Asymmetric synthesis by reduction or by oxidation of prochiral substrates absorbed into chiral polymer supports

Abstract

Prochiral ketones absorbed into chiral polymer supports were reduced with aqueous potassium borohydride. 2-Substituted naphthoquinones absorbed into chiral polymer supports were epoxidized using aqueous alkaline hydrogen peroxide. In both systems asymmetric synthesis was achieved. Best results were obtained with microcrystalline cellulose triacetate as the polymer support: 8.6% ee in a reduction, 4.5% ee in an epoxidation. Use of tetra- n-butylammonium bromide as a phase transfer catalyst tended to improve chemical yields and ees. The potential of this type of approach in asymmetric synthesis is discussed.