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    34577 results match your criteria Angewandte Chemie International Edition [Journal]

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    Manganese-Catalyzed Carbonylative Annulations for Redox-Neutral Late-Stage Diversification.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    Georg-August-Universitaet Goettingen, Institut fuer Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Goettingen, GERMANY.
    An inexpensive, non-toxic manganese catalyst enabled unprecedented redox-neutral carbonylative annulations under ambient pressure. The manganese catalyst outperformed all other typically used base and precious metal catalysts. The outstanding versatility of the manganese catalysis manifold was reflected by ample substrate scope, setting the stage for effective late-stage manipulations under racemization-free conditions on a wealth of marketed drugs and natural products, including alkaloids, amino acids, steroids and carbohydrates. Read More

    A Rational Delamination Strategy towards Defect-Free, High-Mobility, Few-Layered Black Phosphorus Flakes.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    Technische Universitaet Dresden, Chair for Molecular Functional Materials, Mommsenstrasse 4, D-01062, Dresden, GERMANY.
    The extraordinary electronic and photonic features render black phosphorus (BP) an important material for the development of novel electronics and optoelectronics. Despite the recent progress in the preparation of few-layered BP flakes, scalable synthesis of large-size, pristine BP flakes represents one of the main challenges. Here we demonstrate an electrochemical delamination strategy, based on the intercalation of diverse cations in non-aqueous electrolytes, to peel off bulk BP crystals into few-layer, defect-free flakes. Read More

    Pathway complexity versus hierarchical self-assembly in N-annulated perylenes. Structural effects in seeded supramolecular polymerization.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    UCM, Quimica Organica, Ciudad Universitaria s/n, 28040, Madrid, SPAIN.
    The self-assembly of a series of N-annulated perylenes are investigated. Compound 1, endowed with inner amides, shows a pathway complexity in which the inactivated monomeric species, stored as an off-pathway aggregate, kinetically switch into on-pathway, helical structures. This out-of-equilibrium process can be accelerated by the addition of seeds. Read More

    Rapid Analysis of Cell-Nanoparticle Interaction using Single Cell Raman Trapping Microscopy.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    GERMANY.
    Iron oxide nanoparticles have been used in preclinical studies to label stem cells for non-invasive tracking and homing. There is continuous search for novel particle candidates that are suitable for clinical applications. Since standard analyses to investigate cell-particle interaction and safety are labor-intensive, an efficient procedure is required to guide future particle development and to exclude adverse health effects. Read More

    An Amorphous Noble-Metal-Free Electrocatalyst Enables N2 Fixation under Ambient Conditions.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    The University of Texas at Austin, Materials Science and Engineering, 1 University Station, C2200, 78712, Austin, UNITED STATES.
    The N2 fixation via the electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is regarded as a potential approach to achieve NH3 production, which still heavily relies on the Haber-Bosch process at the cost of huge energy and massive production of CO2. In this paper, we report a noble-metal-free Bi4V2O11/CeO2 hybrid with amorphous phase (BVC-A) as cathode for electrocatalytic NRR. The amorphous Bi4V2O11 owns significant defects, which play a role as active sites. Read More

    Dual C(sp3)-H Bond Functionalization of N-Heterocycles via Visible-Light Photocatalyzed Dehydrogenation/[2+2] Cycloaddition Sequential Reaction.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    Lanzhou University, Dept. Chem, 222 Tianshuisouth Road, Lanzhou, 730000, Lanzhou, CHINA.
    Here we describe a mild method to achieve dual C(sp3)-H bond functionalization of saturated nitrogen-containing heterocycles via a sequential visible-light photocatalyzed dehydrogenation/[2+2] cycloaddition procedure. As a complementary approach to the well-established iminium ion and α-amino radical intermediates, the elusive cyclic enamine intermediates are effectively generated via photoredox catalysis under mild conditions, which are efficiently captured by acetylene ester to form a wide array of bicyclic amino acid derivatives and realize the simultaneous functionalization of two vicinal C(sp3)-H bonds. Read More

