Palladium-Catalyzed Coupling Reactions of Tetrafluoroethylene with Arylzinc Compounds

Abstract

Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with arylzinc reagents in the presence of lithium iodide, giving α,β,β-trifluorostyrene derivatives in excellent yields.

Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

“…Therefore, this reaction was carried out under a TFE atmosphere (1 atm), leading to an improvement in the yield of 6. By contrast, as already mentioned above, the corresponding palladium fluoride analog could not be generated at all by heating the PPh 3 analog 2a [41]. In the 19 F NMR spectrum of 6, characteristic upfield-shifted resonance attributable to a fluorine adjacent to palladium appeared at −317.9 ppm.…”

“…Thus, we started developing a base-free C-C bond formation reaction of 1 with arylboronates in the presence of a Pd(0) catalyst. We began by seeking an active species that could cleave the C-F bond of 1 without additives, because our original protocol using LiI eliminated the chance to generate a transition-metal fluoride intermediate in return for efficient C-F bond cleavage [41,[54][55][56]90]. As a result, the thermolysis of (η 2 -CF 2 =CF 2 )Pd(PCy 3 ) 2 (2b) in THF at 100 °C under a N 2 atmosphere underwent a C-F bond activation of 1 to give an expected trifluorovinylpalladium(II) fluoride (6) in 45% yield (Scheme 5).…”

“…Against such a background, we started developing a novel strategy for their preparation from 1, because 1 is an economical bulk organofluorine feedstock for the production of poly(tetrafluoroethylene) and co-polymers with other alkenes [38][39][40]. However, to the best of our knowledge, no catalytic reactions involving 1 had been reported until we reported the first catalytic transformation reaction [41], while homogeneous catalytic reactions involving C-F bond activation have received an increasing amount of attention [42][43][44][45][46][47][48][49][50][51][52][53]. The C-F bond activation reaction of 1 had been achieved only in a few stoichiometric reactions [54][55][56].…”

“…The first palladium-catalyzed cross-coupling reaction of 1 with aryl zinc compounds in the presence of LiI is also discussed [41,57]. We then discuss the development of the active Pd(0)/PR 3 species that enabled the oxidative addition of the C-F bond of 1 using no additives.…”

Palladium-Mediated Organofluorine Chemistry

“…224 Thus, LiI has been used as additive to ease R-F activation by forming a [PdRIL 2 ] and LiF which has a larger lattice energy than LiI. 245,246 Also, a the addition of a hard Lewis acid which can form an adduct with fluoride has the same effect. 246 Oxidative addition of arylfluorides is preceded by arene coordination and this has been shown experimentally for Ni(0) compounds which coordinate octafluoronaphthalene, 305 and fluorobenzenes.…”