Method for preparing penoxsulam midbody

The invention provides a method for preparing a penoxsulam midbody, belonging to the technical field of pesticide synchronization. The method comprises the following steps: in a dried organic solvent, by taking 2-fluoro-6-trifluoromethyl benzene sulfonyl chloride and 5,8-dimethoxyl-[1,2,4] triazole[1,5-c] pyrimidine-2-amine as raw materials, performing condensation reaction under the action of non-nucleophilic alkali or weak-nucleophilic alkali, thereby obtaining a crude 2-fluoro-6-trifluoromethyl-N-(5,8-dimethoxyl-[1,2,4] triazol [1,5-c] pyrimidine-2-yl) benzsulfamide product; and treating the crude product, and purifying, thereby obtaining a finished product of which the HPLC purity is greater than or equal to 99%, namely, the midbody for preparing herbicide penoxsulam. The yield of the product prepared by using the process provided by the invention is relatively high, and the reaction time is shorted to be 30-60 minutes from the conventional about 9 days reported in documents, so that the production efficiency is greatly improved; the raw materials and the reagents used in the reaction process are safe and low in price, high-toxicity reagents or solvents are not used, and the production cost is relatively low; the reaction materials are convenient to treat later, a small amount of wastes are generated, the environment-friendly requirements are met, and the method is applicable to industrialization production and application.