Thioarylation

Thioarylation is a class of chemical reactions in which a thioaryl group is introduced into a substrate, forming a thioaryl bond. A thioaryl fragment consists of an aryl group bonded to sulfur, and thioarylation can yield products such as aryl thioethers (Ar–S–R) or Ar–S–H derivatives depending on the sulfur substituent. The term is commonly used to describe processes that install an arylthio fragment onto carbon or heteroatoms in a substrate.

Most thioarylation approaches rely on the formation of C–S bonds and employ strategies such as transition-metal–catalyzed cross-coupling or radical methods. Palladium-, copper-, and nickel-catalyzed cross-couplings between aryl halides or arenes and thiols or thio derivatives are widely reported to produce aryl thioethers. In addition, three-component and C–H functionalization protocols can introduce thioaryl groups directly onto arenes or alkenes. Radical thioarylation methods use thiyl radicals, generated from disulfides or thioesters, to add to multiple bond partners, followed by capture of the sulfur-containing fragment.

Photoredox catalysis has expanded thioarylation to milder conditions and broader substrate scopes, enabling thioaryl transfer from diverse thioaryl sources. Reagents such as thiols, thioesters, disulfides, and aryl sulfinates serve as sulfur- and aryl- bearing partners in these transformations. The resulting thioaryl compounds are valuable in medicinal chemistry, natural product synthesis, and materials science due to the chemical and electronic properties of the Ar–S bond.

Challenges in thioarylation include controlling chemoselectivity, avoiding oxidation or disulfide formation of thiols, and achieving broad functional-group tolerance. Ongoing research seeks to improve efficiency, selectivity, and sustainability of these processes.