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https://www.readbyqxmd.com/read/28548850/highly-enantioselective-copper-and-iron-catalyzed-intramolecular-cyclopropanation-of-indoles
#1
Huan Xu, Li Yi-Pan, Yan Cai, Guo-Peng Wang, Shou-Fei Zhu, Qi-Lin Zhou
We report the first intramolecular enantioselective cyclopropa-nation of indoles, which was accomplished in good to high yield (up to 94%) with excellent enantioselectivity (up to >99.9% ee) by using copper or iron complexes of chiral spiro bisoxa-zolines as catalysts. This reaction is a straightforward, efficient method for constructing polycyclic compounds with an all-carbon quaternary chiral center at the 3-position of the indole skeleton, a core structure shared by numerous natural products and bioactive compounds...
May 26, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28548174/the-mechanism-change-by-switching-the-reactants-from-water-to-hydroxyl-ions-for-electrocatalytic-water-oxidation-a-case-study-of-copper-oxide-microspheres
#2
Xiaoqiang Du, Jingwei Huang, Yong Ding
Developing noble metal-free water oxidation catalysts is essential for many energy conversion/storage processes (e.g., water splitting). Herein, we report a facile synthesis of CuO microspheres composed of ultrathin, single-crystal-like nanosheets via a simple solution method. The as-obtained CuO microspheres can serve as an active and stable water oxidation catalyst under electrochemical reaction conditions, owing to their unique structural features. In electrochemical water oxidation, this catalyst affords a current density of 10 mA cm(-2) (a value related to practical relevance) at an overpotential of ∼0...
May 26, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28544781/pd-nanoparticles-immobilized-on-individual-calcium-carbonate-plate-derived-from-mussel-shell-waste-an-eco-friendly-catalyst-for-copper-free-sonogashira-coupling-reaction
#3
Trin Saetan, Chutiparn Lertvachirapaiboon, Ekgasit Sanong, Mongkol Sukwattanasinitt, Sumrit Wacharasindhu
Conversion of waste into high value materials has been considered an important sustainability strategy in modern chemical industries. Large volume of shell waste is generated globally from mussel cultivation. In this work, mussel shell wastes (Perna viridis) are transformed into individual calcium carbonate plate (ICCP) and apply as a support for heterogeneous catalyst. Palladium nanoparticles (3-6 nm) are deposited with even dispersion on ICCP surface as demonstrated by X-ray diffraction and scanning electron microscopy...
May 22, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28544744/structural-basis-for-copper-oxygen-mediated-c-h-bond-activation-by-the-formylglycine-generating-enzyme
#4
Marcel Meury, Matthias Knop, Florian P Seebeck
The formylglycine-generating enzyme (FGE) is a unique copper-protein that catalyzes oxygen-dependent C-H activation. We describe 1.66 Å- and 1.28 Å-resolution crystal structures of FGE from Thermomonospora curvata in complex with either Ag (I) or Cd (II) providing definitive evidence for a high-affinity metal-binding site in this enzyme. The structures reveal a bis-cysteine linear coordination of the monovalent metal, and tetrahedral coordination of the bivalent metal. Similar coordinational change may occur in the active enzyme as a result of Cu (I)/(II) redox cycling...
May 22, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28544004/new-insights-of-the-role-of-al2o3-in-the-promotion-of-cuznal-catalysts-a-model-study
#5
Jun Hu, Yanying Song, Junjie Huang, Yangyang Li, Mingshu Chen, Huilin Wan
The Cu/Al2O3/ZnO(0001)Zn ternary model catalysts, as well as their binary ones, were prepared and characterized. It was found that Al2O3 grew on the ZnO(0001)Zn surface by a layer-by-layer model, while Cu grew on the ZnO(0001)Zn surface as tow dimensional clusters until 0.2 ML, then three dimensional clusters. Because of the layer-by-layer growth of Al2O3 on the ZnO(0001)Zn, Cu/Al2O3 can be considered without the effect of ZnO. The ternary model catalyst of Cu/Al2O3/ZnO(0001)Zn which contains all of the three parts on the surface was prepared by deposition of Cu on the surface of Al2O3/ZnO(0001)Zn...
