Perfluoroalkene

The reaction of perfluoroalkenes with alkaline hydrogen peroxide is a good general method for the preparation of the corresponding epoxides with the exception of the most reactive of the series, TFEO (eq. 6). 

Reaction of perfluoroaLkenes and hypochlorites has been shown to be a general synthesis of perfluoroepoxides (32) (eq. 7). This appears to be the method of choice for the preparation of epoxides from internal fluoroalkenes (38). Excellent yields of HFPO from hexafluoropropylene and sodium hypochlorite using phase-transfer conditions are claimed (34). 

The oxidation may be carried out with an inert solvent thermally (35), with a sensitizer such as bromine (36), with uv radiation (37), or over a suitable catalyst (38). Principal by-products of all these oxidation processes are the acyl fluoride products derived from oxidative cleavage of the perfluoroaLkene (eq. 

A convenient agent for the preparation of perfluoroalkene epoxides is sodium hypochlorite in a mixture with aqueous acetonitrile or another aprotic solvent cis-and tr<3 5-perfluoroalkenes are oxidized with retention of configuration [9, 10, 11, 12 13] (equation 7, Table 1)... 

Cyclic perfluoroalkenes are oxidized to the corresponding epoxides in high yields by sodium hypochlorite in aqueous acetonitrile at 0-20 C [13, 75J (equations 9 and 10) Perfluorocycloheptene gives the epoxide after 1 h in 85% yield [17] Epoxidation of perfluoro-1-methylcyclohexene is accomplished with... 

PerfluoroaUcenes are converted to vicinal diols when no fluonne atom is present at the double bond Configurational isomers of perfluoroalkenes [29] (equations 20 and 21) are oxidized stereospecifically Perfluorbicyclo[4 3 0]non-1(6) ene gives the corresponding 1,6 diol m a 24% yield upon oxidation with potassium permanganate at 18 °C for 1 h [29]... 

Bis(dimethylamino)carboniiim bifluoride catalyzes the addition of acyl fluorides to perfluoroalkenes by the generation of readily acylated carbanions [4] (equation 4)... 

Reactions of fluorinated dipolarophiles. Electron-deficient unsaturated species generally make better dipolarophiles, therefore, fluonnated alkenes become better dipolarophiles when vinylic fluonnes are replaced by perfluoroalkyl groups For example, perfluoro-2-butene is unreactive with diazomethane, but more highly substituted perfluoroalkenes, such as perfluoro-2-methyl-2-pentene, undergo cycloadditions in high yields [5] (equation 2) Note the regiospecificity that IS observed in this reaction... 

Knunyants showed that such perfluoroalkenes, under forcing conditions, undergo Diels-Alder reactions with cyclic dienes such as cyclohexadiene [72] (equation 65) or furan [7J] (equation 66). 

The mechanism of attack of 1,3-dipolar reagents on fluoroalkenes can be considered to be either stepwise or concerted. Heteroaromatic N-imines react by a stepwise 1,3 addition to perfluoroalkenes and -alkynes to give fluorinated pyrazolo[l,5-a]pyridines [82JCS(P1)1593]. Pyridinium /-butoxycarbonylmethylide with fluoroalkenes gave pyrrolo[l,2-a]pyri-dines [86JCS(P 1) 1769] and indolizines (22) are obtained with pyridinium phenacylide [91JFC(51)407]. 

Perfluoroalkenes and perfluorocycloalkanes (C2F4) (C2H5)2NC(0), -C5HhCHNH2, C4H9C(0)CH2+H,... 

The uncatalyzed hydroboration-oxidation of an alkene usually affords the //-Markovnikov product while the catalyzed version can be induced to produce either Markovnikov or /z/z-Markovnikov products. The regioselectivity obtained with a catalyst has been shown to depend on the ligands attached to the metal and also on the steric and electronic properties of the reacting alkene.69 In the case of monosubstituted alkenes (except for vinylarenes), the anti-Markovnikov alcohol is obtained as the major product in either the presence or absence of a metal catalyst. However, the difference is that the metal-catalyzed reaction with catecholborane proceeds to completion within minutes at room temperature, while extended heating at 90 °C is required for the uncatalyzed transformation.60 It should be noted that there is a reversal of regioselectivity from Markovnikov B-H addition in unfunctionalized terminal olefins to the anti-Markovnikov manner in monosubstituted perfluoroalkenes, both in the achiral and chiral versions.70,71... 

A-perfluoroalkenes are not as good solvents for perfluorocarbons as cyclic perfluoroalkanes.The cyclic solvents give solutions with lower melting and crystallization temperatures and higher LCSTs. 

Sulfur tetrafluoride undergoes addition to perfluoroalkenes, e.g. 1 and 4, in the presence of cesium fluoride to give bis(perfluoroalkyl)sulfur difluorides and perfluoroalkylsulfur trifluorides.188,198 The ratio of the products is controlled by the reactant ratios. The role of cesium fluoride is ascribed to the formation of perfluorocarbanions which then subsequently attack sulfur tetrafluoride.188 Perfluoroalkyl disulfides, which are formed as side products, arise from the pyrolysis and disproportionation of bis(perfluoroalkyl)sulfur difluoridcs.189... 

On the other hand, variable yields of fluorinated 2-alkoxy-2//-pyrans 64 were found108,109 in mixtures formed in the reaction of perfluoroalkenes with dialkyl malonates. 

In the presence of freeze-dried potassium fluoride, perfluoro-2-methylpent-2-ene reacts with activated methylene compounds to yield pyrans (81MI22400). The fluoride ion abstracts a proton from the methylene group and subsequent condensation of the carbanion with the perfluoroalkene affords a dienone (19) which ring closes to the pyran (20 Scheme 3). In the case of pentane-2,4-dione a divinyl ether (21) is also formed. This product is considered to arise from reaction of the alkene at the oxygen of the enolate ion. 

Due to their industrial applications, tetrafluorooxirane and perfluoro(2-methyloxirane) are the most frequently mentioned epoxides in the literature, and a number of methods have been developed for their synthesis. Although the epoxidation of perfluoroalkenes with hydrogen peroxide in alkaline media appears to be the most general method for the synthesis of per-fluorinated epoxides, it cannot be used in the preparation of tetrafluorooxirane due to the hydrolytic decomposition of the alkene. 

The reaction of perfluoroalkenes with antimony(V) fluoride has been extensively studied by German and others from his group.3 Perfluoroalk-1-enes 1 react under mild conditions with antimony(V) fluoride to give ( )-perfluoroalk-2-enes 2.818... 

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