A one-pot visible-light strategy for cyclobutanone synthesis via sequential [2 + 2] cycloaddition and Nef reaction of nitroalkenes and 2-vinylpyridines.

A visible-light-driven one-pot strategy for pyridinyl-cyclobutanone synthesis has been developed, involving sequential [2 + 2] photocycloaddition and photo-Nef reactions of nitroalkenes and 2-vinylpyridines. Under violet LED irradiation, nitrostyrenes underwent catalyst-free [2 + 2] cycloaddition in ethanol to give cyclobutanes in good yields with good substrate generality. Ethanol was found to be the best solvent for the [2 + 2] photocycloaddition reaction. The resulting nitrocyclobutanes were converted to cyclobutanones under blue LED light with photocatalyst Ir(dtbbpy)(ppy)2PF6, Et3N, DIPEA, and Mg(ClO4)2, followed by acidic hydrolysis. This three-step sequence was integrated into a one-pot process, allowing direct access to cyclobutanones without the isolation of intermediates.