Mechanisms for vicinal disulfonoxylation, lactonization, and geminal disulfonoxylation are presented in Scheme 6A. Stirring a di-acetoxy or a di-trifluoroacetoxy I(III) oxidant with two equivalents of a sulfonic acid generates a di-sulfonoxy I(III) species in situ. Reaction with alkene substrate forms a cyclic iodonium species, liberating two equivalents of a sulfonate. These act as nucleophiles to sequentially displace the aryl iodide, accounting for the observed syn selectivity of this transformation. In the case of lactonization, the pendant ester acts as the first nucleophile to ring-open the cyclic iodonium species. This is followed by de-alkylation of the lactone carbonyl oxygen and displacement of the aryl iodide by sulfonate nucleophiles. Indeed, in lactonization reactions (Scheme 4), we have observed significant amounts of ethyl methanesulfonate (MeSO3Et) and methyl methanesulfonate (MeSO3Me) in 1 H NMR analyses of the crude reaction residues. For geminal disulfonoxylation, we invoke the intermediacy of a phenonium ion. Disulfonoxylation requires a strongly acidic environment to be successful. We attempted to generate a di-sulfonoxy I(III) species under basic conditions from Koser's reagent, TsCl, and DMAP, but this led to only trace product (Scheme 6B). Furthermore, for this reaction, sulfonic acids are remarkably privileged. With trifluoroacetic acid, only trace product was observed (Scheme 6C).