Chiral Phosphoric Acid and BF 3 ·THF Relay Catalytic System Enables a Formal Asymmetric Aza-Baeyer–Villiger Rearrangement

A relay catalytic system comprising chiral phosphoric acid (CPA) and BF₃·THF enables a formal asymmetric aza-Baeyer-Villiger rearrangement of cyclobutanones with a newly designed dinaphthylphosphinyl hydroxylamine (DNPH) reagent. The strategy combines the highly enantioselective CPA-catalyzed condensation of cyclobutanones with DNPH (generally >90% ee) and BF₃·THF-promoted Beckmann rearrangement involving an axial-to-point chirality transfer with excellent enantiospecificity (>98% es). This one-pot method offers operational simplicity and excellent enantiocontrol, facilitating the synthesis of valuable γ-lactams.