Electrochemical study of 3,4-dihydroxybenzoic acid in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone: Application to electrochemical synthesis of new benzofuran derivative

Electrochemical oxidation of 3,4-dihydroxybenzoic acid (1a) has been studied in the presence of 4-hydroxy-1-methyl-2(1H)-quinolone (3) as a nucleophile in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that 1a via a 1,4-(Michael) addition reaction under electro-decarboxylation reaction converts to benzofuran (or isochromeno[4,3-c]quinoline) derivative (6a). The electrochemical synthesis of 6a has been successfully performed in an undivided cell in good yield and purity. The oxidation mechanism was deduced from voltammetric data and by coulometry at controlled-potential. The product has been characterized after purification by IR, 1H NMR, 13C NMR and MS.