Synthesis of ethyl 3-ethyl-5-pyrazolecarboxylate

Ethyl 3-ethyl-5-pyrazolecarboxylate,which is a key intermediate for tebufenpyrad,was synthesized using acetic acid as catalyst in higher yield,faster rate and less by-product than traditional method.The optimal experimental conditions were obtained.Under 0~5 ℃ for 4 h,with a 1∶2∶1.2 molar ratio of ethylpropionylpyruvate,acetic acid and hydrazine hydrate,the optimized yield of 98.53% and purity of 96.2% were obtained.