Novel Brϕnsted Acidic Ionic Liquid Based on a Cyclic Guanidinium Cation: a Green, Efficient, and Recyclable Dual Slovent-catalyst System for Fisher Esterification

A novel Brϕnsted acidic ionic liquid (IL) based on the cyclic guanidinium cation has been synthesized. This IL, as a strong Brϕnsted acid catalyst or solvent, shows high catalytic activity and biphsaic behavor in the esterifications of carboxylic acids and alcohols. The produced esters as a separate phase can be conveniently decanted out from the IL and the IL is recyclable without any loss of catalytic activity.