Visible-Light-Mediated Cascade Construction of Polysubstituted Naphthalene Scaffolds from 2-Methylbenzophenones and (Trifluoromethyl)alkenes

We report a novel visible light-promoted cascade reaction for the efficient synthesis of substituted naphthalenes in good yields. Upon visible-light irradiation, 2-methylbenzophenones generate transient hydroxy-o-quinodimethanes, which act as nucleophiles to attack (trifluoromethyl)alkenes, forming key intermediates containing carbonyl and 1,1-difluoroalkene moieties. Subsequently, a visible light-driven intramolecular Paternò-Büchi reaction ([2 + 2] cycloaddition) occurs, followed by a retro-[2 + 2] process that yields substituted 1,2-dihydronaphthalenes with concomitant release of carbonyl fluoride. Finally, a dehydrogenative aromatization step affords the desired substituted naphthalenes.