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

摘要

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+center dot) 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 pew 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. (C) 2015 Elsevier B.V. All rights reserved.