Diastereoselective Imino–Aldol Condensation of Chiral 3-(p-Tolylsulfinyl)-2-furaldimine and Ester Enolates

Abstract

(S_s)-3-(p-Tolylsufinyl)-2-furaldimine was synthesized, and condensation of the chiral furaldimine with lithium ester enolates has been examined. The product distribution of the reaction is dependent upon reaction conditions and on the kind of the substituent placed on the esters. Disubstituted ester enolate resulted in the exclusive formation of (4R)-β-lactam, while unsubstituted, tert-butyl ester enolate preferentially gave (3R)-β-amino ester. With the monosubstituted ester enolates, the condensation afforded (4R)-β-lactams and/or (3R)-β-amino esters as major products. This method has been applied to an efficient route to chiral furyl β-lactams.