Asymmetric protonation of lithium enolate using 5-substituted pyrrolidin-2-one as a chiral proton source

Abstract

Asymmetric protonation of the lithium enolate moiety of a 2-substituted α-tetralone (3,4-dihydronaphthalen-1(2H)-one) was examined using 5-substituted pyrrolidin-2-ones as chiral proton sources. Among the three types of pyrrolidin-2-ones bearing either a hydroxymethyl group or steric bulk or a chelation site at the 5-position, the pyrrolidin-2-ones bearing steric bulk gave the enantiomerically enriched α-tetralone derivative in up to 72% ee.