstract: Supramolecular materials, in which small organic molecules are assembled into regular structures by non-covalent interactions, attract tremendous interests because of their highly tunable functional groups and porous structure. Supramolecular adsorbents are expected to fully expose their abundant adsorptive sites in a dynamic framework. In this contribution, we introduced cucurbit[6]uril as a supramolecular capsule for reversible storage/delivery of mobile polysulfides in lithium-sulfur (Li-S) batteries to control undesirable polysulfide shuttle. The Li-S battery equipped with the supramolecular capsules retains a high Coulombic efficiency and shows a large increase in capacity from 300 to 900 mAh g−1 at a sulfur loading of 4.2 mg cm−2. The implementation of supramolecular capsules offers insights into intricate multi-electron-conversion reactions and manifests as an effective and efficient strategy to enhance Li-S batteries and analogous applications that involve complex transport phenomena and intermediate manipulation.Smarter Energiespeicher: Lösungen für die effektive Transportkontrolle von Polysulfiden in Li-S-Batterien befassen sich mit dem Shuttle. Eine supramolekulare Kapsel mit der Fähigkeit der reversiblen Polysulfid-Speicherung/Lieferung wurde in Li-S-Batterien verwendet.
      PubDate: 2017-11-20T05:52:32.466391-05:
      DOI: 10.1002/ange.201710025
       
  • Temperature-Mediated Template Release: Facile Growth of Copper(I) Mixed
           Ethynediide/Isopropylethynide Nanoclusters
    • Authors: Leon Li-Min Zhang; Thomas C. W. Mak
      Pages: 16446 - 16450
      Abstract: In the comproportionation reaction of CuIIX2 and Cu0 with isopropylacetylene (iPr−C≡C−H), the ethynediide species C22− is generated via concomitant C−H/C−C bond cleavage of the iPr−C≡C−H precursor under moderate temperature to direct the formation of CuI mixed ethynediide/isopropylethynide nanoclusters (potentially explosive). The active ethynediide dianion C22− exhibits chameleon-like templating behavior to form C2@Cum (m=6 (3, 4), 7 (2, 4), 8 (1)) central structural units for successive formation of {C22−⊂Cu24} (1, 2), {6 C22−⊂Cu48} (3), and {18 C22−⊂Cu92} (4) complexes. Bearing the highest C22− content, complex 4 features an unprecedented nanoscale Cu2C2 kernel. Furthermore, 1–3 exhibit structure-controlled photoluminescence in the solid state.Temperaturänderungen lösen die Freisetzung von Ethindiid, C22−, aus Isopropylacetylen unter C-H-/C-C-Bindungsspaltung aus, bei der gemischte Ethindiid/Alkinid-CuI-Nanocluster entstehen. Die Synthese von {C22−⊂Cu24}, {6 C22−⊂Cu48} und {18 C22−⊂Cu92} etabliert eine Klasse von Nanostrukturen, deren Kernzahl mit steigender Zahl an Ethindiid-Einheiten zunimmt.
      PubDate: 2017-11-22T03:11:23.925473-05:
      DOI: 10.1002/ange.201708760
       
  • Functional Cellular Mimics for the Spatiotemporal Control of Multiple
           Enzymatic Cascade Reactions
    • Authors: Xiaoling Liu; Petr Formanek, Brigitte Voit, Dietmar Appelhans
      Pages: 16451 - 16456
      Abstract: Next-generation therapeutic approaches are expected to rely on the engineering of biomimetic cellular systems that can mimic specific cellular functions. Herein, we demonstrate a highly effective route for constructing structural and functional eukaryotic cell mimics by loading pH-sensitive polymersomes as membrane-associated and free-floating organelle mimics inside the multifunctional cell membrane. Metabolism mimicry has been validated by performing successive enzymatic cascade reactions spatially separated at specific sites of cell mimics in the presence and absence of extracellular organelle mimics. These enzymatic reactions take place in a highly controllable, reproducible, efficient, and successive manner. Our biomimetic approach to material design for establishing functional principles brings considerable enrichment to the fields of biomedicine, biocatalysis, biotechnology, and systems biology.Stoffwechselmimikry in Zellmimetika: Multikompartiment-Systeme mit pH-responsiven Ada-Polymersomen als Mimetika von Organellen wurden entwickelt. Die Systeme wurden als Zellmimetika zur Nachahmung des zellulären Stoffwechsels eingesetzt, indem verschiedene Stimuli zur Regulierung enzymatischer Reaktionskaskaden und zur Steuerung der simultanen und/oder nachgeschalteten Freisetzung der verkapselten (therapeutischen) Moleküle integriert wurden.
      PubDate: 2017-11-22T04:06:11.73407-05:0
      DOI: 10.1002/ange.201708826
       
  • Supramolecular Radical Anions Triggered by Bacteria In Situ for
           Selective Photothermal Therapy
    • Authors: Yuchong Yang; Ping He, Yunxia Wang, Haotian Bai, Shu Wang, Jiang-Fei Xu, Xi Zhang
      Pages: 16457 - 16460
      Abstract: A supramolecular complex that can be selectively reduced to radical anions in situ by facultative anaerobic bacteria is reported. To this end, a water-soluble bifunctional monomer bearing perylene diimide was synthesized, and its supramolecular complex with cucurbit[7]uril was fabricated on the basis of host–guest complexation, which could be reduced to forming radical anions in the presence of E. coli. It was found that this supramolecular complex could display different ability of generating radical anions by facultative anaerobic and aerobic bacteria in terms of their various reductive abilities. The selective antibacterial activity of the supramolecular complex could be realized by the photothermal performance of the radical anions under near-infrared irradiation. It is anticipated that this method may lead to a novel bacteria-responsive photothermal therapy to regulate balance of bacterial flora.Photothermische Therapie: Ein supramolekularer Komplex aus einem Perylendiimid-Derivat und Cucurbit[7]uril wird durch fakultative anaerobe oder aerobe Bakterien auf unterschiedliche Weise zu Radikalanionen reduziert. Die selektive antibakterielle Aktivität des supramolekularen Komplexes beruht auf dem photothermischen Effekt der Radikalanionen, die unter Nahinfrarotlicht optische Energie in Wärme umwandeln.
      PubDate: 2017-11-28T09:30:55.836805-05:
      DOI: 10.1002/ange.201708971
       
  • Adsorption-Induced Structural Phase Transformation in Nanopores
    • Authors: Bogdan Kuchta; Ege Dundar, Filip Formalik, Philip L. Llewellyn, Lucyna Firlej
      Pages: 16461 - 16464
      Abstract: We report a new type of structural transformation occurring in methane adsorbed in micropores. The observed methane structures are defined by probability distributions of molecular positions. The mechanism of the transformation has been modeled using Monte Carlo method. The transformation is totally determined by a reconstruction of the probability distribution functions of adsorbed molecules. The methane molecules have some freedom to move in the pore but most of the time they are confined to the positions around the high probability adsorption sites. The observed high-probability structures evolve as a function of temperature and pressure. The transformation is strongly discontinuous at low temperature and becomes continuous at high temperature. The mechanism of the transformation is influenced by a competition between different components of the interaction and the thermal energy. The methane structure represents a new state of matter, intermediate between solid and liquid.Zwischen fest und flüssig: Ein neuartiger Strukturübergang, dessen Mechanismus auf einer Wahrscheinlichkeitsverteilung beruht, wurde in einem Modell für adsorbierte Methanmoleküle in Mikroporen des Metall-organischen Gerüsts IRMOF-1 entdeckt. Die Methanstruktur in den Poren wird durch die eingeschränkte Beweglichkeit bestimmt und stellt eine Mischung aus festem und flüssigem Zustand dar.
      PubDate: 2017-11-20T05:41:56.482405-05:
      DOI: 10.1002/ange.201708993
       
