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https://www.readbyqxmd.com/read/28318257/copper-i-catalyzed-enantioselective-addition-of-enynes-to-ketones
#1
Xiao-Feng Wei, Xiao-Wei Xie, Yohei Shimizu, Motomu Kanai
A copper(I)-catalyzed enantioselective addition of enynes to ketones was developed. The method allows facile construction of enantiomerically enriched tertiary alcohols using skipped enynes as stable hydrocarbon pronucleophiles. The combination of a soft copper(I)-conjugated Brønsted base catalyst with a chiral diphosphine ligand, (S,S)-Ph-BPE, enabled chemoselective deprotonation of the skipped enynes in the presence of ketones bearing intrinsically more acidic α-protons. The catalytically generated chiral allylcopper species enantio-, diastereo-, regio-, and chemoselectively reacted with ketones, thereby demonstrating excellent substrate generality with functional group tolerance...
March 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28304029/convenient-preparation-of-4-diazoisochroman-3-imines-and-3-subsituted-3-5-dihydroisochromeno-3-4-d-1-2-3-triazoles
#2
Anni Ren, Ping Lu, Yanguang Wang
A novel and convenient preparation of 4-diazoisochroman-3-imines through the copper(i)-catalyzed cascade reaction of (2-ethynylphenyl)-methanols with sulfonyl azides is described. The synthesized cyclical α-diazo imidates could readily react with a variety of primary amines to furnish 3-substituted 3,5-dihydroisochromeno[3,4-d][1,2,3]-triazoles under catalyst-free conditions.
March 17, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28300072/unravelling-the-hidden-link-of-lithium-halides-and-application-in-the-synthesis-of-organocuprates
#3
Hong Yi, Dali Yang, Jie Xin, Xiaotian Qi, Yu Lan, Yi Deng, Chih-Wen Pao, Jyh-Fu Lee, Aiwen Lei
As a versatile metal, copper has demonstrated a wide application in acting as both organometallic reagent and catalyst. Organocuprates are among the most used organometallic reagents in the formation of new carbon-carbon bonds in organic synthesis. Therefore, revealing the real structures of organocuprates in solution is crucial to provide insights into the reactivity of organocuprates. Here we provide several important insights into organocuprate chemistry. The main finding contains the following aspects. The Cu(0) particles were detected via the reduction of CuX by nBuLi or PhLi...
March 16, 2017: Nature Communications
https://www.readbyqxmd.com/read/28293880/catalytic-amyloid-fibrils-that-bind-copper-to-activate-oxygen
#4
Alex Sternisha, Olga Makhlynets
Amyloid-like fibrils assembled from de novo designed peptides lock ligands in a conformation optimal for metal binding and catalysis in a manner similar to how metalloenzymes provide proper coordination environment through fold. These supramolecular assemblies efficiently catalyze p-nitrophenyl ester hydrolysis in the presence of zinc and phenol oxidation by dioxygen in the presence of copper. The resulting heterogeneous catalysts are inherently switchable, as addition and removal of the metal ions turns the catalytic activity on and off, respectively...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28285531/copper-contamination-of-self-assembled-organic-monolayer-modified-silicon-surfaces-following-a-click-reaction-characterized-with-laps-and-spim
#5
Fan Wu, Dewen Zhang, Jian Wang, Michael Watkinson, Steffi Krause
A copper(I) catalyzed azide alkyne cycloaddition (CuAAC) reaction, combined with microcontact printing was employed successfully to pattern alkyne terminated self-assembled organic monolayer modified silicon surfaces. Despite the absence of a copper peak in X-ray photoelectron spectra (XPS), copper contamination was found and visualized using light-addressable potentiometric sensors (LAPS) and scanning photo-induced impedance microscopy (SPIM) after the 'click' modified silicon surfaces were rinsed with hydrochloric acid (HCl) solution, which has been frequently used to remove copper residues in the past...
