Synthesis of raspberry ketone via Friedel-Crafts alkylation reaction catalyzed by sulfonic acid-functional ionic liquids

Phenol and butanolone catalyzed by different SO3H-functionalized ionic liquids (ILs) for synthesis of raspberry ketone (RK) had been investigated. The influences of different ionic liquids, reaction time, reaction temperature, reactant ratio, the amount of ionic liquid were investigated. The yield of raspberry ketone was 82.5% under the optimum reaction condition. In addition, the ILs (3-sulfo)propyltriamine bisulfate ([TEA-PS][HSO4]) can be recycled up to five consecutive times without loss of activity. This method had the advantages of mild conditions, high product yield, easy to separate from the product, as well as environmentally friendly procedure. At the same time, the possible reaction mechanism was discussed.