Hydrazine → 4-chloro-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-1H-pyrazole-3-carbohydrazide

A solution of ethyl 4-chloro-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-1H-pyrazole-3-carboxylate (3.1 g, 7.2 mmol) in ethyl alcohol (30 ml) was added hydrazine (5 ml, 64% solution in water) in one portion. The reaction mixture was refluxed 100° C. for 6 hours, and then cooled down to room temperature. After volatile solvent was removed in reduced pressure, the residue was purified with silica gel column (5% methanol in methylene chloride) to obtained title compound (3 g, quantitatively) as slightly yellow solid.