Study On The Synthesis Of 1,3-Cyclohexanedione

Mesotrione is a top-selling,highly selective triketone herbicide,which accounted for 4.4% of the global herbicide market in 2017.1,3-Cyclohexanedione is an important intermediate in its synthesis process.At present,the industrial production route of 1,3-cyclohexanedione is mainly resorcinol hydrogenation,and the hydrogenation method involves resorcinol production.It is complicated,the raw material is expensive,the catalyst is deactivated quickly in the hydrogenation process,the reaction conditions are harsh,and the equipment requirements are high.In this paper,ethyl acetoacetate and ethyl acrylate were used as raw materials to synthesize ethyl 5-oxohexanoate by Michael addition,hydrolysis and decarboxylation,and then condensation and cyclization to obtain 1,3-cyclohexanedione.The total yield of three steps was 65 %.At the same time,the new synthesis method of the intermediate 5-oxohexanoate ethyl ester was expanded.The main research contents of this subject are:1.Study on the synthesis process of diethyl 2-acetylglutarate.Using ethyl acrylate and ethyl acetoacetate as raw materials,[BMIM]OH was designed and developed as the best catalyst for the reaction,and the synthesis process was optimized.10%,ethyl acrylate was added dropwise to the reaction solution,When ethyl acrylate and ethyl acetoacetate reacted at 25°C for 2.5h,and the ratio of ethyl acrylate: ethyl acetoacetate was 1:1.3.At this time,the conversion rate of ethyl acrylate was greater than 99%,The yield of diethyl 2-acetylglutarate was 93%.2.Study on the synthesis process of ethyl 5-oxohexanoate.The ethyl 5-oxohexanoate was synthesized by hydrolysis and decarboxylation of diethyl 2-acetylglutarate,and cation exchange resin,concentrated hydrochloric acid and concentrated sulfuric acid were compared as catalysts.Using cation exchange resin with a mass dosage of 35% as a catalyst,reacting at 90 ℃ for 10 h,the conversion rate of diethyl 2-acetylglutarate is more than 99%,and the yield of ethyl 5-oxohexanoate is85%;Using 30% concentrated hydrochloric acid of raw material as catalyst,reacting at 80 ℃ for 8h,the conversion rate of diethyl 2-acetylglutarate is more than 99%,and the yield of ethyl 5-oxohexanoate is 79%.Aiming at the synthesis of ethyl 5-oxohexanoate,the Michael addition of acetone and ethyl acrylate was explored,and it was found that acid-base bifunctional catalyst A can obtain better catalytic effect.The best process conditions are:the molar amount of catalyst is acrylic acid 20% of ethyl ester,reacting at80 ℃ for 5 h,the ratio of reactants is ethyl acrylate:acetone is 1:5,the conversion rate of ethyl acrylate is 12%,and the yield of ethyl 5-oxohexanoate is 10%.3.Study on the synthesis process of 1,3-cyclohexanedione.Using ethyl 5-oxohexanoate as raw material to condense 1,3-cyclohexanedione,a series of catalysts and solvents were compared,and the better conditions were: tert-butanol as solvent,and the molar amount of sodium methoxide as 5-oxo 1.3 times that of ethyl hexanoate,reacting at 55 ℃ for 40 min,the yield of 1,3-cyclohexanedione was the highest,reaching 91%.When the recrystallization solvent was toluene,the yield was the highest,reaching 83%.