Synthesis of 1-(4-Chlorophenyl)-3-hydroxypyrazole as the Key Intermediate of Pyraclostrobin
l-(4-Chlorophenyl)-3-pyrazolol is the key intermediate of the methoxyacrylate fungicide pyraclostrobin.The p-chlorophenylhydrazine hydrochloride was synthesized from p-chloroaniline by a dynamic tube sequential method,and the intermediate 1-(4-chlorophenyl)-3-pyrazolone was obtained by the cyclization reaction with ethyl acrylate,and then 1-(4-chlorophenyl)-3-pyrazolol was obtained by the continuous oxidation using low-temperature photocatalytic oxidation of hydrogen peroxide,The experimental results were analyzed in different reaction conditions,and the optimized reaction conditions were as follows:the residence time of diazotized material was 40 min,the reaction temperature was 5 ℃,the stirring rate was 150 r/min,the temperature of the cyclization reaction was 60 ℃,and the oxidation reaction was carried out under UVA light source,and the total yield of the product was greater than 88.0％,and the purity was greater than 98.0％.This method is inherently safe for diazotization and oxidation reactions,with high yield and purity,low cost,simple operation,and is suitable for industrial production.
1-(4-chlorophenyl)-3-pyrazololkey intermediate of pyraclostrobinfungicidecontinuous synthesis
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