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copper catalyst

Grant J Sherborne, Sven Adomeit, Robert Menzel, Jabor Rabeah, Angelika Brückner, Mark R Fielding, Charlotte E Willans, Bao N Nguyen
A mechanistic investigation of Ullmann-Goldberg reactions using soluble and partially soluble bases led to the identification of various pathways for catalyst deactivation through (i) product inhibition with amine products, (ii) by-product inhibition with inorganic halide salts, and (iii) ligand exchange by soluble carboxylate bases. The reactions using partially soluble inorganic bases showed variable induction periods, which are responsible for the reproducibility issues in these reactions. Surprisingly, more finely milled Cs2CO3 resulted in a longer induction period due to the higher concentration of the deprotonated amine/amide, leading to suppressed catalytic activity...
October 1, 2017: Chemical Science
Iván Rivilla, Abel de Cózar, Thomas Schäfer, Frank J Hernandez, Alexander M Bittner, Aitziber Eleta-Lopez, Ali Aboudzadeh, José I Santos, José I Miranda, Fernando P Cossío
A novel catalytic system based on covalently modified DNA is described. This catalyst promotes 1,3-dipolar reactions between azomethine ylides and maleimides. The catalytic system is based on the distortion of the double helix of DNA by means of the formation of Pt(ii) adducts with guanine units. This distortion, similar to that generated in the interaction of DNA with platinum chemotherapeutic drugs, generates active sites that can accommodate N-metallated azomethine ylides. The proposed reaction mechanism, based on QM(DFT)/MM calculations, is compatible with thermally allowed concerted (but asynchronous) [π4s + π2s] mechanisms leading to the exclusive formation of racemic endo-cycloadducts...
October 1, 2017: Chemical Science
Zhu Chen, Coleman X Kronawitter, Xiaofang Yang, Yao-Wen Yeh, Nan Yao, Bruce E Koel
A new catalyst is presented for the oxygen evolution reaction (OER) based on cerium-modified copper oxide (CuOx) prepared using a facile electrodeposition procedure. Incorporation of Ce into CuOx leads to greatly improved OER activity, which reached an optimal value at a surface concentration of 6.9 at% Ce. Specifically, the OER current density at 400 mV overpotential for the most active Ce-modified CuOx catalyst (6.9 at% Ce) was 3.3 times greater compared to the pure CuOx. Coincident with the improved OER activity, Ce incorporation also leads to significant structural changes that manifested in increasing degrees of disorder...
November 14, 2017: Physical Chemistry Chemical Physics: PCCP
Aurora López, Timothy B Clark, Alejandro Parra, Mariola Tortosa
In this report, the enantioselective, copper-catalyzed borylation of β-amidoacrylates is disclosed. A broad variety of biologically important α-aminoboronates has been prepared with consistently high levels of enantiocontrol using an inexpensive copper catalyst and a commercially available chiral ligand. The method can be applied to the synthesis of novel boron-containing dipeptides and hemiboronates.
November 13, 2017: Organic Letters
Long Shao, Xiang-Ping Hu
A copper-catalyzed asymmetric Friedel-Crafts propargylic alkylation of electron-rich phenol derivatives with a variety of propargylic esters has been described. With Cu(OTf)2 decorated with a chiral tridentate ketimine P,N,N-ligand as the catalyst, asymmetric Friedel-Crafts propargylic alkylation of 3,5-dialkoxyphenol derivatives proceeded smoothly in high yields and with good to excellent enantioselectivities. The present study suggested that the presence of an electron-rich substituent on the meta-position of phenol is essential for the promotion of Friedel-Crafts propargylic alkylation, and the substrate bearing two electron-rich groups on both the 3,5-positions of phenol tends to give a satisfactory performance...
November 13, 2017: Organic & Biomolecular Chemistry
Xia Cui, Bo Song, Shisu Cheng, Yun Xie, Yijiang Shao, Yueming Sun
We demonstrated the utility of carbon nanotubes (CNTs) as a catalyst and conductive agent to synthesize CNT-entangled copper nanowire (CuNW-CNT) networks within a melted mixture of hexadecylamine and cetyltrimethy ammounium bromide. The CuNW-CNT networks were further in situ thermally oxidized into CuO nanotube-CNT (CuONT-CNT) with the high retention of network structure. The binder- and conducting-additive-free anodes constructed using the CuONT-CNT networks exhibited high performance, such as high capability (557...
November 13, 2017: Nanotechnology
S Calvo-Losada, J J Quirante
The regioselectivity of the dinuclear-Cu(I)-catalyzed version of the Huisgen reaction, abbreviated in this paper to Cu2AAC, was analyzed using quantum topological methods in order to study how the electronic charge distribution evolved along different reaction paths. Electronic densities were computed at the LC-wPBE/6-311++G(2d,2p)//LC-wPBE/6-311++G(d,p) level. The presence of two copper ions in the catalyst was found to lead to an electrophilic site in the external alkyne carbon that, in a generalized Sharpless-type mechanism, undergoes an initial donor-acceptor interaction with the azide molecule, but with an inverted electrophile-nucleophile pattern when compared with the corresponding mononuclear process (CuAAC)...
