In the present work, 3,3′-(butane-1,4-diyl)bis(1-methyl-1H-imidazol-3-ium) dichloride ([C 4 (MIm) 2 ]•2Cl) and 3,3 ′ -(butane-1,4-diyl)bis(1-methyl-1H-imidazol-3-ium) hydrogen sulfate ([C 4 (MIm) 2 ]•2HSO 4 ) were prepared via adequate, solvent-free methods and characterized using FT-IR, 1 H NMR, 13 C NMR, and potentiometric titration techniques. These reagents were investigated in the synthesis of 5-arylidene (thio)barbituric acids, 2-arylidene malononitriles, 4H-pyrans, and pyrano[2,3d] pyrimidineones, and their catalytic activities were compared in the promotion of these reactions. Based on the obtained results, we found that [C 4 (MIm) 2 ]•2Cl showed more catalytic efficiency where a basic or weak acidic media is needed. In contrast, [C 4 (MIm) 2 ]•2HSO 4 is a powerful catalyst in reactions needing acidic catalysts to enhance the reaction rate. Using these reagents, the products were formed under mild and eco-friendly conditions in excellent yields during short reaction times without needing column chromatography for work-up. Keywords Imidazole-based dicationic ionic liquids • [C 4 (MIm) 2 ]•2Cl • [C 4 (MIm) 2 ]•2HSO 4 • Knoevenagel condensation • 4H-pyrans • Pyrano[23-d] pyrimidineones