Simple Strategy for Benzo[]chromene Synthesis via a Photochemical Intramolecular Cyclization Reaction.

Photochemical reactions are often a desirable strategy for organic synthesis because they do not require toxic and expensive reagents and produce less waste than thermal reactions. Herein, a facile photochemical strategy is described to synthesize benzo[]chromene derivatives. This strategy utilizes the photoredox reaction of quinones, which allows C-H bond oxidation in the vicinity of the photoexcited quinone carbonyl group. The reaction mechanism was investigated using H NMR analysis. The intramolecular cyclization reaction proceeded via the formation of 1,3-dioxole compounds as intermediates by the photoredox reaction of -quinone, followed by re-cyclization. The synthesized benzo[]chromene derivatives are important heterocyclic skeletons with useful biological and pharmacological properties.