The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Masahiko Arai - One of the best experts on this subject based on the ideXlab platform.
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the leaching and re deposition of metal species from and onto conventional supported palladium catalysts in the heck reaction of Iodobenzene and methyl acrylate in n methylpyrrolidone
Journal of Molecular Catalysis A-chemical, 2002Co-Authors: Fengyu Zhao, Masayuki Shirai, Yutaka Ikushima, Masahiko AraiAbstract:When supported palladium catalysts are used for Heck vinylation of Iodobenzene with methyl acrylate in N-methylpyrrolidone (NMP) in the presence of triethylamine and sodium carbonate bases, the reaction proceeds homogeneously with dissolved active palladium species that are formed through coordination of NMP and triethylamine with palladium. These active species easily react with Iodobenzene (oxidative addition), beginning the catalytic cycle of Heck coupling. The last step of catalyst regeneration takes place with the action of sodium carbonate. The active palladium species are not stable and deposit the metal to support when they cannot find Iodobenzene to react in the reaction mixture after this substrate is completely consumed. The re-deposition of palladium occurs on the surfaces of bare support and/or palladium particles remaining on it, depending on the nature of support surface and the number and size of residual metal particles. The growth of palladium particles has been observed after the reuse of catalyst in some case. However, the supported catalysts are recyclable without loss of activity.
Fengyu Zhao - One of the best experts on this subject based on the ideXlab platform.
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the leaching and re deposition of metal species from and onto conventional supported palladium catalysts in the heck reaction of Iodobenzene and methyl acrylate in n methylpyrrolidone
Journal of Molecular Catalysis A-chemical, 2002Co-Authors: Fengyu Zhao, Masayuki Shirai, Yutaka Ikushima, Masahiko AraiAbstract:When supported palladium catalysts are used for Heck vinylation of Iodobenzene with methyl acrylate in N-methylpyrrolidone (NMP) in the presence of triethylamine and sodium carbonate bases, the reaction proceeds homogeneously with dissolved active palladium species that are formed through coordination of NMP and triethylamine with palladium. These active species easily react with Iodobenzene (oxidative addition), beginning the catalytic cycle of Heck coupling. The last step of catalyst regeneration takes place with the action of sodium carbonate. The active palladium species are not stable and deposit the metal to support when they cannot find Iodobenzene to react in the reaction mixture after this substrate is completely consumed. The re-deposition of palladium occurs on the surfaces of bare support and/or palladium particles remaining on it, depending on the nature of support surface and the number and size of residual metal particles. The growth of palladium particles has been observed after the reuse of catalyst in some case. However, the supported catalysts are recyclable without loss of activity.
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A kinetic study of Heck reaction of Iodobenzene and methyl acrylate using homogeneous Pd/TPP catalyst
Studies in Surface Science and Catalysis, 1999Co-Authors: Fengyu Zhao, Bhalchandra M. Bhanage, Masayuki Shirai, M. AraiAbstract:Abstract A kinetics of Heck vinylation of Iodobenzene with methyl acrylate has been studied using homogeneous Pd(OAc) 2 /TPP catalyst in the temperature range of 50-70 °C. The rate of reaction shows linear dependence with Iodobenzene concentration. The effect of catalyst and methyl acrylate concentrations shows linear dependence initially and marginally increases afterwards. The effect of triethylamine concentration passes through a maximum. An empirical rate equation has been derived to fit the experimental data, showing accuracy in the range of ±8%, and the activation energy was found to be 23 kcal/mol.
Shinji Tanimori - One of the best experts on this subject based on the ideXlab platform.
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facile access to 1h indazoles through Iodobenzene catalyzed c h amination under mild transition metal free conditions
ChemInform, 2015Co-Authors: Mitsuhiro Kashiwa, Motohiro Sonoda, Shinji TanimoriAbstract:Multisubstituted 1H-indazoles having an N-aryl substituent are prepared by Iodobenzene-catalyzed oxidative intramolecular C-H amination of hydrazones.
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facile access to 1h indazoles through Iodobenzene catalyzed c h amination under mild transition metal free conditions
European Journal of Organic Chemistry, 2014Co-Authors: Mitsuhiro Kashiwa, Motohiro Sonoda, Shinji TanimoriAbstract:The transition-metal- and halogen-free synthesis of N-aryl-substituted 1H-indazole and derivatives was accomplished on the basis of the Iodobenzene-catalyzed intramolecular C–H amination of hydrazones under mild conditions. Reactions of hydrazones derived from ketones and hydrazines with a catalytic amount of Iodobenzene in the presence of Oxone as an oxidant in trifluoroacetic acid took place to afford 1H-indazoles in moderate to good yields. A plausible reaction mechanism was described on the basis of the control experiments.
