The Synthesis of Research on Pyrithiobac-acid and Diarylsulfide

Recently herbicides have been greatly developed and practically used in the developed countries.These chemicals have contributed to the saving of energy for the agricultural operations and the improvement of the production efficiency.However, Herbicides in China is less development than in USA,Japan and other European Countries.So it is necessary for China to research herbicide following the international patent.The herbicide of Pyrithiobac-sodium was developed by the Japanese Combinatorial Chemical Company in 1994.The herbicide exhibits excellent herbicidal effects against perennial weeds as well as annual weeds,at the same time,it has a high level of safety to crop plants,particularly to cotton.In this thesis,a process to synthesize Pyrithiobac-sodium has been optimized, which increases the yield,reduces the cost and facilitates the final purification.In connection with this process,a synthetic method to diarylthio-ether has been researched in order to explore the substitute effect of benzene on the yield of sulfide.The main results are described as follows:1.Thiosalicylic acid has been synthesized by the method:taking 2-nitrotoluene as starting material,by oxidation,reduction and Sandmeyer Reaction,to produce the intermediateⅠ.2.4,6-dimethoxy-2-methylsulfonylpyrimidine as the intermediateⅡhas been successfully synthesized through an improved route.3.The intermediateⅠreacts with the intermediateⅡto produce 2-{(4, 6-dimethoxy-2-pyrimidinyl intermediate)thio} benzoic acid as the first target.4.6-Chloro-2-mercaptobenzoic acid as the intermediateⅢhas been prepared through the same route as the intermediateⅠ:taking 6-chloro-2-nitrotoluene as starting material,by oxidation,reduction and Sandmeyer Reaction.5.Pyrithiobac-sodium as the second target has been prepared through the reaction between the intermediateⅢand the intermediateⅡ.The 11 intermediate products and the two target compounds have been fully characterized by IR、~1HMR or MS.