The Experts below are selected from a list of 63 Experts worldwide ranked by ideXlab platform
Felipe J. González - One of the best experts on this subject based on the ideXlab platform.
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Self-decarboxylation of trichloroacetic acid redox catalyzed by trichloroacetate ions in acetonitrile solutions
Organic & biomolecular chemistry, 2012Co-Authors: Drochss P. Valencia, Pablo D. Astudillo, Annia Galano, Felipe J. GonzálezAbstract:In mixtures of trichloroacetate ion and trichloroacetic acid in acetonitrile, trichloromethyl radicals are produced as a result of the redox Reaction between the acid and its conjugate base. The Reaction follows a loop mechanism in which the trichloroacetic acid is slowly consumed by proton reduction while the trichloroacetate ion is oxidized like in an electrochemical Kolbe Reaction. The hydroquinone–trichloroacetate complex was a good sensor of this unexpected self-decarboxylation redox Reaction.
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the effect of substituents on the anodic oxidation of aliphatic carboxylates and the passage towards a pseudo Kolbe Reaction
Journal of Electroanalytical Chemistry, 2012Co-Authors: Monica Galicia, Drochss P. Valencia, Miguel A Gonzalezfuentes, Felipe J. GonzálezAbstract:The oxidation of a series of tetrabutylammonium aliphatic carboxylates, and the chloroacetate and methoxyacetate ions has been performed in acetonitrile on glassy carbon electrodes. The electron transfer activation step and the decarboxylation Reaction are stepwise and they occur under a mixed kinetic control. In the case of acetate, butyrate, hexanoate and chloroacetate ions, the high rate of cleavage of the electrochemically produced acyloxy radicals allows the generation of free radicals and carbocations, which react with acetonitrile to afford N-acylamides. The electrochemical oxidation of methoxyacetate is pseudo-Kolbe since it involves the oxidation of methoxy-group instead of the carboxylate group. As products of this Reaction, an N-acylamide and dimethoxyethane are yielded. Although this Reaction is globally a one-electron transfer process, it involves the competition between a Kolbe and a Non-Kolbe pathways. This pseudo-Kolbe Reaction represents an example of intramolecular dissociative electron transfer mechanism.
Drochss P. Valencia - One of the best experts on this subject based on the ideXlab platform.
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Self-decarboxylation of trichloroacetic acid redox catalyzed by trichloroacetate ions in acetonitrile solutions
Organic & biomolecular chemistry, 2012Co-Authors: Drochss P. Valencia, Pablo D. Astudillo, Annia Galano, Felipe J. GonzálezAbstract:In mixtures of trichloroacetate ion and trichloroacetic acid in acetonitrile, trichloromethyl radicals are produced as a result of the redox Reaction between the acid and its conjugate base. The Reaction follows a loop mechanism in which the trichloroacetic acid is slowly consumed by proton reduction while the trichloroacetate ion is oxidized like in an electrochemical Kolbe Reaction. The hydroquinone–trichloroacetate complex was a good sensor of this unexpected self-decarboxylation redox Reaction.
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the effect of substituents on the anodic oxidation of aliphatic carboxylates and the passage towards a pseudo Kolbe Reaction
Journal of Electroanalytical Chemistry, 2012Co-Authors: Monica Galicia, Drochss P. Valencia, Miguel A Gonzalezfuentes, Felipe J. GonzálezAbstract:The oxidation of a series of tetrabutylammonium aliphatic carboxylates, and the chloroacetate and methoxyacetate ions has been performed in acetonitrile on glassy carbon electrodes. The electron transfer activation step and the decarboxylation Reaction are stepwise and they occur under a mixed kinetic control. In the case of acetate, butyrate, hexanoate and chloroacetate ions, the high rate of cleavage of the electrochemically produced acyloxy radicals allows the generation of free radicals and carbocations, which react with acetonitrile to afford N-acylamides. The electrochemical oxidation of methoxyacetate is pseudo-Kolbe since it involves the oxidation of methoxy-group instead of the carboxylate group. As products of this Reaction, an N-acylamide and dimethoxyethane are yielded. Although this Reaction is globally a one-electron transfer process, it involves the competition between a Kolbe and a Non-Kolbe pathways. This pseudo-Kolbe Reaction represents an example of intramolecular dissociative electron transfer mechanism.
Osamu Onomura - One of the best experts on this subject based on the ideXlab platform.
