Selective fluoroalkylation of thiophenols by 1,2-dibromotetrafluoroethane activated by sulfur dioxide

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

“…In contrast to the reported easy funtionalization of similar compounds [18,20,21], compound 2 was found to be fairly unreactive. The attempted substitution of bromine with fluorine by treatment with 20% KOH/Bu 4 NBF 4 in a water-benzene system failed.…”

“…However, most of the reported examples involved halophilic reactions of phenolates and thiophenolates [17,18] or salts of heterocyclic amines [19,20] which resulted in O-, S-and N-alkylations. Reported reactions of BrCF 2 CF 2 Br with free thiophenols under free-radical conditions (SO 2 , pyridine) also lead exclusively to S-alkylation [21], however in the case of sterically hindered phenols, C-alkylation occurred [22]. Some of the obtained bromotetrafluoro derivatives were further funtionalized by nucleophilic replacement of the remaining bromine atom [18][19][20].…”

Activation of free-radical polyfluoroalkylation of organic substrates with freon BrCF2CF2Br using a system of organic base-electron transfer mediator

“…A similar dependence has been observed by us for thiophenols, in particular for p-chlorothiophenol E p = À0.083 pK a + 1.272, r = 0.971) [14]. As the process of electrochemical oxidation of pyrrole in the presence of pyridines is complicated due to the pyrrole polymerisation on the electrode to form a passivating polymer film, therefore it has been rather difficult to determine the precise values of E p for the pyrrole.…”

“…The possibility of similar free-radical processes has been shown also for the mild polyfluoroalkylation of thiophenols with freons BrCF 2 CF 2 Br and CICF 2 CFCl 2 [14,15] and of sterically hindered phenols with dibromotetrafluoroethane [16], involving an organic base and an electron transfer mediator. Interestingly, the process feasibility and the products yield have been essentially dependent on the strength of the bases -substituted pyridines -added to the solution [14].…”

“…Interestingly, the process feasibility and the products yield have been essentially dependent on the strength of the bases -substituted pyridines -added to the solution [14]. This paper has explored a possibility of employing the abovementioned ''electron transfer mediator-organic base'' activating system for polyfluoroalkylation with freons of other classes of organic compounds such as phenols and nitrogen heterocycles, in particular pyrrole.…”