Electrochemical syntheses of 2-indolyl-5-arylsulfonyl-p-benzoquinone derivatives were carried out in two successive oxidation steps. The first involves the oxidation of hydroquinone, 4-(piperazin-1-yl) phenol) and 1-(4-(4-hydroxyphenyl) piperazin-1-yl) ethanone in the presence of arylsulfinic acids as nucleophiles. Our voltammetric data indicate that electrochemically generated p-benzoquinone participates in Michael addition reaction with arylsulfinic acids leading to the 2-(arylsulfonyl) benzene-1,4-diols. The second consists of the oxidation of 2-(arylsulfonyl) benzene-1,4-diols in the presence of 1,2-dimethylindole and the formation of 2-indolyl-5-arylsulfonyl-p-benzoquinone derivatives as the final products. A plausible mechanism for the synthesis of 2-indolyl-5-arylsulfonyl-p-benzoquinone derivatives is also presented.
