Synthesis of chiral alcohols by asymmetric reductions of various ketones including alpha-aminophenones

LiAlH4 previously treated with 2.5 equiv. of (S)-(+) or (R)-(-)-2-(2-isoindolinyl)butan-1-ol 1 reduced the six alpha-aminophenones 4-9 into the corresponding optically active beta-aminoalcohols 10-15 whose ee's were in the range 40-97% after chromatography and recrystallization. The asymmetric reduction of the ortho-dimethylaminobenzophenone 18, using the same reducing agents afforded the enantiomerically pure benzhydrols (R)-(-)-19 and (S)-(+)-19, respectively, and in 86-100% yields. The ortho-aminobenzhydrol (S)-(+)-20 and a-fluorenyl ethanol (R)-(+)-23 and (S)-(-)-23 were similarly obtained from the corresponding ketones 17 and 25, respectively. The latter carbinols were obtained in an enantiomerically pure state after recrystallization. Copyright (C) 1996 Elsevier Science Ltd