Dichlorotris(triphenylphosphine)ruthenium-Catalyzed Hydrogen Transfer from Alcohols to Saturated and α,β-Unsaturated Ketones

Yoel Sasson, Jochanan Blum*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

230 Scopus citations

Abstract

Dichlorotris(triphenylphosphine)ruthenium has been shown to be an efficient catalyst for the selective transfer hydrogenation of α,β-unsaturated ketones by primary and secondary carbinols. Kinetic studies were carried out using 1-phenylethanol as hydrogen donor and benzylideneacetophenone as acceptor. The catalysis is inferred to proceed in the following order: (a) dissociation of RuCl2(PPh3)3, (b) coordination of the acceptor to the metal, (c) coordination of the alcohol and the formation of a metal alkoxide, (d) hydrogen transfer from the alkoxyl ligand to the coordinated ketone, and (e) release of product. These data are compatible with the expression rate = kK1K2[S1][S2][C]0/(1 + K1[S1] + K1K2S1][S2] + K3[S2]) where [S1], [S2], and [C]0 are acceptor, donor, and catalyst concentration, respectively. Step d was considered rate determining on bases of kinetic isotope effect measurements. RuCl2(PPh3)3 has been shown to catalyze also hydrogen transfer from secondary carbinols to saturated ketones provided that the ketones involved in the reaction have significantly different oxidation potentials. Kinetic studies of the reaction of dibenzyl ketone and 1-phenylethanol indicate similarity of the three intial steps to those of the former catalysis, but the following step is assumed to involve hydrogen transfer from the alkoxyl ligand to the metal. The hydride attacks then the coordinated ketone with the higher oxidation potential.

Original languageEnglish
Pages (from-to)1887-1896
Number of pages10
JournalJournal of Organic Chemistry
Volume40
Issue number13
DOIs
StatePublished - 1 Jun 1975

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