Single-Step Photoinduced Radical Pentafluorosulfanylation and Cyclization of Alkenes for the Synthesis of SF₅-Containing Cyclic Sulfinamides

Abstract

The pentafluorosulfanyl (SF₅) moiety has garnered significant attention as a fluorinated functional group in the fields of medicinal chemistry, agrochemistry, and materials science, attributable to its distinctive physicochemical properties. In comparison to its structural analogue, trifluoromethyl, the SF₅ group demonstrates notably increased lipophilicity and pronounced electron-withdrawing capacity. However, the direct pentafluorosulfanylation of unactivated alkenes remains challenging due to the intrinsic propensity of SF₅Cl to undergo spontaneous chloropentafluorosulfanylation. Herein, we report a photoinduced radical pentafluorosulfanylation-cyclization of alkenes enabled by an in situ substrate-derived radical moderator strategy. Upon irradiation with LEDs, homolytic cleavage of the S–Cl bond in SF₅Cl affords an electrophilic SF₅ radical, which undergoes addition to the alkene unit of the sulfinamide substrate, thereby generating a carbon-centered radical intermediate. Subsequent intramolecular S_Hi cyclization yields the cyclic sulfinamide product, while a tert-butyl radical partakes in an XAT process with SF₅Cl to regenerate the SF₅ radical and perpetuate the radical chain mechanism. Intriguingly, intramolecular hydrogen-bonding interactions between the sulfinyl group and the CH₂SF₅ moiety are posited to be responsible for the exceptional stereocontrol observed. Furthermore, the resulting SF₅-containing motifs are readily amenable to further functionalization, thereby highlighting the broad synthetic utility and potential applications of these cyclic sulfinamides in pharmaceutical and materials science research.

Keywords

Pentafluorosulfanylation / Radical reactions / Cyclic sulfinamides / syn-Selectivity / Chain propagation / Rapid reaction / Radical moderator / Photochemistry

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