Efficient Palladium‐Catalyzed Aerobic Oxidative Carbocyclization to Seven‐Membered Heterocycles

The use of molecular oxygen in palladium‐catalyzed oxidation reactions is highly widespread in organic chemistry. However, the direct reoxidation of palladium by O 2 is often kinetically unfavored, thus leading the deactivation of the palladium catalyst during the catalytic cycle. In the present work, we report a highly selective palladium‐catalyzed carbocyclization of bisallenes to seven‐membered heterocycles under atmospheric pressure of O 2 . The use of a homogenous hybrid catalyst (Co(salophen)‐HQ, HQ=hydroquinone) significantly promotes efficient electron transfer between the palladium catalyst and O 2 through a low‐energy pathway. This aerobic oxidative transformation shows broad substrate scope and functional group compatibility and allowed the preparation of O ‐containing seven‐membered rings in good yields in most cases.