Fluoro-olefins

The reaction of H atoms with fluorine-substituted ethylenes has been studied by Penzhom and Sandoval [31]. Relative rates were calculated from competition using ethylene with vinyl fluoride and the other fluorinated ethylenes. The absolute rate coefficient for ethylene as determined by these workers (see Table 1) was extremely low, as compared with the results from other laboratories, and the rate coefficients in Table 8 have been recalculated using a more acceptable value for ethylene (log k = 8.92 at 298°K). 

The values for log k are difficult to rationalize. The relative rates oscillate between slower, then faster, than ethylene as one proceeds through heavier fluorine substitution. The presence of fluorine in the olefin ought to have a primary effect in decreasing electron density, but with increasing substitution, eventually a substantial destabilization of the olefin occurs at tetrafluoroethylene, and a marked increase in reactivity 

Hydrogen atom addition to various fluoroethylenes (compared with ethylene) 

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RITCHIE, p. D. (Ed.), Vinyl and Allied Polymers, Vol. 1 —Aliphatic Polyolefins and Polydienes Fluoro-olefin Polymers, Iliffe, London (1968)... 

A more efficient agent than peroxy compounds for the epoxidation of fluoro-olefins with nonfluonnated double bond is the hypofluorous acid-acetomtrile complex [22] Perfluoroalkylethenes react with this agent at room temperature within 2-3 h with moderate yields (equation 13), whereas olefins with strongly electron-deficient double bond or electron-poor, sterically hindered olefins, for example l,2-bis(perfluorobutyl)ethene and perfluoro-(l-alkylethyl)ethenes, are practically inert [22] Epoxidation of a mixture of 3 perfluoroalkyl-1-propenes at 0 C IS finished after 10 mm in 80% yield [22] The trifluorovinyl group in partially fluorinated dienes is not affected by this agent [22] (equation 13)... 

In the reactions of the fluoro-olefins, steric factors are of lesser importance because of the relatively small size of the fluoro-substitucnt.3 Fluorine and hydrogen are of similar bulk. In these circumstances, it should be expected that polar factors could play a role in determining regiospecificity. Application of the usual rules to vinylidene fluoride leads to a prediction that, for nucleophilic... 

For olefins with Ji-substitucnts, whether electron-withdrawing or electron-donating, both the HOMO and LUMO have the higher coefficient 021 the carbon atom remote from the substituent. A predominance of tail addition is expected as a consequence. However, for non-conjugated substituents, or those with lone pairs (e.g. the halo-olefins), the HOMO and LUMO are polarized in opposite directions. This may result in head addition being preferred in the case of a nucleophilic radical interacting with such an olefin. Thus, the data for attack of alkyl and fluoroalkyl radicals on the fluoro-olefins (Table 1.2) have been rationalized in terms of FMO theory.16 Where the radical and olefin both have near neutral philicity, the situation is less clear.21... 

Propagation reactions involving the fluoro-olefins, vinyl fluoride (VF)6Q 7 vinylidene fluoride (VF2)69 7""74 and trifluoroethylene (VF3),75 show relatively poor rcgiospccificity. This poor specificity is also seen in additions of small... 

The fraction of head-to-head linkages in the poly(fluoro-olefms) increases in the series PVF2 < PVF PVF3 (Tabic 4.2). This can be rationalized in terms of the propensity of electrophilic radicals to add preferentially to the more electron rich end of monomers (i.e, that with the lowest number of fluorines). This trend is also seen in the reactions of trifluoromethyl radicals wilh the fluoro-olefins (see 2.3). 

The proportion of head-lo-head linkages in fluoro-olefin polymers also depends on the polymerization temperature6 ) 70 72 7j(T able 4.2). 

Table 4.2 Temperature Dependence of Head V.V Tail Addition for Fluoro-olefin...

Certain alkyl iodides give reversible chain transfer with S and some fluoro-olefins (Section 9.5.4). In these cases, the polymerization can show some living characteristics. 

Preparation of Fluoromethyl Phenyl Sulfone, a Reagent for the Synthesis of Fluoro Olefins. 

Stereoselective Synthesis of 2,2-Disubstituted 1-Fluoro Olefins (E)-[[Fluoro(2-phenylcyclohexylidene)methyl]sulfonyl]benzene. 

There are two principal ways to synthesize functional fluoropolymers (a) polymerization of functional fluoromonomers or copolymerization of fluoro-olefins with functional monomers, and (b) modification of common... 

C. (Z)-[2-(Fluoromethylene)cyclohexyl]benzene (3). To a solution of (fluorovinyl)stannane 2 (26.0 g, 0.054 mol) in dry THF (150 mL) is added 65 mL of 1 M sodium methoxide in methanol (prepared by the addition of 1.50 g (0.065 g-atom) of sodium to 65 mL of methanol). The solution is refluxed for 18 hr under nitrogen (Note 14), cooled to ambient temperature and concentrated on a rotary evaporator. The residue is partitioned between water (200 mL) and hexane (200 mL). The aqueous layer is separated and extracted with hexane (100 mL). The combined organic layers are dried (magnesium sulfate) and concentrated on a rotary evaporator to give a colorless oil (30 g). Kugelrohr distillation gives 10.0-10.2 g (97-100%) of fluoro olefin 3 (bp 85-90°C, 0.4 mm) as a colorless oil (Note 15). 

When the addition is carried out in acetonitrile-dj, mono and di-deuterated [l-i F]l,l,l,2-tetrafluoroethanes are obtained, suggesting that the solvent acts as a source of protons. This reaction was the first demonstration of an efficient addition of [ F]fluoride to a fluoro-olefin it achieves the equivalent of the addition of hydrogen [ F] fluoride. 

R.J. Abraham, S.L.R. Ellison, P. Schonholzer, W.A. Thomas, A theoretical and crystallographic study of the geometries and conformations of fluoro-olefins as peptide analogs. Tetrahedron 42 (1986) 2101-2110. 

S.J. Veenstra, K. Hauser, P. Felber, Studies on the active conformation of the NK1 antagonist CGP 49823. Part 2. Fluoro-olefin analogs of tertiary amide rotamers, Bioorg. Med. Chem. Lett. 7 (1997) 351-354. 

P. Van der Veken, I. Kertesz, K. Senten, A. Haemers, K. Augustyns, Synthesis of ( )- and (Z)-fluoro-olefin analogs of potent dipeptidyl peptidase IV inhibitors. Tetrahedron Lett. 44 (2003) 6231-6234. 

C. Chen, K. Wilcoxen, C.Q. Fluang, N. Strack, J.R. McCarthy, New methods for the synthesis of fluoro olefins via the palladium catalyzed cross-coupling reaction of 1-fluorovinyl halides with organoboranes and organostannanes, J. Fluor. Chem. 101 (2000) 285-290. 

S.S. Salim, R.K. Bellingham, V. Satcharoen, R.C.D. Brown, Synthesis of heterocyclic and carbocyclic fluoro-olefins by ring-closing metathesis, Org. Lett. 5 (2003) 3403-3406. 

New and Revisited Transition Metal Chemistry of Fluoro-Olefins and Fluorodienes ... 

Extremely high regioselectivity has been observed for hydroformylation of fluoro-olefins RfCH=CH2, catalysed by group VIII transition metals. While a Co catalyst gives the normal product 345 on hydroformylation of 344, a Rh catalyst gives mostly the isomeric aldehyde 346470. In another study, hydroformylation of 1-hexene was catalysed by rhodium(I) with concomitant isomerization471. 

The relative rate of addition of methyl radicals to fluoro olefins at 437 K ... 

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