    Design, Synthesis and Application of Novel Chiral C2-symmetric Spiroketal-containing Ligands in Transition Metal Catalysis.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    University of Michigan, Chemistry, 930 N. University Avenue, 48109, Ann Arbor, UNITED STATES.
    We present an expedient and economical route to a new spiroketal-based C2-symmetric chiral scaffold termed SPIROL. Based on this spirocyclic scaffold, several chiral ligands were generated and successfully employed in an array of stereoselective transformations including Ir-catalyzed hydroarylation (up to 95% ee), Pd-catalyzed allylic alkylation (up to 97% ee), intermolecular Pd-catalyzed Heck reaction (up to 95% ee), and Rh-catalyzed hydrogenations of dehydroalanine (up to 93% ee). Read More

    Chaotropic Monovalent Anion Induced Rectification Inversion at Polyimidazolium Brushes Modified Nanopipettes.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Chinese Academy of Sciences, Institute of Chemistry, North first street No. 2, zhonguancun, 100190, Beijing, CHINA.
    Here we report a nonintuitive observation of monovalent anion-induced ion current rectification inversion at polyimidazolium brush (PimB) modified nanopipettes. The rectification inversion degree is found to be strongly dependent on the concentration and species of monovalent anions. For chaotropic anions , the rectification inversion is easily observed at a low concentration (5 mM), while there is no rectification inversion observed for kosmotropic anions (e. Read More

    Li2B12 and Li3B12: Prediction of the smallest tubular and cage-like boron structures.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    MEXICO.
    We report an intriguing structural transition from the quasi-planar form of B12 cluster upon the interaction with lithium atoms. High-level computations show that the lowest energy structures of LiB12, Li2B12, and Li3B12 have quasi-planar (Cs), tubular (D6d), and cage-like (Cs) geometries, respectively. The energetic cost of distorting the B12 quasi-planar fragment is overcompensated by an enhanced electrostatic interaction between the Li cations and the tubular or cage-like B12 fragments, which is the main reason of such drastic structural changes, resulting in the smallest tubular (Li2B12) and cage-like (Li3B12) boron structures reported until now. Read More

    Fluoride-Catalyzed Deblocking as a New Route to Polymeric Urethanes.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    University of Massachusetts, Polymer Science and Engineering, 120 Governors Drive, Conte Center for Polymer Research, 01003, Amherst, UNITED STATES.
    We report a fluoride-catalyzed deblocking of urethanes as "blocked" isocyanates. Organic and inorganic sources of fluoride ion proved effective for deblocking urethanes and for converting polyurethanes to small molecules. Distinct from conventional deblocking chemistry involving organometallic compounds and high temperatures, the method we describe is metal-free and operates at or slightly above room temperature. Read More

    Metal-Free Dehydrogenation of N-Heterocycles by Ternary h-BCN Nanosheets with Visible Light.
    Angew Chem Int Ed Engl 2018 Feb 23. Epub 2018 Feb 23.
    Fuzhou University, Chemistry, 523 Gongye Rd, Gulou, 350000, Fuzhou, CHINA.
    An efficient metal-free catalytic system has been developed using hexagon boron carbon nitride (h-BCN) nanosheets for the dehydrogenations of N-heterocycles with visible light, while releasing hydrogen gas (H2), and thus no proton acceptor is needed. This acceptorless dehydrogenation of hydroquinolines, hydroisoquinolines or indolines to the corresponding aromatic N-heterocycles has been achieved with excellent yield by visible light irradiation under the ambient temperature. With h-BCN as the photocatalyst and water as the solvent, this protocol shows broad substitution tolerance, environment benign and high efficiency. Read More

