Perfluoroalkenes synthesis

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). 

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. 

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. 

A related 3-elimination occurs when alkali-metal salts of perfluoroalkanecarboxylic acids are pyrolysed [34] (Figure 6.25). The most likely process involves decarboxylation with elimination of fluoride ion from the resultant carbanion. Indeed, the method can be very useful for the synthesis of perfluoroalkenes (Chapter 7), the most important example of which is shown in Figure 6.26 and is used in the production of fluorinated membranes [35]. 

Several perfluoroalkene derivatives have been made and used successfully in synthesis. Trifluorovinylmagnesium bromide and the lithium derivative may be obtained [39 1] from bromotrifluoroethene but preparation from HFC 134a, which involves metallation of trifluoroethene generated in situ, is now the more accessible route (see Section lA). However, direct metallation of fluorinated alkenes and fluorinated cycloalkenes has also been reported [26, 28] (Figure 10.9). 

Carbonyl difluoride is a particularly versatile fluorinating agent, and an important material for the synthesis of organofluorine compounds [1079], Its reactions with perfluoroalkenes gives perfluoroacyl fluorides in the presence of a fluoride ion source, and its facile reaction with amines or alcohols results in the formation of carbamoyl fluorides or fluoroformates, respectively. The fluorination of carbonyl compounds, such as aldehydes and ketones, with COF can give gem-difluorides by replacement of the carbonyl oxygen atom with two atoms of fluorine e.g.-. 

Suzuki, H. Sakai, N. Iwahara, R. Fujiwaka, T. Satoh, M. Kakehi, A. Konakahara, T. Novel synthesis of 7-fluoro-8-(trifluoromethyl)-l/f-l,6-naphthyridin-4-one derivatives intermolecular cyclization of an A-silyl-l-azaallyl anion with perfluoroalkene and subsequent intramolecular skeletal transformation of the resulting pentasubstituted pyridines. J. Org. Chem. 2007, 72(15),5878-5881. 

Silicon-Mediated Synthesis of Poly(Fluorovinyl Ethers) and Poly(Perfluoroalkenes)... 

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