Synthesis of fluoromethyl, difluoromethyl and trifluoromethyl analogues of pyrazosulfuron-ethyl as herbicides

Ethyl 1-fluoromethyl-5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)pyrazole-4-carboxylate 1b, a new fluoromethyl analogue of the herbicide pyrazosulfuron-ethyl la, was prepared from ethyl 1-fluoromethylpyrazole-4-carboxylate 4b. The difluoromethyl and trifluoromethyl analogues 1c,d were also synthesized from ethyl pyrazole-4-carboxylate 2 via difluorocarbene reaction.