    Spectroscopic and computational characterization of DTPA-transplutonium chelates: evidencing heterogeneity in the heavy actinide(III) series.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Lawrence Berkeley National Laboratory, Chemical Sciences Division, One Cyclotron Road, MS 70A-1150, 94720, Berkeley, UNITED STATES.
    The chemistry of trivalent transplutonium ions (Am3+, Cm3+, Bk3+, Cf3+, Es3+) is usually perceived as monotonic and parallel to that of the trivalent lanthanide series. Herein, we present the first extended X-ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to a much shorter metal-oxygen nearest-neighbor bond lengths in the case of Cf3+. Read More

    Gene Expression on DNA Biochips Patterned with Strand Displacement Lithography.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Technische Universitat Munchen, Physik-Department E14 and ZNN/WSI, Am Coulombwall 4a, 85748, Garching, GERMANY.
    Lithographic patterning of DNA molecules enables spatial organization of cell-free genetic circuits under well-controlled experimental conditions. Here, we present a biocompatible, DNA-based resist termed "Bephore" based on commercially available components, which can be patterned by both photo- and electron beam lithography. The patterning mechanism is based on cleavage of a chemically modified DNA hairpin by ultraviolet light or electrons, and a subsequent strand displacement reaction. Read More

    Nanobody-enabled reverse pharmacology on GPCRs.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Vrije Universiteit Brussel, VIB-VUB center for Structural Biology, pleinlaan 2, 1050, Brussels, BELGIUM.
    The conformational complexity of G protein-coupled receptor (GPCR) transmembrane signaling is a central hurdle for the design of screens for receptor agonists. In their basal states, GPCRs have lower affinities for agonists compared to their G protein-bound active state conformations. Moreover, different agonists can stabilize distinct active receptor conformations and do not uniformly activate all cellular signaling pathways linked to a given receptor (agonist bias). Read More

    Electron Transfer around a Molecular Corner.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Universität Basel, Departement für Chemie, St. Johanns-Ring 19, 4056, Basel, SWITZERLAND.
    The distance dependence of electron transfer (ET) is commonly investigated in linear rigid rod-like compounds, but studies of molecular wires with integrated corners imposing 90° angles are very rare. By using spirobifluorene as a key bridging element and by substituting it at different positions, two isomeric series of donor-bridge-acceptor compounds with either nearly linear or angled geometries were obtained. Photoinduced ET in both series is dominated by rapid through-bond hole hopping across oligo-fluorenes over distances of up to 70 Å. Read More

    Fire-retardant and thermally insulating phenolic-silica aerogels.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    University of Science and Technology of China, Division of Nanomaterials & Chemistry, Jinzhai Road 96, Hefei National Laboratory for Physical Sciences at Microscale, 230026, Hefei, CHINA.
    Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by a poor fire resistance and inorganic insulation materials display a high thermal conductivity. Here we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Read More

    Rational tuning of fluorobenzene probes for cysteine-selective protein modification.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    University of Copenhagen, Department of Chemistry, Universitetsparken 5, DK2100, Copenhagen, DENMARK.
    Fluorobenzene probes for protein profiling through selective cysteine labeling have been developed by rational reactivity tuning. Tuning was achieved by selecting an electron-withdrawing para-substituent combined with variation of the number of fluorine substituents. Optimized probes chemo-selectively arylated cysteine residues in proteins under aqueous conditions. Read More

    Covalent Functionalization of Black Phosphorus with Conjugated Polymer for Information Storage.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    CHINA.
    Major disadvantages of black phosphorus (BP) are its poor air-stability and poor solubility in common organic solvents. The best way to solve this problem is to incorporate BP into a polymer backbone or a polymer matrix to form novel functional materials that can provide both challenges and opportunities for new innovation in e.g. Read More

    Molecular recognition by a short partial peptide of adrenergic receptor - Bottom-up approach.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Tokyo Institute of Technology, Chemical Resources Laboratory R1-15, 4259 Nagatsuta-cho, Midori-ku, Midori-ku, 226-8503, Yokohama, Kanagawa, JAPAN.
    Receptor-neurotransmitter molecular recognition is key of neurotransmission. Although crystal structures of the receptors are known, the mechanism for recognition is not clear. At present, the trial-and-error approach is the only sure method to identify ligands (e. Read More

