Construction of Bridged <i>N,O</i> -Heterocycles via Palladium-Catalyzed [5 + 4] Cycloadditions of Azabicyclo[2.1.0]pentanes and Vinyl Oxiranes

We report a palladium-catalyzed formal [5 + 4] annulation between readily accessible vinyl oxiranes and azabicyclo[2.1.0]pentanes, enabling the regioselective synthesis of bridged nine-membered <i>N,O</i>-heterocycles. The reaction proceeds via a palladium-stabilized intermediate formed through selective oxidative addition of the vinyl oxirane under Pd(0) catalysis, which serves as a five-membered synthon in the cycloaddition. This method affords structurally complex carbon-bridged heterocycles in good to excellent yields. Further derivatization of the products highlights the broad synthetic utility of this strategy.