- Mechanistic studies on the Pd-catalyzed vinylation of aryl halides with vinylalkoxysilanes in water: The effect of the solvent and NaOH promoter
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The mechanism of the Pd-catalyzed vinylation of aryl halides with vinylalkoxysilanes in water has been studied using different catalytic precursors. The NaOH promoter converts the initial vinylalkoxysilane into a highly reactive water-soluble vinylsilanolate species. Similarly, deuterium-labeling experiments have shown that, irrespective of the catalytic precursor used, vinylation occurs exclusively at the CH vinylic functionality via a Heck reaction and not at the C-Si bond via a Hiyama cross-coupling. The involvement of a Heck mechanism is interpreted in terms of the reduced nucleophilicity of the base in water, which disfavors the transmetalation step. The Heck product (β-silylvinylarene) undergoes partial desilylation, with formation of a vinylarene, by three different routes: (a) hydrolytic desilylation by the aqueous solvent (only at high temperature); (b) transmetalation of the silyl olefin on the PdH Heck intermediate followed by reductive elimination of vinylarene; (c) reinsertion of the silyl olefin into the PdH bond of the Heck intermediate followed by β-Si syn-elimination. Both the Hiyama and Heck catalytic cycles and desilylation mechanisms b and c have been computationally evaluated for the [Pd(en)Cl2] precursor in water as solvent. The calculated Gibbs energy barriers support the reinsertion route proposed on the basis of the experimental results.
- Gordillo, Alvaro,Ortuno, Manuel A.,Lopez-Mardomingo, Carmen,Lledos, Agusti,Ujaque, Gregori,De Jesus, Ernesto
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supporting information
p. 13749 - 13763
(2013/10/01)
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- MULTINUCLEAR COMPLEX AND CONDENSATION PRODUCT THEREOF
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A multinuclear complex comprising a plurality of metal atoms and a ligand L coordinating to the metal atoms, and satisfying the following conditions (i), (ii), (iii) and (iv): (i) The ligand L has a monovalent group represented by the following general fo
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Page/Page column 16
(2009/03/07)
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- POLYNUCLEAR COMPLEX AND POLYMER THEREOF
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To provide a multinuclear complex including at least one ligand L satisfying the following requirements (i), (ii) and (iii), and a plurality of metal atoms in a molecule: (i) having a group having polymerizable reactive multiple bonds, and/or a ring-opening polymerizable ring, (ii) having five or more coordination atoms bonding to the metal atoms, and (iii) being soluble in a solvent.
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Page/Page column 24
(2008/12/08)
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