Reactions in NN-dimethylformamide. Part II. Halogen replacement in the anthraquinone series

Abstract

In the condensation of 1-chloroanthraquinone with arylamines, the use of NN-dimethylformamide as solvent can lead to the formation of 1-arylaminoanthraquinone, 1-alkylaminoanthraquinone, or mixtures thereof, depending on the basicity of the arylamine. 1-Chloroanthraquinone reacted with NN-dimethylformamide with initial formation of 1-dimethylaminoanthraquinone; prolonged reaction resulted in demethylation and ultimate formation of 1-methylaminoanthraquinone. A similar replacement was observed with 2-chloro- and 1,2-, 1,4-, 1,5-, and 1,8-dichloroanthraquinones. Dealkylation of 1-dimethylaminoanthraquinone occurs in other dipolar aprotic solvents, e.g. dimethyl sulphoxide, but none occurs in comparatively high-boiling basic (e.g. β-picoline and pyridine) or neutral (e.g. ethylene glycol monomethyl ether) solvents.