Perfluoroalkenes epoxidation

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)... 

Perfluoroalkene epoxides. The hydroxylamine is able to transfer an oxygen atom... 

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). 

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... 

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. 

As a resirlt of the differences in polarity between the carbon fluorine and the carbon-hydrogen bond, fluorocarbon chemistry is wrought with more differences than similarities to hydrocarbon chemistry despite their similarities in van der Waal s radii (1.20 vs. 1.35 A). A great body of chemistry for the functionalized fluorocarbons has been developed in the areas of perfluoroalkenes, halofluoroalkanes, ethers, epoxides, peroxides, ketones, acids, and esters. 

Fluorinated epoxides are very important synthetically. Perfluoroalkenes can be oxidized by numerous means to the corresponding epoxides. The most commonly encormtered epoxide is hexafluoropropene oxide (HFPO), which is made from hexafluoropropene and is used in the synthesis of oligomers and as a source of difluorocarbene. HFPO is a colorless, nonflammable gas, boiling at -27.4 °C it can be ring-opened easily by nncleophiles or electrophiles imder a variety of conditions. HFPO can be rearranged by flnoride ion to perfluoropropionyl flnoride and by Lewis acids snch as UO2 to hexafluoroacetone (HFA). Nncleophiles typically attack the most substituted carbon of the epoxide, freeing the oxyanion to lose fluoride or act as a nucleophile itself Some examples of HFPO reactivity are shown in Scheme 3. 

Ono, T. Henderson, P. Novel epoxidation reaction of perfluoroalkenes with trimethylamine N-oxide and iodosylbenzene. Tetrahedron Lett. 2002, 43, 7961. 

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