Nickel-Catalyzed Regio- and Stereoselective Hydrocarboxylation of Alkynes with Formic Acid through Catalytic CO Recycling

By the combination of a Ni­(II) salt, a bisphosphine ligand, and a catalytic amount of carboxylic acid anhydride, atom-economic hydrocarboxylation of various alkynes with formic acid can be achieved with high selectivity and remarkable functional group compatibility, affording α,β-unsaturated carboxylic acids regio- and stereoselectively. Both terminal and internal alkynes are amenable substrates. A mechanism proceeding through carbon monoxide recycling in a catalytic amount is demonstrated to be crucial for the success of this transformation.