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copper catalyst

Lijun Zheng, Dachi Yang, Rong Chang, Chengwen Wang, Gaixia Zhang, Shuhui Sun
We have developed "crack-tips" and "superlattice" enriched Pt-Cu nanoflakes (NFs), benefiting from the synergetic effects of "crack-tips" and "superlattice crystals"; the Pt-Cu NFs exhibit 4 times higher mass activity, 6 times higher specific activity and 6 times higher stability than those of the commercial Pt/C catalyst, respectively. Meanwhile, the Pt-Cu NFs show more enhanced CO tolerance than the commercial Pt/C catalyst.
June 23, 2017: Nanoscale
Qing Tang, Yongjin Lee, Dai-Ying Li, Woojun Choi, C W Liu, Dongil Lee, De-En Jiang
Copper electrocatalysts can reduce CO2 to hydrocarbons at high overpotentials. However, mechanistic understanding of CO2 reduction on nanostructured Cu catalysts has been lacking. Herein we show that the structurally precise ligand-protected Cu-hydride nanoclusters, such as Cu32H20L12 (L is a dithiophosphate ligand), offer unique selectivity for electrocatalytic CO2 reduction at low overpotentials. Our density functional theory (DFT) calculations predict that the presence of the negatively charged hydrides in the copper cluster plays a critical role in determining the selectivity of the reduction product, yielding HCOOH over CO with a lower overpotential...
June 22, 2017: Journal of the American Chemical Society
Daniel H Lukamto, Matthew J Gaunt
A copper-catalyzed enantioselective arylative semi-pinacol rearrangement of allylic alcohols using diaryliodonium salts is reported. Chiral Cu(II)-bisoxazoline catalysts initiate an electrophilic alkene arylation, triggering a 1,2-alkyl migration to afford a range of non-racemic spirocyclic ketones with high yields, diastero- and enantioselectivities.
June 22, 2017: Journal of the American Chemical Society
Hoda Keipour, Virginie Carreras, Thierry Ollevier
The following review will explore the historical development of Si-H bond insertion reactions, giving an up-to-date account on the metal catalysts often employed, in addition to an assessment of their strengths and weaknesses. Diazo compounds have great synthetic potential as versatile reagents for the formation of metal carbenes, allowing the selective formation of C-C and C-heteroatom bonds and thus the introduction of functional groups into organic molecules. C-Si bond-forming methods, that introduce silicon motifs into organic molecules, rely on catalysts derived from metals such as rhodium, copper, iridium, silver, ruthenium, and iron to achieve the desired activities and selectivities...
June 22, 2017: Organic & Biomolecular Chemistry
Bar Gavriel, Ronit Sharabi, Lior Elbaz
In this work, new catalyst for the direct electro-oxidation of dimethyl ether (DME) was synthesized and studied using an array of techniques. One of the most prominent catalysts for this reaction, platinum copper alloy (PtCu), was synthesized in an easy and low cost approach. Structural characterizations such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and elemental analysis revealed that the synthesized PtCu nanoparticles (3 nm on average), formed homogeneous NanoChains without aggregation of metallic platinum or copper...
June 18, 2017: ChemSusChem
Cheng Liu, Zhi-Wei Lin, Zhao-Hui Zhou, Hong-Bin Chen
Chiral amino alcohol-copper(ii) catalysts Cu-L1c and Cu-ent-L1c were utilized to promote the diastereoselective nitroaldol reactions of chiral aldehydes (S)-3 or (R)-3 with nitromethane, which respectively led to the preferential formation of certain stereoisomer for nitro diol derivatives 4. Using this catalytic protocol, all the four stereoisomers of the antidepressant reboxetine were divergently prepared. The highest overall yield of this synthetic route reached up to 30.5% from aldehyde (S)-3.
June 16, 2017: Organic & Biomolecular Chemistry
Pedro Leo, Gisela Orcajo, David Briones, Guillermo Calleja, Manuel Sánchez-Sánchez, Fernando Martínez
The activity and recyclability of Cu-MOF-74 as a catalyst was studied for the ligand-free C-O cross-coupling reaction of 4-nitrobenzaldehyde (NB) with phenol (Ph) to form 4-formyldiphenyl ether (FDE). Cu-MOF-74 is characterized by having unsaturated copper sites in a highly porous metal-organic framework. The influence of solvent, reaction temperature, NB/Ph ratio, catalyst concentration, and basic agent (type and concentration) were evaluated. High conversions were achieved at 120 °C, 5 mol % of catalyst, NB/Ph ratio of 1:2, DMF as solvent, and 1 equivalent of K₂CO₃ base...
