Design, characterization and application of new ionic liquid 1-sulfopyridinium chloride as an efficient catalyst for tandem Knoevenagel–Michael reaction of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one with aldehydes Original Research Article

In this work, novel ionic liquid 1-sulfopyridinium chloride {[Pyridine–SO3H]Cl} is synthesized, and characterized by IR, 1H and 13C NMR, UV as well as mass spectra. The ionic liquid is used as an efficient, homogeneous and reusable catalyst for the synthesis of 4,4′-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s by tandem Knoevenagel–Michael reaction of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one with various aromatic and hetero-aromatic aldehydes under mild reaction conditions.