Asymmetric Reduction of Acetophenone with Borane Catalyzed by Chiral Oxazaborolidine Prepared from (1R, 2S)-Epherdrine

Some new oxazaborolidines 1- 5, Prepared from the reaction of (\R, 25) -epherdrine and BH3 ·SMe2 or RB(OH)2, Serve as chiral catalysts for the asymmetric reduction of acetophenone with borane to give the (R)-1-phenylethanol with 38.5-72.4% e.e. in high yield. The structure-reaction relationship of the catalysts and the effect of reaction parameters (the amount of catalyst and reaction temperature) on enantioselectivity of the reduction are discussed.