Synthesis Of Highly Effective Herbicide Topramezone

Topramezone is a new specific environmental herbicide for corn. It was very important for corn weed control because of its wide selectivity and safety.A novel and simple synthesis method was offered through summarizing domestic and foreign literature, experimenting and comparing three routes which used 2,3- dimethyl nitrobenzene, 2,3-dimethyl benzoic acid, and 2-methyl-3-amino benzoic acid methyl ester as raw material, respectively. In this paper, the method with 2,3-dimethyl aniline as raw material was offered, which would undergo the reaction of sulfide oxidation, bromination,oximation, cyclization. And then, the first segment 3-(3-bromine-2-methyl-6-sulfonyl phenyl)-4,5-isoxazole was synthesized. Then the second segment 1-methyl-5-hydroxy pyrazole was synthesized using methoxy methyl acrylate and methyl hydrazine as raw materials. Finally, the first fragment and the secongd fragment was combined to prepare title product topramezone by plugging carbonyl reaction and rearrangement reaction.Many of the problems in the process of experiment were summarized and optimized,such as the selectivity of solvents, the ratio of materials in different steps, the reaction time,the control of by-products, the reaction monitoring, the reaction postprocessing method and the analysis and purifying for product, and so on. As such, the quality and purity of product has a high level. And the process of the first five steps could be industrialized entirely.In addition, the various products of every step had been characterized and ensured by H-NMR. In conclusion, the experimental results showed that this process can be used in the production of topramezone, and the potential ability to industrialization.