November 9, 2017: Journal of Molecular Modeling
Karol Grela, Anupam Jana, Krzysztof Woźniak, Damian Trzybiński
Highly stereoselective conjugate β-borylation, using a new chiral NHC-based copper catalyst, has been achieved. The chiral NHC copper complex was prepared in gram scale and showed high enantioselectivity and activity (up to 10 000 turnovers at 100 ppm of catalyst loading). This method was employed in the synthesis of chiral β-borylated ester from simple unconjugated alkenes though unprecedented one-pot cross metathesis-asymmetric borylation sequence.
November 9, 2017: Chemistry: a European Journal
Sethuraman Muthuramalingam, Themmila Khamrang, Marappan Velusamy, Ramasamy Mayilmurugan
New copper(ii) complexes, [Cu(L1)2(H2O)](ClO4)2, 1 [L1 = 2-pyridin-2-yl-quinoline], [Cu(L2)2(H2O)](ClO4)2, 2 [L2 = 2-pyridin-2-yl-quinoxaline], [Cu(L3)2(H2O)](ClO4)2, 3 [L3 = 6,7-dimethyl-2-pyridin-2-yl-quinoxaline], [Cu(L4)2(H2O)](ClO4)2, 4 [L4 = 4-phenyl-2-pyridin-2-yl-quinoline] and [Cu(L5)2(H2O)](ClO4)2, 5 [L5 = 4-phenyl-2-pyridin-2-yl-quinazoline], were synthesized and characterized as catalysts for selective fixation of atmospheric CO2. The molecular structure of 2 was determined by single-crystal X-ray studies and shown to have an unusual trigonal bipyramid geometry (τ, 0...
November 9, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Ivan Merino-Garcia, Jonathan Albo, Angel Irabien
Copper-based surfaces appear as the most active catalysts for CO2 electroreduction to hydrocarbons, even though formation rates and efficiencies still need to be improved. The aim of the present work is to evaluate the continuous gas-phase CO2 electroreduction to hydrocarbons (i.e. ethylene and methane) at copper nanoparticulated-based surfaces, paying attention to particle size influence (ranging from 25 nm to 80 nm) on reaction productivity, selectivity, and Faraday efficiency for CO2 conversion. The effect of the current density and the presence of a microporous layer within the working electrode are then evaluated...
November 9, 2017: Nanotechnology
Runsheng Xu, Rongrong Cai, Sixian Zhou, Zhuoda Zhou, Beibei Li, Dihui Xu
The reaction mechanism of Cu-catalyzed C-H hydroxylation/C-S coupling was studied using electrospray ionization high resolution mass spectrometry (ESI-HR MS) and density functional theory calculations (DFT). Notably, a series of Cu(I) and Cu(III) complexes were observed as key intermediates and identified using ESI-HR MS. Furthermore, a catalyst cycle involving proton abstraction/oxidative addition/reductive elimination was proposed. This study is important and valuable with respect to C-H functionalization...
November 6, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Nicolas Alonso-Vante, Yun Luo, Björn Kirchhoff, Donato Fantauzzi, Laura Calvillo, Luis Alberto Estudillo-Wong, Gaetano Granozzi, Timo Jacob
Improving the efficiency of Pt-based oxygen reduction reaction (ORR) catalysts while also reducing costs remains an important challenge in energy research. To this end, we synthesized highly stable and active carbon-supported Mo-doped PtCu (Mo-PtCu/C) nanoparticles (NPs) from readily available precursors in a facile one-pot reaction. Mo-PtCu/C displays two- to four-fold higher ORR half-cell kinetics than reference PtCu/C and Pt/C materials - a trend which was confirmed in proof-of-concept experiments using a H2/O2 micro-laminar fuel cell...
November 7, 2017: ChemSusChem
Zachary W Schroeder, L K Hiscock, Louise Nicole Dawe
Benzothiazole derivatives are a class of privileged molecules due to their biological activity and pharmaceutical applications. One route to these molecules is via intramolecular cyclization of thioureas to form substituted 2-aminobenzothiazoles, but this often requires harsh conditions or employs expensive metal catalysts. Herein, the copper(II)- and gold(III)-mediated cyclizations of thioureas to substituted 2-aminobenzothiazoles are reported. The single-crystal X-ray structures of the thiourea N-(3-methoxyphenyl)-N'-(pyridin-2-yl)thiourea, C13H13N3OS, and the intermediate metal complexes aquabis[5-methoxy-N-(pyridin-2-yl-κN)-1,3-benzothiazol-2-amine-κN(3)]copper(II) dinitrate, [Cu(C13H11N3OS)2(H2O)](NO3)2, and bis{2-[(5-methoxy-1,3-benzothiazol-2-yl)amino]pyridin-1-ium} dichloridogold(I) chloride monohydrate, (C13H12N3OS)2[AuCl2]Cl·H2O, are reported...
