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https://www.readbyqxmd.com/read/30118168/functional-precision-polymers-via-stereo-and-regioselective-polymerization-using-group-6-metal-alkylidene-and-group-6-and-8-metal-alkylidene-n-heterocyclic-carbene-complexes
#1
Michael R Buchmeiser
The concepts of functional precision polymers and the latest accomplishments in their synthesis are summarized. Synthetic concepts based on chain growth polymerization are compared to iterative synthetic approaches. Here, the term "functional precision polymers" refers to polymers that are not solely hydrocarbon-based but contain functional groups and are characterized by a highly ordered primary structure. If insertion polymerization is used for their synthesis, olefin metathesis-based polymerization techniques, that is, ring-opening metathesis polymerization (ROMP), acyclic diene metathesis (ADMET) polymerization, and the regio- and stereoselective cyclopolymerization of α,ω-diynes are almost exclusively applied...
August 17, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/30114388/kinetic-mechanism-of-time-dependent-inhibition-of-cyp2d6-by-3-4-methylenedioxymethamphetamine-mdma-functional-heterogeneity-of-the-enzyme-and-the-reversibility-of-its-inactivation
#2
John T Rodgers, Nadezhda Y Davydova, Erickson M Paragas, Jeffrey P Jones, Dmitri R Davydov
We investigate the mechanism of time-dependent inhibition (TDI) of human cytochrome P450 2D6 (CYP2D6) by 3,4-methylenedioxymethamphetamine (MDMA, ecstasy), one of the most widespread recreational drugs of abuse. In an effort to unravel the kinetic mechanism of the formation of metabolic inhibitory complex (MIC) of CYP2D6 with MDMA-derived carbene we carried out a series of spectrophotometric studies paralleled with registration of the kinetics of time-dependent inhibition (TDI) in CYP2D6-incorporated proteoliposomes...
August 13, 2018: Biochemical Pharmacology
https://www.readbyqxmd.com/read/30113848/copper-catalyzed-propargylic-reduction-with-diisobutylaluminum-hydride
#3
Yuna Kim, Hanseul Lee, Sunga Park, Yunmi Lee
A mild and efficient method for the synthesis of allenes through selective copper-catalyzed hydride addition to propargylic chlorides using commercially available diisobutylaluminum hydride has been developed. This transformation, which is promoted by a readily accessible N-heterocyclic carbene-copper complex, provides a wide range of new and versatile functionalized allenes in good to excellent yields with high regio- and stereoselectivities.
August 16, 2018: Organic Letters
https://www.readbyqxmd.com/read/30113838/nhc-ligated-group-11-metal-arylthiolates-containing-an-azide-functionality-amenable-to-click-reaction-chemistry
#4
Vaishnavi Somasundaram, Praveen N Gunawardene, Alexander M Polgar, Mark S Workentin, John F Corrigan
The reaction of N-heterocyclic carbene (NHC) Group 11 metal complexes, [(NHC)M-X] (X = chloride, acetate), with the new azide-modified arylthiol 1-HSCH2 -2,5-Me2 -4-N3 CH2 -C6 H2 , 1 (for M = Au; X = Cl), or 1-Me3 SiSCH2 -2,5-Me2 -4-N3 CH2 -C6 H2 , 2 (for M = Cu, X = Cl; M = Ag, X = OAc), affords the "clickable" NHC-metal thiolates [( i Pr2 -bimy)Au-(1-SCH2 -2,5-Me2 -4-N3 CH2 -C6 H2 )], 5; [(IPr)Au-(1-SCH2 -2,5-Me2 -4-N3 CH2 -C6 H2 )], 6; [(IPr)Ag-(1-SCH2 -2,5-Me2 -4-N3 CH2 -C6 H2 )], 7; and [(IPr)Cu-(1-SCH2 -2,5-Me2 -4-N3 CH2 -C6 H2 )], 8 ( i Pr2 -bimy = 1,3-di-isopropylbenzimidazol-2-ylidene, IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2-ylidene)...
