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    33827 results match your criteria Angewandte Chemie International Edition [Journal]

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    Dynamic Cross-Exchange in Halophosphonium Species: First Direct Observation of Stereochemical Inversion in the Course of an SN2 Process.
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    UCD, chemistry, Belifield, Dublin, IRELAND.
    The complex fluxional interconversions between, otherwise very similar, phosphonium bromides and chlorides R3PX+X- (R = Alk, Ar, X = Cl or Br) was studied by NMR techniques. Their energy barriers are typically ca. 11 kcal/mol but rise rapidly as bulky groups are attached to phosphorus, revealing the importance of steric factors. Read More

    Control of N-Heterocyclic Carbene Catalyzed Switchable Linear and Cycloaddition Reactions of Enals: Asymmetric Synthesis of Oxindole-γ-Amino Acid Derivatives.
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    RWTH Aachen, Institute of Organic Chemistry, Landoltweg 1, 52072, Aachen, GERMANY.
    A strategy to control the switchable linear and cycloaddition reactions of enals through NHC catalyisis has been developed. The new scalable protocol leads to γ-amino acid esters bearing a tetrasubstituted stereocenter in good yields and high stereoselectivities via homo-Mannich reactions of enals and isatin-derived ketimines. By simply changing the N-ketimine substituent to an ortho-hydroxy phenyl group, the corresponding spirocyclic oxindolo-γ-lactams are obtained. Read More

    The Weakly Coordinating Tris(trichlorosilyl)silyl Anion.
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    Universität Bremen, Institut fuer Biologie und Chemie, Leobener Str., 28359, Bremen, GERMANY.
    Closely following the procedure for the preparation of the base-stabilized dichlorosilylene complex NHCDipp∙SiCl2 by Roesky and Stalke et al. (Angew. Chem. Read More

    A redox-activated G-quadruplex DNA binder based on a platinum(IV)-salphen complex.
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    Imperial College London, Chemistry, South Kensington , SW7 2AZ, London, UNITED KINGDOM.
    There has been increasing interest in the development of small molecules that can selectively bind to G-quadruplex DNA structures. The latter have been associated to a number of key biological processes and therefore are proposed to be potential targets for drug development. In this paper we report the first example of a reduction-activated G-quadruplex DNA binder. Read More

    Controlled Sol-Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Machine.
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    Yokohama National University, Department of Chemistry & Biotechnology, Hodogaya-ku, 240-8501, Yokohama, JAPAN.
    Producing ionic liquids (ILs) that function as molecular machines for macroscopic change is a challenging issue. We report that photoisomerization of an azobenzene IL at the molecular level could evoke a macroscopic response (light-controlled mechanical sol-gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a low critical solution temperature in the IL mixture containing azobenzene while the B midblock, poly(methyl methacrylate), is compatible with the mixture. Read More

    Double Regioselective Asymmetric C-Allylation of Isoxazolinones: Iridium Catalyzed N-Allylation Followed by an Aza-Cope-Rearrangement.
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    Universität Stuttgart, Institut für Organische Chemie, Pfaffenwaldring 55, Raum 06.301, 70569, Stuttgart, GERMANY.
    Isoxazolinones are biologically and synthetically interesting densely functionalized heterocycles, which for a long time were not accessible in enantioenriched form by asymmetric catalysis. Next to the deficit of enantioselective methods, the functionalization of isoxazolinones is often plagued by regioselectivity issues due to the competition of various nucleophilic centers within the heterocycles. Here we report the first regio- and enantioselective C-allylations of isoxazolinones. Read More

    Can coordination-driven supramolecular self-assembly reactions be conducted from fully aliphatic linkers ?
    Angew Chem Int Ed Engl 2017 Nov 17. Epub 2017 Nov 17.
    Universite Rennes I. Campus de Beaulieu, UMR 6226, 263 av. du General Leclerc, 35042, Rennes Cedex, FRANCE.
    A series of fully aliphatic cyano-capped ditopic linkers with increasing lengths were reacted with a pre-assembled Cu(I) bimetallic molecular clip bearing short intermetallic distances. It is shown that, depending on the length of the ditopic linkers, a rational design of unprecedented supramolecular compact metallacycles bearing fully aliphatic walls is possible. The specific pre-organized molecular arrangement of the molecular clip used favors stabilizing interlinker London dispersion interactions allowing, as the linkers' lengths increase, the selective formation of discrete compact metallacycles at the expense of 1D coordination polymers. Read More

