Benzoquinone imines. Part XII. Reactions of 2-aminoindamines [2-amino-N-(4-aminophenyl)-p-benzoquinone di-imines] in aqueous solution

Abstract

The fate of 2-aminoindamines [2-amino-N-(4-aminophenyl)-p-benzoquinone di-imines] in aqueous solution has been found to be highly pH dependent. At high pH (>9) the major reaction involves hydrolysis of the unsubstituted imino-group to produce 2-aminoindoanilines [2-amino-N-(4-aminophenyl)-p-benzoquinone mono-imines]. At low pH ( <4), the major reaction involves hydrolysis of the azomethine bridge to give a mixture of a p-phenylenediamine and a 2-amino-p-benzoquinone monoimine. In the intermediate pH range, the amino-indamines undergo intramolecular cyclisation to give 2,8-diaminophenazines. Mechanisms are proposed for these reactions on the basis of kinetic studies of the effect of pH on the rate.