NHC-Catalyzed Access to Benzoxazepinones via Aromatization-Driven Rearrangement

Benzazepine derivatives, including benzoxazepines, constitute a privileged class of nitrogen-containing medium-sized heterocycles with significant pharmaceutical relevance. Herein, we report a carbene-catalyzed strategy for the efficient construction of oxazepine derivatives via aza-spirocyclization followed by an aromatization-driven rearrangement. The reaction between β-methyl enals and 5-enepyrrolin-4-ones proceeds efficiently through a key spirocyclic pyrrolidone intermediate, ultimately delivering the desired benzo-fused seven-membered products under oxidative conditions. This method provides rapid access to structurally diverse oxazepines and allows for further functional elaboration, underscoring the synthetic utility of NHC catalysis in the construction of complex heterocyclic frameworks.