Introduction 1,1′-butylenebis(3-methyl-3H imidazol-1-ium) Hydrogen Sulfate as an Efficient Binuclear Brönsted Acidic Ionic Liquid for Three-Component and One-Pot Synthesis of Benzo[f]indenoquinoline Derivatives

1,1′-Butylenebis(3-methyl-3H-imidazol-1-ium) hydrogen sulfate as an efficient, halogen-free and reusable Brönsted ionic liquid catalyzed the synthesis of 13-(aryl)-12H-benzo[f]indeno[1,2-b]quinoline-12-one derivatives in ethanol under refluxing conditions. This method has the advantages of high yield, clean reaction, simple methodology, and short reaction time. The ionic liquid catalyst could be recycled and reused seven times without significant loss of activity. The structures of the new compounds were confirmed by IR, 1H NMR, 13C NMR and elemental analysis.