Stable bis(2-chloro-2,2-difluoroethoxy)-fluoromethyl cation at room temperature

First examples of stable polyfluorinated bis- and tris-(alkoxy)methyl cations

“…Despite the fact that the values of chemical shifts and coupling constants of 1 H, 13 C and 19 F NMR spectra found in this work for cation (ClCF 2 CH 2 O) 2 CF + (3a) do not coincide with previously reported data [14], the internal consistency of the NMR data (chemical shits, coupling constants, multiplicity and relative intensities of signals) obtained in this study for the solutions of cations 3a (SO 2 ClF), 1a and 2a (both in SO 2 ClF and SbF 5 solvents; Table 2) along with data reported for CH 3 OCFH + [5] and R f CH 2 OCFX + cations [8] unambiguously support the existence of cation 3a as long-lived intermediate at low temperature, albeit one not stable at ambient temperature.…”

“…Slow decomposition of 3a was observed already at À40 to À30 8C and all signals of the cation were gone in the solution of 3a in SO 2 ClF, prepared at low temperature and stored at 25 8C for 2 h. It should be also pointed out that the signals of 3a were not observed in samples prepared by treatment of 3 with an excess of SbF 5 at ambient temperature in the absence of SO 2 ClF solvent (an exothermic reaction and therefore hard to control). Instead, chemical shifts of major peaks observed in 1 H and 19 F NMR (rather complex) spectra of several samples prepared at ambient temperature were similar to NMR data reported previously ( 1 H: 2.15 (q, 7.3 Hz), 19 F: À75.01 (t, J = 7.3 Hz), À81.0 (br, s) ppm vs. 1 H: 2.2, 19 F: À76.0, À82.0 ppm [14]). …”

“…[14], we were not able to detect by NMR spectroscopy any (ClCF 2 CH 2 ) 2 C O after the hydrolysis of the mixture 3/SbF 5 (see Section 3.2). Instead, CF 3 CH 2 Cl and (CF 3 CH 2 O) 2 C O were identified by 1 H and 19 F NMR spectroscopy as major components of the Fig.…”

“…Recently, however, it was reported [14] that the generation of stable at ambient temperature, bis(2-chloro-2,2-difluoroethoxy)fluoromethyl cation (ClCF 2 CH 2 O) 2 CF + by ionization of (ClCF 2 CH 2 O) 2 CF 2 with SbF 5 , results in an upfield (instead of downfield) shift of the resonance of the fluorine substituent connected to the carbocationic center. Intrigued by this discrepancy and by the unusually small value of the shift (Dd F $ 19 ppm) reported for (ClCF 2 CH 2 O) 2 CF + [14], we decided to revisit the reaction of difluoroformals of polyfluorinated alcohols with SbF 5 .…”

“…Intrigued by this discrepancy and by the unusually small value of the shift (Dd F $ 19 ppm) reported for (ClCF 2 CH 2 O) 2 CF + [14], we decided to revisit the reaction of difluoroformals of polyfluorinated alcohols with SbF 5 .…”