2,2,3,3-Tetrafluoronickelacyclopentanes Generated via the Oxidative Cyclization of Tetrafluoroethylene and Simple Alkenes: A Key Intermediate in Nickel-Catalyzed C–C Bond-Forming Reactions

Abstract

Oxidative cyclization of tetrafluoroethylene (TFE) and ethylene with Ni(0) resulted in the formation of a five-membered nickelacycle. In the presence of PPh 3 as an auxiliary ligand, the partially fluorinated five-membered nickelacycle was isolated and the structure was determined by X-ray analysis. This nickelacycle was found not only to react stoichiometrically with enones to give a cross-trimerization product but also to be a key reaction intermediate in the Ni(0)-catalyzed cotrimerization of TFE and ethylene, leading to 5,5,6,6tetrafluoro-1-hexene.

Transition-Metal Mediated Transformations of Tetrafluoroethylene intoVarious Polyfluorinated Organic Compounds

“…The exposure of (phen)CuPh (22), 30 which was prepared by the reaction of 5,5 dimethyl 2 phenyl 1,3,2 dioxaborinane 8a, CuO t Bu, and 1,10 phenanthroline (phen), to TFE in THF at 40 for 24 h resulted in the clean formation of (phen) CuCF 2 CF 2 Ph (23) in 88% yield as a brown solid (Scheme 14). 31 Although organoboron compounds are less common in the preparation of organocopper reagents, 32 their use confers great advantages with regard to ease of handling and functional group tolerance.…”

“…40 The X ray diffraction study of 28 clearly demonstrated that the nickelacyclopentane framework was derived from one TFE and one ethylene unit ( Figure 3). Further treatment of 28 with ethylene led to the formation of 5,5,6,6 tetra uoro 1 hexene (29) in 80% yield, and (η 2 CH 2 CH 2 )Ni(PPh 3 ) 2 was generated concomitantly in the crude reaction mixture.…”

“…40 Attempts at expanding the substrate scope with respect to other alkenes failed; neither the use of vinylidene uoride, or chlorotri uoroethylene in place of TFE nor the use of 1 hexene or styrene instead of ethylene gave the corresponding co trimerization products. In contrast, the catalytic reaction of 2 allylstyrene (31) with TFE in the presence of Ni(cod) 2 and PPh 3 (1 and 2 mol %, respectively) resulted in smooth progress, and afforded a 2 methylene 2,3 dihydroindene derivative (32) in 58% yield.…”

“…For instance, both ethyl acrylate and chalcone reacted with 28 to afford the corresponding β disubstituted ketones (34 and 35) in 27 and 60% isolated yields, respectively (Scheme 22a). 40 On the other hand, the use of phenyl 1 propenyl ketone resulted in the formation of an E/Z mixture of 6,6,7,7 tetra uoro 3 methyl 1 phenyl 2 hepten 1 one (36) in 61% isolated yield, while the formation of another η 3 oxallyl nickelacycle intermediate (37) was isolated when the reaction was conducted at room temperature (Scheme 22b). 3.3 Ni(0) Catalyzed Linear Selective Cress trimerization of TFE, Ethylene, and Aldehydes On the basis of the aforementioned unique reactivity of the α CH 2 moiety in 28, we formulated another hypothetical catalytic cycle that involves the nucleophilic addition of a ve membered nickelacycle to aldehyde (Scheme 23).…”

“…The role of lithium iodide in this reaction was to the formation of reactive zincates such as Li[ArZnXI] (X Ar or I, vide infra). 14 In line with these stoichiometric reactions, the cross coupling reaction of TFE with 4a, which was prepared by treating ZnCl 2 with 2 equiv of PhMgCl in situ, proceeded efciently at 40 in the presence of 0.01 mol% of Pd 2 (dba) 3 and lithium iodide, affording 5a in 81% yield (TON 8,100, Scheme 4). 11 It should be mentioned that this reaction gave neither bisaryl substituted nor higher substituted products, which indicated that the monoarylated product would be smoothly released from the catalyst in the presence of an excess amount of TFE.…”