    Visible-Light-Mediated Metal-Free Hydrosilylation of Alkenes through Selective Hydrogen Atom Transfer for Si-H Activation.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    National University of Singapore, Chemistry, Block S15, Level 5, 15-05-02, 3 Science Drive 2, 117543, Singapore, SINGAPORE.
    Although developments on the transition-metal-catalyzed hydrosilylation of alkenes have achieved great progress over the past several decades, metal-free hydrosilylation is still rare and highly desirable. Herein, we report a convenient visible-light-driven metal-free hydrosilylation of both electron-deficient and electron-rich alkenes via selective hydrogen atom transfer for Si-H activation. By the synergistic combination of an organo-photocatalyst 4CzIPN and quinuclidin-3-yl acetate catalyst, the hydrosilylation of electron-deficient alkenes exclusively occurred with Si-H activation. Read More

    Controlled radical polymerization of ethylene using organotellurium compounds.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    The first successfully controlled radical polymerization (CRP) of ethylene is reported using several organotellurium chain-transfer agents (CTAs) under mild conditions (70 °C, 200 bar of ethylene) within the concept of organotellurium-mediated radical polymerization (TERP). In contrast to preceding works on CRPs of ethylene applying reversible addition-fragmentation chain-transfer (RAFT), the organotellurium-mediated system provided a high livingness and chain-end functionalization of polyethylene chains. Molar-mass distributions with dispersities between 1. Read More

    Silicon-based dielectric metamaterials: Focus on the current synthetic challenges.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    Institut de Chimie de la Matière Condensée de Bordeaux, Supercritical Fluids, 87 Avenue du Dr Albert Schweitzer, 33608, Pessac Cedex, FRANCE.
    Metamaterials have optical properties that are unprecedented in nature. They have opened new horizons in light manipulation, with the ability to bend, focus, and completely reflect, transmit or absorb an incident wave front. Optically active metamaterials in particular could be used for applications ranging from 3D information storage, more efficient photovoltaic cells, high security watermarks, and fiber optics. Read More

    A Strontium- and Chlorine-Free Pyrotechnic Illuminant of High Color Purity.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    The need to develop a red-light-emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community due to potential Environmental Protection Agency (EPA) regulations of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium-based red-light-emitting pyrotechnic compositions of high purity and color is described. These formulations do not contain strontium or chlorinated organic materials. Read More

    A Gold-Catalyzed Domino Cyclization Enabling Rapid Construction of Diverse Polyheterocyclic Frameworks.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    KU Leuven, Department of Chemistry, Celestijnenlaan 200F, 3001, Leuven, BELGIUM.
    We report herein an efficient gold(I)-catalyzed post-Ugi domino dearomatization/ipso-cyclization/Michael sequence that enables access to libraries of diverse (hetero)arene-annulated tricyclic heterocycles. This process affords novel complex polycyclic scaffolds in moderate to good yields from readily available acyclic precursors with excellent chemo-, regio-, and diastereo-selectivity. The power of this strategy has been demonstrated by the rapid synthesis of 40 highly functionalized polyheterocycles bearing indole, pyrrole, (benzo)furan, (benzo)thiophene, pyrazole and electron-rich arenes in two-operational steps. Read More

    A Copper(II)-Phenanthroline Metallopeptide that Targets and Disrupts Mitochondrial Function in Breast Cancer Stem Cells.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    King's College London, Chemistry, 7 Trinity Street, SE1 1DB, London, UNITED KINGDOM.
    The breast cancer stem cell (CSC) and bulk breast cancer cell potency of a series of metallopeptides, 1-4 containing dichloro(1,10-phenanthroline) copper(II) and various organelle-targeting peptide sequences, is reported. The mitochondrial-targeting metallopeptide, 1 exploits the higher mitochondrial load in breast CSCs over corresponding non-CSCs, and the vulnerability of breast CSCs to mitochondrial damage, to potently and selectivity kill breast CSCs. Strikingly, 1 reduces the formation and size of mammospheres to a better extent than salinomycin, an established CSC-potent agent. Read More

