Oxidative [4+2] annulation of styrenes with alkynes under external-oxidant-free conditions

The sequenced Diels–Alder/oxidation reaction represents a powerful route for the construction of aromatic compounds in organic synthesis. The oxidative Diels–Alder reaction with H(2) evolution would be a more ideal approach that can avoid the additional oxidation procedure and stoichiometric oxidant. Herein, an oxidative [4 + 2] annulation reaction of styrene derivatives with electron-rich dienophiles accompanying the H(2) generation has been developed by using the synergistic merger of photoredox and cobaloxime catalyst. With respect to atom and step-economy ideals, this dual catalytic system enables the formation of high-value molecules from feedstock chemicals in a single step under room temperature.