  • Synthesis of a Phlorin from a Meso-Fused Anthriporphyrin by a
           Diels–Alder Strategy
    • Authors: Adil S. Aslam; Jung-Ho Hong, June-Ho Shin, Dong-Gyu Cho
      Pages: 16465 - 16469
      Abstract: An anthracene-containing meso-fused carbaporphyrin, which has extended π-conjugation pathways as compared to the corresponding naphthalene-containing carbaporphyrin, has been synthesized. The weak global aromaticity of the anthriporphyrin also allowed its use as the diene for a Diels–Alder reaction with dimethyl acetylenedicarboxylate (DMAD). The resulting phlorin contains an interesting bicyclic structure. Moreover, to the best of our knowledge, this phlorin is the first Diels–Alder adduct of a diene forming part of the global π-conjugation pathway of an aromatic porphyrinoid.Horizonte erweitern: Ein Meso-Carbaporphyrin mit einem Anthracenring wurde synthetisiert und als Dienkomponente in einer Diels-Alder-Reaktion eingesetzt, um es weiter zu einem Meso-Phlorin zu expandieren (siehe Schema). Die Metallkoordination des Anthriporphyrins und des neuartigen Phlorins wurde durch die Synthese von Palladium(II)-Komplexen untersucht.
      PubDate: 2017-11-27T03:50:08.262251-05:
      DOI: 10.1002/ange.201709026
       
  • Microporous Cyclic Titanium-Oxo Clusters with Labile Surface Ligands
    • Authors: Chaowei Zhao; Ying-Zi Han, Shuqi Dai, Xumao Chen, Juanzhu Yan, Weijie Zhang, Haifeng Su, Shuichao Lin, Zichao Tang, Boon K. Teo, Nanfeng Zheng
      Pages: 16470 - 16474
      Abstract: By using ethylene glycol and monocarboxylic acid as surface ligands, a series of cyclic Ti-oxo clusters (CTOC) with permanent microporosity are successfully synthesized. With a cyclic {Ti32O16} backbone made of eight connected Ti4 tetrahedral cages that are arranged in a zigzag fashion, the clusters have a “donut” shape with an inner diameter of 8.3 Å, outer diameter of 26.9 Å and height of 10.4 Å. While both inner and outer walls of the “donut” clusters are modified by double-deprotonated ethylene glycolates, their upper and lower surfaces are bound by carboxylates and mono-deprotonated ethylene glycolates. The clusters are readily packed into one-dimensional tubes which are further arranged in two different modes into crystalline microporous solids with surface areas over 660 m2 g−1, depending on the surface carboxylates. The solid with olefin-bearing carboxylates exhibits a superior CO2 adsorption capacity of 40 cm3 g−1 at 273 K under 1 atm. Moreover, the mono-deprotonated ethylene glycolates on the clusters are demonstrated to be highly exchangeable by other alcohols, providing a nice platform for creating microporous solids or films with a wide variety of surface functionalities.Mikroporöse Materialien: Ethylenglycol und Monocarbonsäure wurden als Oberflächenliganden genutzt, um makrocyclische Titan-Oxo-Cluster (TOCs) herzustellen. Die Donut-TOCs verzahnen sich zu eindimensionalen Nanoröhren, die einen mikroporösen Festkörper bilden. Die labilen Oberflächenliganden ermöglichen außerdem die Herstellung mikroporöser TOCs mit einer breiten Auswahl von Oberflächenfunktionalitäten.
      PubDate: 2017-11-28T09:31:04.014358-05:
      DOI: 10.1002/ange.201709096
       
  • On the Non-Metallicity of 2.2 nm Au246(SR)80 Nanoclusters
    • Authors: Meng Zhou; Chenjie Zeng, Yongbo Song, Jonathan W. Padelford, Gangli Wang, Matthew Y. Sfeir, Tatsuya Higaki, Rongchao Jin
      Pages: 16475 - 16479
      Abstract: The transition from molecular to plasmonic behaviour in metal nanoparticles with increasing size remains a central question in nanoscience. We report that the giant 246-gold-atom nanocluster (2.2 nm in gold core diameter) protected by 80 thiolate ligands is surprisingly non-metallic based on UV/Vis and femtosecond transient absorption spectroscopy as well as electrochemical measurements. Specifically, the Au246 nanocluster exhibits multiple excitonic peaks in transient absorption spectra and electron dynamics independent of the pump power, which are in contrast to the behaviour of metallic gold nanoparticles. Moreover, a prominent oscillatory feature with frequency of 0.5 THz can be observed in almost all the probe wavelengths. The phase and amplitude analysis of the oscillation suggests that it arises from the wavepacket motion on the ground state potential energy surface, which also indicates the presence of a small band-gap and thus non-metallic or molecular-like behaviour.Nichtmetallisches Metall' Ultraschnelle Studien zur Elektronen- und Phononendynamik von Au246(SR)80-Nanoclustern zeigen, dass Au246 – bei einem Durchmesser von immerhin 2.2 nm – noch nicht metallisch ist. Eine hervorstechende Oszillation mit einer Frequenz von 0.5 THz deutet auf die Existenz einer kleinen Bandlücke hin, und damit auf nichtmetallisches oder molekülartiges Verhalten.
      PubDate: 2017-11-22T06:05:26.007781-05:
      DOI: 10.1002/ange.201709095
       
  • Ligand-controlled Regiodivergent C−H Alkenylation of Pyrazoles and its
           Application to the Synthesis of Indazoles
    • Authors: Hyun Tae Kim; Hyeri Ha, Geunhee Kang, Og Soon Kim, Ho Ryu, Abul Kalam Biswas, Sang Min Lim, Mu-Hyun Baik, Jung Min Joo
      Pages: 16480 - 16484
      Abstract: Regioselective C4-, C5-, and di-alkenylations of pyrazoles were achieved. An electrophilic Pd catalyst generated by trifluoroacetic acid (TFA) and 4,5-diazafluoren-9-one (DAF) leads to C4-alkenylation, whereas KOAc and mono-protected amino acid (MPAA) ligand Ac-Val-OH give C5-alkenylation. A combination of palladium acetate, silver carbonate, and pivalic acid affords dialkenylation products. Annulation through sequential alkenylation, thermal 6π-electrocyclization, and oxidation gives functionalized indazoles. This comprehensive strategy greatly expands the range of readily accessible pyrazole and indazole derivatives, enabling useful regiodivergent C−H functionalization of pyrazoles and other heteroaromatic systems.Eine regioselektive C-H-Funktionalisierung von Pyrazolen ergibt C4- und C5-Alkenylpyrazole sowie Dialkenylpyrazole mithilfe dreier unterschiedlicher Pd-Katalysesysteme (siehe Schema). Die systematische Herstellung von Alkenylpyrazolen ermöglichte die Synthese mehrfach funktionalisierter Indazole und π-erweiterter Pyrazole ausgehend von leicht erhältlichen, kostengünstigen Pyrazolen und Olefinen.
      PubDate: 2017-11-27T03:50:18.409212-05:
      DOI: 10.1002/ange.201709162
       
  • Controlled and Reversible Stepwise Growth of Linear Copper(I) Chains
           Enabled by Dynamic Ligand Scaffolds
    • Authors: Orestes Rivada-Wheelaghan; Sandra L. Aristizábal, Joaquín López-Serrano, Robert R. Fayzullin, Julia R. Khusnutdinova
      Pages: 16485 - 16489
      Abstract: Reversible stepwise chain growth in linear CuI assemblies can be achieved by using the dynamic, unsymmetric naphthyridinone-based ligand scaffolds L1 and L2. With the same ligand scaffolds, the length of the linear copper chain can be varied from two to three and four copper atoms, and the nuclearity of the complex is easily controlled by the stepwise addition of a CuI precursor to gradually increase the chain length, or by the reductive removal of Cu atoms to decrease the chain length. This represents a rare example of a stepwise controlled chain growth in extended metal atom chains (EMACs). All complexes are formed with excellent selectivity, and the mutual transformations of the complexes of different nuclearity were found to be fast and reversible. These unusual rearrangements of metal chains of different nuclearities were achieved by a stepwise “sliding” movement of the naphthyridinone bridging fragment along the metal chain.Die schrittweise Bildung von linearen Kupfer(I)-Kettenkomplexen gelang durch die Verwendung von dynamischen Ligandengerüsten. Komplexe mit dem gleichen Liganden und ein, zwei, drei oder vier Kupfer(I)-Atomen können durch Änderungen in der Stöchiometrie oder Lösungsmittelpolarität sowie durch Redoxreaktionen reversibel ineinander überführt werden.
      PubDate: 2017-11-23T09:18:26.122243-05:
      DOI: 10.1002/ange.201709167
       
