N-Trimethylsilyl Imines: Applications to the Synthesis of β-Lactams

Ester enolates and N-trimethylsilyl imines react to afford N-protio-β-lactams. The stereochemical course of the reaction depends on the ester enolate geometry. Therefore (E)-enolates give mainly cis β-lactams while (Z)-enolates give nearly equal mixtures of cis and trans β-lactams. The use of ethyl β-hydroxybutyrate as the ester component allows the preparation of β-lactams of potential use in carbapenem synthesis. The differences in the behavior of N-trimethylsilyl and N-aryl imines in ester-inline condensations are also discussed.