Anodic oxidation of catechols in the presence of 1,3-indandione. A green electrosynthetic approach to new catechol derivatives

Efficient carbon-carbon bond-forming reaction at the 5- and 6-positions of catechol skeleton was achieved through anodic oxidation of catechol, 3-methylcatechol, and 4-methylcatechol in the presence of 1,3-indandione as a nucleophile. The electrochemical synthesis was carried out in aqueous solution, which is a green solvent, using cyclic voltammetry and control led-current coulometry techniques. The results indicate that the electrogenerated benzoquinone from the electrooxidation of the corresponding catechol participates in a Michael addition reaction with 1,3-indandione. The mechanism of anodic oxidation was deduced from voltammetric and spectroscopic data. The galavanostatic electrochemical synthesis of compounds 2a, 2b, and 2c was successfully performed in an undivided cell in good yield. The products were characterized by (HNMR)-H-1, (CNMR)-C-13, DEPT, FT-IR, and mass spectrometry.