Diethyl Phosphite Initiated Coupling of α-Ketoesters with Imines for Synthesis of α-Phosphonyloxy-β-amino Acid Derivatives and Aziridine-2-carboxylates

Coupling of alpha-ketoesters with imines initiated by diethyl phosphite in the presence of alkaline metal hexamethyldisilazides is reported. Base-promoted addition of diethyl phosphite to a-ketoesters, followed by [1,2]-phosphonate/phosphate rearrangement, generates alpha-phosphonyloxy enolates that are subsequently intercepted by imines. The use of suitable azomethine coupling partners allows selective construction of syn-alpha-hydroxy-beta-amino acid derivatives or trans-aziridine-2-carboxylates in high yields with excellent diastereoselectivities.