Diastereoselectivity in the reduction of acyclic carbonyl compounds with diisopropoxytitanium(III) tetrahydroborate

Diisopropoxytitanium(III) tetrahydroborate, ((PrO)-Pr-i)(2)TiBH4, formed in situ in dichloromethane from diisopropoxytitanium dichloride and benzyltri ethylammonium tetrahydroborate (1:2) reduces alpha-hydroxyketones/1,2-diket ones and beta-hydroxyketones/1,3-diketones to the corresponding diols with high stereoselectivity. In the case of alpha-hydroxyketones and 1,2-diketon es, the anti isomer is the major product while reduction of beta-hydroxyket ones and 1,3-diketones leads to the syn isomer as the major product.