Route Design and Development of Tetrachlorantraniliprole: Copper- Catalyzed Cyclization and One-Pot Preparation of Pyrazole Acid Chloride

Synthetic strategies for preparing insecticide tetrachlorantraniliprole (1) were explored. Target compound 1 was synthesized from 2,3,5-trichloropyridine (2) using a six-step process. The obtained yield of 51.7% was considerably higher than the 4.7% yield of the initial seven-step process. Process highlights include copper-catalyzed cyclization of 3-chloro-2-hydrazinopyridine (3) for forming the key intermediate 2-(3,5-dichloropyridin-2-yl)-5-oxopyrazolidine-3-carboxylate (4), one-pot preparation of pyrazole acid chloride (9) from thionyl chloride, and a coupling reaction of pyrazole acid chloride (9) with benzamide (10) to afford target compound 1 without an acid scavenger. The process represents a reliable alternative for large-scale manufacturing of tetrachlorantraniliprole (1).