Synthetic approaches to monocatenar and bolaform choline-based ionic liquids

For more than three decades, ionic liquids (ILs) have already proven themselves as a promising class of materials with widespread applications in catalysis, electrochemistry, and biotechnology. Among the various types, choline-based ionic liquids have attracted considerable attention due to their unique properties and potential applications for use in pharmaceutical and biological systems. The present study addresses two different synthetic approaches used to prepare monocatenar and bolaform choline-based ionic liquids (ChILs), highlighting recent advances and challenges in this field. Nine cholinium based derivatives have been prepared, cholinium lactate and levulinate, three cholinium ester perchlorate, lactate and levulinate and four bolaforms. To obtain these bolaforms, the first approach consists of esterifying choline with an unsaturated fatty acid, followed by a cross-metathesis catalyzed by a Grubbs catalyst; the second one consists of synthesizing the fatty diacid and then esterifying it in the presence of choline. Both approaches have been discussed and preliminary physical properties (viscosities, degradation temperatures) of some of these ChILs are given.