Studies on sulfenamides. XV. Semi-empirical calculation of reactivity of 4'-substituted benzenesulfenanilidyl radicals

The mechanism of the formation of 2,7-disubstituted phenazine in the oxidat ion of 4'-substituted benzensulfenanilide was studied by employing the PM3 method. Calculation of the total energy suggested that the homolytic cleava ge of the S-N bond of cation radical (A) derived from benzenesulfenanilides was not a spontaneous reaction at room temperature. The following mechanis m has been suggested. Dimerization of A followed by proton migration gives (4-substituted phenyl) (5-substituted-2-(phenylthioamino)phenylthioamine (5 ), which is oxidized to give a cation, which is then cyclized to give 2,7-d isubstituted 5,10-phenylthio-5,10-dihydrophenazine (6). The acid hydrolysis of 6 gives diphenylthiosulfinate and 2,7-disubstituted-5,10-dihydrophenazi ne and the latter is oxidized to 2,7-disubstituted phenazine by dissolved o xygen in the reaction solution.