Protonation of some arenes in an aprotic medium

The dissolution of anthracene (up to 5 mol%) in an aprotic liquid, anhydrous SbCl3-10 mol% AlCl3, at 80-1300C, results in the prompt formation of stable solutions of the 9-anthracenium ion (1) in 50-60% yields. The proton source for this reaction is the condensation-dehydrogenation of a part of the anthracene combined with the reduction of SbCl3 to amorphous metal. The principal condensed product is anthra[2,1-a]aceanthrylene(2). The identity of 1 was confirmed by a comparison of its integrated 1H NMR spectrum with that obtained from an authentic sample of 9-anthracenium heptachlorodialuminate. The NMR spectra of 2 was not resolved, but appeared as a broad, nondescript envelope in the aromatic region. The AlCl3 appears to enhance the oxidizing power of the SbCl3 solvent