Chemistry in Superacids. 6. Perfluoroalkanesulfonic Acid-Boron Perfluoroalkanesulfonates: New Superacid Systems for Generation of Carbocations and Catalysts for Electrophilic Transformations of Hydrocarbons

Article abstract of DOI:10.1021/jo00198a004

Boron trihalides (BX3, X = Cl, Br) react with excess perfluoroalkanesulfonic acids to give conjugate superacids of the type R_FSO2OH2⁺F)4>^- (R_F = CF3, C4F9, and C10F21).The systems were characterized by spectroscopy and their chemical (catalytic) properties were studied.The parent of the series CF3SO3H2^+- (1) (first reported by Engelbrecht and Tschager) was found to O-protonate ketones and to generate stable tert-alkyl- and methyl-substituted benzylic cations at low temperature in SO2ClF.Stable ions are similarly generated in B(OSO2CF3)3/SO2ClF.The catalytic activity of the conjugate superacid 1 has been demonstrated in transbromination/transalkylation of aromatics as well as in isomerization of n-butane, n-hexane, and trimethylenenorbornane to adamantane under mild conditions.