Photoinduced [4+2] cycloaddition of dienes and quinonemethides

A visible light-induced cycloaddition of 1,3-dienes and p-quinonemethides through EDA complexation is reported. The reaction does not require any external photocatalyst, oxidant or additive. The generality of the method is established through a broad substrate scope. This newly developed strategy presents an exciting prospect for the development of metal-free photocatalytic [4+2] cycloaddition reactions.

Brønsted acid catalyzed radical addition to quinone methides

A fundamental quest for alkyl radical generation under mild conditions through photoinduced Brønsted acid catalysis is addressed. The optimized protocol does not require any organic dyes or transition metal photocatalyst. Under blue light irradiation with diphenyl phosphate as a catalyst and dihydropyridine derivatives as a radical source, functionalized arylmethane derivatives are obtained in high yield.