Microwave-accelerated esterification of salicylic acid using Brönsted acidic ionic liquids as catalysts

A variety of Brönsted acidic ionic liquids were screened as catalysts for the esterification of salicylic acid. The experimental results indicated that SO3H-functionalized ionic liquids with HSO4- performed high catalytic activity under microwave irradiation, and the yields can reach 91.9–93.6%. Furthermore, ionic liquids can be easily separated by simple decantation and have a fair reusability. The Brönsted acidity–catalytic activity relationships were also investigated and the results showed that the activity of the acidic ionic liquids is in excellent agreement with their acidity order.