Light-Promoted Palladium-Catalyzed Regiodivergent Transfer Hydrothiocarbonylation of Alkynes Regulated by Coordinating Anions

α,β-Unsaturated thioesters are fundamental building blocks in organic synthesis, but their efficient and regioselective construction remains a significant challenge. Traditional palladium-catalyzed carbonylations of alkynes typically require hazardous high-pressure carbon monoxide (CO) and suffer from poor regiocontrol, largely due to catalyst poisoning by CO. To address these limitations, we have developed a visible-light-driven palladium-catalyzed protocol that employs thioformates as safe, bench-stable surrogates under ambient, CO-gas-free conditions. This mild system operates at room temperature without the need for exogenous acids or silanes to generate the key Pd–H species. Remarkably, the regioselectivity of the transformation can be predictably switched between linear and branched α,β-unsaturated thioesters simply by the presence or absence of iodide ions (I – ). This work provides a practical and switchable platform for the synthesis of these valuable motifs.