Masayuki Shirai - One of the best experts on this subject based on the ideXlab platform.
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the leaching and re deposition of metal species from and onto conventional supported palladium catalysts in the heck reaction of Iodobenzene and methyl acrylate in n methylpyrrolidone
Journal of Molecular Catalysis A-chemical, 2002Co-Authors: Fengyu Zhao, Masayuki Shirai, Yutaka Ikushima, Masahiko AraiAbstract:When supported palladium catalysts are used for Heck vinylation of Iodobenzene with methyl acrylate in N-methylpyrrolidone (NMP) in the presence of triethylamine and sodium carbonate bases, the reaction proceeds homogeneously with dissolved active palladium species that are formed through coordination of NMP and triethylamine with palladium. These active species easily react with Iodobenzene (oxidative addition), beginning the catalytic cycle of Heck coupling. The last step of catalyst regeneration takes place with the action of sodium carbonate. The active palladium species are not stable and deposit the metal to support when they cannot find Iodobenzene to react in the reaction mixture after this substrate is completely consumed. The re-deposition of palladium occurs on the surfaces of bare support and/or palladium particles remaining on it, depending on the nature of support surface and the number and size of residual metal particles. The growth of palladium particles has been observed after the reuse of catalyst in some case. However, the supported catalysts are recyclable without loss of activity.
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A kinetic study of Heck reaction of Iodobenzene and methyl acrylate using homogeneous Pd/TPP catalyst
Studies in Surface Science and Catalysis, 1999Co-Authors: Fengyu Zhao, Bhalchandra M. Bhanage, Masayuki Shirai, M. AraiAbstract:Abstract A kinetics of Heck vinylation of Iodobenzene with methyl acrylate has been studied using homogeneous Pd(OAc) 2 /TPP catalyst in the temperature range of 50-70 °C. The rate of reaction shows linear dependence with Iodobenzene concentration. The effect of catalyst and methyl acrylate concentrations shows linear dependence initially and marginally increases afterwards. The effect of triethylamine concentration passes through a maximum. An empirical rate equation has been derived to fit the experimental data, showing accuracy in the range of ±8%, and the activation energy was found to be 23 kcal/mol.
Brian E Bent - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of the ullmann coupling reaction in adsorbed monolayers
Journal of the American Chemical Society, 1993Co-Authors: Ming Xi, Brian E BentAbstract:Ninety years ago, Ullmann and co-workers discovered that copper powder catalyzes the coupling of aromatic halides to produce biaryls, yet the role of the copper surface in this reaction remains controversial today. Recently, it has been shown that Ullmann'coupling of submonolayer coverages of iodobenzede to form bipbenyl occurs with 100% selectivity on a Cu(111) single crystal surface under ultrahigh-vacuum conditions (Xi, M.; Bent, B. E. Surf. Sci. 1992, 278, 19). We report here on studies in which surface analysis techniques have been applied to determine the mechanism of this reaction. Two mechanisms are found. At low surface coverages (<1 monolayer), Iodobenzene dissociates at ∼175 K on the Cu(111) surface to form adsorbed phenyl groups, which subsequently couple at 300-400 K to form biphenyl
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Iodobenzene on Cu(111): formation and coupling of adsorbed phenyl groups
Surface Science, 1992Co-Authors: Brian E BentAbstract:Abstract The chemistry of Iodobenzene on a Cu(111) surface has been studied by Auger electron spectroscopy (AES), high resolution electron energy loss spectroscopy (HREELS), temperature-programmed reaction (TPR) spectroscopy, and work function change measurements. The results from these techniques and from H atom titration experiments show that Iodobenzene dissociates at 175 K to form phenyl groups and iodine atoms and that the phenyl groups are thermally stable to above 300 K. The HREELS spectral intensities indicate that these phenyl groups bond with their π-rings approximately parallel to the surface plane. A possible reason for this unexpected adsorption geometry is the formation of phenyl anions. Biphenyl, formed by coupling of the phenyl groups, is evolved at temperatures above 300 K, while the iodine remains adsorbed on the surface until temperatures above 900 K. Comparison of the biphenyl evolution rate after Iodobenzene adsorption with the rate after biphenyl adsorption indicates that phenyl coupling as opposed to biphenyl desorption is the rate-determining step in yielding biphenyl from adsorbed phenyl groups. Factors affecting the coupling rate are discussed.
