In an aqueous solution containing oxindole as a nucleophile, electrochemical oxidation of 2,3-dimethylhydroquinone and some catechols have been studied using cyclic voltammetry and controlled potential coulometry. The voltammetric data show that electrochemically generated para- and ortho-benzoquinones participate in Michael addition reactions with oxindole to form the corresponding dihydroxyphenyl-indolin-2-one derivatives. In this work, we have proposed a mechanism for the electrode process, and we report an efficient and one-pot green method for the synthesis of dihydroxyphenyl- indolin-2-one derivatives based on the Michael reaction of electrochemically generated ortho- and para-benzoquinones with oxindole in an undivided cell using an environmentally friendly reagentless method in ambient conditions.
