| abstract |
The present invention relates to a novel and effective preparation of 5-amino-1-(2,6-dichloro-4-(trifluoromethyl)phenyl)-4-(trifluoromethylthio)-1H-pyrazole- The method of 3-nitrile (hereinafter referred to as formula I compound), this compound can be used as the intermediate of antiparasitic drug fipronil, and the present invention also relates to the preparation of 5-amino-3-cyano-1-(2,6 - the method of dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfinylpyrazole (hereinafter referred to as compound of formula II or fipronil). In one embodiment, there is provided a process for the preparation of fipronil, said process comprising: a) the step of reacting CF3S (=O)ONa with a compound of formula (III) in the presence of a reducing/halogenating agent; and b) a step of oxidizing, under suitable conditions, the compound of formula (I) obtained in step a) in the presence of a selective oxidizing agent, wherein said selective oxidizing agent selectively oxidizes formula (I) to the corresponding sulfoxide , namely fipronil. In certain exemplary embodiments, the selective oxidizing agent is MHSO5 , wherein M is an alkali metal cation. |