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

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Hidetaka Fujihara and Kiyoshi Tomioka


Abstract

Asymmetric protonation of the lithium enolate moiety of a 2-substituted α-tetralone (3,4-dihydronaphthalen-1(2H[hair space])-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.


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