Generation of arenium ions by a self-protonation reaction in an aprotic molten salt medium

We have examined the reaction behavior of a group of polycyclic aromatic hydrocarbons in the aprotic liquid SbC1/sub 3/-10 mol % AlCl/sub 3/ from 100 to 130/sup 0/C by /sup 1/H NMR and by quench and separation techniques. For anthracene, pyrene, 9,10-dimethylanthracene, 9,10-diphenylanthracene, and naphthacene, we have observed a novel arene self-protonation reaction for which the proton source is the condensation-dehydrogenation of a portion of the arene combined with arene oxidation by SbCl/sub 3/. Naphthalene and phenanthrene, however, do not undergo this reaction. Evidence is presented which indicates that the self-protonation reaction proceeds through the oxidation of the arene to its radical cation by SbCl/sub 3/, and that the function of AlCl/sub 3/ is to enhance the oxidizing power of the Sb/sup 3 +//Sb/sup 0/ couple.