Photocycloaddition of 1-aminoanthraquinones to dienes by visible light irradiation
Abstract
1-Aminoanthraquinones have been found to undergo cycloaddition reactions with dienes in ethanol to produce the corresponding oxetans when subjected to visible light irradiation. Monoene and acetylenic compounds do not react and the reaction in ethanol is restricted to 1-aminoanthraquinones, 2-aminoanthraquinones showing no reactivity. The reaction does not appear to be a conventional photocycloaddition via the nπ* triplet state of the quinone, but a new type occurring via the intramolecular charge-transfer (ππ*) excited state.