Ring opening reactions of 6H‐anthra[1,9‐cd]isoxazol‐6‐ones and related compounds

Nucleophilic attack of anthra[1,9‐cd]isoxazol‐6‐ones, and of anthra[1,9‐cd:5,10‐c'd']isoxazole by various sulfoxides, triphenyl phosphine, and aliphatic or aromatic phosphites proceeded with cleavage of the nitrogenoxygen bond of the isoxazole ring. This method provided ready access to substituted anthraquinones bearing sulfoximido‐, triphenylphosphazo‐, and dialkyl(aryl)phosphoramidic groups attached to the 1‐ and the 1,5‐positions of the anthraquinone system. The structures of the newly synthesized anthraquinone derivatives were supported by analytical and spectral data. l‐S,S‐dimethyl‐N‐(5‐benzamidoanthraquinon‐1‐yl)‐sulfoximide yielded in 90% sulfuric acid the l‐amino‐5‐sulfoximido anthraquinone without hydrolyzing the sulfoximido group.