Electrochemical synthesis of 6-arylsulfonyl caffeic acid derivatives in aqueous medium

The anodic oxidation of caffeic acid in the presence of sodium benzenesulfinate in aqueous solution was studied by cyclic voltammetry and controlled potential coulometry. The results showed that similar to other simple catechol derivatives where the substituents attached directly to the benzene ring, caffeic acid was oxidized to the corresponding o-benzoquinone which underwent further Michael-addition with sodium benzenesulfinate or sodium p-methyl benzenesulfinate to produce 6-arylsulfonyl caffeic acid derivative 7a or 7b.