A FeCl3-based ionic liquid for the oxidation of anthracene to anthraquinone

N-butylpyridinium bromide ferric trichloride (NBPBFTC), a FeCl3-based ionic liquid, was prepared by a two-step method. NBPBFTC significantly catalyzed the oxidation of anthracene to anthraquinone (AQ) using aqueous hydrogen peroxide (AHPO) as the oxidant. The optimal conditions were determined to be 50 degrees C, 45 min, 100 mg NBPBFTC, and 1 mL AHPO for the oxidation of 50 mg anthracene. Under the conditions, AQ was obtained in a yield of 99.5%. NBPBFTC can be reused at least 3 times without substantial decrease in activity. With the intense pi-pi interaction between anthracene and pyridine-based cation in NBPBFTC, anthracene is soluble in the reaction system. Meanwhile, the iron-based anion and AHPO form a Fenton-like reagent to produce HOO center dot and HO center dot, which attack 9-position in anthracene to induce anthracene oxidation to AQ. (C) 2014 Elsevier B.V. All rights reserved.