Asymmetric Reductions of α,β-Acetylenic Ketones and Acetophenone Using Lithium Aluminum Hydride Complexed with Optically Active 1,3-Amino Alcohols

Article abstract of DOI:10.1021/jo01292a006

Asymmetric reduction of the α,β-acetylenic ketones 9a-f using the freshly prepared complex derived from LiAlH4 and (2S,3R)-(+)-4-(dimethylamino)-3-methyl-1,2-diphenyl-2-butanol (Darvon alcohol; 10) at -70 deg C gives mainly the (R)-carbinols 1a-f in yields of 62-99percent and enantiomeric excesses of 34-90percent.Similar treatment of 9e with the complex formed from LiAlH4 and 11, the enantiomer of 10, affords 2e, a useful intermediate for the synthesis of (2R,4'R,8'R)-α-tocopherol (vitamin E), in 96percent yield and 90percent ee.The optically pure 1,3-amino alcohol ligands 12-16, which are structurally related to 10, were prepared by starting from the known (S)-ether sulfonate 23 and its enantiomer.Reduction of 9a and acetophenone using the LiAlH4-12 complex gives an excess of the corresponding (S)-carbinols 2a (36percent ee) and 27 (60percent ee), respectively.