Study On The Synthesis Of Sulfonylurea Herbicides Mesosulfuron-methyl And Triflusulfuron

The content of my graduation thesis mainly involves the synthesis of Mesosulfuron-methyl and trifluorosulfuron,both of which are novel sulfonylurea herbicides.Methyldisulfuron is generally used to remove single and dicotyledonous weeds in wheat fields that are related to wheat,while triflusulfuron is used to remove broad-leaved weeds in cotton fields.Compared with other herbicides,sulfonylurea herbicides have better herbicidal effect,broader herbicidal spectrum,and low toxicity and high safety.In this paper,we consulted the relevant literature,sorted out the synthetic routes of two sulfonylurea herbicides.We have successfully developed a method for preparing sulfonamide after nucleophilic substitution of nitro group on benzene ring with chlorinated ammonium chloride gas.Using this method,two new routes for synthesizing methyl disulfuron and a new route for trifluorosulfuron were obtained.At the same time,conditional selection and optimization of each step of the new route.1.Study on the synthesis of Mesosulfuron-methyl(1)Study on the first routeSynthesis of Mesosulfuron-methyl with p-toluenecarbonitrile as the starting material:First,p-toluenecarbonitrile undergoes a nitration reaction under the condition of mixed acid,and then the methyl group is oxidized to a carboxyl group under the condition of potassium dichromate as an oxidant.The carboxyl product reacts with dimethyl sulfate to obtain methyl 4-cyano-2-nitrobenzoate,and then undergoes a nucleophilic substitution reaction with benzyl mercaptan.Then,using Raney nickel as a catalyst to reduce the cyano group with hydrogen to obtain the benzylamine product.After the benzylamine product undergoes a methanesulfonylation reaction,it is oxidized with chlorine gas to obtain sulfonyl chloride,and then passed through ammonia gas to be ammoniated to obtain the key intermediate Sulfonamide,and finally Pyrimidinate condensation to obtain the target product mesosulfuron-methyl.(2)Study on the second routeIn view of the new synthetic route one,we also use the nitro group as the leaving group to react with the benzyl mercaptan,and then the method of introducing chlorine gas oxidation followed by ammonia gas ammoniation introduces the sulfonamide group,which mainly improves the method of introducing ester groups and amine methyl P-bromobenzaldehyde is used as a starting material:First nitrify,and then use cuprous cyanide as the cyanating reagent.The obtained cyano product undergoes a nucleophilic substitution reaction with benzyl mercaptan and then reacts with hydroxylamine hydrochloride to obtain an oxime intermediate.The oxime is reduced with zinc powder to obtain benzylamine.Next,it reacts with methanesulfonyl chloride,and then the cyano group is hydrolyzed under alkaline conditions to obtain carboxylic acid.After the carboxylic acid is esterified,it is oxidized with chlorine gas to obtain sulfonyl chloride,and then ammoniated to obtain the key intermediate Sulfonamide,and finally Pyrimidinate condensation to obtain the target product mesosulfuron-methyl.Comparing the two routes,although the second route avoids the use of the strong oxidant potassium dichromate,there is no need for post-treatment of the generated chromium salts,which reduces the generation of COD wastewater,so it is more environment friendly.2.Study on the synthesis of TrifloxysulfuronRegarding the synthesis of trifluorosulfuron-methyl,we followed the method of introducing sulfonamide groups in the above two routes.We use 2-nitro-3-hydroxy as the starting material:the first step is to react with methanesulfonyl chloride and then to undergo a nucleophilic substitution reaction with benzyl mercaptan.After reacting with 2,2,2-trifluoroethyl methanesulfonate to obtain the trifluoroethoxy product.After the oxidation of sodium hypochlorite to obtain sulfonyl chloride,ammonia gasification to obtain the key intermediate 3-(2,2,2-trifluoroethoxy)pyridine-2-sulfonamide,and finally Pyrimidinate condensation to obtain the target product trifloxysulfuron.