March 13, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28282608/impact-of-lignin-structure-on-oil-production-via-hydroprocessing-with-a-copper-doped-porous-metal-oxide-catalyst
#6
Sebastien Gillet, Laurene Petitjean, Mario Aguedo, Chun-Ho Lam, Christophe Blecker, Paul T Anastas
A copper-catalyzed depolymerization strategy was employed to investigate the impact of lignin structure on the distribution of hydroprocessing products. Specifically, lignin was extracted from beech wood and miscanthus grass. The extracted lignins, as well as a commercial lignin (P1000), were then fractionated using ethyl acetate to provide three different portions for each source of lignin [total of 9 fractions]. Each fraction was structurally characterized and treated with a copper-doped porous metal oxide (Cu-PMO) catalyst under 4MPa H2 and at 180°C for 12h...
February 23, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28271098/a-dinuclear-biomimetic-cu-complex-derived-from-l-histidine-synthesis-and-stereoselective-oxidations
#7
Maria L Perrone, Elena Salvadeo, Eliana Lo Presti, Luca Pasotti, Enrico Monzani, Laura Santagostini, Luigi Casella
A dinuclear copper(ii) complex derived from the chiral N6 ligand (2S,2'S)-N,N'-(ethane-1,2-diyl)bis(2-((1-methyl-1H-imidazol-4-ylmethyl)-amino)-3-(1-trityl-1H-imidazol-4-yl)propanamide) (EHI) was synthesized and studied as a catalyst in stereoselective oxidation reactions. The ligand contains two sets of tridentate binding units, each of them giving rise to a coordination set consisting of a pair of 5- and 6-membered chelate rings, connected by an ethanediamide linker. Stereoselectivity effects were studied in the oxidations of a series of chiral l/d biogenic catechols and the pair of l/d-tyrosine methyl esters, in this case as their phenolate salts...
March 8, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28267185/enantioselective-copper-catalysed-intramolecular-c-h-insertion-reactions-of-%C3%AE-diazo-%C3%AE-keto-sulfones-%C3%AE-diazo-%C3%AE-keto-phosphine-oxides-and-2-diazo-1-3-diketones-the-influence-of-the-carbene-substituent
#8
Amy E Shiely, Catherine N Slattery, Alan Ford, Kevin S Eccles, Simon E Lawrence, Anita R Maguire
Enantioselectivities in C-H insertion reactions, employing the copper-bis(oxazoline)-NaBARF catalyst system, leading to cyclopentanones are highest with sulfonyl substituents on the carbene carbon, and furthermore, the impact is enhanced by increased steric demand on the sulfonyl substituent (up to 91%ee). Enantioselective intramolecular C-H insertion reactions of α-diazo-β-keto phosphine oxides and 2-diazo-1,3-diketones are reported for the first time.
March 7, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28267169/stabilisation-effects-of-phosphane-ligands-in-the-homogeneous-approach-of-sunlight-induced-hydrogen-production
#9
C M Strabler, S Sinn, R Pehn, J Pann, J Dutzler, W Viertl, J Prock, K Ehrmann, A Weninger, H Kopacka, L De Cola, P Brüggeller
Most of the systems for photochemical hydrogen production are not stable and suffer from decomposition. With bis(bidentate) tetraphosphane ligands the stability increases enormously, up to more than 1000 h. This stability was achieved with a system containing osmium(ii) as a light harvesting antenna and palladium(ii) as a water reduction catalyst connected with a bis(bidentate) phosphane ligand in one molecule with the chemical formula [Os(bpy)2(dppcb)Pd(dppm)](PF6)4. With the help of electrochemical measurements as well as photophysical data and its single crystal X-ray structure, the electron transfer between the two active metal centres (light harvesting antenna, water reduction catalyst) was analysed...
March 7, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28260494/hemoglobin-and-myoglobin-as-reducing-agents-in-biological-systems-redox-reactions-of-globins-with-copper-and-iron-salts-and-complexes
#10
REVIEW
G B Postnikova, E A Shekhovtsova
In addition to reversible O2 binding, respiratory proteins of the globin family, hemoglobin (Hb) and myoglobin (Mb), participate in redox reactions with various metal complexes, including biologically significant ones, such as those of copper and iron. HbO2 and MbO2 are present in cells in large amounts and, as redox agents, can contribute to maintaining cell redox state and resisting oxidative stress. Divalent copper complexes with high redox potentials (E0, 200-600 mV) and high stability constants, such as [Cu(phen)2](2+), [Cu(dmphen)2](2+), and CuDTA oxidize ferrous heme proteins by the simple outer-sphere electron transfer mechanism through overlapping π-orbitals of the heme and the copper complex...
