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copper catalyst

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https://www.readbyqxmd.com/read/28800224/ullmann-reaction-catalyzed-by-heterogeneous-mesoporous-copper-manganese-oxide-a-kinetic-and-mechanistic-analysis
#1
Kankana Mullick, Sourav Biswas, Chiho Kim, Ramamurthy Ramprasad, Alfredo M Angeles-Boza, Steven L Suib
A heterogeneous copper oxide supported on mesoporous manganese oxide (meso Cu/MnOx) was explored for Ullmann-type cross-coupling reactions. An inverse micelle-templated evaporation-induced self-assembly method with in situ addition of copper was adopted to synthesize the mesoporous catalyst. Broad substrate scope and excellent functional group tolerability in C-O, C-N, and C-S bond formation reactions were observed using the optimized reaction conditions. The catalytic protocol was ligand free, and the catalyst was reusable without any significant loss of activity...
August 11, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28797164/universal-surface-engineering-of-transition-metals-for-superior-electrocatalytic-hydrogen-evolution-in-neutral-water
#2
Bo You, Xuan Liu, Guoxiang Hu, Sheraz Gul, Junko Yano, De-En Jiang, Yujie Sun
The development of low-cost hybrid water splitting-biosynthetic systems that mimic natural photosynthesis to achieve solar-to-chemical conversion is of great promise for future energy demands, but often limited by the kinetically sluggish H2 evolu-tion reaction (HER) on the surface of nonprecious transition metal catalysts in neutral media. It is thus highly desirable to rationally tailor the reaction interface to boost the neutral HER catalytic kinetics. Herein, we report a general surface nitro-gen modification of diverse transition metals (e...
August 10, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28791652/fabrication-of-yolk-shell-cu-c-nanocomposites-as-high-performance-catalysts-in-oxidative-carbonylation-of-methanol-to-dimethyl-carbonate
#3
Juan Wang, Panpan Hao, Ruina Shi, Leilei Yang, Shusen Liu, Jinxian Zhao, Jun Ren, Zhong Li
A facile way was developed to fabricate yolk-shell composites with tunable Cu cores encapsulated within hollow carbon spheres (Cu@C) with an average diameter about 210 nm and cavity size about 80 nm. During pyrolysis, the confined nanospace of hollow cavity ensures that the nucleation-and-growth process of Cu nanocrystals take place exclusively inside the cavities. The size of Cu cores can be easily tuned from 30 to 55 nm by varying the copper salt concentration. By deliberately creating shell porosity through KOH chemical activation, at an optimized KOH/HCS mass ratio of 1/4, the catalytic performance for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) of the activated sample is enhanced remarkably with TOF up to 8...
August 8, 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28783437/a-divergent-approach-to-indoles-and-oxazoles-from-enamides-by-directing-group-controlled-cu-catalyzed-intramolecular-c-h-amination-and-alkoxylation
#4
Chiaki Yamamoto, Kazutaka Takamatsu, Koji Hirano, Masahiro Miura
A directing-group-controlled, copper-catalyzed divergent approach to indoles and oxazoles from enamides has been developed. The picolinamide-derived enamides undergo the intramolecular aromatic C-H amination in the presence of a Cu(OPiv)2 catalyst and an MnO2 oxidant to form the corresponding indoles in good yields. On the other hand, simpler aryl- or alkyl-substituted enamides are converted to the 2,4,5-trisubstituted oxazole frameworks via vinylic C-H alkoxylation under identical conditions. The copper catalysis can provide uniquely divergent access to indole and oxazole heteroaromatic cores of great importance in medicinal and material chemistry...
August 7, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28783200/copper-catalyzed-silylation-reactions-of-propargyl-epoxides-easy-access-to-2-3-allenols-and-stereodefined-alkenes
#5
Xi-Hao Chang, Zheng-Li Liu, Yun-Cheng Luo, Chao Yang, Xiao-Wei Liu, Bing-Chao Da, Jie-Jun Li, Tanveer Ahmad, Teck-Peng Loh, Yun-He Xu
Efficient silylation reactions of propargyl epoxides catalyzed by copper catalysts have been developed. Under mild reaction conditions, tri- and tetra-substituted functionalized allenols and alkenes could be selectively obtained in moderate to high yields via tuning the bases and solvents used in the reactions. This work provides straightforward and efficient approaches to the synthesis of multifunctionalized 2,3-allenols and stereodefined alkenes from the same starting material of propargyl epoxides.
