Diastereospecific Synthesis of Vicinally Substituted 2-Oxazolidinones via Oxidative Rearrangement of α,β-Unsaturated γ-Lactams

A diastereospecific synthesis of vicinally substituted 2-oxazolidinones from α,β-unsaturated lactams using m-chloroperoxybenzoic acid is reported. Several highly substituted 2-oxazolidinones were obtained in 19-46% yields in a one-pot reaction with complete control over the relative stereochemistry. The proposed reaction sequence consists of a Baeyer-Villiger oxidation, an epoxidation, and a concerted rearrangement. Experimental results and density functional theory calculations indicate that a CH₂COOEt substituent at position 4 of the lactam is necessary for the diastereospecific rearrangement to take place.