Regioselective Hydroesterification and Hydrocarboxylation of 3,3,3-Trifluoropropene and Pentafluorostyrene Catalyzed by Phosphine-Palladium Complex

The hydroesterification and hydrocarboxylation of 3,3,3-trifluoropropene (TFP) and pentafluorostyrene (PFS) catalyzed by phosphine-palladium complexes were studied. It was found that the efficiency and the product distribution of the reaction depended markedly on the nature of nucleophile, i.e., water or alcohol, the structures of olefin and phosphine ligand, and other reaction variables such as solvent, temperature, and carbon monoxide pressure. Under optimal conditions either unbranched products or branched products were obtained in high yields with high regioselectivities. For example, 4,4,4-trifluorobutyric acid (5a) was obtained in 93% yield with 99% regioselectivity by using PdCl2(dppf)-SnCl2 as the catalyst in the hydrocarboxylation of TFP while ethyl 2-methyl-3,3,3-trifluoropropionate (2a) was obtained in 96% yield with 79% regioselectivity in the hydroesterification of TFP by using PdCl2(PPh3)2 as the catalyst. Similarly, 3-(pentafluorophenyl)propionic acid (5b) was obtained in 93% yield with 99% regioselectivity in the hydrocarboxylation of PFS catalyzed by PdCl2(dppf), and methyl 2-(pentafluorophenyl)propionate (2b) was obtained in 89% yield with 95% regioselectivity in the hydroesterification of PFS catalyzed by PdCl2(PPh3)2. Possible mechanisms of the present reactions are discussed. The hydro-carboxylations of TFP and PFS may involve (hydroxycarbonyl)palladium(II) intermediates while the hydro-esterifications of TFP and PFS may proceed via alkylpalladium(II) and acylpalladium(II) intermediates.