A convenient procedure for the quantitative generation of carbocations in super acid media

Abstract

A method is described for the preparation of relatively concentrated (c.1 M) solutions of alkyl carbocations in SbF₅-SO₂ClF suitable for ¹³C n.m.r, investigations. This method, which uses syringe techniques, allows the quantitative conversion of precursors, which are soluble in SO₂CIF at -78º, into the corresponding cations. The carbocations prepared in this way include isopropyl (1), t-butyl (2), 1,l-dimethylpropyl (3) 1,l-dimethylbutyl (4), 1-ethyl-1-methylpropyl (5), 1,1,2-trimethylpropyl (6), 1-methylcyclopentyl (7), 1,2-dimethylcyclopentyl (8), 2-norbornyl (10), 2-methylnorbornyl (11) and 1-methyl-1-phenylethyl(12). Other methods were needed to generate the bicyclo[3,3,0]octyl(9), 1-adamantyl (l3), 2-methyladamantyl(14) and benzhydryl(l5) cations. ¹³C parameters are given for all the cations.