Di fluorocarbene

Hexafluoropropylene oxide (HFPO), which decomposes reversibly to di-fluorocarbene and trifluoroacetyl fluonde with a half-life of about 6 h at 165 °C [30], is a versatile reagent. Its pyrolysis with olefins is normally carried out at 180-2(X) °C, and yields are usually good with either electron-nch or electron-poor olefins [31, 32, 33, 34, 35, 36, 37] (Table 2). The high reaction temperatures allow the eyclopropanation of very electron poor double bonds [58] (equation 10) but can result in rearranged products [39, 40, 41] (equations 11-13)... 

When the dihalocarbene is generated thermally or photochemically the product of cheletropic addition to the alkyne is usually isolable in adequate yield. For example, pyrolysis of (trichloromethyl)trifluorosilane at 140°C and 6.5 atm in the presence of perfluorobut-2-yne provides " 3,3-dichloro-l,2-bis(trifluoromethyl)cyclopropene in 93 % yield. The corresponding perfluorocyclopropene is available from addition of di-fluorocarbene which can be generated by thermolysis of perfluoropropene oxide ... 

ChLorofluorocarbene generated by the thermal decomposition of dichlorofluoro-methylphenylmercury reacts with 2,3-dimethylindole to give 3-fluoro-2,4-di-methylquinoline, 3-chloro-2,4-dimethylqumoline and 3-(chlorofluoromethyl)-2,3-dimethylindole [f] (equation 1). Similar results are obtained when the chloro-fluorocarbene is generated from dichlorofluoromethane by base-catalyzed de-hydrohalogenation using a phase-transfer catalyst in an aqueous-organic solvent system [21 (equation 1). 

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