December 2016: Biochemistry. Biokhimii︠a︡
https://www.readbyqxmd.com/read/28256577/copper-catalyzed-direct-2-arylation-of-benzoxazoles-and-benzoimidazoles-with-aryl-bromides-and-cytotoxicity-of-products
#11
Nan-Nan Jia, Xin-Chuan Tian, Xiao-Xia Qu, Xing-Xiu Chen, Ya-Nan Cao, Yun-Xin Yao, Feng Gao, Xian-Li Zhou
An efficient copper-catalyzed direct 2-arylation of benzoxazoles and benzoimidazoles with aryl bromides is presented. The CuI/PPh3-based catalyst promotes the installation of various aryl and heteroaryl groups through a C-H activation process in good to excellent yields. The cytotoxicity of obtained 2-aryl benzoxazoles (benzoimidazoles) was also evaluated and 1-methyl-2-(naphthalen-1-yl)benzoimidazole showed potential cytotoxicity.
March 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28251052/microfluidic-patterning-of-metal-structures-for-flexible-conductors-by-in-situ-polymer-assisted-electroless-deposition
#12
Suqing Liang, Yaoyao Li, Tingjiao Zhou, Jinbin Yang, Xiaohu Zhou, Taipeng Zhu, Junqiao Huang, Julie Zhu, Deyong Zhu, Yizhen Liu, Chuanxin He, Junmin Zhang, Xuechang Zhou
A low-cost, solution-processed, versatile, microfluidic approach is developed for patterning structures of highly conductive metals (e.g., copper, silver, and nickel) on chemically modified flexible polyethylene terephthalate thin films by in situ polymer-assisted electroless metal deposition. This method has significantly lowered the consumption of catalyst as well as the metal plating solution.
February 2017: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
https://www.readbyqxmd.com/read/28248112/n-mannich-bases-of-aromatic-heterocyclic-amides-synthesis-via-copper-catalyzed-aerobic-cross-dehydrogenative-coupling-under-ambient-conditions
#13
Shailendra K Singh, Nisha Chandna, Nidhi Jain
An efficient and facile method to synthesize N-Mannich bases has been developed using an inexpensive copper(I) bromide/air catalyst system at ambient temperature. A cross-dehydrogenative coupling of N,N-dimethylarylamines occurs efficiently with aromatic heterocyclic amides (oxindoles, isatins), cyclic amides (lactams), simple amides (benzamide), as well as imides (succinimide, phthalimide) to furnish the corresponding amidated/imidated derivatives in good to excellent yields. Preliminary mechanistic and isotope-labeling studies suggest the reaction follows a radical pathway and involves an iminium ion intermediate...
March 1, 2017: Organic Letters
https://www.readbyqxmd.com/read/28243657/nonstoichiometric-copper-chalcogenides-for-photo-activated-alkyne-azide-cycloaddition
#14
Hong Yan Zou, Ming Xuan Gao, Tong Yang, Qiao Ling Zeng, Xiao Xi Yang, Feng Liu, Mark T Swihart, Na Li, Cheng Zhi Huang
Nonstoichiometric copper chalcogenides with heavy copper vacancies can be used as an effective photo-activated catalyst for the Huisgen [3+2] cycloaddition reaction as Cu(i) can be released corresponding to holes (Cu-defects) under light irradiation. These strategies expand new possibilities for carrying out prototypical click chemistry in the presence of functional groups.
February 28, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28240399/copper-nitride-nanowires-array-an-efficient-dual-functional-catalyst-electrode-for-sensitive-and-selective-non-enzymatic-glucose-and-hydrogen-peroxide-sensing
#15
Xuping Sun
It is highly attractive to develop non-noble-metal nanoarray architecture as a 3D catalyst electrode for molecular detection due to its large specific surface area and easy accessibility to target molecules. In this communication, we report the development of copper nitride nanowires array on copper foam (Cu3N NA/CF) as a dual-functional catalyst electrode for efficient glucose oxidation in alkaline solutions and hydrogen peroxide (H2O2) reduction in neutral solutions. Electrochemical tests indicate that such Cu3N NA/CF possesses superior non-enzymatic sensing ability toward rapid glucose and H2O2 detection with high selectivity...