August 16, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/30113837/n-heterocyclic-carbene-catalyzed-formal-conjugate-hydroacylation-an-atom-economic-synthesis-of-1h-indol-3-yl-esters
#5
Jindong Zhu, Shuaishuai Fang, Kewen Sun, Chao Fang, Tao Lu, Ding Du
An atom-economic synthesis of useful 1 H-indol-3-yl esters has been demonstrated by an N-heterocyclic carbene (NHC)-catalyzed formal conjugate hydroacylation of 2-phenyl-indol-3-ones with readily accessible aldehydes. This reaction involves a reductive hydride transfer process that was rarely investigated in the field of NHC catalysis. In this process, the hydrogen from the aldehydes was formally transferred to a heteroatom with NHC catalysis for the first time.
August 16, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30113052/metal-vapor-synthesis-of-ultrasmall-pd-nanoparticles-functionalized-with-n-heterocyclic-carbenes
#6
Patricia Tegeder, Marcello Marelli, Matthias Freitag, Laura Polito, Sebastian Lamping, Rinaldo Psaro, Frank Glorius, Bart Jan Ravoo, Claudio Evangelisti
The synthesis of N-heterocyclic carbene (NHC)-stabilized palladium nanoparticles (PdNPs) by an entirely new strategy comprising the NHC functionalization of ligand-free PdNPs obtained by metal vapor synthesis is described. Detailed characterization confirms the formation of very small monodisperse PdNPs (2.3 nm) and the presence of the NHC ligand on the Pd surface. The stable NHC-functionalized PdNPs dispersed onto a carbon support showed high activity in the hydrogenation of limonene with enhanced regioselectivity in comparison to bare PdNPs on carbon...
August 16, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/30112524/elucidation-of-the-inverse-trans-influence-in-uranyl-and-its-imido-and-carbene-analogues-via-quantum-chemical-simulation
#7
Izaak Fryer-Kanssen, Andy Kerridge
The inverse trans influence (ITI) is investigated in uranyl, UO22+, and its isoelectronic imido (U(NH)22+) and carbene (U(CH2)22+) analogues at the density functional and complete active space self consistent field levels of theory. The quantum theory of atoms in molecules is employed to quantify, for the first time, the effect of the ITI on covalent bond character and its relationship to bond lengths and complex stability.
August 16, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30110951/synthesis-and-cytotoxicity-studies-of-novel-nhc-gold-i-complexes-derived-from-lepidiline-a
#8
Danielle Curran, Oyinlola Dada, Helge Müller-Bunz, Matthias Rothemund, Goar Sánchez-Sanz, Rainer Schobert, Xiangming Zhu, Matthias Tacke
Ten novel N -heterocyclic carbene gold(I) complexes derived from lepidiline A (1,3-dibenzyl-4,5-dimethylimidazolium chloride) are reported here with full characterisation and biological testing. (1,3-Dibenzyl-4,5-diphenylimidazol-2-ylidene)gold(I) chloride (NHC*-AuCl) ( 1 ) was modified by substituting the chloride for the following: cyanide ( 2 ), dithiocarbamates ( 3 ⁻ 5 ), p -mercaptobenzoate derivatives ( 12 ⁻ 14 ) and N -acetyl-l-cysteine derivatives ( 15 ⁻ 17 ). All complexes were synthesised in good yields of 57⁻78%...
August 14, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/30110157/accurate-spin-state-energetics-for-aryl-carbenes
#9
Reza Ghafarian Shirazi, Frank Neese, Dimitrios A Pantazis
A test set of twelve aryl carbenes (AC12) is compiled with the purpose of establishing their adiabatic singlet-triplet energy splittings using correlated wave function based methods. The set covers both singlet and triplet ground state aryl carbenes, as well as a range of magnitudes for the ground state to excited state gap. The performance of coupled cluster methods is examined with respect to the reference wave function, the basis set, and a number of additional methodological parameters that enter the calculation...
