Biphase Reduction of Heptanal and Cyclohexanone by Sodium Formate Catalyzed by Ether-Phosphine Ruthenium(II) Complexes

Abstract

RuCl2[P(C6H5)2OCH2CH2OCH3]2 has efficiently catalyzed the reduction of cyclohexanone and heptanal by sodium formate in chlorobenzene-water, using cetylpyridinium bromide as the phase transfer catalyst. In both cases, the reduction was first order both in the substrate and in the initial concentration of the catalyst. The catalyst activity in the aldehyde reduction could be increased by the addition of the free ligand while in the ketone reduction the ligand in excess decreased the reaction rate. Several other phosphines of the type P(C6H5)2L where L = C6H5, C4H9, C2H5OCH2CH2, C4H9OCH2CH2, 1,4-dioxanemethyl, tetrahydrofurfuryl, and P(i-C3H7)3) gave the less efficient catalysts. Kinetic and activation data for the reduction of both substrates are reported.