  • Controlling the Host–Guest Interaction Mode through a Redox Stimulus
    • Authors: György Szalóki; Vincent Croué, Vincent Carré, Frédéric Aubriet, Olivier Alévêque, Eric Levillain, Magali Allain, Juan Aragó, Enrique Ortí, Sébastien Goeb, Marc Sallé
      Pages: 16490 - 16494
      Abstract: A proof-of-concept related to the redox-control of the binding/releasing process in a host–guest system is achieved by designing a neutral and robust Pt-based redox-active metallacage involving two extended-tetrathiafulvalene (exTTF) ligands. When neutral, the cage is able to bind a planar polyaromatic guest (coronene). Remarkably, the chemical or electrochemical oxidation of the host–guest complex leads to the reversible expulsion of the guest outside the cavity, which is assigned to a drastic change of the host–guest interaction mode, illustrating the key role of counteranions along the exchange process. The reversible process is supported by various experimental data (1H NMR spectroscopy, ESI-FTICR, and spectroelectrochemistry) as well as by in-depth theoretical calculations performed at the density functional theory (DFT) level.Stimuli-responsive metallierte Käfige: Ein selbstorganisierter redoxaktiver Käfig aus Platin und einem ausgedehnten Tetrathiafulvalen-Liganden kann reversibel in den stabilen tetrakationischen Zustand oxidiert werden. Durch Variation der Ladung von 0 bis +4 können die Bindung eines polyaromatischen Gasts im Hohlraum und seine Freigabe gesteuert werden.
      PubDate: 2017-11-23T04:56:52.542254-05:
      DOI: 10.1002/ange.201709483
       
  • Aqueous Bismuth Titanium–Oxo Sulfate Cluster Speciation and
           Crystallization
    • Authors: Pedro I. Molina; Karoly Kozma, Melissa Santala, Clément Falaise, May Nyman
      Pages: 16495 - 16499
      Abstract: Inorganic aqueous metal–oxo clusters are both functional “molecular metal oxides” and intermediates to understand metal oxide growth from water. There has been a recent surge in discovery of aqueous Ti-oxo clusters but without extensive solution characterization. We use small-angle and total X-ray scattering, dynamic light scattering, transmission electron microscopy, and a single-crystal X-ray structure to show that heterometals such as bismuth stabilize labile Ti–oxo sulfate clusters in aqueous solution.[Ti22Bi7O41(OH)(OH2)30(SO4)12]2+ features edge-sharing between the Ti and Bi polyhedra, in contrast to the dominant corner-linking of Ti-oxo clusters. Bi stabilizes the Ti-polyhedra, which are synergistically stabilized by the bidentate sulfates. Gained stability and potential functionality from heterometals is an incentive to develop more broadly the landscape of heterometallic Ti–oxo clusters.Stabile Titan-Oxo-Cluster in Wasser: Titanoxysulfat ordnet sich beim Lösen in Wasser sofort zu monodispersen vielkernigen Clustern an. Gemäß Röntgenstreuung sind diese Cluster hoch labil und ohne klare innere Ordnung. Durch Versetzen mit Salpetersäure und BiIII werden sie schrittweise zersetzt; die resultierende Lösung enthält einen Heterometall-Ti-Oxo-Cluster.
      PubDate: 2017-11-24T04:45:47.939588-05:
      DOI: 10.1002/ange.201709539
       
  • Sorting of C4 Olefins with Interpenetrated Hybrid Ultramicroporous
           Materials by Combining Molecular Recognition and Size-Sieving
    • Authors: Zhaoqiang Zhang; Qiwei Yang, Xili Cui, Lifeng Yang, Zongbi Bao, Qilong Ren, Huabin Xing
      Pages: 16500 - 16505
      Abstract: C4 olefin separations present one of the great challenges in hydrocarbon purifications owing to their similar structures, thus a single separation mechanism often met with limited success. Herein we report a series of anion-pillared interpenetrated copper coordination for which the cavity and functional site disposition can be varied in 0.2 Å scale increments by altering the anion pillars and organic linkers (GeFSIX-2-Cu-i (ZU-32), NbFSIX-2-Cu-i (ZU-52), GeFSIX-14-Cu-i (ZU-33)), which enable selective recognition of different C4 olefins. In these materials the rotation of the organic linkers is controlled to create a contracted flexible pore window that enables the size-exclusion of specific C4 olefins, while still adsorbing significant amounts of 1,3-butadiene (C4H6) or 1-butene (n-C4H8). Combining the molecular recognition and size-sieving effect, these materials unexpectedly realized the sieving of C4H6/n-C4H8, C4H6/iso-C4H8, and n-C4H8/iso-C4H8 with high capacity.Duale Trennwirkung: Drei verzahnte Kupfer-Koordinationsgerüste mit anionischen Säulen wurden zur hoch effizienten Trennung von C4-Olefinen über molekulare Erkennung und Größensiebeffekte hergestellt. Die funktionellen Materialien unterscheiden sich bezüglich ihrer Anionen und organischen Brücken, und sie trennen die isomeren Kohlenwasserstoffe anhand mehrerer Merkmale.
      PubDate: 2017-10-24T11:31:16.183784-05:
      DOI: 10.1002/ange.201708769
       
  • Record High-Nuclearity Polyoxoniobates: Discrete Nanoclusters {Nb114},
           {Nb81}, and {Nb52}, and Extended Frameworks Based on {Cu3Nb78} and
           {Cu4Nb78}
    • Authors: Lu Jin; Zeng-Kui Zhu, Yan-Lan Wu, Yan-Jie Qi, Xin-Xiong Li, Shou-Tian Zheng
      Pages: 16506 - 16510
      Abstract: A series containing the highest nuclearity polyoxoniobate (PONb) nanoclusters, ranging from dimers to tetramers, has been obtained. They include one 114-nuclear {Li8⊂Nb114O316}, one 81-nuclear {Li3K⊂Nb81O225}, and one 52-nuclear {H4Nb52O150}. The Nb nuclearity of these PONbs is remarkably larger than those of all known high-nuclearity PONbs (≤32). Furthermore, the introduction of 3d Cu2+ ions can lead to the generation of extended inorganic–organic hybrid frameworks built from novel, high-nuclearity, nanoscale heterometallic PONb building blocks {H3Cu3Nb78O222} or {H3Cu4(en)Nb78O222}. These building blocks also contain the largest number of Nb centers of any heterometallic PONbs reported to date. The synthesis of new-type PONbs has long been a challenging subject in PONb chemistry.Sehr große PONbs, von einer {Nb52}- über eine {Nb81}- zu einer {Nb114}-Spezies, wurden hergestellt. Durch Einführung von 3d-Ionen (Cu2+) werden ausgedehnte organisch-anorganische PONb-Hybridgerüste aufgebaut, die riesige {Cu3Nb78}- und {Cu4Nb78}-Heterometallnanocluster enthalten.
      PubDate: 2017-11-22T03:12:00.942666-05:
      DOI: 10.1002/ange.201709565
       
  • Asymmetric Synthesis of Less Accessible α-Tertiary Amines from
           Alkynyl Z-Ketimines
    • Authors: Taichi Kano; Yusuke Aota, Keiji Maruoka
      Pages: 16511 - 16514
      Abstract: A highly stereoselective synthesis of hitherto less accessible chiral α-tertiary amines with multiple structurally similar linear carbon chains was achieved through chiral auxiliary mediated addition of organolithium reagents to the geometrically well-controlled alkynyl Z-ketimines. This stereoselective nucleophilic addition offers a general approach to the asymmetric synthesis of nitrogen-containing chiral materials.In geometrisch kontrollierter Weise wurden Alkinyl-Z-Ketimine als Substrate für die asymmetrische Synthese schwer zugänglicher α-tertiärer Amine mit mehreren Kohlenstoffketten hergestellt. Bei dieser Umsetzung wurde die nukleophile Addition von Organolithiumreagentien durch die chirale Hilfsgruppe Aux* gesteuert.
      PubDate: 2017-11-27T03:51:04.072999-05:
      DOI: 10.1002/ange.201710084
       
