Palladium-catalyzed thiocarbonylation of alkenes toward branched thioesters using CO₂

Thioesters are important intermediates in natural transformations and versatile precursors in organic synthesis. Here, for the first time, thiocarbonylation of alkenes using CO2 was developed for the preparation of a broad array of thioesters from the reactions of alkenes with different thiols under neutral conditions (40 examples, up to 94% yields, b/l > 99/1). Using the combination of a Pd catalyst and the N-P type carbazophosphine ligand, the reactivity and selectivity were well tuned. Experimental and DFT mechanistic studies imply that this reaction might proceed via the direct insertion of CO2 into the Pd-C bond to generate the Pd-carboxylate species and enable the formation of Markovnikov thioester products.