TY - JOUR
T1 - Dichlorotris(triphenylphosphine)ruthenium-Catalyzed Hydrogen Transfer from Alcohols to Saturated and α,β-Unsaturated Ketones
AU - Sasson, Yoel
AU - Blum, Jochanan
PY - 1975/6/1
Y1 - 1975/6/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0001337101&partnerID=8YFLogxK
U2 - 10.1021/jo00901a004
DO - 10.1021/jo00901a004
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AN - SCOPUS:0001337101
SN - 0022-3263
VL - 40
SP - 1887
EP - 1896
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 13
ER -