ABSTRACT
The anodic oxidation of 2,2-bis(ethylthio )propane producing acetone and an oxidation product of diethyl disulfide, claimed to be the corresponding disulfoxide, was reported many years ago [133]. A renewed interest in this reaction involving a C-S bond cleavage arose when bis(phenylthio )methane and some of its p-substituted ring derivatives were anodically oxidized in dry MeCN on Pt electrodes and afforded diary! disulfides and formaldehyde, with the latter identified after aqueous workup (39, 134]. The same cleavage was observed when MeCN-H20 (9: I v/v) was the solvent, but aryl benzenethiosulfonates were the main products [39]:
-2e MeCN ArSSAr + (HCHO)
anod. ox. 5.7 - 6.1 F MeCN/H2O
ArSO2SAr + HCHO (84)
The mechanism of this transformation has been investigated [135, 136]. In the absence ofnucleophiles and using carefully dried MeCN, the oxidation step of 1,3-dithiane derivatives corresponds to an EEC process involving one electron per molecule. To rationalize this process, the formation of a dication (XXX2+) is suggested, which supposedly exists in equilibrium with a dimer (XXXI) originated by the reaction of xxx2+ with the starting material (XXX) [Eq. (85)] [135].
