Difluoroorganometalate-Assisted Generation of Perfluorocarbanions from Trimethylsilyl Synthons and Their Interactions with Perfluoroaryl Compounds

Barbier-type reactions of ICF 2 CF 2 OCF 2 CF 2 SO 2 F, I(CF 2 CF 2 ) 4 OCF 2 CF 2 SO 2 F, and I(CF 2 CF 2 ) 4 OCF(CF 3 ) 2 with MeMgBr and ClSiMe 3 in 3:1 tetrahydrofuran (THF)/diethyl ether mixtures at −78 °C gave Me 3 SiCF 2 CF 2 OCF 2 CF 2 SO 2 F ( 1 ), Me 3 Si(CF 2 CF 2 ) 4 OCF 2 CF 2 SO 2 F ( 2 ), and Me 3 Si(CF 2 CF 2 ) 4 OCF(CF 3 ) 2 ( 3 ) in 65−89% yields. The anions in three difluorometalates, [(Me 2 N) 3 S] + [Me 3 SiF 2 ] - (TASF), [Bu 4 N] + [Me 3 SiF 2 ] - (TBAT), and [(Pip 2 N) 3 S] + [Me 3 SnF 2 ] - (TPSF), were reacted with 1 − 3, to generate 2 equiv of Me 3 SiF for TASF and TBAF or 1 equiv each of Me 3 SnF and Me 3 SiF for TPSF, and the perfluoroalkyl ether nucleophiles - CF 2 CF 2 OCF 2 CF 2 SO 2 F, - (CF 2 CF 2 ) 4 OCF 2 CF 2 SO 2 F, and - (CF 2 CF 2 ) 4 OCF(CF 3 ) 2, respectively. The sulfonium or ammonium countercation interacted with hexafluorobenzene, monosubstituted pentafluorobenzenes, and pentafluoropyridine over a range of temperatures between −78 and 25 °C to also generate aryl carbocationic species that reacted with - CF 2 CF 2 OCF 2 CF 2 SO 2 F to give XC 6 F 4 CF 2 CF 2 OCF 2 CF 2 SO 2 F, where C−X = C−F ( 4 ), C−NO 2 ( 5 ), C−CN ( 6 ), C−CF 3 ( 7 ), C−CH CH 2 ( 8 ), N ( 9 ), with - (CF 2 CF 2 ) 4 OCF 2 CF 2 SO 2 F to give XC 6 F 4 (CF 2 CF 2 ) 4 OCF 2 CF 2 SO 2 F, where C−X = C−NO 2 ( 10 ), C−CN ( 11 ), C−CF 3 ( 12 ), N ( 13 ), and with - (CF 2 CF 2 ) 4 OCF(CF 3 ) 2 to give XC 6 F 4 (CF 2 CF 2 ) 4 OCF(CF 3 ) 2, where C−X = C−F ( 14 ), C−NO 2 ( 15 ), C−CN ( 16 ), C−CF 3 ( 17 ), C−CH CH 2 ( 18 ), N ( 19 ). The new products were obtained in 22−73% yields, and purification was carried out by separation of fractions either by silica gel preparative thin-layer chromatography (TLC) by using a diethyl ether/cyclohexane mixture as the mobile phase eluent (XC 6 F 4 (CF 2 CF 2 ) 4 OCF(CF 3 ) 2 type compounds) or by octadecyl bonded reverse-phase thin-layer chromatography (rp-TLC) by using an acetonitrile/water mixture as eluent. Reaction of compound 16 with 2 mol equiv of Me 3 SiOOCMe resulted in the disubstitution product at ortho positions of the nitrile. Compound 5 was transformed via a five-step process to the tricarboxylate o -(MeCOO) 2 O 2 NC 6 F 4 CF 2 CF 2 OCF 2 COOMe ( 24 ). The new products were characterized by elemental analyses and NMR and high-resolution mass spectral analysis.