Research on Synthesis of Rimsulfuron
|School||Central China Normal University|
|Keywords||Sulfonylureas herbicide Acetolactate synthase Rimsulfuron 2-bromo-3-(ethylsulfonyl)pyridine Carbamate|
Based on the consulting of the literatures about herbicide, the current world herbicide condition and the domestic herbicide condition in corn field carried in our country were summarized. The history of sulfonylureas herbicide development, the main species, function mechanism and toxicity were also particularly introduced. Some information about rimsulfuron, a high effect sulfonylureas herbicide, was expounded such as the physics and chemistry property, toxicity, function mechanism and application activity. The reported preparation about rimsulfuron and its intermediates were also introduced in detail.With the maket requesting and literature researched, the thesis focuses on the preparation of the rimsulfuron . Adopting the chloroacetonitrile, sodium hydroxide and ethanethiol for the main beginning raw material, the 3-(ethylsulfonyl)pyridine-2-sulfonamide was given by the ether reaction, the oxidation, the condensation reaction, the cyclization reaction, the sulfhydryl reaction, the sulfonamide reaction.Phenyl 4,6-dimethoxypyrimidin-2-ylcarbamate was prepared with phenyl carbonochloridate and 4,6-dimethoxypyrimidin-2-amine. And the rimsulfuron was prepared with 3-(ethyl-sulfonyl)-pyridine-2-sulfonamide and phenyl 4,6-dimethoxypyrimidin-2-yl-carbamate. The total yield reached to 42.3 %.A good yield and lower cost of ethylthio acetonitrile were given by using sodium hydroxide water liquor to replace methylsodium DMF liquor. During the preparing of ethylsulfonyl acetonitrile, the dosage of acetic acid was reduced to the degree that we can ignore it, and the cost and the work intensity were also reduced. During preparing of 2-bromo-3-(ethylsulfonyl)pyridine, the most important intermediates, the synthesis of (2E,4Z)-2-(ethylsulfonyl)-5-methoxypenta-2,4-dienenitrile and the synthesis 2-bromo-3-(ethylsulfonyl)pyridine was put into one step, which heightened the yield consumedly , made the craft operates easy and resolved the crux problem on synthesis of rimsulfuron and obtained a more great innovation. During the preparation of 3-(ethylsulfonyl)-pyridine-2-thiol, a wrong way of preparing 3-(ethylsulfonyl)-pyridine-2-thiol was rectified in detail, which gives a good purity. The traditional carbonylation reagent of the sulfonylureas herbicide was avoided by using phenyl carbonochloridate in preparing phenyl 4,6-dimethoxy-pyrimidin-2-yl-carbamate, the possibility of explosive accident caused by the creation of peroxide in callback process was avoided by reducing the dosage of 1,4-dioxane. During the preparing of rimsufuron, the expensive catalyst 1,8-diaza-bicyclo[5.4.0]undec-7-ene(DBU) was avoided by using triethylamine, and the yield exceeds literature to a 25%, the product purity reaches 96% above, and reached export standard. By the creative method above, the yield in this way increased about 20%, and its cost reduced to about 330 thousands yuan.The ultimate product and its important intermediates were proveded to be consilient with the molecule constructure of by nuclear magnetic resonance spectra and mass spectroscopic.