    Total Synthesis of (-)-Enigmazole A.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Chuo University, Department of Applied Chemistry, 1-13-27 Kasuga, Bunkyo-ku, 112-8551, Tokyo, JAPAN.
    Total synthesis of (-)-enigmazole A, a marine macrolide natural product with cytotoxic activity, has been accomplished. The tetrahydropyran moiety was constructed by means of a domino olefin cross-metathesis/intramolecular oxa-Michael addition of a δ-hydroxy olefin. After coupling of advanced intermediates, the macrocycle was forged via a gold-catalyzed rearrangement of a propargylic benzoate, followed by a ring-closing metathesis of the resultant α,β-unsaturated ketone. Read More

    Sensor Technologies Empowered by Materials and Molecular Innovations.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Department of Chemistry, Massachusetts Institute of Technology, USA.
    Functional synthetic designer materials can impact many advanced technologies, and the chemical sensor area is intimately reliant on these new chemical innovations. The transduction of chemical and biological signals is necessary for low cost omnipresent chemical sensing and will be realized by chemical designs of new transduction materials. We are poised for many new innovations to empower new generations of sensor technologies. Read More

    The [2+2] Cycloaddition-Retroelectrocyclization (CA-RE) Click Reaction: Facile Access to Molecular and Polymeric Push-Pull Chromophores.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093, Zurich, Switzerland.
    The [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction between electron-rich alkynes and electron-deficient alkenes is an efficient procedure to create nonplanar donor-acceptor (D-A) chromophores in both molecular and polymeric platforms. They feature attractive properties including intramolecular charge-transfer (ICT) bands, nonlinear optical properties, and redox activities for use in next-generation electronic and optoelectronic devices. This Review summarizes the development of the CA-RE reaction, starting from the initial reports with organometallic compounds to the extension to purely organic systems. Read More

    Dye-incorporated Polynaphthalenediimide Acceptor for Additive-free High-performance All-polymer Solar Cells.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    CHINA.
    All-polymer solar cells (all-PSCs) can offer unique advantages for applications in flexible devices, and naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors. However, their power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells, due to low light absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor. In this work, by means of simple random copolymerization, a rhodanine-based dye molecule was introduced into the NDI-based polymer acceptor and showed an improved light absorption coefficient, an up-shifted lowest unoccupied molecular orbital level and reduced crystallization. Read More

    The Fourth Alloying Mode by Way of Anti-Galvanic Reaction.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    Institute of Solid State Physics, Key Laboratory of Materials Physics, 350 Shushanhu Road, 230031, Hefei, CHINA.
    Anti-galvanic reaction (AGR) not only defies classic galvanic theory but also is a promising method for tuning noble metal nanoparticles' compositions, structures and properties. In particular, employing AGR for the preparation of alloy nanoparticles has recently received extensive interest. Herein, we report on a unprecedented alloying mode by way of AGR, in which the foreign atoms induce the structural transformation of the mother nanoparticles and enter the novel nanoparticles in a non-replacement fashion. Read More

    The Cyclic Hydrogen-Bonded 6-Azaindole Trimer and Its Prominent Excited-State Triple Proton Transfer Reaction.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    National Taiwan University, Department of Chemistry, 10617, Taipei, TAIWAN.
    We report a previously unrecognized feature in that 6-azaindole undergoes self-assembling via N(1)-H... Read More

