Chemistry of indanthrone. Part XIII. The constitution of indanthren B

Abstract

It is suggested that “indanthren B” is not the mono- or di-hydroxy-derivative of the linear isomer of indanthrone as proposed by earlier workers, and an alternative structure is put forward. A mechanism is proposed for the formation of “indanthren B” from 2-aminoanthraquinone by the intermediate formation of 2-amino-1′-hydroxy-1,2′-dianthraquinonylamine, followed by cyclisation. The action of fused potassium hydroxide on compounds of the dihydrodinaphthophenazinediquinone series has been examined. These diquinones were found to be stable to alkali fusion and no evidence of direct hydroxylation was encountered; instead a small amount of ring fission occurred with the possible formation of o-benzoylphenazine carboxylic acid derivatives.