Mechanism of electrochemical oxidation of catechol and 3-substituted catechols in the presence of barbituric acid derivatives. Synthesis of new dispiropyrimidine derivatives

Abstract

The electrochemical oxidation mechanism of catechol (1a), 3-methylcatechol (1b) and 3-methoxycatechol (1c) in the presence of barbituric acid (3a) and 1,3-dimethylbarbituric acid (3b) as nucleophile in aqueous solution has been studied in detail by cyclic voltammetry and controlled-potential coulometry. The results indicate that 1a–1cvia an ECEC (E, electrochemical; C, chemical) pathway, participating in a 1,4 (Michael) addition reaction, are converted to dispiropyrimidine derivatives 6a–6f. The homogeneous rate constants were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. The electrochemical synthesis of 6a–6f has been successfully performed in an undivided cell in good yields and high purity.