Asymmetric Reduction of 4-Phenyl-3 (E)-buten-2-one by Using Lithium Aluminum Hydride Partially Decomposed with (-)-N-Methylephedrine and Achiral Secondary Amine

Abstract

The optical rotation of optically pure (S)-(-)-4-phenyl-3 (E)-buten-2-ol ((S)-(-)-2) was determined on the basis of nuclear magnetic resonance (NMR) spectral measurements of the acetate in the presence of a chiral shift reagent. Our former result on the asymmetric reduction of 4-phenyl-3 (E)-buten-2-one (1) had to be corrected. The title chiral hydride prepared by using diphenylamine or 2-anilinopyridine as an achiral additive was found to reduce 1, affording (S)-(-)-or (R)-(+)-2 in 66% or 53% optical yield.