Stereoselectivity in hydrosilylative reduction of substituted cyclohexanone derivatives with chiral rhodium-bis(oxazolinyl)pyridine catalyst

Abstract

Stereoselectivity in the reduction of substituted cyclohexanones, 4-tert-butylcycohexanone, 2-methylcycohexanone, 2-phenylcyclohexanone, and 2-methoxycarbonyl-methylcyclohexanone, was examined with chiral rhodium-bis(oxazolinyl)pyridine catalyst and diphenylsilane. 4-tert-Butylcyclohexanone gave the corresponding trans( equatorial)-alcohol predominantly; the ratio of the trans/cis alcohols, 67:33. Other 2-substituted cyclohexanones showed exclusive enantioselectivities for each diastereomer in terms of the kinetic resolution; e.g. from 2-phenylcyclohexanone, 99 % ee of (1S, 2R)-trans-2-phenylcyclohexanol and 96 % ee of (1S, 2S)-cis-2-phenylcyclohexanol in 92 % yield (the trans/cis ratio = 51:49).