Dual Semiconductor-Photoredox/Halogen-Bonding Organocatalyzed Cascade Sulfonylation/Cyclization of Alkynes and Alkenes with RSO2Cl.

The dual semiconductor-photoredox/halogen-bonding organocatalyzed cascade sulfonylation/cyclization of (hetero)arene-tethered alkynes and alkenes with RSO2Cl is first developed. This method proceeds efficiently under mild reaction conditions, delivering a variety of sulfonylated fused-(hetero)arenes with good functional group compatibility. Mechanistic investigations reveals that XantPhos interacts with RSO2Cl to form a halogen-bonding complex, which facilitates S─Cl bond cleavage under blue light irradiation. Specifically, the Sr3N2 semiconductor catalyst promotes heterolytic S─Cl bond cleavage through a SET process, generating a sulfonyl radical and chloride ion. In contrast, the sulfonylated fused-(hetero)arene facilitates homolytic S─Cl bond cleavage via an EnT pathway, proudcing a sulfonyl radical.