Highly stereoselective synthesis of β-lactams utilizing α-chloroimines as new and powerful chiral inductors

A study was conducted to demonstrate stereoselective synthesis of βlactams by using α-chloroimines as chiral inductors. The study is based on the mechanistic rationale of the [2 + 2]-cycloaddition of ketenes and imines, and used α-chloroimines as chiral inductors for the synthesis of azetidin-2-ones. The study found that α-chloroimines are the powerful chiral inductors for the stereoselective Staudinge synthesis of β-lactams. The study applied (S)-α-chloroaldimines for the synthesis for novel 4-(1-chloroethyl)-β-lactams in high diastereomeric and enantiomeric excess. N-(2-chloro-1-methylpropylidene)-amines was prepared in the study through condensation of racemic 3-chloro-2-butanone and primary amines with addition of titanium (IV) chloride in THF.