Asymmetric borane reduction of prochiral ketones catalyzed by C3-symmetric sulfonamide

A novel, recoverable, C(3)-symmetric sulfonamide L-1 has been developed for the asymmetric borane reduction of prochiral ketones in refluxing THF. The optically active secondary alcohols were obtained in excellent enantiometric excesses (up to 97% ee) and good yields. The C(3)-symmetric sulfonamide L-1 can be easily recovered and reused four times without any significant loss of catalytic activity. (C) 2008 Elsevier Ltd. All rights reserved.