13031-45-3

16357-40-7

4.3 Synthesis of 3-acetyl-4-hydroxybenzoic acid: magnesium perchlorate (Mg(ClO4)2, 0.602 mmol, 0.134 g, 2 mol%) was added to a solution of ethyl 4-hydroxybenzoate (30.1 mmol, 5 g) in acetic anhydride (Ac2O, 45.15 mmol, 4.25 mL) and the reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the reaction solution was diluted with dichloromethane (DCM) and subsequently washed with water. The organic phase was dried with anhydrous magnesium sulfate (MgSO4) and concentrated under reduced pressure to remove the solvent to give a clarified oil. The oil was azeotropized twice with toluene to remove residual water to give a clear oily intermediate (5.73 g, 92% yield). Subsequently, the intermediate was mixed with aluminum trichloride (AlCl3, 82.5 mmol, 10.99 g, 3 eq.) and potassium chloride (KCl, 28.9 mmol, 2.15 g, 1.05 eq.) and heated to react at 150 °C for 1.5 h. Dark-colored foam was formed during the reaction. At the end of the reaction, the reaction mixture was cooled in an ice bath and pre-cooled aqueous 2M hydrochloric acid solution (100 mL) was slowly added. After stirring for 5 minutes, ethanol (20 mL) was added and the mixture was heated to reflux for 45 minutes. Upon completion of the reaction, the mixture was again cooled in an ice bath and the precipitated solid was collected by filtration. Finally, the target product, 3-acetyl-4-hydroxybenzoic acid, was purified by solvent recrystallization from tetrahydrofuran (THF)/ethanol (EtOH) mixture to give the target product, 3-acetyl-4-hydroxybenzoic acid, as a cream-colored solid (1.30 g, 26% yield).