Electrochemical oxidation of catechol in the presence of indole: a facile and one-pot method for the synthesis of trisindolyl-o-benzoquinone

The electrochemical oxidation of catechol has been studied in the presence of indole as the nucleophile in water/acetonitrile (50:50) using cyclic voltammetry and controlled-potential coulometry methods. The results revealed that the quinone derived from the oxidation of catechol participates in Michael addition reactions with indole, and via a novel ECECECE mechanism, converts it to the trisindolyl-o-quinone in a good yield via electrochemical oxidation under controlled-potential conditions without any toxic reagents at the carbon electrode in a two-compartment cell.