    Reaction of thiocarbonyl fluoride formed from difluorocarbene with amines.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Key Laboratory of Organofluorine Chemistry, 345 Lingling Road, 200032, Shanghai, CHINA.
    The reaction of thiocarbonyl fluoride generated from difluorocarbene with various amines under mild conditions is described. Secondary amines, primary amines, and o-phenylenediamines are converted to thiocarbamoyl fluorides, isothiocyanates, and difluoromethylthiolated heterocycles, respectively. Thiocarbamoyl fluorides were further transformed into trifluoromethylated amines using a one-pot process. Read More

    Restoration of ribozyme tertiary contact and function using a molecular glue for RNA.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    The Institute of Scientific and Industrial Research, Osaka University, Department of Regulatory Bioorganic Chemistry, 8-1 Mihogaoka, JAPAN.
    Some RNA classes require folding into the proper higher-order structures to exert their functions. Hammerhead ribozyme (HHR) requires a folding conformation stabilized by tertiary interaction for full activity. Here, we developed a rationally engineered HHR that was inactive, but could be activated by a synthetic RNA-binding ligand, naphthyridine carbamate tetramer with Z-stilbene linker (Z-NCTS). Read More

    Atropoenantioselective Redox-Neutral Amination of Biaryls Via Borrowing Hydrogen and Dynamic Kinetic Resolution.
    Angew Chem Int Ed Engl 2017 Nov 16. Epub 2017 Nov 16.
    Tsinghua University, School of Pharmaceutical Sciences, Beijing, CHINA.
    We report here a novel atropoenantioselective redox-neutral amination of biaryls triggered by a cascade of borrowing hydrogen and DKR strategy under the co-catalysis of chiral Ir-complex and achiral Brønsted acid. This protocol features broad substrate scope and good functional group tolerance, and allows the rapid assembly of axially chiral biaryls in good to high yields and with high to excellent enantioselectivities. Read More

    Bioinspired Chemical Communication between Synthetic Nanomotors.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    UCSD, Department of Nanoengineering, 9500 Gilman Drive, 92093-0403, La Jolla, UNITED STATES.
    While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. Here we demonstrate the design and operation of bio-inspired synthetic nanomotors capable of chemical communication among themselves that influences their propulsion behavior. The chemical message is sent from a moving 'activator' motor to a nearby 'activated' (receiver) one, and involves release of silver ions from a Janus PS/Ni/Au/Ag 'activator' motor to the 'activated' Janus SiO2/Pt nanomotor. Read More

    Distal Weak Coordination of Acetamides in Ruthenium(II)-Catalyzed C-H Activation Processes.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    Georg-August-Universitaet Goettingen, Institut fuer Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Goettingen, GERMANY.
    C-H activations with challenging arylacetamides were accomplished by versatile ruthenium(II) biscarboxylate catalysis. The distal C-H functionalization was characterized by 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. Read More

    PbS/CdS core/shell QDs suppress charge transfer and enhance triplet transfer.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    UNIVERSITY OF CALIFORNIA, RIVERSIDE, Chemistry, 501 Big Springs Rd, 92521, Riverside, UNITED STATES.
    Here, we observe that a sub-monolayer CdS shell on PbS quantum dots (QDs) enhances triplet energy transfer (TET) by suppressing competitive charge transfer from QDs to molecules. The CdS shell increases the linear photon upconversion quantum yield (QY) from 3.5% for PbS QDs to 5. Read More

    Fluorine in a C-F Bond as the Key to Cage Formation.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    Johns Hopkins University, Chemistry, 3400 N. Charles Street, 21218-2685, Baltimore, UNITED STATES.
    Cage molecules have long been employed to trap reactive or fleeting species, as their rigid nature allows them to enforce situations that otherwise would not persist. In this minireview, we discuss our use of rigid cage structures to investigate the close noncovalent interactions of fluorine with other functional groups and determine how mutual proximity affects both physical properties and reactivity. Unusual covalent interactions of fluorine are also explored: the cage can close to form the first solution-phase C-F-C fluoronium ion. Read More

    Highly Selective Manganese(I)/Lewis Acid Cocatalyzed Direct C-H Propargylation using Bromoallenes.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    WWU Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, GERMANY.
    A manganese(I)/Lewis acid cocatalyzed direct C-H propargylation with high selectivity has been developed. BPh3 was discovered to not only promote the reactivity, but also enhance the selectivity to afford the propargylation products rather than allene derivatives. Secondary, tertiary or even quaternary carbon centers at the propargylic position could be directly constructed. Read More