August 15, 2018: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/30109896/asymmetric-reactions-involving-lewis-base-catalyst-tethered-dearomatizative-intermediates
#10
Ying-Chun Chen, Ben-Xian Xiao, Xin-Yue Gao, Wei Du
Numerous protocols have been developed for the functionalizations of aromatic substances. Among them, the strategy in which aromatic substrates are activated by in situ generating dearomatizative intermediates represents a highly efficient but challenging one, especially in the field of asymmetric catalysis. In this Concept, the application of some well-established chiral Lewis base catalysis, including primary/ secondary amines and N-heterocyclic carbenes, which can covalently form catalyst-tethered dearomatizative ortho/para-quinodimethane species with diverse heteroaryl or aryl carbonyl substrates, is summarized in a number of asymmetric cycloaddition or addition reactions with diverse reagents generally having electrophilic properties...
August 15, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30109328/photochemical-activation-of-sf-6-by-n-heterocyclic-carbenes-to-provide-a-deoxyfluorinating-reagent
#11
Pooja Tomar, Thomas Braun, Erhard Kemnitz
The activation of the greenhouse gas SF6 using electron-rich N-heterocyclic carbenes gave 2,2-difluoroimidazolines or 2,2-difluoroimidazolidines as well as 2-thio derivatives of the carbene precursors. The N-heterocyclic carbenes can also convert SF4 to give similar products. The difluoroimidazolidine derivatives were applied in deoxyfluorination reactions. Furthermore, the activation of SF6 and the fluorination can be coupled in a one-pot process to convert 1-octanol into 1-fluorooctane.
August 15, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30102528/rhodium-catalyzed-b-h-bond-insertion-reactions-of-unstabilized-diazo-compounds-generated-in-situ-from-tosylhydrazones
#12
Yue Pang, Qiao He, Zi-Qi Li, Ji-Min Yang, Jin-Han Yu, Shou-Fei Zhu, Qi-Lin Zhou
Although transition-metal-catalyzed B-H bond insertion of carbenes into stable borane adducts has emerged as a promising method for or-ganoborane synthesis, all the diazo compounds used to date as carbene precursors have had an electron-withdrawing group to stabilize them. Herein, we report a protocol for rhodium-catalyzed B-H bond insertion reactions of unstabilized diazo compounds generated in situ from to-sylhydrazones. In addition, by using chiral dirhodium catalysts, we also achieved an asymmetric version of the reaction with good to excellent enantioselectivities (up to 98:2 e...
August 13, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30101432/mechanochemical-activation-of-fluorogenic-cuaac-click-reactions-for-stress-sensing-applications
#13
Philipp Michael, Michel Biewend, Wolfgang H Binder
Strategies for visualizing stress within polymeric materials are of growing interest during the past decade. In this paper, stress-sensing materials, triggered by a mechanoresponsive catalytic system based on latent copper(I)bis(N-heterocyclic carbene) mechanophores, are reported, which can be activated by compression force to trigger a fluorogenic copper(I)-catalyzed alkyne/azide "click" cycloaddition reaction, activating a fluorescent dye useful for stress-sensing applications in bulk polymeric materials...
August 12, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/30101417/imine-n-heterocyclic-carbene-as-versatile-ligands-in-ruthenium-ii-p-cymene-anticancer-complexes-a-structure-activity-relationship-study
#14
Yuliang Yang, Guo Lihua, Zhenzhen Tian, Xicheng Liu, Yuteng Gong, Hongmei Zheng, Xingxing Ge, Zhe Liu
A family of novel imine-N-heterocyclic carbene ruthenium(II) complexes of the general formula [(η6-p-cymene)Ru(C^N)Cl]PF6- (where C^N is imine-N-heterocyclic carbene chelating ligand with varying substituents) have been prepared and characterized. In this imine-N-heterocyclic carbene chelating ligand framework, there are three potential sites that can be modified, which distinguishes this class of ligand and provides a body of flexibilities and opportunities to tune the cytotoxicity of these ruthenium(II) complexes...
