The Visible-Light-Triggered Catalytic Triarylamine EDA Complex Enabled Synthesis of Sulfonylated Quinolines, Pyrroloindoles, and Chromenes by Radical Sulfonylation-Cyclization of Substituted Alkynes with Sulfonyl Chlorides

Electron donor-acceptor (EDA) complex catalysis has emerged as a sustainable alternative to conventional metal- or dye-based photoredox methodologies. Sulfonylated heterocycles constitute privileged structural motifs widely found in bioactive and pharmaceutically relevant scaffolds. In this work, we describe a radical sulfonylation-cyclization (RSC) strategy for alkynes, enabled by catalytic tris(4-methoxyphenyl)amine (TMPA) and aryl sulfonyl chlorides through in situ EDA complex formation under visible-light irradiation (λ = 427 nm, 40 W Kessil) at room temperature. This protocol affords highly functionalized sulfonylated 1,2-dihydroquinoline, pyrroloindole, and chromene derivatives in good to excellent yields (60-90%) within short reaction times (≈2 h), delivering 60 examples with broad functional group compatibility under redox-neutral conditions. A detailed investigation of EDA complex formation was also carried out. Furthermore, the resulting sulfonylated 1,2-dihydroquinolines undergo photo-oxidative, catalyst, and base-free aromatization to furnish the corresponding 3-sulfonylquinolines under ambient conditions. In addition, terminal alkynes participated in EDA-mediated hydrosulfonylation, providing the corresponding (Z)-vinyl sulfones with complete stereoselectivity when tris(trimethylsilyl)silane (TTMSS) was employed as the hydride source. In total, we report a library of 94 compounds in this work.