Tetrabutylphosphonium hydrogen difluoride

Tetrabutylphosphonium fluoride, tetrabutylphosphonium hydrogen difluoride and tetrabutylphosphonium dihydrogen trifluonde can be prepared from tetrabutylphosphonium hydroxide and hydrogen fluoride (equation 19)... 

Tetrabutylphosphonium hydrogen difluoride [Bu4PF (HF)] and dihydrogen trifluoride [Bu4PF (HF)2] have been shown to be expedient reagents for nucleophilic fluorination of aromatic substrates containing a chlorine or bromine atom or a nitro group under mild conditions in non polar solvents. Thus, for example l-chloro-4-nitrobenzene (28) is converted to l-fluoro-4-nitrobenzene (29) in 90% yield.219... 

Bromine fluoride can also be added by means of various reagents. The source of bromine is most often iV-bromoacetamide,171,172,198,251 iV-bromosuccinimide (NBS), 21 5,217.220.245-24-8. 254,696,698 i,3-dibromo-5,5-dimethylhydantoin (DBH).245,275,278 l-bromo-3,5,5-trimethyl-hydantoin(BTH),316 or bromine.108,197,217,227-229-261 The fluoride source is usually hydrogen fluoride,217,245,251,254 boron trifluoride,260 bromine trifluoride.227,261 xenon difluoride,108 tet-rabutylammonium dihydrogen trifluoride,694 tetrabutylphosphonium dihydrogen trifluo-... 

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