Solvent-free synthesis of benzoic esters and benzyl esters in novel Bronsted acidic ionic liquids under microwave irradiation

摘要

Fischer esterifications of benzoic acid with a variety of alcohols and a variety of acids with benzyl alcohol could be promoted by four novel Bronsted acidic ionic liquids a-d that bear a benzyl on the imidazolium or pyridinium cation. The reactions were carried out smoothly without the need of added catalyst with good to excellent isolated yields (77-98.5%) under solvent-free microwave irradiation conditions in the presence of 50 mol% ionic liquids. These ionic liquids could be recovered easily and recycled three times without any significant loss in their catalytic activity.