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 la 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 con trolled-potential. The product has been characterized after purification by IR, H-1 NMR, C-13 NMR and MS. (c) 2005 Elsevier B.V. All rights reserved.