Ba. Omotowa et Jm. Shreeve, Difluoroorganometalate-assisted generation of perfluorocarbanions from trimethylsilyl synthons and their interactions with perfluoroaryl compounds, ORGANOMETAL, 19(14), 2000, pp. 2664-2670
Barbier-type reactions of ICF2CF2OCF2CF2SO2F, I(CF2CF2)(4)OCF2CF2SO2F, and
I(CF2CF2)(4)OCF(CF3)(2) with MeMgBr and ClSiMe3 in 3:1 tetrahydrofuran (THF
)/diethyl ether mixtures at -78 degrees C gave Me3SiCF2CF2OCF2CF2SO2F (1),
Me3Si(CF2CF2)(4)OCF2CF2SO2F (2), and Me3Si(CF2CF2)(4)OCF(CF3)(2) (3) in 65-
89% yields. The anions in three difluorometalates, [(Me2N)(3)S](+)[Me3SiF2]
(-) (TASF), [Bu4N](+)[Me3SiF2](-) (TBAT), and [(Pip(2)N)(3)S](+)[Me3SnF2](-
) (TPSF), were reacted with 1-3, to generate 2 equiv of Me3SiF for TASF and
TBAF or 1 equiv each of Me3SnF and Me3SiF for TPSF, and the perfluoroalkyl
ether nucleophiles -CF2CF2OCF2CF2SO2F, (-)(CF2CF2)(4)OCF2CF2SO2F, and (-)(
CF2CF2)(4)OCF(CF3)(2), respectively. The sulfonium or ammonium countercatio
n interacted with hexafluorobenzene, monosubstituted pentafluorobenzenes, a
nd pentafluoropyridine over a range of temperatures between -78 and 25 degr
ees C to also generate aryl carbocationic species that reacted with -CF2CF2
OCF2CF2SO2F to give XC6F4CF2CF2OCF2CF2SO2F, where C-X = C-F (4), C-NO2 (5),
C-CN (6), C-CF3 (7), C-CH = CH2 (8), N (9), with (-)(CF2CF2)(4)OCF2CF2SO2F
to give XC6F4(CF2CF2)(4)OCF2CF2SO2F, where C-X = C-NO2 (10), C-CN (11), C-
CF3 (12), N (13), and with (-)(CF2CF2)(4)OCF(CF3)(2) to give XC6F4(CF2CF2)(
4)OCF(CF3)(2), where C-X = C-F (14), C-NO2 (15), C-CN (16), C-CF3 (17), C-C
H=CH2 (18), N (19). The new products were obtained in 22-73% yields, and pu
rification was carried out by separation of fractions either by silica gel
preparative thin-layer chromatography (TLC) by using a diethyl ether/cycloh
exane mixture as the mobile phase eluent (XC6F4(CF2CF2)(4)OCF(CF3)(2) type
compounds) or by octadecyl bonded reverse-phase thin-layer chromatography (
rp-TLC) by using an acetonitrile/water mixture as eluent. Reaction of compo
und 16 with 2 mol equiv of Me3SiOOCMe resulted in the disubstitution produc
t at ortho positions of the nitrile. Compound 5 was transformed via a five-
step process to the tricarboxylate o-(MeCOO)(2)O2NC6F4CF2CF2OCF2COOMe (24).
The new products were characterized by elemental analyses and NMR and high
-resolution mass spectral analysis.