  • An in situ Dynamic Continuum of Supramolecular Phosphoglycopeptides
           Enables Formation of 3D Cell Spheroids
    • Authors: Huaimin Wang; Junfeng Shi, Zhaoqianqi Feng, Rong Zhou, Shiyu Wang, Avital A. Rodal, Bing Xu
      Pages: 16515 - 16519
      Abstract: Higher-order assemblies of proteins, with a structural and dynamic continuum, is an important concept in biology, but these insights have yet to be applied in designing biomaterials. Dynamic assemblies of supramolecular phosphoglycopeptides (sPGPs) transform a 2D cell sheet into 3D cell spheroids. A ligand–receptor interaction between a glycopeptide and a phosphopeptide produces sPGPs that form nanoparticles, which transform into nanofibrils upon partial enzymatic dephosphorylation. The assemblies form dynamically and hierarchically in situ on the cell surface, and interact with the extracellular matrix molecules and effectively abolish contact inhibition of locomotion (CIL) of the cells. Integrating molecular recognition, catalysis, and assembly, these active assemblies act as a dynamic continuum to disrupt CIL, thus illustrating a new kind of biomaterial for regulating cell behavior.Erzwungene Geselligkeit: Enzymatisch erzeugte dynamische Biomaterialien modulieren interzelluläre Wechselwirkungen in Zellmedium, sodass dreidimensionale Zellsphäroide entstehen.
      PubDate: 2017-11-22T03:12:44.681675-05:
      DOI: 10.1002/ange.201710269
       
  • Cyclic Triimidazole Derivatives: Intriguing Examples of Multiple Emissions
           and Ultralong Phosphorescence at Room Temperature
    • Authors: Elena Lucenti; Alessandra Forni, Chiara Botta, Lucia Carlucci, Clelia Giannini, Daniele Marinotto, Alessandro Pavanello, Andrea Previtali, Stefania Righetto, Elena Cariati
      Pages: 16520 - 16525
      Abstract: The performance of solid luminogens depends on both their inherent electronic properties and their packing status. Intermolecular interactions have been exploited to achieve persistent room-temperature phosphorescence (RTP) from organic molecules. However, the design of organic materials with bright RTP and the rationalization of the role of interchromophoric electronic coupling remain challenging tasks. Cyclic triimidazole has been shown to be a promising scaffold for such purposes owing to its crystallization-induced room-temperature ultralong phosphorescence (RTUP), which has been associated with H-aggregation. Herein, we report three triimidazole derivatives as significant examples of multifaceted emission. In particular, dual fluorescence, RTUP, and phosphorescence from the molecular and supramolecular units were observed. H-aggregation is responsible for the red RTUP, and Br substituents favor yellow molecular phosphorescence while halogen-bonded Br⋅⋅⋅Br tetrameric units are involved in the blue-green phosphorescence.Drei Triimidazol-Derivate wurden synthetisiert, die duale Fluoreszenz, ultralange Phosphoreszenz bei Raumtemperatur (RTUP) und Phosphoreszenz aus den molekularen und supramolekularen Einheiten zeigen. H-Aggregate verursachen die rote RTUP, Br-Substituenten die gelbe molekulare Phosphoreszenz und Halogen-verbrückte Br⋅⋅⋅Br-Tetramere die blau-grüne Phosphoreszenz.
      PubDate: 2017-11-30T04:37:15.719877-05:
      DOI: 10.1002/ange.201710279
       
  • Organocatalytic Atroposelective Arylation of 2-Naphthylamines as a
           Practical Approach to Axially Chiral Biaryl Amino Alcohols
    • Authors: Ye-Hui Chen; Liang-Wen Qi, Fang Fang, Bin Tan
      Pages: 16526 - 16530
      Abstract: The first phosphoric acid catalyzed direct arylation of 2-naphthylamines with iminoquinones for the atroposelective synthesis of axially chiral biaryl amino alcohols has been developed. This reaction constitutes a highly functional-group-tolerant route for the rapid construction of enantioenriched axially chiral biaryl amino alcohols, and is a rare example of 2-naphthylamines acting as nucleophiles in an organocatalytic enantioselective transformation. Furthermore, the products, which feature various halogen atoms, provide access to structurally diverse axially chiral amino alcohols through further transformations.Die Phosphorsäure-katalysierte direkte Arylierung von 2-Naphthylaminen mit Iminochinonen ermöglicht die atropselektive Synthese von Biaryl-substituierten Aminoalkoholen mit axialer Chiralität. Viele funktionelle Gruppen werden in dieser Reaktion toleriert, die wiederum eines von wenigen Beispielen für die Verwendung von 2-Naphthylaminen als Nucleophile in einer organokatalysierten enantioselektiven Umsetzung ist.
      PubDate: 2017-11-23T04:57:14.013102-05:
      DOI: 10.1002/ange.201710537
       
  • Three-Dimensional Anionic Cyclodextrin-Based Covalent Organic Frameworks
    • Authors: Yuanyuan Zhang; Jiyun Duan, Dou Ma, Pengfei Li, Siwu Li, Haiwei Li, Junwen Zhou, Xiaojie Ma, Xiao Feng, Bo Wang
      Pages: 16531 - 16535
      Abstract: Three-dimensional covalent organic frameworks (3D COFs) are promising crystalline materials with well-defined structures, high porosity, and low density; however, the limited choice of building blocks and synthetic difficulties have hampered their development. Herein, we used a flexible and aliphatic macrocycle, namely γ-cyclodextrin (γ-CD), as the soft struts for the construction of a polymeric and periodic 3D extended network, with the units joined via tetrakis(spiroborate) tetrahedra with various counterions. The inclusion of pliable moieties in the robust open framework endows these CD-COFs with dynamic features, leading to a prominent Li ion conductivity of up to 2.7 mS cm−1 at 30 °C and excellent long-term Li ion stripping/plating stability. Exchanging the counterions within the pores can effectively modulate the interactions between the CD-COF and CO2 molecules.Dreidimensionale anionische kovalente organische Gerüste (COFs) mit unterschiedlichen Gegenionen wurden aus aliphatischen flexiblen makrocyclischen γ-Cyclodextrin(γ-CD)-Einheiten aufgebaut, die über Spiroborat-Linker verknüpft wurden. Das CD-COF mit Li+ ist ein guter Lithiumionenleiter, und verschiedene Gegenionen führen zu unterschiedlichen Wechselwirkungen mit CO2.
      PubDate: 2017-11-22T04:06:25.332667-05:
      DOI: 10.1002/ange.201710633
       
  • Enantiospecific sp2–sp3 Coupling of ortho- and para-Phenols with
           Secondary and Tertiary Boronic Esters
    • Authors: Claire M. Wilson; Venkataraman Ganesh, Adam Noble, Varinder K. Aggarwal
      Pages: 16536 - 16540
      Abstract: The coupling of ortho- and para-phenols with secondary and tertiary boronic esters has been explored. In the case of para-substituted phenols, after reaction of a dilithio phenolate species with a boronic ester, treatment with Ph3BiF2 or Martin's sulfurane gave the coupled product with complete enantiospecificity. The methodology was applied to the synthesis of the broad spectrum antibacterial natural product (−)-4-(1,5-dimethylhex-4-enyl)-2-methyl phenol. For ortho-substituted phenols, initial incorporation of a benzotriazole on the phenol oxygen atom was required. Subsequent ortho-lithiation and borylation gave the coupled product, again with complete stereospecificity.Die Kupplung von Phenolen in ortho- und para-Stellung mit Boronsäureestern wurde untersucht. Für para-Bromphenole ergab die Umsetzung mit Ph3BiF2 oder Martins Sulfuran, nach Reaktion der Dilithioarylspezies mit dem Boronsäureester, das gekuppelte Produkt mit vollständiger Enantiospezifität. Für ortho-funktionalisierte Phenole war zunächst die Anknüpfung eines Benzotriazols am Phenol-O-Atom erforderlich.
      PubDate: 2017-11-28T07:56:41.089819-05:
      DOI: 10.1002/ange.201710777
       
