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 oxidation of 4'-substituted benzen-sulfenanilide was studied by employing the PM3 method. Calculation of the total energy suggested that the homolytic cleavage of the S-N bond of cation radical (A) derived from benzenesulfenanilides was not a spontaneous reaction at room temperature. The following mechanism 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-disubstituted 5, 10-phenylthio-5, 10-dihydrophenazine (6). The acid hydrolysis of 6 gives diphenylthiosulfinate and 2, 7-disubstituted-5, 10-dihydrophenazine, and the latter is oxidized to 2, 7-disubstituted phenazine by dissolved oxygen in the reaction solution.