August 7, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28783181/migration-of-copper-species-in-cexcu1-xo2-catalyst-driven-by-thermal-treatment-and-the-effect-on-co-oxidation
#6
Yan Xiong, Lulu Li, Lei Zhang, Yuan Cao, Shuohan Yu, Changjin Tang, Lin Dong
A Cu-doped CeO2 solid solution was constructed by co-precipitation and additional acid treatment to investigate the behavior of doped copper under thermal treatment. Acid treatment was used to intentionally remove the surface Cu species. Surface properties and fundamental characteristics of the catalysts were characterized by several techniques, as well as the CO oxidation performance. The results reveal that doped Cu ions could gradually migrate from the matrix to the catalyst surface during calcination. The degree of migration was mostly dependent on the calcination temperature, and also the concentration gradient of Cu between the surface and matrix...
August 7, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28782960/copper-catalyzed-c-h-difluoroalkylations-and-perfluoroalkylations-of-alkenes-and-hetero-arenes
#7
Xiaoyang Wang, Shuang Zhao, Jing Liu, Dingsheng Zhu, Minjie Guo, Xiangyang Tang, Guangwei Wang
A general and facile synthetic method for C(sp(2))-H difluoroalkylations and perfluoroalkylations of alkenes and (hetero)arenes with commercially available fluoroalkyl halides has been developed with a copper-amine catalyst system. This method is characterized by high yields, mild reaction conditions, low-cost catalyst, broad substrate scope, and excellent functional group compatibility, therefore providing a convenient synthetic strategy toward various difluoroalkyl- and perfluoroalkyl-substituted alkenes and (hetero)arenes...
August 7, 2017: Organic Letters
https://www.readbyqxmd.com/read/28773097/dealloyed-ruthenium-film-catalysts-for-hydrogen-generation-from-chemical-hydrides
#8
Ramis B Serin, Nazrin Abdullayeva, Mehmet Sankir
Thin-film ruthenium (Ru) and copper (Cu) binary alloys have been prepared on a Teflon™ backing layer by cosputtering of the precious and nonprecious metals, respectively. Alloys were then selectively dealloyed by sulfuric acid as an etchant, and their hydrogen generation catalysts performances were evaluated. Sputtering time and power of Cu atoms have been varied in order to tailor the hydrogen generation performances. Similarly, dealloying time and the sulfuric acid concentration have also been altered to tune the morphologies of the resulted films...
July 2, 2017: Materials
https://www.readbyqxmd.com/read/28773040/temperature-and-copper-concentration-effects-on-the-formation-of-graphene-encapsulated-copper-nanoparticles-from-kraft-lignin
#9
Weiqi Leng, H Michael Barnes, Zhiyong Cai, Jilei Zhang
The effects of temperature and copper catalyst concentration on the formation of graphene-encapsulated copper nanoparticles (GECNs) were investigated by means of X-ray diffraction, Fourier transform infrared spectroscopy-attenuated total reflectance, and transmission electron microscopy. Results showed that higher amounts of copper atoms facilitated the growth of more graphene islands and formed smaller size GECNs. A copper catalyst facilitated the decomposition of lignin at the lowest temperature studied (600 °C)...
June 21, 2017: Materials
https://www.readbyqxmd.com/read/28771304/non-sacrificial-template-synthesis-of-magnetic-based-yolk-shell-nanostructures-for-the-removal-of-acetaminophen-in-fenton-like-systems
#10
Quoc Cuong Do, Do-Gun Kim, Seok-Oh Ko
Recently, yolk-shell structured materials with active metal cores have received considerable attention in heterogeneous Fenton-like systems, which have excellent catalytic performance. In this study, we initially attempted the non-sacrificial template synthesis of yolk-shell structured nanoparticles with magnetite cores encapsulated in a mesoporous silica shell (Fe3O4@SiO2) via a modified sol-gel process, and then evaluated their catalytic activity for acetaminophen degradation in Fenton-like systems. Secondly, copper nanoparticles were decorated on the surface of the Fe3O4@SiO2 microspheres (Fe3O4@SiO2@Cu) in order to enhance the catalytic activity...