June 16, 2017: Nanomaterials
Guangli Zhan, Wei Zhong, Zhenhong Wei, Zhenzhen Liu, Xiaoming Liu
Herein, six copper(ii) complexes with multidentate ligands, [Cu(HL1)(OAc)(HOAc)] (1), [Cu(HL2)(OAc)] (2), [Cu(HL3)(OAc)] (3), [CuL4(OAc)] (4), [Cu(HL2)Cl] (5), and [Cu(HL3)Cl] (6) {H2L1 = [bis(3-tert-butyl-2-hydroxybenzyl)](2-pyridylmethyl)amine, H2L2 = [(3-tert-butyl-2-hydoxybenzyl)(3-trifluoromethyl-2-hydroxybenzyl) (2-pyridylmethyl)]amine, H2L3 = [bis(3-trifluoromethyl-2-hydroxybenzyl)] (2-pyridylmethyl)amine, and HL4 = [bis(2-pyridylmethyl)] (3-tert-butyl-2-hydroxybenzyl)amine}, are reported. The complexes were characterized by UV-vis spectroscopy, high-resolution mass spectrometry, X-ray single-crystal diffraction analysis and electrochemistry...
June 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Takaaki Ikuno, Jian Zheng, Aleksei Vjunov, Maricruz Sanchez-Sanchez, Manuel A Ortuño, Dale Pahls, John L Fulton, Donald M Camaioni, Zhanyong Li, Debmalya Ray, B Layla Mehdi, Nigel D Browning, Omar K Farha, Joseph T Hupp, Christopher J Cramer, Laura Gagliardi, Johannes A Lercher
Copper oxide clusters synthesized via atomic layer deposition on the nodes of the metal-organic framework NU-1000 are active for oxidation of methane to methanol under mild reaction conditions. Analysis of chemical reactivity, in situ X-ray absorption spectroscopy, and density functional theory calculations are used to determine structure/activity relations in the Cu-NU-1000 catalytic system. The Cu-loaded MOF contained Cu as clusters of a few atoms each. The Cu was present at ambient conditions as a mixture of ~15 % Cu(+) and ~ 85 % Cu(2+)...
June 14, 2017: Journal of the American Chemical Society
Chang-Sheng Wang, Xiao-Feng Wu, Pierre H Dixneuf, Jean-Francois Soule
A copper-catalyzed oxidative C(sp3)-H/N-H coupling of NH-heterocycles with affordable (cyclo)alkanes was developed. This protocol involved C(sp3)-N bond formation via a radical pathway generated by a homolytic cleavage of di-tert-butyl peroxide and trapping of the radical(s) by copper catalysts. The reaction tolerated a series of functional groups, such as bromo, fluoro, ester, ketone, nitrile, methyl and methoxy. NH-free indoles, pyroles, pyrazoles, indazoles and benzotriazoles have been successfully N-alkylated...
June 14, 2017: ChemSusChem
Jufang Hu, Jing Dong, Xianqiang Huang, Yingnan Chi, Zhengguo Lin, Jikun Li, Song Yang, Hongwei Ma, Changwen Hu
Two ionic organic-inorganic hybrid compounds, [Cu(II)(C2N2H8)2]4[Cu(II)(C2N2H8)2(H2O)2]2[PNb12O40V(V)V(IV)O2]·(OH)2·11H2O (1) and [Co(III)(C2N2H8)3]2[Co(III)(C2N2H8)2(H2O)2]0.5[H2.5PNb12O40 V(V)V(IV)O2]·20H2O (2), based on P-centered dicapped polyoxoniobates and organometallic cations were isolated and structurally characterized by routine techniques. The trivalent cobalt complex-containing compound exhibits a looser arrangement compared with its divalent copper complex-containing counterpart, with a space volume of 34...
June 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Marco Favaro, Hai Xiao, Tao Cheng, William A Goddard, Junko Yano, Ethan J Crumlin
A national priority is to convert CO2 into high-value chemical products such as liquid fuels. Because current electrocatalysts are not adequate, we aim to discover new catalysts by obtaining a detailed understanding of the initial steps of CO2 electroreduction on copper surfaces, the best current catalysts. Using ambient pressure X-ray photoelectron spectroscopy interpreted with quantum mechanical prediction of the structures and free energies, we show that the presence of a thin suboxide structure below the copper surface is essential to bind the CO2 in the physisorbed configuration at 298 K, and we show that this suboxide is essential for converting to the chemisorbed CO2 in the presence of water as the first step toward CO2 reduction products such as formate and CO...
June 12, 2017: Proceedings of the National Academy of Sciences of the United States of America
Bin Xu, Uttam Krishan Tambar
The first highly enantioselective, diastereoselective, and regioselective [2,3]-rearrangement of iodonium ylides has been developed as a general solution to catalytic onium ylide rearrangements. In the presence of a chiral copper catalyst, substituted allylic iodides couple with α-diazoesters to generate metal-coordinated iodonium ylides, which undergo [2,3]-rearrangements with high selectivities (up to >95:5 rr, up to >95:5 dr, and up to 97% ee). The enantioenriched iodoester products can be converted stereospecifically to a variety of onium ylide rearrangement products, as well as compounds that are not accessible via classical onium ylide rearrangements...
