3-Methyl-1-sulfonic Acid Imidazolium Mesylate as a Novel, Highly Effective and Dual-functional Catalyst for the Solvent-free Production of Bis-coumarins

A novel ionic liquid entitled 3-methyl-1-sulfonic acid imidazolium mesylate ([Msim][OMs]) was synthesized, and characterized by studying its FT-IR, 1H NMR, 13C NMR and mass spectra. This ionic liquid was employed as a dual-functional catalyst for the preparation of bis-coumarins via the one-pot pseudo three-component reaction of 4-hydroxycoumarin (2 eq.) and arylaldehydes (1 eq.) under solvent-free and relatively mild conditions. Owing to dual-functionality of [Msim][OMs] (having acidic and basic sites), it could act as a highly effective catalyst for the reaction. Additionally, an attractive mechanism based on dual-functionality of the catalyst was proposed.