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MEMORY OF CHIRALITY IN THE ELECTROCHEMICAL OXIDATION OF THIAZOLIDINE-4-CARBOXYLIC ACID DERIVATIVES†
2016Co-Authors: George Ng’ang’a Wanyoike, Yoshihiro Matsumura, Masami Kuriyama, Osamu OnomuraAbstract:birthday. Abstract – Memory of chirality in the electrochemical oxidation of thiazolidine-4-carboxylic acid derivatives was observed. The relatively larger size of sulphur atom than the oxygen atom for oxazolidine-4-carboxylic acid derivative may slightly improved the enantioselectivities of the oxidized products. The bulkier penicillamine derivative 1c furnished 2c with much better enantioselectivity (91 % ee) than that of the cysteine derivative 2b (85 % ee). The presence of two extra dimethyl groups, for the penicillamine derivative improved the enantioselectivities of the thiazolidine derivatives from 85 % ee to 91 % ee. The synthesis of optically active compounds on the basis of ‘memory of chirality ’ continues to attract much attention in asymmetric synthesis.1 In our previous studies on asymmetric synthesis via memory of chirality, we reported that the non-Kolbe electrolysis2 of the oxazolidines afforded optically active N,O-acetals with up to 80 % ee (Scheme 1). 3 This highly enhanced enantiomeric excess was attributed to the bulkiness of the ring system as well as the N-protecting group. We report herein that the non-Kolbe Reaction of thiazolidine-4-carboxylic acid derivatives proceeds more efficiently than that of th
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Memory of chirality in the non-Kolbe Reaction of N-arylcarbonylated l-prolines
Journal of Electroanalytical Chemistry, 2001Co-Authors: Yoshihiro Matsumura, George Ng’ang’a Wanyoike, Takayoshi Tanaka, Toshihide Maki, Osamu OnomuraAbstract:Abstract The non-Kolbe Reaction of N -arylcarbonylated l -prolines in methanol gave the decarboxylated α-methoxyamine derivatives, which retained the original chirality to some extent, presenting a new memory of chirality in carbenium ion chemistry.
Zhen Weng - One of the best experts on this subject based on the ideXlab platform.
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the observation of photo Kolbe Reaction as a novel pathway to initiate photocatalytic polymerization over oxide semiconductor nanoparticles
Journal of Photochemistry and Photobiology A-chemistry, 2008Co-Authors: Dan Yang, Weikang Chen, Zhen WengAbstract:Abstract Polymerization of vinyl acetate is achieved under the photocatalysis of TiO 2 nanoparticles in aqueous suspensions. It is clarified that the photocatalytic polymerization is due to the acetic acid generated from the hydrolysis of vinyl acetate. 13 C NMR analysis further demonstrates by using 2- 13 C-acetic acid that vinyl acetate is initiated by methyl radical that results from the photo-Kolbe Reaction. This result reveals a new function of the photo-Kolbe Reaction as a pathway to realizing photocatalytic polymerization. A free radical chain mechanism is established for the polymerization. Kinetics studies show that the rates of initiation increase with the amounts of acetic acid added increasing. If the vinyl acetate aqueous solution is replaced by a vinyl acetate bulk, no polymerization is detected under the identical irradiation condition. This difference is correlated with the acid–base equilibria of the TiO 2 nanoparticles and the anionic CH 3 COO − from the ionization of acetic acid.
Monica Galicia - One of the best experts on this subject based on the ideXlab platform.
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the effect of substituents on the anodic oxidation of aliphatic carboxylates and the passage towards a pseudo Kolbe Reaction
Journal of Electroanalytical Chemistry, 2012Co-Authors: Monica Galicia, Drochss P. Valencia, Miguel A Gonzalezfuentes, Felipe J. GonzálezAbstract:The oxidation of a series of tetrabutylammonium aliphatic carboxylates, and the chloroacetate and methoxyacetate ions has been performed in acetonitrile on glassy carbon electrodes. The electron transfer activation step and the decarboxylation Reaction are stepwise and they occur under a mixed kinetic control. In the case of acetate, butyrate, hexanoate and chloroacetate ions, the high rate of cleavage of the electrochemically produced acyloxy radicals allows the generation of free radicals and carbocations, which react with acetonitrile to afford N-acylamides. The electrochemical oxidation of methoxyacetate is pseudo-Kolbe since it involves the oxidation of methoxy-group instead of the carboxylate group. As products of this Reaction, an N-acylamide and dimethoxyethane are yielded. Although this Reaction is globally a one-electron transfer process, it involves the competition between a Kolbe and a Non-Kolbe pathways. This pseudo-Kolbe Reaction represents an example of intramolecular dissociative electron transfer mechanism.
