Photosensitized, Energy-Transfer-Mediated Cyclization of 2-(1-Arylvinyl)benzaldehydes to Anthracen-9-(10H)-ones

A visible-light-induced photocatalytic intramolecular cyclization of 2-(1-arylvinyl)benzaldehydes is reported. The reaction is promoted in the presence of an Ir-III photocatalyst and an amine base at room temperature under the irradiation of blue LEDs, affording 10-methylanthracen-9(10H)-one derivatives in moderate to good yields with tolerance to various functional groups. A series of mechanistic experiments suggest that the reaction proceeds via energy transfer from the excited Ir-III photocatalyst to the substrate to generate a diradical, which then undergoes 1,5-hydrogen shift, 6 pi electrocyclization, and aromatization leading to the cyclic product.