Comproportionation and Michael addition reactions of electrochemically generated N,N,N’,N’-tetramethyl-1,4-phenylenediamine dication. Synthesis of new unsymmetrical aryl sulfones containing N,N,N’,N’-tetramethyl-1,4-phenylenediamine moiety

Abstract

Abstract Electrochemical oxidation of N , N , N ’, N ’-tetramethyl-1,4-phenylenediamine (TMPD) has been studied in the absence and presence of arylsulfinic acids as nucleophiles in water/ethanol mixtures using cyclic voltammetry. The results imply that, TMPD under two one-electron oxidation steps yields the corresponding radical cation (TMPD + ) and dication (TMPD ++ ). It is found that the observed comproportionation rate constants, K Comp obs , of the reaction of TMPD ++ with TMPD increases with increasing pH and the percent of ethanol in the water/ethanol mixture. In addition, electrochemical synthesis of some new aryl sulfone derivatives of TMPD (3a–3c) was carried out via the electrooxidation of TMPD in the presence of arylsulfinic acids (1a–1c). The results show that electrogenerated TMPD ++ participated in a Michael-type reaction with 1a–1c and, via an overall EC mechanism, was converted to the corresponding aryl sulfone derivatives of TMPD. In this work, some new organosulfur compounds (3a–3c) are provided with good yields in water/ethanol mixture, at a carbon electrode, without toxic reagents and solvents using an environmentally friendly method.