Electrochemical synthesis of N¹,N⁴-diphenyl-2-(phenylsulfonyl)benzene-1,4-diamine derivatives: Introducing an example of EC_DispC_Mich mechanism

Highlights: • Electrochemical oxidation of N,N'-dipheny-l,4-phenylenediamine (DPD). • Study on disproportionation reaction of radical cation (DPD^.+). • Electrochemical synthesis of N-(4-(phenylimino) cyclohexa-2,5-dienylidene) benzenamine. • Mechanistic study of electrochemical oxidation of N,N'-dipheny-l,4-phenylenediamine in the absence and presence of arylsulfinic acids. - Abstract: The electrochemical oxidation of N,N'-diphenyl-l,4-phenylenediamine (DPD) has been studied using cyclic voltammetry and controlled potential coulometry methods. The results revealed that DPD shows two one-electron oxidation–reduction peaks. In the first step DPD via a single-electron process is converted to the related radical cation (DPD^.+) and second step is conversion of DPD^.+ to N-(4-(phenylimino) cyclohexa-2,5-dienylidene) benzenamine (CHD) via a one-electron/two-protons process. Our results also show that DPD^.+ participates in disproportionation reaction and is converted to DPD and CHD. The rate of this reaction is pH dependent and increases with increasing pH. Furthermore, the electrochemical oxidation of DPD has been studied in the presence of arylsulfinic acids as nucleophiles. The results showed that electrochemically generated CHD participates in Michael addition reaction with arylsulfinic acids via a novel "EC_DispC_Mich" mechanism and is converted to the N¹,N⁴-diphenyl-2-(phenylsulfonyl)benzene-1,4-diamine derivatives. In this work, a facile and green electrochemical method for the synthesis of some new N¹,N⁴-diphenyl-2-(phenylsulfonyl)benzene-1,4-diamine derivatives in good yields using controlled-potential electrolysis at a carbon electrode is also reported