Asymmetric borane reduction using mixtures of homochiral amino alcohol ligands

The asymmetric borane reduction of acetophenone is investigated using mixtu res of homochiral B-amino alcohol ligands. With stoichiometric amounts of a mixture of two- or three-amino alcohols, the e.e. remains at the level of the best amino alcohol for a wide composition range. A small but statistica lly significant enhancement in e.e. is observed when 10 mol% of an amino al cohol mixture of (1S,2R)-1-amino-2-indanol and (S)-phenylglycinol is used a s chiral ligand. (C) 1999 Elsevier Science Ltd. All rights reserved.