Photochemical alkylamination of 1-acylaminoanthraquinones

Abstract

The photochemical reaction of 1-acylaminoanthraquinones(1) with primary aliphatic amines in benzene, in air, gave 1-acylamino-4-alkylaminoanthraquinones (2) in 56–78% yields. The reaction was retarded by the addition of triplet quenchers. The quantum yield of the reaction increased on raising the amine concentration. A mechanism via addition of alkylamine to the triplet excited state of (1), followed by oxidation to give the products (2), is proposed. The regioselective 4-amination of (1) has been rationalized by means of the frontier orbital method.