Enantioselective Beckmann Rearrangement through Organocatalytic Desymmetrization of Cyclobutanones for the Synthesis of 4,4-Disubstituted γ-Lactams

The Beckmann rearrangement stands as a powerful and atom economic transformation, and its enantioselective version has not yet been found. This work presents the organocatalytic enantioselective desymmetric synthesis of γ-lactams from prochiral 3,3-disubstituted cyclobutanones through the <i>in situ</i> formation of reactive <i>N</i>-sulfonyl oximes followed by Beckmann rearrangement. The reaction relies on the stereocontrolled generation of the axially chiral cyclobutanone oxime sulfonate intermediate under chiral Brønsted acid catalysis and subsequent axial-to-central chirality transfer.