    Discovery of a Fungal Multicopper Oxidase That Catalyzes the Regioselective Coupling of a Tricyclic Naphthopyranone To Produce Atropisomers.
    Angew Chem Int Ed Engl 2018 Feb 22. Epub 2018 Feb 22.
    Graduate School of Pharmaceutical Sciences, Kitasato University, Laboratory Microbial Chemistry, 5-9-1 Shirokane, Minato-ku, 1088641, Tokyo, JAPAN.
    Atropisomer dinapinones (DP) A1 and A2 were isolated from a culture of Talaromyces pinophilus FKI-3864. Monapinone coupling enzyme (MCE), which dimerizes naphthopyranone monapinone (MP) A, was purified from a cell-free extract of T. pinophilus FKI-3864. Read More

    Readily production of flow reactor cartridges by 3D printing of thermostable enzymes.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    Karlsruher Institut fur Technologie, IBG-1, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, GERMANY.
    Compartmentalization of chemical reactions is an essential principle of life that provides a major source of innovation for the development of novel approaches in biocatalysis. To implement spatially controlled biotransformations, rapid manufacturing methods are needed for the production of biocatalysts applicable in flow systems. While three-dimensional (3D) printing techniques offer high throughput manufacturing capability, they are not usually compatible with the delicate nature of enzymes, which call for physiological processing parameters. Read More

    Highly Stable Lithium Metal Batteries Enabled by Regulating the Li+ Solvation in Nonaqueous Electrolyte.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    Tsinghua University, Department of Chemical Engineering, Gongwu Building 308B, 100084, Beijing, CHINA.
    Safe and rechargeable lithium (Li) metal batteries have been hindered by the uncontrollable Li dendrites, where nonaqueous electrolyte always plays a significant role in practical batteries. Herein an emerging electrolyte based on a simple solvation strategy was proposed for highly stable Li metal anodes in both coin and pouch cells. Fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3) were concurrently introduced into electrolyte, altering the solvation sheath of Li ions and then forming uniform solid electrolyte interphase (SEI) with abundant LiF and LiNxOy on a working Li metal anode that contributes to dendrite-free Li deposition. Read More

    Literally green chemical synthesis of artemisinin from plant extracts.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    GERMANY.
    Active pharmaceutical ingredients are either extracted from biological sources - where they are synthesized in complex, dynamic environments - or prepared via step-wise chemical syntheses by reacting pure reagents and catalysts under controlled conditions. A combination of these two approaches, where plant extracts containing reagents and catalysts are utilized in intensified chemical syntheses, creates expedient and sustainable processes. We illustrate the principle by reacting crude plant extract, oxygen, acid, and light to produce artemisinin, a key active pharmaceutical ingredient of the most powerful anti-malaria drugs. Read More

    Classical N-Heterocyclic Carbenes Derived Crystalline Radicals.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    GERMANY.
    One electron reduction of C2-arylated 1,3-imidazoli(ni)um salts (IPrAr)Br (Ar = Ph, 3a; 4-DMP, 3b; 4-DMP = 4-Me2NC6H4) and (SIPrAr)I (Ar = Ph, 4a; 4-Tol, 4b) derived from classical NHCs (IPr = :C{N(2,6-iPr2C6H3)}2CHCH, 1; SIPr = :C{N(2,6- iPr2C6H3)}2CH2CH2, 2) gives radicals [(IPrAr)]* (Ar = Ph, 5a; 4-DMP, 5b) and [(SIPrAr)]* (Ar = Ph, 6a; 4-Tol, 6b). Each of 5a,b and 6a,b exhibits a doublet EPR signal, a characteristic of monoradical species. The first solid-state characterization of NHC-derived carbon-centered radicals 6a,b by single crystal X-ray diffraction is reported. Read More

    Revealing Transient Concentration of CO2 in a Mixed Matrix Membrane by IR Microimaging and Molecular Modeling.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    University of Leipzig, Department of Interface Physics, Linnéstrasse 5, 04103, Leipzig, GERMANY.
    Through IR microimaging the spatially and temporally resolved development of the CO2 concentration in a ZIF-8@6FDA-DAM mixed matrix membrane was visualized during transient adsorption. By recording the evolution of the CO2 concentration, it is observed that the CO2 molecules propagate from the ZIF-8 filler, which acts as a transport "highway", towards the surrounding polymer. A high-CO2-concentration layer is formed at the MOF/polymer interface, which becomes more pronounced at higher CO2 gas pressures. Read More

