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

• NBPBFTC prepared exhibits temperature- and magnet-responsive behaviors.
• NBPBFTC–H2O2–CH3CN system effectively oxidized anthracene to anthraquinone.
• NBPBFTC acted as both a medium and catalyst during anthracene oxidation.

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 °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 π–π 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· and HO·, which attack 9-position in anthracene to induce anthracene oxidation to AQ.

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