Diastereoselective reduction of cyclohexanones with diisobutylaluminium phenoxides in terms of the isoinversion principle

Abstract

The diastereoselectivity of the reduction of 2-substituted cyclohexanones 1–6 with 4-substituted diisobutylaluminium phenoxides a–d has been investigated as a function of temperature. The high-temperature region is found to be dominated by hydride transfer, which is controlled by steric as well as electronic effects. However, at low temperatures the Meerwein–Ponndorf–Verley reaction gains in importance. This phenomenon is quantified by an isoinversion relationship.