Synthesis
General procedure for the synthesis of ethyl 5-amino-1-(4-chlorophenyl)-1H-pyrazole-4-carboxylate from ethyl 2-cyano-3-methoxyacrylate and p-chlorophenylhydrazine: 5 g (28 mmol) of p-chlorophenylhydrazine, 3.86 g (28 mmol) of potassium carbonate, and 4.7 g (28 mmol) of ethyl 2-cyano-3-methoxyacrylate were sequentially added to a 100 mL round bottomed flask. The reaction mixture was stirred under reflux conditions for 24 hours. Upon completion of the reaction, 150 mL of ethyl acetate was added to the reaction mixture, followed by washing twice with 100 mL of water. The organic layer was separated, dried with anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure to afford 6.88 g (26 mmol) of ethyl 5-amino-1-(4-chlorophenyl)-1H-pyrazole-4-carboxylate of the target compound in 92% yield. The product was analyzed by mass spectrometry (EI) showing a molecular ion peak of 266 (M++1). The nuclear magnetic resonance hydrogen spectrum (1H-NMR, CDCl3) data were as follows: δ 7.78 (1H, s), 7.52-7.47 (4H, m), 5.28 (2H, brs), 4.31 (2H, q, J=8Hz), 1.37 (3H, t, J=8Hz).
