Synthesis of 2,6-Di-tert-butylanthraquinone Cyclically Catalyzed by Brønsted Acidic Ionic Liquids

Alkyl anthraquinones play a crucial role as chemical raw materials in the production of hydrogen peroxide as well as intermediates for the synthesis of drugs and dyes. This study focuses on investigating the oxidation reaction of 2,6-di-tert-butylanthracene with hydrogen peroxide, employing Bronsted acidic ionic liquids as catalysts. The optimization of both the anion and cation components within the Brønsted acidic ionic iquids was carried out, revealing that bis(3-propanesulfonic acid-1-imidazole)propylidene bisulfate ([2(Im-PS)-C3][2HSO4]) exhibited the most effective catalytic performance. Furthermore, the Brønsted acidic ionic liquids demonstrated cyclic catalytic activity during the oxidation reaction. Successful preparation of 2,6-di-tert-butylanthraquinone was achieved with a remarkable yield of up to 92%. The recyclability of the ionic liquid suggests that this study will contribute to technical improvements in the original method while concurrently reducing the cost associated with the synthesis of alkyl anthraquinones via the oxidation method.