关键词: 氟吡菌酰胺, 中间体, 一锅法, 催化加氢, 回收套用

Abstract:

In view of the problems of the current fluopyram intermediate (2-[3-chloro-5-(trifluoromethyl)pyridin-2-yl]ethanamine(5)) synthesis route, complicated operation, low product yield and high industrial production cost, the research and development of the green synthetic process of (5) was systematically carried out. In particular, using 2,3-dichloro-5-(trifluoromethyl)pyridine(1) as raw material, the two-step reaction of nucleophilic substitution and decarboxylation was conducted via one-pot method to prepare 2-[3-chloro-5-(trifluoromethyl)pyridin-2-yl]acetonitrile(3). Afterwards, catalytic hydrogenation reduction and hydrolysis were carried out to obtain fluopyram intermediate (5) hydrochloride. Based on the analysis of the reaction mechanism, the effects of solvent, alkali, pH and other important factors on the yield were investigated in one-pot method. The preferred solvent was DMF, the base was anhydrous potassium carbonate, the pH was 0.5—1, the yield of product (3) reached 88.1%, and the purity was 98.5%. In the hydrogenation reduction and hydrolysis reactions, the effects of catalyst types, hydrogenation reaction time and temperature were explored. The results show that the yield of product (5) reaches 78.8% and the purity is 96.2% by using 5% Pd/C catalyst (type R5K1). The optimal reaction conditions are as follows: the hydrogenation reaction temperature is 15℃, the reaction time is 12h, and the amount of 38% concentrated hydrochloric acid is n_(HCl)∶n₍₃₎ =5.5. At the same time, the efficient reuse of recovered solvent and the Pd/C catalyst in each step is realized, which provides a new technology support for the clean industrial production of the intermediate.

Key words: fluopyram, intermediate, one-pot method, catalytic hydrogenation, reuse