Brønsted acidic ionic liquids of aza-crown ether complex cations: preparation and applications in organic reactions

Abstract

A series of novel Brønsted acidic ionic liquids composed of an aza-crown ether chelated potassium cation and various anions, were designed, synthesized and characterised by FTIR, NMR and mass spectrometry, thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. These new Brønsted acidic ionic liquids of aza-crown ether complex cations (aCBAILs) were applied as catalysts to the Biginelli reaction, Mannich reaction and synthesis of bis-(4-hydroxycoumarin-3-yl)methanes. These organic reactions were achieved in good yields under mild reaction conditions. Moreover, these new IL catalysts can be recycled several times.