    Site-Specific Studies of Nucleosome Interactions by Solid-State NMR.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    Utrecht University, NMR Group, Padualaan 8, 3584CH, Utrecht, NETHERLANDS.
    Chromatin function depends on a dense network of interactions between nucleosomes and wide range of proteins. A detailed description of these protein-nucleosome interactions is required to reach a full molecular understanding of chromatin function in both genetics and epigenetics. Here, we show that the structure, dynamics and interactions of nucleosomes can be interrogated in a residue-specific manner using state-of-the-art solid-state NMR. Read More

    Super-chelators for advanced protein labeling in living cells.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    Johann Wolfgang Goethe-University, Biozentrum, Max-von-Laue-Str.9, 60438, Frankfurt a.M., GERMANY.
    Live-cell labeling, super-resolution microscopy, single-molecule applications, protein localization or chemically induced assembly are emerging approaches, which require specific and very small interaction pairs. The minimal disturbance of protein function is essential to derive unbiased insights into cellular processes. Here, we define a new class of hexavalent N-nitrilotriacetic acid (hexaNTA) chelators, displaying the highest affinity and stability of all NTA-based small interaction pairs described so far. Read More

    Revealing active species for aerobic alcohol oxidation using stoichiometrically uniform supported Pd catalysts.
    Angew Chem Int Ed Engl 2018 Feb 21. Epub 2018 Feb 21.
    CHINA.
    Supported metal catalysts are one of the foundations of modern chemical industry. The active species in such catalysts are always elusive to identify, and in the meanwhile large quantities of inert species can cause significant waste. Herein, using a stoichiometrically precise synthetic method, we prepare atomically dispersed palladium-cerium oxide (Pd1/CeO2) and hexapalladium cluster-cerium oxide (Pd6/CeO2), as confirmed by spherical-aberration-corrected transmission electron microscopy and X-ray absorption fine structure spectroscopy. Read More

    O2 sensitivity of [Fe]-hydrogenase in the Presence of Reducing Substrates.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    Max-Planck-Institute for Terrestrial Microbiology, Department of Biochemistry, Karl-von-Frisch Strasse 10, 35043, Marburg, GERMANY.
    [Fe]-hydrogenase reversibly catalyzes the transfer of a hydride ion from H2 to methenyl-tetrahydromethanopterin (methenyl-H4MPT+) to form methylene-H4MPT. Its iron-guanylylpyridinol (FeGP) cofactor plays a key role in H2 activation. Here, we show that [Fe]-hydrogenase becomes O2-sensitive under turnover conditions in the presence of the reducing-substrates, methylene-H4MPT or methenyl-H4MPT+/H2. Read More

    Customizing the Electrochemical Properties of Carbon Nanodots with Quinones in Bottom-Up Syntheses.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    ITALY.
    We show how the redox potentials of Carbon Nanodots (CNDs) can be modulated by employing quinones as electroactive precursors during the microwave-assisted synthetic step. We prepared and characterized a redox library of CNDs, demonstrating that this approach can promote the use of carbon nanodots for ad-hoc applications, including photocatalysis. Read More

    Odorant receptor 7D4 activation dynamics.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    UNITED STATES.
    Deciphering how an odorant activates an odorant receptor (OR) and how changes in specific OR residues affect its responsiveness are central to understanding how we smell. A joint approach combining site-directed mutagenesis and functional assays with computational modeling has been used to explore the signaling mechanics of OR7D4. In this OR, a genetic polymorphism affects our perception of androstenone. Read More

