1,1′-Butylenebis(3-methyl-3H-imidazol-1-ium) dihydrogensulfate as a halogen-free and reusable binuclear Brönsted ionic liquid catalyzed the synthesis of pyrano[4,3-b]pyran derivatives

Abstract

1,1′-Butylenebis(3-methyl-3H-imidazol-1-ium) dihydrogensulfate as an efficient, halogen-free and reusable binuclear Bronsted ionic liquid catalyzed the synthesis of pyrano[4,3-b]pyran derivatives at 60 °C under solvent-free conditions. This method has the advantages of high yield, clean reactions, simple methodology and short reaction time. The ionic liquid could be recycled without significant loss of activity. The structure of the compounds was confirmed by IR, 1H NMR, 13C NMR, mass and elemental analysis.