Cobalt-Catalyzed Regioselective [4+2] Annulation/Lactonization of Benzamides with 4-Hydroxy-2-Alkynoates under Aerobic Conditions

A cobalt-catalyzed regioselective [4+2] annulation/lactonization reaction of benzamides with 4-hydroxy-2-alkynoates is reported. This reaction utilizes air as an oxidant rather than metal salts. The method is operationally simple, mild, and sustainable. This protocol exhibits a broad substrate scope and compatible with a variety of functional groups furnishing the corresponding 1,4-dihydrofuro[3,4-c]isoquinoline-3,5-dione derivatives in good to excellent yields with high regioselectivity. (Figure presented.).