Potassium borohydride reductions of ketones absorbed into polymer supports: stereochemical effects

Abstract

The proportions of 6α-alcohol obtained from aqueous potassium borohydride reductions of 3β-hydroxy-5α-cholestan-6-one (1) absorbed into various polymers varied from 0 to 90% depending on the polymer used and whether or not a phase transfer catalyst was added; some other ketones show similar stereochemical effects, the greatest effects probably arising when the substrates are adsorbed to the inner surfaces of appropriate polymers.