    Modulation of Quorum Sensing in a Gram Positive Pathogen by Linear Imprinted Copolymers with anti-Infective Properties.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    University of leicester, Chemistry, University Road, LE1 7RH, Leicester, UNITED KINGDOM.
    Here we describe the development, characterization and biological testing of a new type of linear molecularly imprinted polymer (LMIP) designed to act as anti-infective by blocking the quorum sensing (QS) mechanism and so preventing virulence of the pathogen Streptococcus pneumoniae. The LMIP is prepared (polymerized) in presence of a template molecule, but unlike in traditional molecular imprinting approaches no cross-linker is used. This results in soluble low molecular weight polymer that can act as drug agent in vitro and in vivo. Read More

    Simple Access to the Heaviest Alkaline-Earth Metal Hydride: A Strongly Reducing Hydrocarbon-Soluble Barium Hydride Cluster.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    University Erlangen-Nürnberg, Chemistry, Egerlandstrasse 1, 91058, Erlangen, GERMANY.
    Reaction of Ba[N(SiMe3)2]2 with PhSiH3 in toluene gave simple access to the unique Ba hydride cluster Ba7H7[N(SiMe3)2]7 that can be described as a square pyramide spanned by five Ba2+ ions with two flanking BaH[N(SiMe3)2] units. This heptanuclear cluster is well soluble in aromatic solvents and the hydride 1H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined Ba hydride species. Read More

    Time-Resolved Interception of Multiple-Charge Accumulation in a Sensitizer-Acceptor Dyad.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris Sud, CNRS, 91405, Orsay Cedex, France.
    Biomimetic models that contain elements of photosynthesis are fundamental in the development of synthetic systems that can use sunlight to produce fuel. The critical task consists of running several rounds of light-induced charge separation, which is required to accumulate enough redox equivalents at the catalytic sites for the target chemistry to occur. Long-lived first charge-separated state and distinct electronic signatures for the sequential charge accumulated species are essential features to be able to track these events on a spectroscopic ground. Read More

    Subporpholactone, Subporpholactam, Imidazolosubporphyrin, and Iridium Complexes of Imidazolosubporphyrin: Formation of Iridium Carbene Complexes.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    Kyoto University, Graduate School of Science, Department of Chemistry, Kita-shirakawa Oiwake-cho, Sakyo-ku, 606-8502, Kyoto, JAPAN.
    Pyrrole-modified subporphyrins bearing a non-pyrrolic cyclic unit, subporpholactone, subporpholactam, and imidazolosubporphyrin were newly synthesized. They show subporphyrin-like absorption and fluorescence spectra that are red-shifted in the order of subporpholactam < subporpholactone < imidazolosubporphyrin. Metalation of the imidazolosubporphyrin with (pentamethylcyclopentadienyl)iridium(III) dichloride dimer gave a complex, in which the Ir(III) atom was attached at the peripheral nitrogen atom of the imidazole moiety and the ortho-position of the meso-phenyl group. Read More

    Biomimic Peptide-Gated Nanoporous Membrane for On-Demand Molecule Transport.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    Technical Institute of Physical and Chemistry, Chinese Acdemy of Scienes, 29 Zhongguancun East Road, Haidian District, 100190, Beijing, CHINA.
    The controllable molecule transport is crucial to realize many highly valuable applications both in vivo and in vitro. Nanoporous membrane, with nanoscopic pores, high porosity, uniform pore dimension, and controllable surface chemical properties, hold tremendous potential to achieve this function. Here, we report a nano-gating system for on-demand molecule transport based on peptide-gated nanoporous membrane. Read More

    Achieving Strong Positive Cooperativity through Activating Weak Non-Covalent Interactions.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    South University of Science and Technology of China, Department of Chemistry, Xueyuan Blvd 1088, Nanshan District, 518055, Shenzhen, CHINA.
    Positive cooperativity achieved through activating weak non-covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new naphthotubes have been synthesized and the syn isomer binds DABCO-based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion-pairing interactions. Read More

    Photo-induced Pedalo-type Motion in an Azodicarboxamide-based Molecular Switch.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    University of Amsterdam, Van 't Hoff Institute for Molecular Sciences Faculty of Science, Science Park 904, 1098 XH , Amsterdam, NETHERLANDS.
    Well-defined structural changes of molecular units that can be triggered by light are crucial for the development of photoactive functional materials. Here we report on a novel switch that has azodicarboxamide as its photo triggerable element. Time-resolved UV-pump/IR probe spectroscopy in combination with quantum chemical calculations shows that the azodicarboxamide functionality -in contrast to other azo-based chromophores- does not undergo trans-cis photoisomerization. Read More

