In Situ-Generated Iodine(III) Sulfonates as Versatile Oxidants for Sulfonyloxylation and Oxidative Cyclization.

An in situ method for the generation of hydroxyl-(arene- and alkanesulfonyl)-iodobenzenes [PhI-(OH)-(OSO2R)] from phenyliodine diacetate (PIDA) and arene- or alkanesulfonic acids is described. The resulting iodine-(III) sulfonate species functioned as effective oxidants for two distinct transformations. Under these conditions, selective para-sulfonyloxylation of anisole derivatives was achieved without requiring ortho-substitution by electron-withdrawing groups. The same reagent system was also applicable to heteroaromatic substrates, enabling temperature-controlled sulfonyloxylation of naphtho-[2,3-d]-oxazoles to give the corresponding sulfonate esters in good yields. In addition, related oxidative conditions in the presence of AgOTf promoted an unexpected cyclization of ortho-alkynylaryl ketones, providing access to 1,4-naphthoquinone derivatives. Although these reactions proceed through different substrate classes and pathways, both are enabled by the generated in situ iodine-(III) sulfonate reagent. These results expand the scope of hypervalent iodine chemistry by demonstrating the synthetic utility of in situ-generated iodine-(III) sulfonates in sulfonyloxylation reactions and the oxidative formation of 1,4-naphthoquinone frameworks.