  • Enantioselective and Collective Total Syntheses of Xanthanolides
    • Authors: Juan Feng; Xiaoqiang Lei, Ruiyang Bao, Yuanhe Li, Chengqian Xiao, Lihong Hu, Yefeng Tang
      Pages: 16541 - 16545
      Abstract: An enantioselective synthesis of (+)-8-epi-xanthatin hinging on a chiral phosphoric acid catalyzed tandem allylboration/lactonization reaction is reported. With (+)-8-epi-xanthatin as the precursor, the collective synthesis of a series of synthetically challenging xanthanolides was also accomplished. Among them, xanthipungolide, one of the most complex xanthanolide monomers, was accessed through a bioinspired tandem double-bond isomerization/6π electronic cyclization/intramolecular Diels–Alder reaction, and pungiolides A, B, D, E, and L–N, a group of xanthanolide dimers, were assembled through a bioinspired Diels–Alder dimerization followed by late-stage diversification.Vielfalt ist Trumpf: Die enantioselektive Synthese von (+)-8-epi-Xanthatin aus leicht erhältlichen Fragmenten wurde in sieben Stufen (längste lineare Sequenz) und 15 % Gesamtausbeute vollendet. Weitere 1–3 Stufen werden für die kollektive Totalsynthese verschiedener anspruchsvoller Xanthanolid-Monomere und -Dimere basierend auf einer Serie bioinspirierter Transformationen benötigt.
      PubDate: 2017-11-27T03:51:30.753274-05:
      DOI: 10.1002/ange.201710846
       
  • Development of an Efficient Biosensor for the In Vivo Monitoring of Cu+
           and pH in the Brain: Rational Design and Synthesis of Recognition
           Molecules
    • Authors: Wei Liu; Hui Dong, Limin Zhang, Yang Tian
      Pages: 16546 - 16550
      Abstract: An efficient biosensor was created for the ratiometric monitoring of Cu+ and pH in the brain using both current and potential outputs. A series of N,N-bis(2-[2-(ethylthio)ethyl])-based (NS4s) derivatives was designed for the specific recognition of Cu+. After systematically evaluating the electrochemical parameters of Cu+ oxidation by tuning alkyl chain length, polyaromatic structure, and substitute group site of NS4, N,N-bis(2-[2-(ethylthio)ethyl])-2-naphthamide (NS4-C1) was finally optimized for Cu+ detection as it showed the most negative potential and the largest current density. At the same time, 9,10-anthraquinone was used as a selective pH sensor with 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) as an internal reference. This single biosensor with both current and potential signal outputs can simultaneously determine Cu+ concentrations from 0.5 to 9.5 μm and pH values ranging from 6.0 to 8.0. The efficient biosensor was applied to the simultaneous detection of Cu+ and pH in the live brain. The average levels of Cu+ were reported for the first time in the cortex, hippocampus, and striatum in a mouse model of Alzheimer's disease.Cu+ und der pH-Wert spielen wichtige Rollen in der Physiologie und Pathologie des Gehirns. Ein effizienter Biosensor zur ratiometrischen Erfassung von Cu+ und pH in einem Alzheimer-Mausmodell mit zwei elektrischen Ausgabesignalen wird vorgestellt, mit dessen Hilfe Cu+-Durchschnittskonzentrationen in Hirnrinde, Hippocampus und Striatum ermittelt wurden.
      PubDate: 2017-11-30T04:37:29.589822-05:
      DOI: 10.1002/ange.201710863
       
  • In-Situ Microfluidic Study of Biphasic Nanocrystal Ligand-Exchange
           Reactions Using an Oscillatory Flow Reactor
    • Authors: Yi Shen; Milad Abolhasani, Yue Chen, Lisi Xie, Lu Yang, Connor W. Coley, Moungi G. Bawendi, Klavs F. Jensen
      Pages: 16551 - 16555
      Abstract: Oscillatory flow reactors provide a surface energy-driven approach for automatically screening reaction conditions and studying reaction mechanisms of biphasic nanocrystal ligand-exchange reactions. Sulfide and cysteine ligand-exchange reactions with as-synthesized CdSe quantum dots (QDs) are chosen as two model reactions. Different reaction variables including the new-ligand-to-QD ratio, the size of the particles, and the original ligand type are examined systematically. Based on the in situ-obtained UV/Vis absorption spectra during the reaction, we propose two different exchange pathways for the sulfide exchange reaction.Oszillatorische Flussreaktoren wurden zum automatisierten Screening von Reaktionskinetiken und zur Untersuchung der Reaktionsmechanismen des Ligandenaustauschs an CdSe-Quantenpunkten (QDs) in einem Zweiphasensystem eingesetzt. In situ während des Prozesses aufgenommene UV/Vis-Absorptionsspektren weisen auf zwei unterscheidbare Reaktionswege hin.
      PubDate: 2017-11-21T03:31:16.271106-05:
      DOI: 10.1002/ange.201710899
       
  • Consecutive Transformations of Tetrafluoropropenes: Hydrogermylation and
           Catalytic C−F Activation Steps at a Lewis Acidic Aluminum Fluoride
    • Authors: Gisa Meißner; Konrad Kretschmar, Thomas Braun, Erhard Kemnitz
      Pages: 16556 - 16559
      Abstract: Functionalization reactions of the refrigerants HFO-1234yf (2,3,3,3-tetrafluoropropene) and HFO-1234ze (1,3,3,3-tetrafluoropropene) were developed. The selectivity and reactivity towards CF3 groups of C−F activation reactions can be controlled by employing either a germane or a silane as the hydrogen source. Unique transformations were designed to accomplish consecutive hydrogermylation and C−F activation steps. This allowed for an unprecedented transformation of an olefinic C−F bond into a C−H bond by heterogeneous catalysis. These reactions are catalyzed by nanoscopic aluminum chlorofluoride (ACF) under very mild conditions.Funktionalisierungen von Tetrafluorpropenen wie HFO-1234yf wurden entwickelt. Die Umwandlung der CF3-Gruppe in eine olefinische CF2-Einheit gelang mit nanoskopischem Aluminiumchlorfluorid (ACF) und einem Silan. Aufeinanderfolgende Hydrogermylierung und C-F-Aktivierung ermöglichten die Umwandlung der olefinischen C-F-Bindung in eine C-H-Bindung.
      PubDate: 2017-11-23T09:18:38.230935-05:
      DOI: 10.1002/ange.201707759
       
  • Nucleophilic Arylation of N,O-Ketene Acetals with Triaryl Aluminum
           Reagents: Access to α-Aryl Amides through an Umpolung Process
    • Authors: Norihiko Takeda; Erika Futaki, Yukiko Kobori, Masafumi Ueda, Okiko Miyata
      Pages: 16560 - 16564
      Abstract: A novel approach for the umpolung α-arylation of amides is presented. By the nucleophilic phenylation of O-silyl N,O-ketene acetals, generated in situ from N-alkoxy amides, a phenyl group can be introduced onto the α-carbon atom of amides through N−O bond cleavage in a two-step, one-pot process. The asymmetric synthesis of α-aryl amides through the diastereoselective arylation of a chiral N,O-ketene acetal is also described.Mithilfe einer Umpolung, bei der O-Silyl-N,O-ketenacetale in situ aus N-Alkoxyamiden erzeugt werden, wird eine Phenylgruppe am α-Kohlenstoffzentrum von Amiden unter N-O-Bindungsspaltung in einem zweistufigen Ein-Topf-Prozess eingeführt (siehe Schema). Die asymmetrische Synthese von α-Arylamiden durch die diastereoselektive Arylierung eines chiralen N,O-Ketenacetals wird ebenfalls beschrieben.
      PubDate: 2017-11-27T03:50:35.772688-05:
      DOI: 10.1002/ange.201708665
       
