Addition of Azomethine Ylides to Aldehydes: Mechanistic Dichotomy of Differentially Substituted α‐Imino Esters

Abstract

AbstractThe formal 1,3‐dipolar cycloaddition of azomethine ylides and aldehydes is explored, as hydrolysis of the resulting oxazolidine product gives facile access to valuable syn‐β‐aryl‐β‐hydroxy‐α‐amino esters. The use of using benzaldehyde‐derived imines as the ylide precursor results in 1,3‐dipolar cycloaddition with high conversions but low diastereoselectivity. In contrast, the employment of benzophenone‐derived imines as the ylide precursor results in an aldol reaction, which gives the intermediate oxazolidine in high diastereoselectivity and requires a weak acid catalyst to achieve higher conversions.