Electrochemical synthesis of 5,6-dihydroxy-2-methyl-1-benzofuran-3-carboxylate derivatives

Electrochemical oxidation of catechols (1a–c) has been studied in the presence of methyl acetoacetate (2a) and ethyl acetoacetate (2b) as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (1a–c) participate in Michael addition reactions with 2a and 2b to form the corresponding benzofuran derivatives (3a–f). The electrochemical synthesis of 3a–f 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 products have been characterized after purification by IR, 1H NMR, 13C NMR, MS, and single crystal X-ray diffraction.