Fluoro-olefins addition

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... 

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

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. 

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

The relative rates and orientation of addition of perfluoroalkyl radicals to fluoro-olefins at ... 

The silver-carbon bond in compounds containing a perfluoroalkyl group is considerably more stable than in non-fluorinated compounds. The synthesis can be accomplished by the nucleophilic addition of silver fluoride to fluoro-olefines. A typical example of this reaction is given in equation 9. The complexes are soluble in organic solvents and have been isolated as the 1 1 complexes with acetonitrile [RAg(CH3CN)]23. 

However, head addition is usually a very minor pathway and is difficult to determine experimentally. Analysis of the events which follow head addition presents an even more fomiidablc problem. Therefore, there is little experimental data on polymers with which to test the above-mentioned hypothesis. Data for fluoro-olefins indicate that H gives less head addition than T (Section 4.3.1.3). No explanation for the observation was proposed. 

Dmitriev, M.A. Sokol skii, G.A. Knunyants, I.L. Addition of sulfur trioxide to fluoro olefins. Khim. Nauka i Prom. 1958, 3, 826-828. 

Whereas bis-phenols dissolved in the polymer solution rapidly gel the polymer upon addition of a solution of the base or when a solution of the bis-phenol and the base are added to the polymer sollution, addition of only the base or substitution of the bis-phenol by the ocvreqionding monophenol fails to gel the polymer. Addition of base to the polymer, followed after several minutes by addition of the bis-phenol, also fails to gel the polymer. The requirement for the proper sequence of addition in this hydrmide-free system, idiere the enone cannot be formed by ketonization of an intermediate dienol, requires that a fluoro-olefin is the active siiistrate and that the free phenol cannot add to it. 

Addition of singlet CDa (. 1), from the photolysis of CDa C 0, to the fluoro-olefins, Rp CF CFa (Rp = CF3, CFs CFa CFa, or CFs CFa CFa CFa CFa-) in the presence of carbon monoxide yields chemically activated cyclopropane, which may relax or expel difluorocarbene (see Scheme 4). At low pressures, ranging from <650 Torr for Rp = CFa down to <0.25 Torr for the more complex Rp = CsFii, the rate of cyclopropane decay is independent of pressure, but then it increases with increasing pressure. Relaxation of internal vibration energy is not instantaneous, the time required being longest when the vibrational modes available are fewest. ... 

The interesting olefin perfluoromethylenecyclopropane (see p. 59) fails to undergo the familiar [2 + 2] additions of fluoro-olefins possibly for steric reasons, but it is a reactive dienophile in the Diels-Alder reaction. Cyclopentadienc yields adduct (106) at 0 °C buta-1,3-diene and fra s,fra/i,y-hcxa-2,4-diene (but not the CIS,CIS- or cis,trans-isomsrs) react at 100 °C anthracene gives the expected adduct at 100 °C and quadricyclane yields adduct (107) at 25 °C. The isomeric perfluoro-1-methylcyclopropene forms Diels-Alder adducts with cyclopentadiene and buta-1,3-diene with equal facility. ... 

Table 2 Activation parameters for the addition of n-CsF, to fluoro-olefins...

A number of studies have involved the attack of nitrogen nucleophiles upon fluoro-olefins. Reaction of sodium nitrite with fluoro-olefins in wet dimethylformamide results in the addition of HNOj and the formation of nitroaikanes,... 

Silicon difluoride reacts with the fluoro-olefins CH2.CHF, CH2 CFMe, CHj CF2, and CF2 CHF by insertion into the C F bond. Free-radical additions of triethylsilane to 1,2-dichloro-tetrafluorocyclobutene, -hexa-fluorocyclopentene, and -octafluorocyclohexene, and of the silanes HSiCl2Ph. HSiClj, HSiClgMe, HSiClMcj, and HSiEtg to the same cyclo-butene and cyclopentene, and the corresponding monochloro-compounds, have been described (see p. 200). Addition is accompanied by reduction of chlorine. 

Tetramethyldiphosphine adds photochemically to vinyl and vinylidene fluoride to give the bisphosphines Me2P-CH2-CXF-PMe2 (X H or F), and tetrakis(trifluoromethyl)diphosphine similarly adds thermally (at 50 Q or photochemically to the same olefins and to tetrafluoroethylene. Free-radical additions of trifluorothioacetic acid to the olefins CHF CF2, CHarCFa, and CH2 CHF (see p. 138) have been described only one-way addition was observed. Bis(trifluoromethyl) disulphide adds to fluoro-olefins with u.v. Irradiation in Pyrex or silica apparatus in the vapour phase to yield a variety of 1 1 and telomeric adducts. The products are consistent with the following mechanism ... 

Additional details of u.v.-induced liquid-phase reactions of sulphiu dioxide with fluoro-olefins (Vol. 1, p. 158) have appeared ... 

Few examples of additions of 1,3-dipoles to fluoro-olefins have appeared, and fluoro-olefins are less reactive than their hydrocarbon counterparts. However, hexafluoropropene and octafluoroisobutene react with the nitrones... 

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