ECEC and ECE-type mechanisms in electrochemical oxidation of 4-substituted catechols in the presence of 4-hydroxy-6-methyl-2-pyrone

Electrochemical oxidation of 3,4-dihydroxybenzoic acid (1) and 4-tert-butylcatecbol (5) in the presence of 4-hydroxy6-methyl-2-pyrone (2) as nucleophile in aqueous solution has been studied using cyclic voltammetry and controlled-potential coulometry. The results indicate that 1 via Michael reaction under electro-decarboxylation reaction converts to heterocyclic compound 4, and the quinone derived from 4-tert-butylcatechol (5) participates in Michael reaction with 2 and through an ECE mechanism converts to the corresponding o-quinone (6a). The electrochemical synthesis of 4 and 6a has been successfully performed in an undivided cell.