The oxidation of catechol in the presence of two aliphatic and aromatic amines has been investigated. In aqueous solutions of pH 7���0 and 11���7, the substitution pattern of the adduct was dependent on the type of amine used. Aromatic amines produced 4, 5-disubstituted o-quinones, whereas aliphatic amines gave either 2, 4, 5-trisubstituted or 2, 4-disubstituted o-quinone adducts. A rationale based upon the stability of vinylogous amides is presented to account for the observed substitution pattern. �� 1989 ASEG.