August 3, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28768416/manganese-and-cobalt-in-the-nonheme-metal-binding-site-of-a-biosynthetic-model-of-heme-copper-oxidase-superfamily-confer-oxidase-activity-through-redox-inactive-mechanism
#11
Julian H Reed, Yelu Shi, Qianhong Zhu, Saumen Chakraborty, Evan N Mirts, Igor D Petrik, Ambika Bhagi-Damodaran, Matthew Ross, Pierre Moënne-Loccoz, Yong Zhang, Yi Lu
The presence of nonheme metal, such as copper and iron, in the heme-copper oxidase (HCO) superfamily is critical to the enzymatic activity of reducing O2 to H2O, but the exact mechanism the nonheme metal ion uses to confer and fine-tune the activity remains to be understood. We report that manganese and cobalt can bind to the same nonheme site and confer HCO activity in a heme-nonheme biosynthetic model in myoglobin. While the initial rates of O2 reduction by the Mn, Fe and Co derivatives are similar, the percentage of reaction active species formation are 7%, 4% and 1% and the total turnovers are 5...
August 3, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28762735/in-situ-generation-of-quinolinium-ylides-from-diazo-compounds-copper-catalyzed-synthesis-of-indolizine
#12
Rongxiang Chen, Yanwei Zhao, Hongmei Sun, Ying Shao, Yudong Xu, Meihua Ma, Liang Ma, Xiaobing Wan
The Cu-catalyzed three-component reaction between quinolines, diazo compounds, and alkenes has been established for direct construction of indolizine derivatives via quinolinium ylides. This methodology is distinguished by the use of a commercially inexpensive catalyst and readily available starting materials, wide substrate scope, and operational simplicity.
August 11, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28762412/rendering-cross-conjugated-azophenine-derivatives-emissive-to-probe-the-silent-photophysical-properties-of-emeraldine
#13
Hu Lei, Adam Langlois, Daniel Fortin, Paul-Ludovic Karsenti, Shawkat M Aly, Pierre D Harvey
An azophenine derivative was synthesized by coupling truxene and azophenine via the copper-free Sonagashira reaction using Pd2(dba)3 and As(PPh)3 as catalysts. The crystal structure of this heavy azophenine model (∼4000) was made and the identity of the structure was confirmed. By introducing truxene groups into this cross-conjugated structure, the deactivating rotations around the NH-C6H4 bonds were slowed down, which rendered this derivative near-IR emissive at 298 K. This species provided then the appropriate spectral and kinetic signatures for knowing where and what to look for in emeraldine, which was called non-emissive...
August 1, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28759139/catalytic-divergent-3-3-and-3-2-cycloaddition-by-discrimination-between-diazo-compounds
#14
Michael P Doyle, Lynèe Massey, Yongming Deng, Yeray Rodriguez, Hadi Arman
Highly selective divergent cycloaddition reactions of enoldiazo compounds and α-diazocarboximides catalyzed by copper(I) or dirhodium(II) have been developed. With tetrakis(acetonitrile)copper(I) tetrafluoroborate as the catalyst epoxypyrrolo[1,2-a]azepine derivatives were prepared in good yields and excellent diastereoselectivities through the first reported [3+3]-cycloaddition of a carbonyl ylide. Use of Rh2(pfb)4 or Rh2(esp)2 directs the reactants to regioselective [3+2]-cycloaddition generating cyclopenta[2,3]pyrrolo[2,1-b]oxazoles with good yields and excellent diastereoselectivities...
July 31, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28758881/preparation-and-characterization-of-cuo-catalyst-for-the-thermolysis-treatment-of-distillery-wastewater
#15
Deepak Sharma, Abhinesh Kumar Prajapati, Rumi Chaudhari, Rajesh Kumar Kaushal, Dharm Pal, Ashish N Sawarkar
CuO catalyst was prepared from copper sulphate by alkali precipitation method followed by drying and calcination. Characterization of CuO catalyst using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and Barrett-Joyner-Halenda (BJH) surface area analysis envisaged the effectiveness of CuO as a catalyst for the treatment of biodigester effluent emanated from distilleries. The catalytic thermolysis (CT) is an efficient advance treatment method for distillery biodigester effluent (BDE). CT treatment of BDE was carried out in a 0...
