Triethyloxonium tetrafluoroborate catalyst

The most convincing evidence is Vofsi and Tobolsky s (24) work with 14C-labelled triethyloxonium tetrafluoroborate at 0°C. They found good agreement among the molecular weights calculated from the amounts of catalyst charged, determined by 14C end-group analysis and determined by vapor pressure osmometry. Dreyfuss et al. have also obtained NMR data on this initiation reaction (9). The spectra are entirely consistent with Reaction 4. No side reactions are indicated. 

ESTERIFICATION 1,8-DiazabicycIo [5.4.0] -undecene-7. Dicyclohexylcarbodilmide. Dihydro-4,6-dimethyI-2-thioxo-3-pyridinccarbonitrilc. N,N-Dimcthylphos-phoramidic dicbloride. 3-Nitro-2-pyridenesulfenyl chloride. Phase-transfer catalysts. p-Tolylthionochlorocarbonate. Triethyloxonium tetrafluoroborate. Vilsmeicr reagent. 

Another interesting and synthetically useful behavior of aziridines is their tendency to open thermally to azomethine ylides, a process which can also be facilitated by Lewis acid catalysts. These reactive intermediates can be trapped by a variety of dipolarophiles to give new heterocyclic species. Methyl vinyl ethers convert aziridines such as 172 into a pyrrolidine derivative (i.e., 174) in the presence of a zinc(salen) Lewis acid catalyst 171 <04JA2294>. Similarly, nitriles (e.g., 175) lead to the formation of 2,4-disubstituted 177-imidazolines (e.g., 176) under the catalysis of boron triethyloxonium tetrafluoroborate <04TL 1137>. Under almost... 

Problem 10.4 (a) The kinetics of polymerization of tetrahydrofuran was studied [6] with the use of triethyloxonium tetrafluoroborate, (C2Hs)30+BF4, as im tiator and dichloromethane as solvent. Conversion versus time was measured at 0°C with initial catalyst concentration [I]o = 0.61 x 10 mol/L and monomer concentration [M] varying from 3 to 9 mol/L. The initial rates, Rp, determined from these data are given in Table A. 

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