Imidazolium Polyoxometalate: An Ionic Liquid Catalyst for Esterification and Oxidative Esterification

A new family of polyoxometalate‐based ionic liquids (POM‐IL) is synthesized, characterized, and employed as catalysts in the esterification of various alcohols with acetic acid. The ionic liquid catalyst shows high activity and gives excellent yields of esters. An emulsion forms between the IL catalyst and substrates during the reaction and promotes the catalytic process. After reaction, the emulsion can conveniently be broken by the addition of a weakly polar organic solvent to facilitate the separation of the catalyst. On the basis of the above results, a direct transformation of benzaldehyde to methyl ester under relatively mild conditions is also developed in the absence of any cocatalyst. Finally, the scope of the substrates and recyclability of the catalyst are also investigated. I second that emulsion: A novel polyoxometalate‐based ionic liquid (POM‐IL) acts as a catalyst in esterification and oxidative esterification reactions. The emulsion formed by the IL catalyst and substrates during the reaction can facilitate the catalytic process. After reaction, the liquid catalyst is separated easily by breaking the emulsion and proves to be recyclable.