May 23, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28538656/recent-advances-in-c-c-and-c-n-bond-forming-reactions-catalysed-by-polystyrene-supported-copper-complexes
#6
REVIEW
Pavel Drabina, Jan Svoboda, Miloš Sedlák
This present mini-review covers recently published results on Cu(I) and Cu(II) complexes immobilized on polystyrene carriers, which are used as heterogeneous, eco-friendly reusable catalysts applied for carbon-carbon and carbon-nitrogen forming reactions. Recent advances and trends in this area are demonstrated in the examples of oxidative homocoupling of terminal alkynes, the synthesis of propargylamines, nitroaldolization reactions, azide alkyne cycloaddition, N-arylation of nitrogen containing compounds, aza-Michael additions, asymmetric Friedel-Crafts reactions, asymmetric Mukaiyama aldol reactions, and asymmetric 1,3-dipolar cycloaddition of azomethine ylides...
May 24, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28537740/cationic-n-heterocyclic-carbene-copper-catalyzed-1-3-alkoxy-rearrangement-of-n-alkoxyanilines
#7
Itaru Nakamura, Takeru Jo, Yasuhiro Ishida, Hiroki Tashiro, Masahiro Terada
The [1,3]-alkoxy rearrangement reactions of N-alkoxyanilines were efficiently catalyzed by cationic N-heterocyclic carbene (NHC)-Cu catalysts in affording 2-alkoxyaniline derivatives in good to excellent yields with high functional group compatibility. For N-alkoxyanilines having an electron-withdrawing substituent at the meta-position, the alkoxy group selectively migrated to the more hindered ortho-position. In contrast, the alkoxy group migrated to the less hindered ortho-position for N-alkoxyanilines having an electron-donating substituent...
May 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28530403/propitious-dendritic-cu2o%C3%AF-pt-nanostructured-anodes-for-direct-formic-acid-fuel-cells
#8
Gumaa A El-Nagar, Ahmad M Mohammad, Mohamed S El-Deab, Bahgat E El-Anadouli
This study introduces a novel competent dendritic copper oxide-platinum nanocatalyst (nano-Cu2O-Pt) immobilized onto a glassy carbon (GC) substrate for formic acid (FA) electrooxidation (FAO); the prime reaction in the anodic compartment of direct formic acid fuel cells (DFAFCs). Interestingly, the proposed catalyst exhibited an outstanding improvement for FAO compared to the traditional platinum nanoparticles (nano-Pt) modified GC (nano-Pt/GC) catalyst. This was evaluated from steering the reaction mechanism towards the desired direct route producing carbon dioxide (CO2); consistently with mitigating the other undesired indirect pathway producing carbon monoxide (CO); the potential poison deteriorating the catalytic activity of typical Pt-based catalysts...
May 22, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28530224/understanding-trends-in-electrochemical-carbon-dioxide-reduction-rates
#9
Xinyan Liu, Jianping Xiao, Hongjie Peng, Xin Hong, Karen Chan, Jens K Nørskov
Electrochemical carbon dioxide reduction to fuels presents one of the great challenges in chemistry. Herein we present an understanding of trends in electrocatalytic activity for carbon dioxide reduction over different metal catalysts that rationalize a number of experimental observations including the selectivity with respect to the competing hydrogen evolution reaction. We also identify two design criteria for more active catalysts. The understanding is based on density functional theory calculations of activation energies for electrochemical carbon monoxide reduction as a basis for an electrochemical kinetic model of the process...
May 22, 2017: Nature Communications
https://www.readbyqxmd.com/read/28523904/enantioselective-propargylation-of-polyols-and-desymmetrization-of-meso-1-2-diols-by-copper-borinic-acid-dual-catalysis
#10
Ren-Zhe Li, Hua Tang, Ke R Yang, Li-Qiang Wan, Xia Zhang, Jie Liu, Zhengyan Fu, Dawen Niu
A copper/borinic acid dual catalytic reaction enabled the enantioselective propargylation of aliphatic polyols. Readily available reagents and catalysts were used in this transformation, which displayed good to excellent chemo- and stereoselectivity for a broad array of substrates. The method was also applicable to the desymmetrization of meso 1,2-diols to furnish products with three stereogenic centers and a terminal alkyne group in one operation.
