Task-specific ionic liquid incorporating anionic heteropolyacid-catalyzed Hantzsch and Mannich multicomponent reactions. Ionic liquid effect probed by ESI-MS(/MS)

A task-specific ionic liquid with a Bronsted acid (1-(3-sulfopropyl)-3-methylimidazolium hydrogen sulfate, namely MSI) bearing an anionic heteropolyacid derivative ([PW12O40]3−, namely PW) were used as an efficient catalyst for the three-component Mannich and Hantzsch reactions. Using (MSI)3PW as the catalyst supported in imidazolium-based ionic liquids allowed these multicomponent reactions to take place in good to excellent yields. The Mannich reaction, performed at room temperature, was also evaluated by means of electrospray (tandem) mass spectrometry-ESI-MS(/MS). ESI-MS data pointed to the origin of the ionic liquid effect, i.e., formation of ion pairs with the charged reaction intermediates and furthers association into larger supramolecular aggregates. DFT calculations revealed the strength of the supramolecular interactions between the charged species detected by ESI-MS and the spontaneity association of these ion pairs affording larger supramolecular aggregates.