November 1, 2017: Acta Crystallographica. Section C, Structural Chemistry
Xinfang Xu, Yang Zheng, Kemiao Hong, Shanliang Dong, Lihua Qiu
An unprecedented divergent outcome transformation of alkyne tethered N-sulfonyl hydrazones is reported, which provides a direct and effective access to 4-methyl 2H-chromene derivatives and spiro-4H-pyrazoles in the presence of copper catalyst or under thermal conditions, respectively. The salient features of this process include readily available starting materials, inexpensive copper catalyst, mild reaction conditions, broad substrate scope, diverse transformations and potential applications of these generated products...
November 7, 2017: Chemistry: a European Journal
Kyung-Lyul Bae, Jinmo Kim, Chan Kyu Lim, Ki Min Nam, Hyunjoon Song
Developing catalytic systems with high efficiency and selectivity is a fundamental issue for photochemical carbon dioxide conversion. In particular, rigorous control of the structure and morphology of photocatalysts is decisive for catalytic performance. Here, we report the synthesis of zinc oxide-copper(I) oxide hybrid nanoparticles as colloidal forms bearing copper(I) oxide nanocubes bound to zinc oxide spherical cores. The zinc oxide-copper(I) oxide nanoparticles behave as photocatalysts for the direct conversion of carbon dioxide to methane in an aqueous medium, under ambient pressure and temperature...
November 7, 2017: Nature Communications
César Saldías, David Díaz Díaz, Sebastián Bonardd, Cristián Soto-Marfull, Alexander Cordoba, Soledad Saldías, Caterina Quezada, Deodato Radic, Ángel Leiva
Copper nanoparticles were introduced into chitosan/fluorescein (Ch/f) film and hydrogel matrices by immersion of the respective matrix into an aqueous solution containing the precursor metallic salt and further reduction in aqueous medium at 75°C for 3h under nitrogen (N2) atmosphere. TGA was used to estimate the metallic content of Ch/f-Cu film and hydrogel nanocomposites. The prepared nanocomposites were proven to be effective as catalytic materials in the reduction of methylene blue (MB) employing N2H4 as reducing agent...
January 15, 2018: Carbohydrate Polymers
Tian-Nan Ye, Yangfan Lu, Jiang Li, Takuya Nakao, Hongsheng Yang, Tomofumi Tada, Masaaki Kitano, Hideo Hosono
The development of transition metal intermetallic compounds, in which active sites are incorporated in lattice frameworks, has great potential for modulating the local structure and the electronic properties of active sites, and enhancing the catalyt-ic activity and stability. Here we report that a new copper-based intermetallic electride catalyst, LaCu0.67Si1.33, in which Cu sites activated by anionic electrons with low work function are atomically dispersed in the lattice framework and affords selective hydrogenation of nitroarenes with above 40-times higher turnover frequencies (TOFs up to 5084 h-1) than well-studied metal-loaded catalysts...
November 3, 2017: Journal of the American Chemical Society
Quanping Guo, Mengran Wang, Yanfang Wang, Zhaoqing Xu, Rui Wang
In the past few years, Ru and Ir catalyzed photoredox radical coupling reactions have been widely applied in organic synthesis. In contrast, the applications of Cu catalysts in photoredox organic transformations were limited. We here report the first example of photoinduced, Cu-catalyzed three component cyanofluoroalkylation of alkenes by directly using fluoroalkyl iodides as fluoroalkylation reagents.
November 2, 2017: Chemical Communications: Chem Comm
Sombat Ketrat, Thana Maihom, Sippakorn Wannakao, Michael Probst, Somkiat Nokbin, Jumras Limtrakul
The oxidation of CO by N2O over metal-organic framework (MOF) M3(btc)2 (M = Fe, Cr, Co, Ni, Cu, and Zn) catalysts that contain coordinatively unsaturated sites has been investigated by means of density functional theory calculations. The reaction proceeds in two steps. First, the N-O bond of N2O is broken to form a metal oxo intermediate. Second, a CO molecule reacts with the oxygen atom of the metal oxo site, forming one C-O bond of CO2. The first step is a rate-determining step for both Cu3(btc)2 and Fe3(btc)2, where it requires the highest activation energy (67...
October 30, 2017: Inorganic Chemistry
Carlos Jarava-Barrera, Alejandro Parra, Laura Amenós, Ana Arroyo, Mariola Tortosa
Chiral -allenols are prepared with high diastereocontrol through an unprecedented and spontaneous -oxygen elimination of an -epoxy vinyl boronate. Stochiometric experiments and DFT calculations support a dual role of the copper catalyst, which orchestrates the hydroboration and the syn-elimination step.
October 30, 2017: Chemistry: a European Journal
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