Asymmetric synthesis of optically active alcohols with two chiral centres from a racemic aldehyde by the selective addition of dialkylzinc reagents using chiral catalysts

Abstract

Optically active alcohols with two chiral centres have been obtained in good to high e.e.s (enantiomeric excesses) from racemic 2-phenylpropanal 1 by diastereo- and ena ntio-selective addition of dialkylzinc reagents using (1S,2R)-(–)-N,N-dibutylnorephedrine (DBNE) and (S)-(+)-diphenyl(1-methylpyrrolidin-2-yl)methanol (DPMPM) as chiral catalysts. It was found that in the presence of (1S,2R)-(–)-DBNE, dialkylzinc selectively attacked racemic 1 from the Si-face of the aldehyde 1 regardless of the configuration of 1 and that (S)-1 reacted faster with dialkylzinc than did (R)-1.