    Chiral 1,3,2-Diazaphospholenes as Catalytic Molecular Hydrides for Enantioselective Conjugate Reductions.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    SWITZERLAND.
    Secondary 1,3,2-diazaphospholenes have a polarized P-H bond and are emerging as molecular hydrides. A class of chiral conformationally restricted methoxy-1,3,2-diazaphospholene catalysts is reported. We demonstrate their catalytic potential in enantioselective 1,4-reduction of α,β-unsaturated carbonyl derivatives comprising enones, acyl pyrroles and amides in enantioselectivities of up to 95. Read More

    Lewis Acid Catalyzed Enantioselective Desymmetrization of Donor-Acceptor Meso-Diaminocyclopropanes.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    Ecole Polytechnique Federale de Lausanne, ISIC - Laboratory of Catalysis and Organic Synthesis, EPFL BCH 4306 Batiment chimie UNIL, 1015, Lausanne, SWITZERLAND.
    The first example of Lewis acid catalyzed enantioselective ring-opening desymmetrization of donor-acceptor meso-diaminocyclopropanes is reported herein. A copper(II)-catalyzed Friedel-Crafts alkylation of indoles and a pyrrole with an unprecedented meso-diaminocyclopropane delivered enantioenriched diastereomerically pure urea products, which are structurally related to natural and synthetic bioactive compounds. The development of a new ligand through the investigation of an underexplored subclass of BOX ligands was essential for obtaining high enantiomeric ratios. Read More

    One-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single Pd-Carbodicarbene Complex.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    UNITED STATES.
    The combination of conventional transition metal-catalyzed coupling (2e- process) and photoredox catalysis (1e- process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild conditions. We report a Pd-carbodicarbene (CDC) complex that mediates both Suzuki-Miyaura coupling and photoredox catalysis for C-N bond formation upon visible-light irradiation. These two catalytic pathways can be further merged to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C-H arylation under ambient conditions with a single component catalyst in an efficient one-pot process. Read More

    Unprecedented Dearomatized Spirocyclopropane in a Sequential Rh(III)-catalyzed C-H Activation and Rearrangement Reaction.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    WWU Münster, Organisch-Chemisches Institut, Corrensstrasse 40, 48149, Münster, GERMANY.
    An unprecedented dearomatized spirocyclopropane intermediate was discovered in a sequential Cp*Rh(III)-catalyzed C-H activation and Wagner-Meerwein-type rearrangement reaction. How the oxidative O-N bond is cleaved and the role of HOAc were uncovered in this study. Furthermore, a Cp*Rh(III)-catalyzed dearomatization reaction of N-(naphthalen-1-yloxy)acetamide with strained olefins was developed, affording a variety of spirocyclopropanes. Read More

    Enzymatic or in vivo installation of propargyl groups in combination with click chemistry enables enrichment and detection of methyltransferase target sites in RNA.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    University of Muenster, Department of Chemistry, Institute for Biochemistry, Wilhelm-Klemm Strasse 2, 48149, Muenster, GERMANY.
    m6A is the most abundant internal modification in eukaryotic mRNA. It is introduced by METTL3-METTL14 and tunes mRNA metabolism, impacting cell differentiation and development. Precise transcriptome-wide assignment of m6A sites is of utmost importance. Read More

    Direct formation of C-C triple bonded structural motifs by on-surface dehalogenative homocoupling of tribromomethyl molecules.
    Angew Chem Int Ed Engl 2018 Feb 20. Epub 2018 Feb 20.
    Tongji University, CHINA.
    On-surface synthesis shows significant potential in constructing novel nanostructures/nanomaterials, which has been intensely studied over the recent years. The formation of acetylenic scaffoldings provides an important route to the fabrication of emerging carbon nanostructures including carbyne, graphyne and graphdiyne, which involve the chemically vulnerable sp-hybridized carbons. Herein, we designed and synthesized a tribromomethyl group, by using the combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy imaging and density functional theory calculations, we demonstrated that it is feasible to achieve the direct formation of C-C triple bonded structural motifs via on-surface dehalogenative homocoupling reactions. Read More

