A New Method for the Preparation of Oxazaborolidine Catalyst In Situ Using 1,2-Aminoalcohol, Sodium Borohydride, and Diiodomethane for the Asymmetric Reduction of Prochiral Ketones and N-Substituted Imines

Abstract

An oxazaborolidine catalyst is readily prepared in situ at room temperature in THF using 1,2-aminoalcohols and borane generated from sodium borohydride/CH2I2 reagent system. The oxazaborolidine/BH3 reagent system prepared in this way is useful for the reduction of prochiral ketones and N-substituted imines to the corresponding alcohols and amines with moderate to good enantiomeric excesses.