Electrochemical oxidation of catechols in the presence of 4-amino-3-methyl-5-mercapto-1,2,4-triazole bearing two nucleophilic groups

Electrochemical synthesis of o-benzoquinone derivatives and their in situ transformation are one of the versatile approaches for the synthesis of derivatized catechols. In the present work, electrochemical oxidation of catechols 1a–1d in the presence of a unique nucleophile, 4-amino-3-methyl-5-mercapto-1,2,4-triazole 3, bearing two nucleophilic groups (–NH2 and –SH), have been studied in phosphate buffer solutions using cyclic voltammetry and controlled-potential electrolysis (CPE) methods. The results show that only the mercapto group participated selectively in the Michael addition reaction and led to the formation of catechol substituted products of types 4 and 5, bearing a free amino group, potentially useful for further chemical modifications, e.g. of interest in biomedical applications. Various electrolytic conditions, such as the nature of anode material, amount of passed charge, pH of the electrolytic solution and cell configuration (divided or undivided cell), were also investigated to optimize the yields of corresponding products.