N-Alkyl salts derived from ephedrine do not promote enantioselective Corey–Chaykovsky reactions involving sulfonium methylides under phase-transfer conditions

Abstract

N-Alkyl salts derived from ephedrine have twice been reported to act as chiral phase-transfer catalysts in Corey–Chaykovsky reactions between sulfonium ylides and benzaldehyde; reportedly furnishing the terminal epoxide product in moderate–excellent enantiomeric excess. This study unequivocally demonstrates that these reactions proceed without measurable stereoinduction and explains how previous studies mistakenly attributed product optical activity to asymmetric catalysis.