Hydrogenation of Aromatic Hydrocarbons by Al/Ti Reagents

Treatment of anthracene (A) with LiAlH4 (LAH) at 150°C under atmospheric pressure gives 9,10‐di‐ and 1,2,3,4‐tetrahydroanthracene (2H‐A and 4H‐A). At 160–200°C and under hydrogen pressure (10–90 bar) a number of simple and polycyclic aromatic compounds [e. g. toluene, naphthalene (N), A, phenanthene (PH), and pyrene (PY)] are converted to fully or partially hydrogenated arenes. Addition of small amounts of TiCl4 or TiCl3 and the choice of solvents (heptane or glymes) have marked effects on the reaction. The pair triethylaluminium/TiCl4 acts also as efficient hydrogenation catalyst.