  • Supramolecular Recognition Allows Remote, Site-Selective C−H Oxidation
           of Methylenic Sites in Linear Amines
    • Authors: Giorgio Olivo; Giulio Farinelli, Alessia Barbieri, Osvaldo Lanzalunga, Stefano Di Stefano, Miquel Costas
      Pages: 16565 - 16569
      Abstract: Site-selective C−H functionalization of aliphatic alkyl chains is a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. A supramolecular, bioinspired approach is described to address this challenge. A Mn complex able to catalyze C(sp3)-H hydroxylation with H2O2 is equipped with 18-benzocrown-6 ether receptors that bind ammonium substrates via hydrogen bonding. Reversible pre-association of protonated primary aliphatic amines with the crown ether selectively exposes remote positions (C8 and C9) to the oxidizing unit, resulting in a site-selective oxidation. Remarkably, such control of selectivity retains its efficiency for a whole series of linear amines, overriding the intrinsic reactivity of C−H bonds, no matter the chain length.Ferngesteuert: Die supramolekulare Erkennung protonierter primärer Amine durch 18-Krone-6-Rezeptoren bringt bestimmte Methylengruppen an entlegenen Positionen des Gastmoleküls in die Nähe eines aktiven Manganzentrums. Lineare Alkylketten können so selektiv an C8 und C9 mit H2O2 oxidiert werden.
      PubDate: 2017-11-27T03:50:55.261831-05:
      DOI: 10.1002/ange.201709280
       
  • Enantioselective Rhodium-Catalyzed Coupling of Arylboronic Acids,
           1,3-Enynes, and Imines by Alkenyl-to-Allyl 1,4-Rhodium(I) Migration
    • Authors: Michael Callingham; Benjamin M. Partridge, William Lewis, Hon Wai Lam
      Pages: 16570 - 16574
      Abstract: A chiral rhodium complex catalyzes the highly enantioselective coupling of arylboronic acids, 1,3-enynes, and imines to give homoallylic sulfamates. The key step is the generation of allylrhodium(I) species by alkenyl-to-allyl 1,4-rhodium(I) migration.Ein chiraler Rhodiumkomplex katalysiert die hoch enantioselektive Kupplung von Arylboronsäuren, 1,3-Eninen und Iminen zu Homoallylsulfamaten. Der Schlüsselschritt der Reaktion ist die Bildung von Allylrhodium(I)-Spezies über 1,4-Rhodium(I)-Verschiebung von Alkenylspezies. tAm=tert-Amyl.
      PubDate: 2017-11-24T05:50:53.468579-05:
      DOI: 10.1002/ange.201709334
       
  • Formation of Polymeric Nanocubes by Self-Assembly and Crystallization of
           Dithiolane-Containing Triblock Copolymers
    • Authors: Katherine Margulis; Xiangyi Zhang, Lydia-Marie Joubert, Karsten Bruening, Christopher J. Tassone, Richard N. Zare, Robert M. Waymouth
      Pages: 16575 - 16580
      Abstract: Template-free fabrication of non-spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self-assembly from aqueous solutions at room temperature. Nanocubes with edges of 40–200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self-assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solid cubic particle formation. An approach for preserving the structures of these cubes in water by thiol- or photo-induced crosslinking was developed. The ability to solubilize a model hydrophobic drug, curcumin, was also explored.Würfelförmige Polymernanopartikel entstehen durch einen Selbstorganisationsprozess in wässriger Lösung bei Raumtemperatur. Würfel mit 40–200 nm Kantenlänge bilden sich spontan beim Trocknen mizellarer Lösungen von Triblockcopolymeren mit zentralem Poly(ethylenoxid)-Block und äußeren Trimethylencarbonat/Dithiolan-Blöcken. Die Würfelstruktur konnte durch Dithiolan-Vernetzung fixiert werden.
      PubDate: 2017-11-24T05:56:05.776965-05:
      DOI: 10.1002/ange.201709564
       
  • Magnesium Boryl Reactivity with 9-BBN and Ph3B: Rational B−B′ Bond
           Formation and Diborane Isomerization
    • Authors: Anne-Frédérique Pécharman; Michael S. Hill, Claire L. McMullin, Mary F. Mahon
      Pages: 16581 - 16584
      Abstract: Reactions of a magnesium-based pinacolatoboryl nucleophile with the electrophilic organoboranes, 9-BBN and Ph3B, provide facile B−B′ single bond formation. Although the Ph3B derivative is thermally stable, when heated, the unsymmetrical diborane(5) anion derived from 9-BBN is found to isomerize to two regioisomeric species via a proposed mechanism involving dehydroboration of the borabicyclo[3.3.1]nonane and syn-diboration of the resultant alkenyl carbocycle.B-B King: Die Reaktion eines Magnesium-Pinakolatoboryl-Nukleophils mit elektrophilen Organoboranen (9-BBN oder Ph3B) führt glatt zur Bildung von B-B′-Einfachbindungen.
      PubDate: 2017-11-27T03:50:59.610351-05:
      DOI: 10.1002/ange.201709902
       
  • Cobalt-Catalyzed Suzuki Biaryl Coupling of Aryl Halides
    • Authors: Soneela Asghar; Sanita B. Tailor, David Elorriaga, Robin B. Bedford
      Pages: 16585 - 16588
      Abstract: Readily accessed cobalt pre-catalysts with N-heterocyclic carbene ligands catalyze the Suzuki cross-coupling of aryl chlorides and bromides with alkyllithium-activated arylboronic pinacolate esters. Preliminary mechanistic studies indicate that the cobalt species is reduced to Co0 during the reaction.Einfache Cobaltkomplexe mit N-heterocyclischen Carbenliganden katalysieren Suzuki-Kreuzkupplungen mit Arylchloriden und -bromiden.
      PubDate: 2017-11-28T09:26:02.953415-05:
      DOI: 10.1002/ange.201710053
       
  • Cooperative Multifunctional Catalysts for Nitrone Synthesis: Platinum
           Nanoclusters in Amine-Functionalized Metal–Organic Frameworks
    • Authors: Xinle Li; Biying Zhang, Linlin Tang, Tian Wei Goh, Shuyan Qi, Alexander Volkov, Yuchen Pei, Zhiyuan Qi, Chia-Kuang Tsung, Levi Stanley, Wenyu Huang
      Pages: 16589 - 16593
      Abstract: Nitrones are key intermediates in organic synthesis and the pharmaceutical industry. The heterogeneous synthesis of nitrones with multifunctional catalysts is extremely attractive but rarely explored. Herein, we report ultrasmall platinum nanoclusters (PtNCs) encapsulated in amine-functionalized Zr metal–organic framework (MOF), UiO-66-NH2 (Pt@UiO-66-NH2) as a multifunctional catalyst in the one-pot tandem synthesis of nitrones. By virtue of the cooperative interplay among the selective hydrogenation activity provided by the ultrasmall PtNCs and Lewis acidity/basicity/nanoconfinement endowed by UiO-66-NH2, Pt@UiO-66-NH2 exhibits remarkable activity and selectivity, in comparison to Pt/carbon, Pt@UiO-66, and Pd@UiO-66-NH2. Pt@UiO-66-NH2 also outperforms Pt nanoparticles supported on the external surface of the same MOF (Pt/UiO-66-NH2). To our knowledge, this work demonstrates the first examples of one-pot synthesis of nitrones using recyclable multifunctional heterogeneous catalysts.Katalyse im Wechselspiel: Platin-Nanocluster (PtNCs), die in Amin-funktionalisiertem UiO-66-NH2 verkapselt sind (Pt@UiO-66-NH2), wirken als multifunktionelle Katalysatoren in der Ein-Topf-Tandemsynthese von Nitronen. Das kooperative Wechselspiel zwischen selektiver Hydrierungsaktivität der PtNCs und Lewis-Acidität/Lewis-Basizität/Nanoumgebung des MOF verleiht Pt@UiO-66-NH2 eine bemerkenswerte Aktivität und Selektivität.
      PubDate: 2017-11-22T11:04:02.617394-05:
      DOI: 10.1002/ange.201710164
       
