Tandem Transesterification-Esterification Reactions Using a Hydrophilic Sulfonated Silica Catalyst for the Synthesis of Wintergreen Oil from Acetylsalicylic Acid Promoted by Microwave Irradiation.

SiO 2 -SO 3 H, with a surface area of 115 m 2 /g and pore volume of 0.38 cm 3 g -1 , and 1.32 mmol H + /g was used as a 20% w / w catalyst for the preparation of methyl salicylate (wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor over 40 min at 120 °C in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be reused three times.