July 31, 2017: Environmental Technology
https://www.readbyqxmd.com/read/28755552/fabrication-of-novel-nanoporous-copper-powder-catalyst-by-dealloying-of-zrcunial-amorphous-powders-for-the-application-of-wastewater-treatments
#16
Shushen Wang, Lin Liu
The nanoporous copper (Cu) powders (NPCPs) co-existing with Cu2O was fabricated by dealloying of atomized Zr-Cu-Ni-Al amorphous powders. The as-fabricated NPCPs, with an inner core and outer shell, showed a large specific surface area of 7.52m(2)g(-1) and exhibited significantly superior degradation ability in the presence of hydrogen peroxide (H2O2) for the complete elimination of methyl orange (MO) under both acidic and neutral environments. The enhanced catalytic decomposition properties of H2O2 by NPCPs were mainly attributed to the large specific surface area and three-dimensional continuous nanoporous structure with unique atomic steps on the ligament surfaces...
July 20, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28749514/a-copper-templated-bifunctional-organocatalyst-a-strongly-cooperative-dynamic-system-for-the-aldol-reaction
#17
Anna Serra-Pont, Ignacio Alfonso, Jordi Solà, Ciril Jimeno
The study of novel metal-templated dynamic organocatalytic systems has led to the identification of CuSO4 as the most efficient template to assemble monofunctional prolinamide- and thiourea-modified pyridine ligands. The structural and electronic requirements to assemble an efficient catalyst have been disclosed: both pyridine ligands must bear a 1,3-substitution pattern, and the thiourea ligand serves as a reducing agent to copper(i) as well. Eventually, the cooperative effects achieved with such a simple system deliver high reaction rates and stereoselectivities at room temperature in the asymmetric aldol reaction, requiring only 1 mol% of copper salt...
August 9, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28748569/copper-catalyzed-amination-of-congested-and-functionalized-%C3%AE-bromocarboxamides-with-amines-or-ammonia-at-room-temperature
#18
Takashi Nishikata, Syo Ishida, Kentaro Takeuchi, Nobuhiro Taniyama, Yusuke Sunada
There are several reports on the synthesis of alkylamines, but most of the reported methods are not suitable for the synthesis of hindered amines. In this research, we found that a copper catalyst is effective for the formation of congested C-N bonds at room temperature. Control experiments revealed that a copper amide is a key intermediate. Moreover, when a chiral amine was used, a quaternary carbon stereogenic center was created with good selectivity.
July 26, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28745815/robust-cooperative-photooxidation-of-sulfides-without-sacrificial-reagent-under-air-using-a-dinuclear-ruii-cuii-assembly
#19
Duobin Chao, Mengying Zhao
A molecular chromophore-catalyst assembly containing a chromophore ruthenium(II) center (RuIIchro) and a catalytic copper(II) center (CuIIcat) has been prepared facilely. The assembly was employed for photocatalytic oxidation of sulfides without sacrificial reagent in the presence of dioxygen under blue light irradiation. Unprecedented turnover number (TON) up to 32000 was achieved. It was elucidated that an electron transferred from excited state of chromophore RuII*chro to CuIIcat along with generation of CuIcat that was further activated by O2...
July 26, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28742929/a-structurally-characterized-cu-iii-complex-supported-by-a-bis-anilido-ligand-and-its-oxidative-catalytic-activity
#20
Fabrice Thomas, Amelie Kochem, Jennifer K Molloy, Gisèle Gellon, Nicolas Leconte, Christian Philouze, Olivier Jarjayes, Florian Berthiol
Three copper(II) complexes of the (R,R)-N,N'-Bis(3,5-di-tert-butyl-2-aminobenzylidene)-1,2-diaminocyclohexane, namely [Cu(NL)], [Cu(NLH)]+ and [Cu(NLH2)]2+, were prepared and structurally characterized. In [Cu(NLH2)]2+ the copper ion lies in an octahedral geometry with the aniline groups coordinated in equatorial positions. In [Cu(NL)] the anilines are deprotonated (anilido moieties) and coordinated to an almost square metal ion. Complex [Cu(NL)] displays two oxidation waves at E1/2ox,1 = -0.14 V and E1/2ox,2 = 0...
July 25, 2017: Chemistry: a European Journal
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