Diastereoselective synthesis of 2-methoxyimidoyloxiranes via dimethyl phosphite-mediated coupling of α-keto N-sulfinyl imidates with aldehydes

Abstract

Dimethyl phosphite-initiated coupling of α-keto N-tert-butylsulfinyl imidates with aldehydes is reported. The epoxide formation involves a cascade transformation initiated by base-promoted addition of phosphite to α-ketoimidates, followed by [1,2]-phospha-Brook rearrangement. This generates α-phosphonyloxy enolates that are subsequently intercepted by aldehydes, leading to [1,4] O→O dialkoxyphosphinyl migration and finally to intramolecular ring closure. This protocol was used to synthesize a range of enantioenriched trans-α,β-epoxy imidates in moderate to high yields with excellent diastereoselectivities.