Palladium-Catalyzed Highly Regioselective Hydrocarboxylation of Alkynes with Carbon Dioxide

A Pd-catalyzed highly regioselective hydrocarboxylation of alkynes with carbon dioxide has been established. By the combination of Pd(PPh3)(4) and 2,2'-bis(diphenylphosphino)-1,1'-binaphthalene (binap), a variety of functionalized alkynes, including aryl alkynes, aliphatic alkynes, propargylamines, and propargyl ethers, could be leveraged to provide a wide array of alpha-acrylic acids in high yields with high regioselectivity under mild reaction conditions. Experimental and DFT mechanistic studies revealed that this reaction proceeded via the cyclopalladation process of alkynes and carbon dioxide in the presence of binap to generate a five-membered palladalactone intermediate and enabled the formation of Markovnikov adducts. Moreover, this strategy provided an effective method for the late-stage functionalization of alkyne-containing complicated molecules, including natural products and pharmaceuticals.