Hydrosulfonylation of Unactivated Alkenes Involving Sulfonyl Radical Generation via Photocatalytic Activation of Symmetrical Disulfones by an Energy Transfer Mimicry

A visible-light-photocatalyzed hydrosulfonylation of unactivated alkenes with symmetrical disulfones using 2,4,6-triisopropylthiophenol as a hydrogen atom donor (H-D) has been developed. Generation of two sulfonyl radicals from disulfones via activation with visible light photocatalysis is involved. Mechanistic studies rule out that two sulfonyl radicals are generated from a symmetrical disulfone via an energy transfer mechanism as previously found for lower oxidation state sulfur-sulfur-based reactants (i.e., thiosulfonates and disulfides). Instead, an energy transfer mimic process occurs. This involves a photoinduced electron transfer (PET) via oxidative quenching of the excited photocatalyst (*PC) with disulfone, which generates a sulfonyl radical and sulfinate byproduct, followed by the reduction of the oxidized photocatalyst (PC^•+) with this byproduct (SET) generating the second sulfonyl radical and photocatalyst (PC). The hydrosulfonylation reaction can be performed in dimethyl carbonate at room temperature, features a broad functional group compatibility, and allows easy recycling of the generated disulfide byproduct provided 2,4,6-trisubstituted thiophenol is used as H-D. The visible-light-photocatalyzed hydrosulfonylation of unactivated alkenes has been compared with the state-of-the-art using green metrics.