    Atomically dispersed metal sites in MOF-based materials for electrocatalytic and photocatalytic energy conversion.
    Angew Chem Int Ed Engl 2018 Feb 19. Epub 2018 Feb 19.
    National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, , 563-8577, Ikeda, JAPAN.
    Metal sites play an essential role for both electrocatalytic and photocatalytic energy conversion applications. The highly ordered arrangements of the organic linkers and metal nodes and the well-defined pore structures of metal-organic frameworks (MOFs) make them ideal substrates to support atomically dispersed metal sites (ADMSs) located in their metal nodes, linkers, and pores. Besides, porous carbon materials doped with ADMSs can be derived from these ADMS-incorporated MOF precursors through controlled treatments. Read More

    Phosphoric Acid Catalyzed Asymmetric [2+2] Cyclization/Penicillin-penillonic Acid Rearrangement.
    Angew Chem Int Ed Engl 2018 Feb 19. Epub 2018 Feb 19.
    Lanzhou University, Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Tianshui road 222#, 730000, Lanzhou, CHINA.
    The first example of asymmetric penicillin-penillonic acid (PPA) rearrangement was reported that is based on the first [2+2] cyclization followed by acid-catalyzed asymmetric rearrangement. In the presence of a phosphoric acid catalyst, the reaction of azlactones with β-carbolines generates α-amino-β-lactams, which undergo PPA rearrangement with high selectivities. This process represents the first [2+2] cyclization of azlactones with imines and the first PPA rearrangement, which are linked together by the phosphoric acid catalyst. Read More

    Counting the Clicks in Fluorescent Polymer Networks.
    Angew Chem Int Ed Engl 2018 Feb 19. Epub 2018 Feb 19.
    Queensland University of Technology, School of Chemistry, Physics and Mechanical Engineering, 2 George St, 4000, Brisbane, AUSTRALIA.
    We introduce a fluorescence-based methodology enabling the quantification of ligation points in photochemically prepared polymer networks, addressing the vexed question of quantifying the number of linkages within networks. Well-defined α,ω-tetrazole-capped polymer strands prepared via RAFT polymerization are crosslinked under UV irradiation by a trimaleimide via nitrile imine-mediated tetrazole-ene cycloaddition. Thus, for each linkage point a fluorescent pyrazoline ring is formed, resulting fluorescent networks, which are degradable by aminolysis of the trithiocarbonate functionalities, resulting in soluble fragments. Read More

    Iron-Catalyzed Cross-Coupling in the Synthesis of Pharmaceuticals: In Pursuit of Sustainability.
    Angew Chem Int Ed Engl 2018 Feb 19. Epub 2018 Feb 19.
    Rutgers University, Department of Chemistry, 73 Warren St., 07102, Newark, UNITED STATES.
    The scarcity of precious metals has given raise to the development of sustainable strategies for metal-catalyzed cross-coupling reactions. The establishment of new catalytic methods using iron is attractive due to low cost, abundance, ready availability and very low toxicity of iron. In the last few years sustainable methods for iron-catalyzed cross-couplings have entered the critical area of pharmaceutical research. Read More

    NiH-Catalyzed Reductive Relay Hydroalkylation: A Strategy for Remote sp3 C-H Alkylation of Alkenes.
    Angew Chem Int Ed Engl 2018 Feb 19. Epub 2018 Feb 19.
    Nanjing University, Chemistry, No 22 Hankou Road, 210093, Nanjing, CHINA.
    The terminal-selective, remote sp3 C-H alkylation of alkenes was achieved by a NiH-catalyzed reductive, chainwalking and sequential alkylation relay process. This method allows the construction of unfunctionalized C(sp3)-C(sp3) bonds, under mild conditions from two simple feedstock chemicals, olefins and alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent alkylation of isomeric mixtures of olefins with low catalyst loading. Read More

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