  • The MOF+ Technique: A Significant Synergic Effect Enables High Performance
           Chromate Removal
    • Authors: Ming Biao Luo; Yang Yang Xiong, Hui Qiong Wu, Xue Feng Feng, Jian Qiang Li, Feng Luo
      Pages: 16594 - 16597
      Abstract: A significant synergic effect between a metal–organic framework (MOF) and Fe2SO4, the so-called MOF+ technique, is exploited for the first time to remove toxic chromate from aqueous solutions. The results show that relative to the pristine MOF samples (no detectable chromate removal), the MOF+ method enables super performance, giving a 796 Cr mg g−1 adsorption capacity. The value is almost eight-fold higher than the best value of established MOF adsorbents, and the highest value of all reported porous adsorbents for such use. The adsorption mechanism, unlike the anion-exchange process that dominates chromate removal in all other MOF adsorbents, as unveiled by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), is due to the surface formation of Fe0.75Cr0.25(OH)3 nanospheres on the MOF samples.Poren machen Pause: Die MOF+-Methode nutzt statt des Porensystems eines Metall-organischen Gerüsts dessen Oberfläche und ermöglicht die hoch effiziente Entfernung von Chromat aus wässrigen Lösungen von bis zu 796 mg(Cr) g−1. Chromat wird durch FeSO4 reduziert, wobei FeIII- und CrIII-Ionen entstehen; anschließend induziert die MOF-Oberfläche die Bildung von Fe0.75Cr0.25(OH)3-Nanopartikeln.
      PubDate: 2017-11-20T02:56:01.33252-05:0
      DOI: 10.1002/ange.201709197
       
  • Solid-State Structure of Protonated Ketones and Aldehydes
    • Authors: Daniel Stuart; Stacey D. Wetmore, Michael Gerken
      Pages: 16598 - 16602
      Abstract: Protonated carbonyl compounds have been invoked as intermediates in many acid-catalyzed organic reactions. To gain key structural and electronic data about such intermediates, oxonium salts derived from five representative examples of ketones and aldehydes are synthesized in the solid state, and characterized by X-ray crystallography and Raman spectroscopy for the first time. DFT calculations were carried out on the cations in the gas phase. Whereas an equimolar reaction of the carbonyl compounds, acetone, cyclopentanone, adamantanone, and acetaldehyde, with SbF5 in anhydrous HF yielded mononuclear oxonium cations, the same stoichiometry in a reaction with benzaldehyde resulted in formation of a hemiprotonated, hydrogen-bridged dimeric cation. Hemiprotonated acetaldehyde was obtained when a 2:1 ratio of aldehyde and SbF5 was used. Experimental and NBO analyses quantify the significant increase in electrophilicity of the oxonium cations compared to that of the parent ketones/aldehydes.Reaktive Zwischenstufen: Die Kristallstrukturen von protonierten Carbonylverbindungen wurden ermittelt. Während die Protonierung von Ketonen (Aceton, Cyclopentanon und Adamantanon) in supersaurer Lösung einkernige Oxoniumionen liefert, führen die Reaktionen von Benzaldehyd oder Acetaldehyd mit HF/SbF5 zu hemiprotonierten, wasserstoffverbrückten zweikernigen Strukturen im Festkörper.
      PubDate: 2017-11-29T08:30:56.453254-05:
      DOI: 10.1002/ange.201710263
       
  • Spata-13,17-dien-Synthase – ein Enzym mit Sesqui-, Di- und
           Sesterterpen-Synthase-Aktivität aus Streptomyces xinghaiensis
    • Authors: Jan Rinkel; Lukas Lauterbach, Jeroen S. Dickschat
      Pages: 16603 - 16607
      Abstract: Eine Terpensynthase aus dem marinen Bakterium Streptomyces xinghaiensis wurde charakterisiert, einschließlich einer vollen Strukturaufklärung ihrer Produkte aus verschiedenen Substraten. Weiterhin wurden detaillierte Untersuchungen des Enzymmechanismus durch Isotopenmarkierungsexperimente, Variationen des Metallcofaktors und Mutageneseexperimente durchgeführt. Die Daten zeigten eine Abhängigkeit der Mn2+-katalysierten Reaktion von der Gegenwart von Asp-217, einem Rest, der in anderen bakteriellen Terpensynthasen von einem hochkonservierten Glu eingenommen wird.Eine Terpensynthase aus Streptomyces xinghaiensis mit Sesqui-, Di- und Sesterterpen-Synthase-Aktivität wurde identifiziert. Der Enzymmechanismus wurde durch Isotopenmarkierungen untersucht. Ortsgerichtete Mutagenese deckte zuvor unerkannte, hochkonservierte Reste mit Bedeutung für die Katalyse auf. Einer dieser Reste wurde mit den Erfordernissen an den Metallcofaktor – Mg2+ oder Mn2+ – in Verbindung gebracht.
      PubDate: 2017-11-23T04:57:54.831029-05:
      DOI: 10.1002/ange.201711142
       
  • Herstellung von funktionalisierten Diaryl- und
           Diheteroaryl-Lanthanreagenzien mittels eines schnellen
           Halogen-Lanthan-Austausches
    • Authors: Andreas D. Benischke; Lucile Anthore-Dalion, Guillaume Berionni, Paul Knochel
      Pages: 16608 - 16612
      Abstract: Ausgehend von Aryl- und Heteroarylhalogeniden (X=Br, I) erlaubt nBu2LaMe einen schnellen und praktischen Halogen-Lanthan-Austausch, welcher zu funktionalisierten Diaryl- und Diheteroaryl-Lanthanderivaten führt. Deren anschließende Abfangreaktionen mit ausgewählten Elektrophilen, wie Ketonen, Aldehyden oder Amiden, gelangen reibungslos bei −50 °C in THF, und polyfunktionalisierte Alkohole und Carbonylderivate wurden erhalten. Kinetische Vergleichsexperimente zeigen einen ähnlichen Reaktivitätsverlauf wie bei einem Br-Mg-Austausch, jedoch machen um 106 höhere Austauschgeschwindigkeiten ihn eher vergleichbar mit einem Br-Li-Austausch.Lanthan als Alternative zu Lithium: Aryl- und Heteroarylhalogeniden gehen mit nBu2LaMe einen schnellen und praktischen Halogen-Lanthan-Austausch ein, der zu funktionalisierten Diaryl- und Diheteroaryl-Lanthanderivaten führt. Anschließende Abfangreaktionen mit ausgewählten Elektrophilen, wie Ketonen, Aldehyden oder Amiden, bei −50 °C in THF lieferten polyfunktionalisierte Alkohole und Carbonylderivate.
      PubDate: 2017-11-22T11:04:13.637108-05:
      DOI: 10.1002/ange.201709553
       
  • Treten in der N-heterozyklischen Carben-Organokatalyse wirklich Carbene
           auf'
    • Authors: Sascha Gehrke; Oldamur Hollóczki
      Pages: 16613 - 16617
      Abstract: In der Organokatalyse werden häufig Azolium-Kationen in Anwesenheit einer Base eingesetzt, um wertvolle Syntheseschritte zu realisieren. Aufgrund der Annahme, dass durch Deprotonierung des Kations ein freies Carben entsteht, welches mit dem Substrat reagiert und somit dessen Reaktivität entscheidend beeinflusst, werden Reaktionen dieses Types als N-heterozyklische Carben-Katalyse bezeichnet. Wir können hier jedoch zeigen, dass ein Mechanismus, in dem das Azolium-Kation analog der elektrophilen aromatischen Substitution direkt mit dem Substrat reagiert und somit eine freie Carbenspezies vermieden wird, energetisch deutlich günstiger ist.Alternative identifiziert: Für die Organokatalyse mit N-heterozyklischen Carbenen (NHCs) wird ein neuartiger Reaktionsweg vorgestellt. Der Protonentransfer und die Herstellung der Bindung zwischen Katalysator und Substrat geschehen gleichzeitig in einem einzelnen Elementarschritt, ohne dass eine freie Carbenspezies in der Reaktionsmischung auftritt.
      PubDate: 2017-11-22T11:04:19.940442-05:
      DOI: 10.1002/ange.201708305
       