    Deep Level Defect-Enhanced Photothermal Performance of Bismuth Sulfide-Gold Heterojunction Nanorods for CT Imaging-Guided Photothermal Therapy of Cancer.
    Angew Chem Int Ed Engl 2017 Nov 15. Epub 2017 Nov 15.
    Changchun Institute of Applied Chemistry Chinese Academy of Sciences, Laboratory of Chemical Biology, 5625 Renmin Street, 130022, Changchun, CHINA.
    Bismuth sulfide (Bi2S3) nanomaterials are emerging as a promising theranostic platform for CT imaging and photothermal therapy of cancer. Herein, the photothermal property of Bi2S3 nanorods (NRs) was unveiled to intensely correlate to their intrinsic deep level defects (DLDs) that potentially could work as electron-hole nonradiative recombination centers to promote phonon production, ultimately leading to photothermal performance. Bi2S3-Au heterojunction NRs were designed to hold more significant DLD property, exhibiting more potent photothermal performance than Bi2S3 NRs. Read More

    N-Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient Strategy for Enantioselective Remote Functionalizations.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    RWTH Aachen, Institute of Organic Chemistry, Landoltweg 1, 52072, Aachen, GERMANY.
    N-heterocyclic carbene (NHC) catalysis has emerged as a powerful strategy in organic synthesis. In recent years a number of reviews have been published on NHC-catalyzed transformations involving Breslow intermediates, acyl azoliums, α,β-unsaturated acyl azoliums, homoenolate equivalents and azolium enolates. However, the azolium dienolate intermediates generated by NHCs have been employed in asymmetric synthesis only very recently, especially in cycloadditions dealing with remote functionalization. Read More

    In Situ Scatheless Cell Detachment Reveals Connections Between Adhesion Strength and Viability at Single-Cell Resolution.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Tsinghua University, Department of Chemistry, Haidian, 100084, Beijing, CHINA.
    Single-cell biology provides insights to some of the most fundamental processes in biology and promotes the understanding of life's mysteries. And as the technologies to study single-cells expand, they will require sophisticated analytical tools to make sense of various behaviors and components of single-cells as well as their relations in adherent tissue culture. In this paper, we revealed cell heterogeneity and uncovered the connections between cell adhesion strength and cell viability at single-cell resolution by extracting single adherent cells of interest from standard tissue culture via a microfluidic chip based Live Single-Cell Extractor (LSCE). Read More

    Cobalt-catalyzed Suzuki biaryl coupling of aryl halides.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    University of Bristol, School of Chemistry, Cantock's Close, BS8 1TS, Bristol, UNITED KINGDOM.
    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 is reduced to Co(0) during catalysis. Read More

    A Simple Pre-lithiation Strategy to Build High-Rate and Long-life Lithium-ion Battery with Improved Low-temperature Performance.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Lithium-ion batteries (LIBs) are being used to power the commercial electric vehicles (EVs). However, the charge/discharge rate and life of current LIBs still cannot satisfy the further development of EVs. Furthermore, the poor low temperature performance of LIBs limits their application in cold climates and high altitude areas. Read More

    Internal Peptide Late-Stage Diversification: Peptide Isosteric Triazoles for Primary and Secondary C(sp3)-H Activation.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Georg-August-Universitaet Goettingen, Institut fuer Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Goettingen, GERMANY.
    Secondary C(sp3)-H arylations were accomplished by peptide bond isosteric triazoles in palladium catalysis. The unique power of this approach was reflected by enabling secondary C(sp3)-H functionalizations on terminal peptides as well as the unprecedented positional-selective C(sp3)-H functionalization of internal peptides, setting the stage for modular peptide late-stage diversification. Read More

    Conductive Microporous Covalent Triazine-Based Framework for High-Performance Electrochemical Capacitive Energy Storage.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Dalian Institute of Chemical Physics, State Key Lab of Molecular Reaction Dynamics, 457 Zhongshan Road, 116023, Dalian, CHINA.
    Nitrogen enriched porous nanocarbon, graphene and conductive polymers attracted increasing attention in the application of supercapacitors. However, the electrode material possessing large specific surface area (SSA) and high nitrogen doping concentration simultaneously, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane-derived conductive microporous covalent triazine-based frameworks (marked as TCNQ-CTFs) with high nitrogen content (> 8%) and large SSA (> 3600 m²/g) at the same time. Read More

