Studies on sulfenamides. III. Cyclic voltammetry and controlled potential electrolysis of 4'-substituted 2-nitrobenzenesulfenanilides.

Abstract

Anodic oxidation of 4'-substituted 2-nitrobenzenesulfenanilides (4'-OMe (3a), 4'-Me (3b), 4'-Cl (3c), 4'-H (3d)) was investigated by cyclic voltammetry and controlled potential electrolysis at a glassy-carbon anode, and the results were compared with those for 4'-substituted benzenesulfenanilides (1a-d). Electrolysis of 3a in acetonitrile containing NaClO4 gave 2, 7-dimethoxyphenazine (2a), 2, 2'-dinitrodiphenyl disulfide (4), p-anisidine (5), 2-nitrobenzenesulfonic acid (6), and N-(2-nitrophenylthio)-p-benzoquinoneimine (7). Electrolysis of 3a in acetonitrile containing ethyltributylammonium trifluoromethane-sulfonate (ETBT) gave 2a, 4, 5, and 7, but did not give 6. These results indicate that the perchlorate anion does act as an oxidizing agent in the anodic oxidation of 3a, even though sodium perchlorate has been used quite extensively as a supporting electrolyte in anodic systems and usually does not participate in anodic oxidation processes. Since benzenesulfonic acid was not obtained on the anodic oxidation of 1a in acetonitrile containing NaClO4, the formation of 6 was interpreted on the basis of one-step two-electron transfer followed by reaction of the dication with perchlorate anion. The introduction of the 2-nitro group may elicit the one-step two-electron transfer. Electrolysis of 3a in the presence of water (1%) gave 7 almost quantitatively. Electrolysis of 3b and 3c in acetonitrile containing NaClO4 gave the corresponding 2, 7-disubstituted phenazines, 4, and 6, whereas that of 3d did not give phenazine.