Sodium dithionite initiated fluoroalkylation of trimethoxybenzenes, mesitylene and pyrroles with BrCF2CF2Br

1,2-Dibromotetrafluoroethane (Freon 114B2) as a building block for fluorine compounds

“…The reactions were conducted in ethanol and catalysed by copper chloride and 1,2-ethylenediamine [17]. Subsequent elimination of one molecule of HF from 21 by sodium hydroxide resulted in stereospecific formation of Z-isomers of styrene type alkenes (3-bromo-2,2,3-trifluoroprop-1-ene-1-yl)arenes (23). Treatment of 21 with more strong base such as potassium tert-butoxide lead to elimination of two molecules of HF and formation of alkynes bearing CF 2 Br end group (3-bromo-3,3-difluoroprop-1-yn-1-yl)arenes (24).…”

“…The reaction proceeded readily at ambient temperature affording crude crystalline 29 which was pure enough to give correct elemental analysis without purification. Bromine atom in 29 was found to be fairly unreactive but further treatment with large excess of Na 2 S 2 O 4 in an acetonitrile-water system at reflux temperature resulted in reduction of the bromine and elimination of both Br and F radicals to give a mixture of 1-1,1,2,2-tetrafluoroethyl-2,4,6-trimethoxybenzene (30) and 1-(trifluoro-ethenyl)-2,4,6-trimethoxybenzene (31) in a 70% overall yield [23].…”

“…The reaction with 1,2,3-trimethoxybenzene was much less successful; even when elevated temperature and prolonged reaction time were applied, only partial conversion occurred and a mixture containing much of unreacted trimetoxybenzene and all three isomeric alkylation products was formed [23]. Similarly, the reaction with mesitylene gave low yield of oily product containing mostly unreacted substrate, the expected (2-bromotetrafluoro-ethyl)mesitylene and crystalline dimeric product, derivative of hexamethyl-bicyclohexyl-tetraene (isolated yield ca.…”

“…Similarly, the reaction with mesitylene gave low yield of oily product containing mostly unreacted substrate, the expected (2-bromotetrafluoro-ethyl)mesitylene and crystalline dimeric product, derivative of hexamethyl-bicyclohexyl-tetraene (isolated yield ca. 13%) [23].…”

“…Compound 32 was found to be rather unstable and quickly getting dark on contact with the air but N-methyl analog 33 was stable enough to be stored for a couple of weeks in the refrigerator [23].…”