June 9, 2017: Angewandte Chemie
Daniel S Jones, Kim A Lapakko, Zachary J Wenz, Michael C Olson, Elizabeth W Roepke, Michael J Sadowsky, Paige J Novak, Jake V Bailey
The Duluth Complex in northeastern Minnesota hosts economically-significant deposits of copper, nickel, and platinum group elements (PGEs). The primary sulfide mineralogy of these deposits includes the minerals pyrrhotite, chalcopyrite, pentlandite, and cubanite, and weathering experiments show that most sulfide-bearing rock from the Duluth Complex generates moderately acidic leachate (pH 4-6). Microorganisms are important catalysts for metal sulfide oxidation and could influence water quality from mines in the Duluth Complex...
June 9, 2017: Applied and Environmental Microbiology
Bastien Michelet, Christopher Deldaele, Sofia Kajouj, Cécile Moucheron, Gwilherm Evano
A broadly applicable copper catalyst for photoredox transformations of organic halides is reported. Upon visible light irradiation in the presence of catalytic amounts of [(DPEphos)(bcp)Cu]PF6 and an amine, a range of unactivated aryl and alkyl halides were shown to be smoothly activated through a rare Cu(I)/Cu(I)*/Cu(0) catalytic cycle. This complex efficiently catalyzes a series of radical processes, including reductions, cyclizations, and direct arylation of arenes.
June 9, 2017: Organic Letters
Xu Meng, Yanmin Wang, Yuanguang Wang, Baohua Chen, Zhenqiang Jing, Gexin Chen, Peiqing Zhao
In the presence of manganese oxide octahedral molecular sieve (OMS-2) supported copper hydroxide Cu(OH)x/OMS-2, aerobic synthesis of benzoxazoles from catechols and amines via domino oxidation/cyclization at room temperature is achieved. This heterogeneous benzoxazoles synthesis initiated by the efficient oxidation of catechols over Cu(OH)x/OMS-2 tolerates a variety of substrates, especially amines containing sensitive groups (hydroxyl, cyano, amino, vinyl, ethynyl, ester, and even acetyl groups) and heterocycles, which affords functionalized benzoxazoles in good to excellent yields by employing low catalyst loading (2 mol % Cu)...
June 14, 2017: Journal of Organic Chemistry
Carlos M R Abreu, Liye Fu, Sheiliza Carmali, Arménio C Serra, Krzysztof Matyjaszewski, Jorge F J Coelho
Aqueous supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) using inorganic sulfites was successfully carried out for the first time. Under optimized conditions, a well-controlled poly[oligo(ethylene oxide) methyl ether acrylate] (POEOA) was obtained with <30 ppm of soluble copper catalyst using tris(2-pyridylmethyl)amine (TPMA) ligand in the presence of an excess of halide salts (e.g. NaCl). Inorganic sulfites (e.g. Na2S2O4) were continuously fed into the reaction mixture...
January 14, 2017: Polymer Chemistry
Haifeng Zheng, Chaoran Xu, Yan Wang, Tengfei Kang, Xiaohua Liu, Lili Lin, Xiaoming Feng
The catalytic enantioselective [2+2] cycloaddition between quinones and fulvenes was achieved, for the first time, by the use of a chiral copper(ii) complex catalyst. The transformation afforded a series of enantiomerically enriched [6,4,5]-tricyclic cyclobutane derivatives in good yields with excellent regio- and stereoselectivities. Furthermore, the [2+2] adducts could be easily converted into formal [3+2] adducts efficiently and stereoselectively.
June 16, 2017: Chemical Communications: Chem Comm
Aso Navaee, Abdollah Salimi
Development of effective methods for conversion of CO2 to useful chemicals is considered to be a prospective way in terms of energy economy and chemical industry. Due to the thermodynamic stability of CO2, the application of the low-cost eco-friendly catalyst or photocatalyts for CO2 reduction with high efficiency is a challenge. Herein, we report a simple template-free electrochemical approach for the preparation of sulfur doped copper oxide nanoclusters directly on the copper disc electrode using thiourea (TU) as sulfur precursor...
May 27, 2017: Journal of Colloid and Interface Science
Anu Naik, Jawad Alzeer, Therese Triemer, Anna Bujalska, Nathan William Luedtke
A new method for post-synthetic modification of nucleic acids has been developed by mixing a phenyl triazolinedione (PTAD) derivative with DNA containing a vinyl nucleobase. The resulting reactions proceeded via step-wise mechanisms, giving either a formal 4 + 2 cycloaddition product, or, depending on the context of nucleobase, PTAD addition + solvent trapping to give a secondary alcohol in water. Catalyst-free addition between PTAD and the terminal alkene of 5-vinyl-2'-deoxyuridine (VdU) was exceptionally fast, with a second-order rate constant of 2000 M-1s-1...
May 31, 2017: Angewandte Chemie
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