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

Abstract

SiO₂-SO₃H, with a surface area of 115 m²/g and pore volume of 0.38 cm³g^-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.

Keywords: deacetylation (acyl nucleophilic substitution); green chemistry; methyl salicylate; methylating agent; solid acid catalyst; sulfonated silica catalyst (SiO2–SO3H).