To reconcile the mechanism of oxidation of thiols to thiosulfonates with IBX, we monitored the reaction by 1 H NMR spectroscopy to identify possible intermediate(s) en route to the end product(s). For this, the reactions mediated by IBX were considered convenient, as the reaction in CD3CN should permit ready identification of the intermediate(s) where the hypervalent iodanes IBX and IBA, will remain insoluble. As these signals that correspond to the disulfide 3d gradually disappear, one observes the formation of four new signals (iii) at 6.98 and 6.92 ppm as doublets and at 3.86 and 3.82 ppm as singlets. These signals correspond to the S-4methoxyphenyl 4-methoxybenzenesulfonothioate (2d) as the end product. Thus, 1 H NMR spectroscopic monitoring clearly reveals that the conversion of thiols to thiosulfonates proceeds via the intermediary formation of disulfides. Unfortunately, none of the other intermediates could be identified, as all other signals are insignificant as to reveal any identity. Although we have already shown the formation of disulfide intermediates during the solvent optimization studies (Table ), we again treated the disulfide 3d with IBX under similar conditions to verify the formation of acid (IA) was observed during the course of the reaction (cf. Figure ), it indicated that IBA is also involved in the oxidation and gets reduced to IA. For instant, the reaction with 1.0 equiv of IBX producing thiosulfonate in 75% and disulfide in 18% clearly indicated that λ 3 -iodane is participating in the oxidation (Table , entry 4). In fact, the oxidation with PIFA clearly suggested that the disulfides can be obtained from thiol. Consolidating the above observations, a plausible reaction mechanism for the conversion of thiols to thiosulfonates with IBX through the intermediary disulfides is shown. It's needless to mention that the single electron transfer (SET) from e-rich thiols to I(V) species to begin with should lead to the thiyl radicals that dimerize to the disulfide, where IBX is subsequently reduced to IBA (Scheme 3). The reaction might be going through a thioalkoxyperiodinane (TAP) species, similar to the alkoxyperiodinane-adduct formed from the reaction of IBX and alcohol. The disulfide may undergo subsequent oxidation with IBX to thiosulfinate by a single electron transfer process. It is worth mentioning that the direct attack of disulfide to the electrophilic hypervalent iodine center is less feasible due to steric hindrance, such an attack of sulfide is found to be energetically unfavorable; the probability of a nucleophilic attack is thus not considered here. The oxidation of disulfides to thiosulfinates with IBX may follow a single electron or oxygen transfer process. The subsequent oxidation of thiosulfinate with IBX may then lead to thiosulfonate.