Transition-metal-catalyzed C-S bond formation: recent developments and pharmaceutical applications.

Due to widespread applications of sulfur-containing frameworks, the construction of the C-S bond has emerged as a useful tool for synthetic organic and medicinal chemists in recent years. Transition-metal-catalyzed carbon-sulfur (C-S) bond formation represents a cornerstone of advanced organic synthesis due to its pivotal role in pharmaceuticals, agrochemicals, and functional materials. This review provides a comprehensive and structured overview of recent developments in C-S bond formation, covering both classical late transition metals (Pd, Ni, and Cu) and a broad range of miscellaneous metals (Mo, Ir, Rh, Cr, Mn, Zn, and Sc). Palladium catalysis, typically supported by phosphine or N-heterocyclic carbene ligands, enables efficient thiolation of aryl halides using thiols, disulfides, or sulfur surrogates. Nickel catalysis as a cost-effective alternative to Pd, displaying complementary reactivity toward aryl, alkyl, and heteroaryl electrophiles, often under ligand-controlled or reductive conditions, while copper follows Ullmann-type C-S couplings and oxidative thiolations using thiols, sulfinates, or elemental sulfur. Beyond these, molybdenum catalysts promote dehydrative and borrowing-hydrogen thio-etherification of alcohols, whereas iridium-based photoredox catalysis converts sodium aryl sulfinates into thioesters and thioalkynes. This review highlights the high compatibility of these methodologies with drug-like molecules and the significance of these methodologies.