Photochemical substitution of methoxyanthraquinones with amines and other nucleophiles

Abstract

1-Methoxyanthraquinone undergoes photochemical nucleophilic substitution with ammonia and primary aliphatic amines to give good yields of the 1-amino- or 1-alkylamino-anthraquinone. The reaction does not occur with secondary amines and primary arylamines. Photosubstitution is also observed with certain inorganic nucleophiles. 2-Methoxyanthraquinone is less reactive, but undergoes photochemical substitution with ammonia to give 2-amino- and 1-amino-2-methoxy-anthraquinone, the relative proportions depending on the availability of oxygen during the reaction. Less efficient photoreactions occur with primary aliphatic amines and inorganic nucleophiles. The synthetic implications of these reactions are discussed.