Catalytic system for the Heck reaction of fluorinated haloaryls

A catalytic system for the Heck reaction of fluorinated haloaryls, which involves the first catalytic insertion into a metal-perfluoroaryl bond, has been developed. Pentafluorophenyl complexes of palladium which lack ligands other than halides are used as catalysts. The absence of other ligands besides solvent, halides, and substrates is required for an efficient functionalization. Pentafluoro- and tetrafluoro-substituted haloaryls can be efficiently reacted with terminal and disubstituted olefins, such as styrene, α-methylstyrene, and acrylate esters, but nonactivated alkenes give only moderate yields. Coordination-insertion is rate determining for pentafluoroaryl and tetrafluoroaryl bromides, which can be switched to oxidative addition if a large excess of olefin is used. Thus, the best reaction conditions can be reached by adjusting the actual ratio of haloaryl to olefin for each combination of substrates.