Sustainable Thioetherification via Electron Donor–Acceptor Photoactivation Using Thianthrenium Salts

Abstract The synthesis of sulfides has been widely studied because this functional subunit is prevalent in biomolecules and pharmaceuticals, as well as being a useful synthetic platform for further elaboration. Thus, various methods to build C−S bonds have been developed, but typically they require the use of precious metals or harsh conditions. Electron donor–acceptor (EDA) complex photoactivation strategies have emerged as versatile and sustainable ways to achieve C−S bond formation, avoiding challenges associated with previous methods. This work describes an open‐to‐air, photoinduced, site‐selective C−H thioetherification from readily available reagents via EDA complex formation that tolerates a wide range of different functional groups. Moreover, C(sp 2 )−halogen bonds remain intact using this protocol, allowing late‐stage installation of the sulfide motif in various bioactive scaffolds, while allowing yet further modification through more traditional C−X bond cleavage protocols. Additionally, various mechanistic investigations support the envisioned EDA complex scenario.