Application of the Tisler Triazolopyrimidine Cyclization to the Synthesis of a Crop Protection Agent and an Intermediate

A new synthetic route to the Dow AgroSciences early stage sulfonamide herbicide 3-(2-methoxy-4-trifluoromethyl)-N-(5,7-dimethoxy[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)pyridinesulfonamide (pyroxsulam) has been developed. The synthesis is based on formation of the triazole ring as the final step, utilizing the Tisler triazolopyrimidine cyclization. A Tisler cyclization route to 2-amino-5,7-dimethoxy-1,2,4-trazolo[1,5-a]pyrimidine starting with 2-chloro-4,6-dimethoxypyrimidine has also been demonstrated.