Pd-Catalyzed Perfluoroalkylative Aryloxycarbonylation of Alkynes with Formates as CO Surrogates

The highly toxic, inflammable, and odorless nature of CO causes problematic handling on laboratory-scale experiments. Replacement of CO cylinders by CO surrogates is particularly attractive, especially in the case of multicomponent reactions leading to valuable fluorinated products. We report a Pd-catalyzed three-component protocol for the direct synthesis of perfluoroalkyl-substituted alpha,beta-unsaturated esters from acetylenes and perfluoroalkyl iodides, applying formates as convenient CO sources. The tandem reaction proceeds under mild conditions with excellent regio- and stereoselectivities toward the E-isomer (>95:5, E:Z). Detailed mechanistic investigations revealed that the process proceeds through an off-cycle, base-induced decomposition of formate to CO and phenoxide, which are reassembled on the Pd-center into an aryloxycarbonyl moiety, which is ultimately installed on the alkene scaffold. To complete the mechanistic picture of the reaction, the experimental study was supported by DFT calculations.