KEYWORDSThe reactivity of hydrogen atoms at C-4 of pyrazolone 3 towards condensation reactions was studied by its reaction with p-anisaldehyde, malononitrile and/or ethyl acetoacetate in the presence of ammonium acetate and/or piperidine, glucose, phenyl isothiocyanate, 2-amino thiazole and aniline to afford compounds 4-6, 13, 15, 17 and 18, respectively. Reaction of amino carbonitrile 4 with ammonium thiocyanate, and formamide afforded compound 7 and pyrazolo [3,4-b]