Benzoquinone imines. Part IX. Mechanism and kinetics of the reaction of p-benzoquinone di-imines with m-aminophenols

Abstract

The products of the coupling of p-benzoquinone di-imines with m-aminophenols indicate that reaction occurs in the position para to the hydroxy-group to give aminoindoanilines while, if this position is blocked, reaction occurs at the position para to the amino-group to give hydroxyindamines. The reaction of di-imine with 3-amino-4,6-dimethylphenol results in an equilibrium with a compound which is probably a pseudo-quinone imine. Kinetic studies show the reaction of di-imines with m-aminophenols to involve electrophilic attack of the conjugate acid of the di-imine on the phenolate ion and the neutral phenol, the former predominating at pH < 8. Kinetic studies also show that, with 4- and 6-methyl-3-aminophenol, some of the postulated pseudo-quinone imine is formed, but is ultimately converted into the normal indo-dye.

Aminoindoaniline reacts with p-phenylenediamine or other primary arylamines to give trinuclear indoanilines such as (VII) and (VIII). In concentrated solution, hydroxyindamines undergo intramolecular cyclization to give aminophenoxazineimines.