Hydrolytic activation/decomposition pathways of herbicidally active ethyl 5-[N-(5,7-dimethoxy-2H-1,2,4- thiadiazolo[2,3-a] pyrimidin-2-ylidene)sulfamoyl]-1,3- dimethylpyrazole-4-carboxylate

Potent herbicidal ethyl 5-[N-(5,7-dimethoxy-2H-1,2,4-thiadiazolo-[2,3-a] pyrimidin-2-ylidene) sulfamoyl]-1,3-dimethylpyrazole-4-carboxylate (I) was hydrolyzed under weakly basic conditions to afford a sulfonylurea (VII), a 2-pyrimidylcyanamide (IV) and a mercaptopyrazole (VI). The formation of these products was explained by nucleophilic attack at the 1 and 2-positions of the 1,2,4-thiadiazolo [2,3-a] pyrimidine ring. This is believed to mimic the process which occurs on application to the plant. I appears to be a pro-pesticide for the sulfonylurea, VII