Abstract The reactions of quantitatively available 4-phenyl-and 4-(4-antipyrinyl)-2- aminothiazole [“4-antipyrinyl-” is used as a short-term for “4-(1, 5-dimethyl-3-oxo-2-phenyl-2, 3-dihydro-1-H-pyrazol-4yl)-”] with chloroacetyl chloride, acetic anhydride, ethyl cyanoacetate and carbon disulphide are reported. The products are transformed further by Knoevenagel condensations and coupling reactions with aromatic diazonium salts. The latter occur both ...