Preparation and characterization of a novel benzimidazolium bronsted acid ionic liquid and its application in the synthesis of arylic esters

A novel Bronsted acid task specific ionic liquid 1-ethylbenzimidazolium tetrafluoroborate ([Hebim]BF4) with functional benzimidazolium cation was synthesized and characterized by H-1 NMR, IR, MS spectra and elemental analysis. This novel ionic liquid was successfully used as dual solvent-catalyst for the synthesis of arylic esters. Higher yields were obtained in the presence of [Hebim]BF4 in comparison with other imidazolium ionic liquids because of the good solubility of the aromatic alcohols and aromatic carboxylic acids in [Hebim]BF4. The product could be separated conveniently from the reaction system, and the ionic liquid could be easily reused after removal of water under vacuum. After 10 times reuse, the selectivity of the ester was still 100%.