Thiol-Free Sulfenylation Redefined: A Single-Atom Transfer Pathway to Symmetrical Di(hetero)arylthioethers via B(C 6 F 5 ) 3 Catalysis

Diarylated thioethers are privileged scaffolds found across pharmaceuticals, functional materials, and molecular electronics. Conventional approaches to these motifs, typically via C-H functionalization or C-X cross-coupling with thiophenols, disulfides, thiosulfonates, and related sulfenylating agents, remain hampered by foul odors, instability, air- and moisture- sensitivity, tedious synthesis, and poor selectivity, often producing undesired byproducts. In contrast, the few strategies that employ elemental sulfur for symmetrical thioether synthesis are largely confined to copper catalysis and lack generality. Therefore, a straightforward and sustainable route to symmetrical thioethers from readily accessible, bench-stable sulfenylating agents with broad substrate compatibility is highly desirable. Herein, we demonstrate N,N'-thiobisphthalimide as a bench-stable sulfenylating reagent enabling the synthesis of symmetrical diaryl/diheteroaryl thioethers or dibenzothiophenes in yields up to 97%. This transformation precedes via a single-atom transfer (SAT) strategy under metal-free B(C₆F₅)₃ catalysis with electron-rich arene and heteroarene substrates. Mechanistic investigations, supported by DFT calculations, cyclic voltammetry (CV), and UV-vis. studies, reveal a stepwise ionic pathway and rationalize the observed regioselectivity and substrate-dependent reactivity. Beyond synthetic value, the ambipolar redox behavior of the resulting thioethers establishes them as tunable photoredox mediators, bridging small-molecule synthesis and functional material design.