Study On The Synthesis Of 2-phenyl-6-hydroxy-3-pyridazinone

2-phenyl-6-hydroxy-3-pyridazinone is an important organic chemical intermediates which is widely used in medicine, pesticides, catalysis and other fields,especially in the field of pesticides,it is an important intermediate of pyridaphenthion which is a kind of high efficiency, low toxicity, low residue organophosphorus insecticide pesticides.The product has a great potential of development in terms of commercialization because its versatility and high added value. At present, the industrial synthesis of 2-phenyl-6-hydroxy-3-pyridazinone process has a large amount of waste water and the product yield is low. In this paper, aniline was used as the raw material, and the intermediates were prepared by diazotization, reduction, hydrolysis and neutralization.Then the intermediates were reacted with maleic anhydride to obtain 2-phenyl-6-hydroxy-3-pyridazinone. The process conditions of two-step method and one-pot were studied, which could be used as reference for industrial production.The research work of this thesis is divided into three parts:In the first part,phenylhydrazine was synthesized by using aniline as raw material,the optimal conditions were as follows: aniline 9.2ml,concentrated hydrochloric acid 23ml, water 25ml, sodium nitrite 7.24g, diazotization reaction time 45min, diazotization reaction temperature 5?, sodium bisulfite 23.9g, reduction time 2h,reduction temperature 80 ?,hydrolysis time 1.5h.The average yield of phenylhydrazine was 95.6%.In the second part, 2-phenyl-6-hydroxy-3-pyridazinone was synthesized by using phenylhydrazine and maleic anhydride as raw material, the optimal conditions were as follows: phenylhydrazine 5.4g,molar ratio of phenylhydrazine and maleic anhydride 1:1.1,water 25ml, concentrated hydrochloric acid 8ml, reaction temperature 90 ?,reaction time 3h, The average yield of 2-phenyl-6-hydroxy-3-pyridazinone was 88.7%.In the third part, the optimal conditions for the synthesis of 2-phenyl-6-hydroxy-3-pyridazinone by one-pot method were studied on the basis of two-step method. The conditions were as follows: In the first stage of reaction, aniline 4.8ml, concentrated hydrochloric acid 12ml, water 13ml, sodium nitrite 3.78g, diazotization reaction time 45min, diazotization reaction temperature 5?, sodium bisulfite 12.47g, reduction time 2h, reduction temperature 80?, hydrolysis time 1.5h. In the second stage of reaction, maleic anhydride 5.39g,water 25ml, concentrated hydrochloric acid 4ml,keep the temperature of reaction solution when adding the concentrated hydrochloric acid and maleic anhydride, reaction temperature 90?, reaction time 3h,The average yield of the product was 87.2%.