  • O2-Aktivierung an Cerdioxid-Katalysatoren – Zur Bedeutung der
           kristallographischen Orientierung des Substrats
    • Authors: Chengwu Yang; Xiaojuan Yu, Stefan Heißler, Peter G. Weidler, Alexei Nefedov, Yuemin Wang, Christof Wöll, Thomas Kropp, Joachim Paier, Joachim Sauer
      Pages: 16618 - 16623
      Abstract: Das Verständnis der Sauerstoffaktivierung auf Metalloxiden auf atomarer Ebene ist eine der größten Herausforderungen der heterogenen Katalyse. Eine oberflächenwissenschaftliche Untersuchung an allen drei niedrigindizierten Einkristalloberflächen von Cerdioxid, dem vermutlich wichtigsten Redoxkatalysator, ermöglichte den direkten spektroskopischen Nachweis reaktiver Sauerstoffspezies an Fehlstellen an den reduzierten Oberflächen von CeO2(110) und CeO2(100). An CeO2(111), der thermodynamisch stabilsten Oberfläche dieses Oxids, wurden jedoch keine Superoxo- und Peroxo-Spezies gefunden. Mithilfe von Dichtefunktionalrechnungen konnten diese scheinbar widersprüchlichen Ergebnisse auf eine Migration von O-Leerstellen in das Innere der Einkristalle zurückgeführt werden, die jedoch nur im Fall von (111)-Substraten auftritt. Diese Beobachtungen beenden eine lang anhaltende Debatte über die Position von O-Leerstellen an Cerdioxidoberflächen und die Aktivierung von O2 auf Cerdioxid-Pulvern.Ein Rätsel ist gelöst: IRRAS-Daten zur Sauerstoffaktivierung an Oxid-Einkristalloberflächen belegen, in Verbindung mit theoretischen Studien, die Bildung zahlreicher Superoxo- und Peroxo-Spezies an reduzierten CeO2(110)- und CeO2(100)-Oberflächen, nicht jedoch an CeO2(111). Dieser Widerspruch erklärt sich aus der Diffusion von O-Leerstellen unter der Oberfläche.
      PubDate: 2017-11-23T04:56:15.95048-05:0
      DOI: 10.1002/ange.201709199
       
  • Lösung des Problems mangelnder oraler Verfügbarkeit cyclischer
           Hexapeptide: Entwicklung eines selektiven, oral verfügbaren Liganden für
           das Integrin αvβ3
    • Authors: Michael Weinmüller; Florian Rechenmacher, Udaya Kiran Marelli, Florian Reichart, Tobias G. Kapp, Andreas F. B. Räder, Francesco Saverio Di Leva, Luciana Marinelli, Ettore Novellino, José M. Muñoz-Félix, Kairbaan Hodivala-Dilke, Adi Schumacher, Joseph Fanous, Chaim Gilon, Amnon Hoffman, Horst Kessler
      Pages: 16624 - 16629
      Abstract: Ein systematischer Ansatz für die Entwicklung oral verfügbarer wie auch biologisch aktiver, cyclischer, N-methylierter Hexapeptide als hoch affine Liganden für das Integrin αvβ3 beruht auf zwei Konzepten: a) Screening systematisch entwickelter Peptidbibliotheken mit räumlicher Diversität und b) Maskierung der Peptidladung mithilfe lipophiler Schutzgruppen. Die Schlüsselschritte dieser Methode sind 1) Erstellung einer kombinatorischen Bibliothek N-methylierter Analoga des Stammpeptids cyclo(d-Ala-Ala5); 2) Auswahl der cyclischen Peptide mit der höchsten intestinalen Permeabilität; 3) Design von Unterbibliotheken mit der biologisch aktiven RGD-Sequenz in allen möglichen Positionen; 4) Auswahl der besten Liganden für RGD-erkennende Integrinsubtypen; 5) Optimierung der Affinität und Selektivität durch zusätzliche Ala-zu-Xaa-Substitutionen; 6) Schützen der geladenen funktionalen Seitengruppen nach dem Prodrug-Konzept zur Wiederherstellung der intestinalen und oralen Permeabilität; 7) Nachweis der biologischen Aktivität in Mäusen nach oraler Gabe.Die orale Bioverfügbarkeit von Peptiden ist hauptsächlich aufgrund des Transports durch die Epithelzellen in den Blutkreislauf limitiert. Die Entwicklung von oral verfügbaren wie auch biologisch aktiven, cyclischen, N-methylierten Hexapeptiden mithilfe eines systematischen Ansatzes durch das Screening permeabler und räumlich diverser Peptidbibliotheken und durch das Maskieren der Peptide mit lipophilen Schutzgruppen führte zu oral aktiven Liganden für den Integrinsubtyp αvβ3.
      PubDate: 2017-11-23T09:18:15.637696-05:
      DOI: 10.1002/ange.201709709
       
  • Oxidation von organischen Substraten mit einem redoxaktiven
           Guanidinkatalysator
    • Authors: Ute Wild; Florian Schön, Hans-Jörg Himmel
      Pages: 16630 - 16633
      Abstract: Hier wird über die ersten Beispiele für die Verwendung von redoxaktiven Guanidinen als Katalysatoren bei der grünen Oxidation von organischen Substraten mit Sauerstoff berichtet. In einer Halbreaktion wird die oxidierte Form des redoxaktiven Guanidins in die reduzierte, protonierte Form umgewandelt, wodurch eine oxidative Dehydrierung des Substrats (3,5-Di-tert-butylcatecholo-Benzochinon, BenzoinBenzil und 2,4-Di-tert-butylphenolBiphenol) stattfindet. In der anderen Halbreaktion wird eine effiziente Reoxidation des Guanidins in den oxidierten Zustand mit molekularem Sauerstoff in Gegenwart eines Kupfercokatalysators erreicht. Die Ergebnisse ebnen den Weg für eine breitere Verwendung von redoxaktiven Guanidinen als Oxidationskatalysatoren.Die Kombination von hoher Brønsted-Basizität und Elektronendonor-Eigenschaften ermöglicht es, redoxaktive Guanidine als hervorragende organische Redoxkatalysatoren einzusetzen, wie die ersten katalytischen Oxidationsreaktionen mit molekularem Sauerstoff zeigen.
      PubDate: 2017-11-22T03:12:07.184514-05:
      DOI: 10.1002/ange.201709809
       
  • Innenrücktitelbild: A Supramolecular Capsule for Reversible Polysulfide
           Storage/Delivery in Lithium-Sulfur Batteries (Angew. Chem. 51/2017)
    • Authors: Jin Xie; Hong-Jie Peng, Jia-Qi Huang, Wen-Tao Xu, Xiang Chen, Qiang Zhang
      Pages: 16635 - 16635
      Abstract: Eine supramolekulare Kapsel, die einer Krake im Meer ähnelt, ermöglicht die reversible Speicherung und den Transport von Polysulfiden in einer funktionsfähigen Batterie. In ihrer Zuschrift auf S. 16441 berichten Q. Zhang et al. über den Einsatz von Cucurbit[6]uril-Kapseln, die Lithium-Schwefel-Batterien eine gute Stabilität und hohe Wirkungsgrade verleihen und eine hohe Beladung mit Schwefel ermöglichen.
      PubDate: 2017-12-05T08:00:33.979615-05:
      DOI: 10.1002/ange.201712175
       
  • Rücktitelbild: The MOF+ Technique: A Significant Synergic Effect Enables
           High Performance Chromate Removal (Angew. Chem. 51/2017)
    • Authors: Ming Biao Luo; Yang Yang Xiong, Hui Qiong Wu, Xue Feng Feng, Jian Qiang Li, Feng Luo
      Pages: 16636 - 16636
      Abstract: Metall-organische Gerüste …… (MOFs) sind bei der Absorption von Chrom(VI) vor allem durch ihre geringe Kapazität limitiert. F. Luo et al. setzen in ihrer Zuschrift auf S. 16594 auf die sogenannte MOF+-Methode, bei der nicht die Poren, sondern die Oberfläche des MOF genutzt wird, um bis zu 796 Cr mg g−1 an Chrom(VI) zu binden. Der Schlüssel ist ein synergistischer Effekt des MOF mit FeSO4.
      PubDate: 2017-12-05T08:00:30.973744-05:
      DOI: 10.1002/ange.201712176
       
 
 
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