May 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28516775/reagent-design-and-ligand-evolution-for-the-development-of-a-mild-copper-catalyzed-hydroxylation-reaction
#11
Patrick S Fier, Kevin M Maloney
Parallel synthesis and mass-directed purification of a modular ligand library, high-throughput experimentation, and rational ligand evolution have led to a novel copper catalyst for the synthesis of phenols with a traceless hydroxide surrogate. The mild reaction conditions reported here enable the late-stage synthesis of numerous complex, druglike phenols.
May 18, 2017: Organic Letters
https://www.readbyqxmd.com/read/28513898/synthesis-of-bodipy-labelled-cholesterylated-glycopeptides-by-tandem-click-chemistry-for-glycocalyxification-of-giant-unilamellar-vesicles-guvs
#12
Nicolai Stuhr-Hansen, Charikleia-Despoina Vagianou, Ola Blixt
The glycocalyx cover membrane surfaces of all living cells. These complex archtechtures render their interaction mechanisms on the membrane surface difficult to study. Artificial cell-sized membranes with selected and defined glycosylation patterns may serve as a minimalistic approach to systematically study cell surface glycan interactions. Here we developed a facile general synthetic procedure for the synthesis of BODIPY-labelled cholesterylated glycopeptides, which can coat cell-size giant unilamellar vesicles (GUVs)...
May 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28513753/two-step-conversion-of-carboxylic-esters-into-distally-fluorinated-ketones-via-ring-cleavage-of-cyclopropanol-intermediates-application-of-sulfinate-salts-as-fluoroalkylating-reagents
#13
Yulia A Konik, Marina Kudrjashova, Nele Konrad, Sandra Kaabel, Ivar Järving, Margus Lopp, Dzmitry G Kananovich
Tertiary cyclopropanols easily available from carboxylic esters have been used in the synthesis of distally fluorinated ketones. Cyclopropane ring cleavage reactions in methanol with aqueous tert-butyl hydroperoxide in the presence of a copper(ii) acetate catalyst and sodium triflinate (Langlois reagent) afford β-trifluoromethyl ketones in 16-74% isolated yields. Sodium triflinate serves as a precursor of reactive trifluoromethyl copper species, enabling ring-opening trifluoromethylation, as evidenced by mechanistic studies...
May 17, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28513734/strained-alkynes-derived-from-2-2-dihydroxy-1-1-biaryls-synthesis-and-copper-free-cycloaddition-with-azides
#14
Alessandro Del Grosso, Lavrentis-Dimitrios Galanopoulos, Cookson K C Chiu, Guy J Clarkson, Peter B O Connor, Martin Wills
A series of strained alkynes were prepared from 2,2'-dihydroxy-biaryls. Several were characterised by X-ray crystallography, revealing strained C(sp)-C(sp)-C(sp(3)) bond angles in the range of 163-167°. Their cycloadditions with azides proceed without a catalyst. Functionalised versions of these reagents have potential applications to materials synthesis and bioconjugations.
May 17, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28513657/copper-catalyzed-hydroallylation-of-allenes-employing-hydrosilanes-and-allyl-chlorides
#15
Tetsuaki Fujihara, Ken Yokota, Jun Terao, Yasushi Tsuji
The hydroallylation of allenes was developed by employing a hydrosilane and allyl chlorides in the presence of a copper catalyst. The reaction provided (E)-1,5-dienes mainly in good to high yields.
