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When 0.25 mol of CF2Br213 (52.5 g, 22.8 ml) was added to a solution of 0.25 mol of Ph3P (65.5 g) in 450 ml of dry triglyme, a heavy precipitate of [Ph3P+CF2-Br]Br~quickly formed. The solution was stirred for 30 min under dry nitrogen followed by addition of 0.25 mol of Me2C=CHMe (17.5 g, 26.25 ml) and 1.0 mol of anhydrous KF (58.1 g). The solution was stirred vigorously for 24 hr and then flash distilled at ca. 3 mm.Fractionation of the distillate yielded 20.0 g of product (bp = 69-70°) which was 99 % pure by glpc analysis. The nmr showed a multiple! at 0.85-1.35 ppm and the 19F nmr consisted of two signals, 139.8 ppm (d of m) and 151.9 ppm (d of broad singlets) ( *, CFC13) with a doublet splitting of 153.6Hz. The mass spectrum was consistent with the assigned structure of the product, 1, 1-difluorotrimethylcyclopropane. The isolated yield was 67 %.The use of these phosphonium salts compares favorably with other precursors of difluorocarbene. In most cases, however, the availability of reagents, ease of scaling up the reaction, mild conditions of the reaction, and the ease of isolation of the products make this mode of carbene generation the method of choice.Related work in our laboratories indicates that other phosphonium salts may be useful carbene precursors.8 Details of these experiments will be presented in due course.

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