    Organocatalyzed photo-controlled radical polymerization of semi-fluorinated (meth)acrylates driven by visible light.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Fudan University, State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Yangpu, Handan Road 220, Yuejin Building 505, 200433, Shanghai, CHINA.
    Fluorinated polymers are important materials that are widely used in many areas. Herein, we report the development of a metal-free photo-controlled radical polymerization of semi-fluorinated (meth)acrylates with a new visible light absorbing organocatalyst. This method allows the production of a variety of semi-fluorinated polymers with narrow molar weight distributions from semi-fluorinated trithiocarbonates or perfluoroalkyl iodide. Read More

    Oxime Ether Radical Cations Stabilized by N-Heterocyclic Carbene.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    POSTECH, Department of Chemistry and Division of Advanced Materials Science, 77 Cheongam-Ro, Nam-Gu, 790-784, Pohang, KOREA, REPUBLIC OF.
    N-heterocyclic carbene nitric oxide (NHCNO) radicals, which can be regarded as iminoxyl radicals stabilized by NHCs, were found to react with a series of silyl and alkyl triflates to generate the corresponding oxime ether radical cations. The structures of the resulting oxime ether radical cations were determined by X-ray crystallography, along with EPR and computational analysis. In contrast, lutidinium triflate produced a 1:1 mixture of [NHCNO+][OTf-] and [NHCNHOH+][OTf-] upon the reaction with NHCNO. Read More

    A General Strategy for Development of Near-Infrared Fluorescent Probes for Bioimaging.
    Angew Chem Int Ed Engl 2017 Nov 13. Epub 2017 Nov 13.
    Division of Cancer Epidemiology and Genetics, NCI, NIH, UNITED STATES.
    Near-infrared (NIR) fluorescent dyes with favorable photophysical properties are highly useful for bioimaging, but such dyes are still rare. Here, we describe the development of a unique class of NIR dyes via modifying the rhodol-scaffold with fused tetrahydroquinoxaline rings. These new dyes showed large Stokes shifts (>110 nm). Read More

    Crochelins, siderophores with a novel iron-chelating moiety from the nitrogen-fixing bacterium Azotobacter chroococcum.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Princeton University, Chemistry, Washington University, Frick Chemistry Lab, Room 333, 08544, Princeton, UNITED STATES.
    Microbes utilize siderophores to access essential iron resources. Over 500 siderophores are known, but they utilize a small set of common moieties to bind iron. Azotobacter chroococcum expresses iron-rich nitrogenases with which it reduces N2. Read More

    One-pot synthesis of contracted and expanded porphyrins with meso-CF3 groups, from affordable precursors.
    Angew Chem Int Ed Engl 2017 Nov 13. Epub 2017 Nov 13.
    Technion Israel Institute of Technology, Chemistry, Technion City, 32000, Haifa, ISRAEL.
    Corrole and sapphyrin with the smallest meso-substituents reported so far were prepared in a one-pot synthesis that relies on a non-aldehydic precursor for introducing CF3 groups. The substantial amounts of products obtained by this facile pathway allowed for the full characterization of 5,10-15-tris(trifluoromethyl)corrole, the access to a variety of stable chelates thereof and investigations that disclose the unique structural and chemical properties induced by the CF3 substituents. The novel 5,10,15,20-tetra(trifluoromethyl)sapphyrin does undergo only single protonation, which according to its crystal structure is stabilized by favorable non-bonding F/H interaction between the meso-CF3 and the inverted pyrrolic NH. Read More

    Transition Metal pi-Ligation of a Tetrahalodiborane.
    Angew Chem Int Ed Engl 2017 Nov 14. Epub 2017 Nov 14.
    Julius Maximilians Universität Würzburg, Department of Chemistry, Am Hubland, 97074, Würzburg, GERMANY.
    The reaction of tetraiododiborane (B2I4) with trans- [Pt(BI2)I(PCy3)2] led to isolation of the diplatinum(II) complex [{(Cy3P)(I2B)Pt}2(μ2:h3:h3-B2I4)], supported by the bridging diboranyl dianion ligand [B2I4]2-. The complex is the first transition metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B2X4 (X = halide) unit of any type to a metal center. Read More

