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.