Aryl sulfinates are precursors to a diverse number of sulfonyl-derived arenes, which are common motifs in pharmaceuticals and agrochemicals. Here, we report a site-selective two-step C−H sulfination sequence via aryl sulfonium salts to access aryl sulfonamides. Combined with site-selective aromatic thianthrenation, an operationally simple one-pot palladium-catalyzed protocol introduces the sulfonyl group using sodium hydroxymethylsulfinate (Rongalite) as a source of SO 2 2− . The hydroxymethyl sulfone intermediate generated from the catalytic process can be employed as a synthetic handle to deliver a variety of sulfonyl-containing compounds.

We report a late-stage heteroarylation of aryl sulfonium salts through activation with a-amino alkyl radicals in a mechanistically distinct approach from previously reported halogen-atom transfer (XAT). The new mode of activation of aryl sulfonium salts proceeds in the absence of light and photoredox catalysts, engaging a wide range of hetarenes. Furthermore, we demonstrate the applicability of this methodology in synthetically useful cross-coupling transformations.

We report a nucleophilic substitution reaction of five-membered hetarylsulfonium salts that results in a change of the substitution pattern on the arene. The products of these cine -substitutions are hard to access synthetically otherwise. The sulfonium salts that serve as starting materials are generated by a highly site-selective C–H functionalization reaction.

Rigid 1,3-disubstituted bicyclo[1.1.1]pentanes (BCPs) are linear bioisosteres for para-substituted benzene rings in drug development and can lead to an improved pharmacokinetic profile. The construction of BCPs commonly requires the cumbersome use of labile [1.1.1]propellane in solution, and more stable reagents do not show the versatile reactivity of propellane itself. Here we report stable thianthrenium-based BCP reagents for practical O-, N- and C-alkylation reactions that expand the scope of bicyclopentylation beyond that of any other reagent, including [1.1.1]propellane. The redox and stereoelectronic properties of the thianthrene scaffold are relevant for both the synthesis of the BCP-thianthrenium reagents via strain release as well as their subsequent reactivity. The weak exocyclic C–S bond can undergo selective mesolytic cleavage upon single-electron reduction to produce BCP radicals that engage in transition metal-mediated C–O, C–N and C–C bond formations, even at a late stage of multistep reactions with a wide variety of functional groups present.