    Magnetic actuation of discrete liquid entities with a deformable paramagnetic liquid substrate.
    Angew Chem Int Ed Engl 2017 Nov 12. Epub 2017 Nov 12.
    Ecole Normale Supérieure, Department of Chemistry, 24, rue Lhomond, 75005, Paris, FRANCE.
    Magnetic actuation of 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 or oil, unless magnetosensitive particles are added. Here, we describe a new way to magnetically control the motion of discrete liquid entities, in an additive-free and surface tension-independent manner. 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. Read More

    Columnar Liquid-Crystal from a Giant Macrocycle Mesogen.
    Angew Chem Int Ed Engl 2017 Nov 12. Epub 2017 Nov 12.
    Nagoya University, Department of Chemistry, Graduate School of Science, Furo-cho, Chikusa-ku, 464-8602, Nagoya, JAPAN.
    Columnar liquid crystals composed of a giant macrocyclic mesogen were prepared. The giant macrocyclic mesogen has a square hollow with a 2.5 nm diagonal, which was bounded by diindolo[3,2-b:2',3'-h]carbazole (diindolocarbazole) moieties as the edges and bis(salicylidene)-o-phenylenediamine (salphen) moieties as the corners. Read More

    Fluorinated Vinylsilanes from the Copper-Catalyzed Defluorosilylation of Fluoroalkene Feedstocks.
    Angew Chem Int Ed Engl 2017 Nov 12. Epub 2017 Nov 12.
    Osaka University, Department of Applied Chemistry Faculty of Engineering, Yamadaoka 2-1, 565-0871, Suita, JAPAN.
    Herein, a copper-catalyzed C-F bond defluorosilylation reaction of tetrafluoroethylene and other polyfluoroalkenes is described. Mechanistic studies, based on a series of stoichiometric reactions with copper complexes, revealed that the key steps of this defluorosilylation reaction are: i) the 1,2-addition of a silylcopper intermediate to the polyfluoroalkene, and ii) a subsequent selective β-fluorine elimination, which generates a Cu-F species. The β-fluorine elimination is facilitated by the Lewis acidic F-Bpin, which is generated in situ during the defluorosilylation. Read More

    Total Syntheses of the Monoterpenoid Indole Alkaloids (±)-Alstoscholarisine B and C.
    Angew Chem Int Ed Engl 2017 Nov 13. Epub 2017 Nov 13.
    Penn State University, Chemistry, 104 Chemistry Building, 16802, University Park, UNITED STATES.
    Total syntheses of the monoterpenoid indole alkaloids (±)-alstoscholarisine B (2) and C (3) have been accomplished starting from readily available indole-2-acetic ester 6 and unsaturated N-sulfonyllactam 7. Read More

    Oxidative Dissolution of Resoles: A Versatile Approach to Intricate Nanostructures.
    Angew Chem Int Ed Engl 2017 Nov 13. Epub 2017 Nov 13.
    Building 75,Cnr College Rd & Cooper Rd, 4067, Brisbane, AUSTRALIA.
    Resoles are base-catalyzed phenol-formaldehyde resins with a 3-dimensional cross-linked framework. The chemistry of resoles is generally considered as highly chemical resistant, thus calcination is always used in the treatment of resole-type resin, which significantly limit the diversity of nanostructured materials derived from resole-type resins. Here we report that selected metal nitrate solutions can be applied to dissolve various types of nanostructured resoles through an oxidative dissolution mechanism. Read More

    Three-Dimensional Graphene Networks with Abundant Sharp Edge Sites for Efficient Electrocatalytic Hydrogen Evolution.
    Angew Chem Int Ed Engl 2017 Nov 11. Epub 2017 Nov 11.
    Technical Institute of Physics and Chemistry, the Chinese Academy of Sciences, 100190, Beijing, CHINA.
    To achieve sustainable production of hydrogen (H2) through water splitting, establishing efficient and earth-abundant electrocatalysts is of great necessity. Here, we firstly reveal that morphology engineering of graphene can modulate the electronic structure of carbon skeleton and in turn endow it with excellent ability of proton reduction. Three-dimensional (3D) graphene networks with the high density of sharp edge sites are synthesized. Read More

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