August 12, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/30099254/pharmacomodulation-on-gold-nhc-complexes-for-anticancer-applications-is-lipophilicity-the-key-point
#15
Chen Zhang, Marie-Lise Maddelein, Raymond Wai-Yin Sun, Heinz Gornitzka, Olivier Cuvillier, Catherine Hemmert
A series of four new mononuclear cationic gold(I) complexes containing nitrogen functionalized N-heterocyclic carbenes (NHCs) was synthesized and fully characterized by spectroscopic methods. The X-ray structures of three complexes are presented. These lipophilic gold(I) complexes originate from a pharmacomodulation of previously described gold(I)-NHC complexes, by replacing an aliphatic spacer with an aromatic one. The Log P values of the resulting complexes increased by 0.7-1.5, depending on the substituents in comparison to the aliphatic-linker systems...
August 2, 2018: European Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/30094906/rh-catalyzed-regioselective-n2-alkylation-of-benzotriazoles-with-diazo-compounds-enynones-via-a-nonclassical-pathway
#16
Jiangtao Sun, Kai Wang, Ping Chen, Danqing Ji, Xinhao Zhang, Guangyang Xu
A novel rhodium-catalyzed highly selective N2-alkylation of benzotriazoles with diazo compounds/enynones is achieved, providing N2-alkylated benzotriazoles in good to excellent yields and with excellent N2 selectivities. Importantly, different with traditional carbene insertion into X-H (X = N, O etc) bonds, DFT calculations disclose that this selective N2-alkylation probably proceed through a formal 1,3- rather than 1,2-H shift to give the final products。.
August 9, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30094440/cofacial-porphyrin-dimers-assembled-from-n-heterocyclic-carbene-metal-bonds
#17
Clémence Rose, Aurélien Lebrun, Sébastien Clément, Sébastien Richeter
A porphyrin bearing four imidazolium rings on the meso positions was used as an N-heterocyclic carbene (NHC) precursor for the synthesis of porphyrin dimers with face-to-face orientations. The porphyrins are connected through the formation of eight M-CNHC bonds, with M = AgI or AuI.
August 10, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/30092137/oligo-ethylene-glycol-length-effect-of-water-soluble-ru-based-olefin-metathesis-catalysts-on-reactivity-and-removability
#18
Cheoljae Kim, Hoyong Chung
A study of reaction kinetics and removal efficiency of a family of ruthenium (Ru)-based olefin metathesis catalysts containing ethylene-glycol-oligomer-tethered N-heterocyclic carbene (NHC) ligands has been carried out, with a focus on variation of ethylene glycol oligomer length. The length of ethylene glycol oligomer was precisely defined by sequential addition of repeating units. Due to the dual solubility of ethylene glycol oligomer, the produced catalyst was highly soluble in both aqueous and organic solvents (dichloromethane)...
August 9, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30090299/carbene-derived-diradicaloids-building-blocks-for-singlet-fission
#19
Julian Messelberger, Annette Grünwald, Piermaria Pinter, Max M Hansmann, Dominik Munz
Organic singlet diradicaloids promise application in non-linear optics, electronic devices and singlet fission. The stabilization of carbon allotropes/cumulenes (C1 , C2 , C4 ) by carbenes has been equally an area of high activity. Combining these fields, we showed recently that carbene scaffolds allow as well for the design of diradicaloids. Herein, we report a comprehensive computational investigation (CASSCF/NEVPT2; fractional occupation DFT) on the electronic properties of carbene-bridge-carbene type diradicaloids...
July 28, 2018: Chemical Science
https://www.readbyqxmd.com/read/30084249/dictating-the-reactivity-of-%C3%AE-3-oxoallyl-pd-intermediate-toward-5-exo-trig-cyclization-access-to-indano-spirooxindoles
#20
Dhanarajan Arunprasath, Balasubramanian Devi Bala, Govindasamy Sekar
A facile synthesis of indanone-fused spirooxindoles is disclosed by directing the reactivity of η3 -oxoallyl Pd-intermediate toward 5- exo-trig mode of cyclization. The Pd-catalyzed reaction of the rationally designed starting material 3-arylidene oxindoles with isatin-derived tosylhydrazone afforded the spirooxindoles having all-carbon quaternary center through carbene migratory insertion followed by Heck-type cyclization sequence. The photophysical studies and DFT calculations were conducted to understand their electronic properties...
August 15, 2018: Journal of Organic Chemistry
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