Efficient combination of recyclable task specific ionic liquid and microwave dielectric heating for the synthesis of lipophilic esters

Mild and efficient esterification reactions of carboxylic acids with neo-pentanol were carried out using task-specific ionic liquids with hydrogen sulphate counteranion under microwave irradiation. The latent acidity of the ionic liquid was introduced by anion metathesis from hydrogen sulphate with the corresponding imidazolium or pyridinium halides. The catalyst [C-4-mim][HSO4] modified with 5% of concentrated sulfuric acid was reused three times without considerable loss of activity in esterification using classical heating in oil bath.