February 27, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28230746/oxidation-of-5-chloromethylfurfural-cmf-to-2-5-diformylfuran-dff
#16
Ana I Vicente, Jaime A S Coelho, Svilen P Simeonov, Hristina I Lazarova, Margarita D Popova, Carlos A M Afonso
2,5-Diformylfuran (DFF) is an important biorenewable building block, namely for the manufacture of new polymers that may replace existing materials derived from limited fossil fuel resources. The current reported methods for the preparation of DFF are mainly derived from the oxidation of 5-hydroxymethylfurfural (HMF) and, to a lesser extent, directly from fructose. 5-Chloromethylfurfural (CMF) has been considered an alternative to HMF as an intermediate building block due to its advantages regarding stability, polarity, and availability from glucose and cellulose...
February 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28224255/thiol-oxidase-ability-of-copper-ion-is-specifically-retained-upon-chelation-by-aldose-reductase
#17
Francesco Balestri, Roberta Moschini, Mario Cappiello, Umberto Mura, Antonella Del-Corso
Bovine lens aldose reductase is susceptible to a copper-mediated oxidation, leading to the generation of a disulfide bridge with the concomitant incorporation of two equivalents of the metal and inactivation of the enzyme. The metal complexed by the protein remains redox active, being able to catalyse the oxidation of different physiological thiol compounds. The thiol oxidase activity displayed by the enzymatic form carrying one equivalent of copper ion (Cu1-AR) has been characterized. The efficacy of Cu1-AR in catalysing thiol oxidation is essentially comparable to the free copper in terms of both thiol concentration and pH effect...
February 21, 2017: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/28221360/why-copper-is-preferred-over-iron-for-oxygen-activation-and-reduction-in-haem-copper-oxidases
#18
Ambika Bhagi-Damodaran, Matthew A Michael, Qianhong Zhu, Julian Reed, Braddock A Sandoval, Evan N Mirts, Saumen Chakraborty, Pierre Moënne-Loccoz, Yong Zhang, Yi Lu
Haem-copper oxidase (HCO) catalyses the natural reduction of oxygen to water using a haem-copper centre. Despite decades of research on HCOs, the role of non-haem metal and the reason for nature's choice of copper over other metals such as iron remains unclear. Here, we use a biosynthetic model of HCO in myoglobin that selectively binds different non-haem metals to demonstrate 30-fold and 11-fold enhancements in the oxidase activity of Cu- and Fe-bound HCO mimics, respectively, as compared with Zn-bound mimics...
March 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28220164/an-efficient-noble-metal-free-supported-copper-catalyst-for-selective-nitrocyclohexane-hydrogenation-to-cyclohexanone-oxime
#19
Qian-Qian Zhang, Jing Dong, Yong-Mei Liu, Yong Cao, He-Yong He, Yang-Dong Wang
It was shown for the first time that cyclohexanone oxime (CHO) can be selectively produced by heterogeneous copper-catalyzed hydrogenative transformation of nitrocyclohexane (NC). The combination of Cu(0) and Cu(+) and their cooperative interaction with weakly acidic SiO2 supports elicited a significantly unique and selective catalysis in the hydrogenation of NC to CHO.
February 21, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28218001/preventing-alkyne-alkyne-i-e-glaser-coupling-associated-with-the-atrp-synthesis-of-alkyne-functional-polymers-macromonomers-and-for-alkynes-under-click-i-e-cuaac-reaction-conditions
#20
Porakrit Leophairatana, Sanjoy Samanta, Chathuranga C De Silva, Jeffrey T Koberstein
Alkyne-functional polymers synthesized by ATRP exhibit bimodal molecular weight distributions indicating the occurrence of some undesirable side reaction. By modeling the molecular weight distributions obtained under various reaction conditions, we show that the side reaction is alkyne-alkyne (i.e., Glaser) coupling. Glaser coupling accounts for as much as 20% of the polymer produced, significantly compromising the polymer functionality and undermining the success of subsequent click reactions in which they are used...
March 6, 2017: Journal of the American Chemical Society
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