AbstractIn this research, initial production and characterization of a novel Brønsted-acidic ionic liquid, namely,N,N,N′,N′-tetramethylethylenediaminium-N,N′-disulfonic acid hydrogen sulfate ([TMEDSA][HSO4]2), has been described (characterization was achieved using Fourier-transform infrared spectroscopy,1H nuclear magnetic resonance (NMR),13C NMR, and mass and thermal gravimetric spectra). Thereafter, utilization of [TMEDSA][HSO4]2as a highly effectual catalyst for the synthesis of 4,4′-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) derivatives through the one-pot pseudo five-component reaction of phenylhydrazine (2 eq.) with ethyl acetoacetate (2 eq.) and arylaldehydes (1 eq.) in relatively mild conditions, has been reported.