Metal-Free Photoinduced Hydrogen Atom Transfer for Direct Thiolation of Hydridic α‑C(sp3)-H of Ethers.

C-S bond formation via hydrogen atom transfer (HAT) remains underdeveloped despite the importance of thioethers in organic synthesis, materials science, and medicinal chemistry. Herein, we report a mild, rapid, and operationally simple method for the direct α-C-(sp3)-S bond formation in ethers using alkyl or aryl thiosulfonates as sulfur sources and (4-methoxyphenyl)-(4-(trifluoromethyl)-phenyl)-methanone as the diaryl ketone catalyst. The reaction proceeds at room temperature under a 390 nm irradiation, delivering a broad range of thioethers in the absence of metals or stoichiometric oxidants. The method exhibits excellent functional group tolerance, predictable regioselectivity favoring the most hydridic C-H bonds, and compatibility with various cyclic and acyclic ethers and amides. Preliminary mechanistic studies support a radical pathway consistent with a well-established photoexcited ketone-mediated HAT followed by radical addition to the thiosulfonate. This approach expands the toolkit for redox-neutral C-(sp3)-S bond construction.