May 17, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28513650/photo-induced-copper-catalyzed-c-h-chalcogenation-of-azoles-at-room-temperature
#16
Parthasarathy Gandeepan, Jiayu Mo, Lutz Ackermann
Inexpensive copper catalysts enabled direct C-H chalcogenations at ambient temperature by means of photo-induced catalysis. The expedient copper catalysis set the stage for C-S and C-Se bond formation from readily accessible non-volatile elemental chalcogens. The photo-assisted copper catalysis manifold proved suitable for a wide range of substrates with good functional group tolerance and exhibited high catalytic efficacy even at a reaction temperature of 25 °C.
May 17, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28510358/bottom-up-design-of-a-novel-curu-nanoparticulate-catalyst-for-low-temperature-ammonia-oxidation
#17
Debasish Chakraborty, Christian Damsgaard, Hugo Silva, Christian Conradsen, Hudson Carvalho, Benjamin Mutz, Thomas Bligaard, Max Hoffmann, Felix Studt, Ib Chorkendorff, Jakob Lind Olsen
A novel nanoparticulate catalyst of copper and ruthenium is designed for low temperature ammonia oxidation at near stoichiometric mixtures using a bottom up approach. A synergistic effect of the two metals is found: an optimum CuRu catalyst shows reaction rate three-fold higher than Ru and fourty-fold higher than Cu. X-ray Absorption Spectroscopy (XAS) suggests that in the most active catalyst Cu forms one or two monolayer thick patches on Ru and the catalysts are less active once 3D Cu-islands form. The good performance of Cu/Ru is attributed to the change in the electronic structure and thus the altered adsorption properties of the surface Cu sites...
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28509537/-18-c-6-k-n%C3%A2-c-cu-i-sime2ph-a-potassium-silylcyanocuprate-as-a-catalyst-model-for-silylation-reactions-with-silylboranes-syntheses-structures-and-catalytic-properties
#18
Jacqueline Plotzitzka, Christian Kleeberg
Cu(I)-catalyzed silylation reactions involving silylboranes (in particular, pinB-SiMe2Ph (1)) as silyl sources have recently gained considerable attention. One of the most efficient and versatile and yet simplest catalyst systems consists of CuCN/NaOMe; however, nothing is known about the catalytically relevant species. Using an NHC-based model catalyst, copper silyl complexes of the type [(NHC)Cu-SiMe2Ph] have been established to be crucial species in these catalytic processes. The well-defined and spectroscopically and structurally characterized complex [(18-C-6)K][NC-Cu-OtBu] (2), as a model for the catalytic system, CuCN/NaOMe, shows comparable catalytic activity toward established, exemplary substrates (aldehydes, imines, α,β-unsaturated carbonyls) and in extension allows the efficient silylation of ketones...
May 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28508647/copper-promoted-desulfitative-n-arylation-of-sulfonamides-and-sulfoximines-with-sodium-arylsulfinates
#19
Yangji Jiang, Yaping You, Wanrong Dong, Zhihong Peng, Yingjun Zhang, Delie An
A general and direct N-arylation of sulfonamides and NH-sulfoximines by sodium arylsulfinates through a desulfitative pathway was herein demonstrated. The reaction proceeded with catalytic loadings of Cu(II)-catalysts without any external ligands. And the novel arylation protocol featured for high efficiency (up to 93% yields) and good substituent tolerance (up to 53 examples). Moreover, a plausible reaction mechanism was also discussed.
May 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28508490/copper-catalyzed-divergent-synthesis-of-disulfanes-and-benzenesulfonothioates-bearing-2-aminofurans-from-n-tosylhydrazone-bearing-thiocarbamates
#20
Qiuling Song, Shaoyu Mai
An efficient and convenient synthesis of valuable disulfanes and benzenesulfonothioates with 2-aminofuran framework has been developed via a copper-catalyzed cascade transformation of readily available N-tosylhydrazones-bearing thiocarbamate. This method features with inexpensive metal catalyst, mild condition, good functional group tolerance, short reaction time and valuable and complex products. A copper carbene generated from N-tosylhydrazone-bearing thiocarbamate is proposed as the key intermediate for the transformation, and cascade processes were triggered subsequently...
May 15, 2017: Angewandte Chemie
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