The general procedure for the synthesis of 5-chloro-N,N-dimethyl-3-(trifluoromethyl)-1H-pyrazole-1-sulfonamide from 5-chloro-N,N-dimethyl-3-(trifluoromethyl)-1H-pyrazole is as follows: 5-chloro-N,N-dimethyl-3-(trifluoromethyl)-1H-pyrazole-1-sulfonamide (8.0 g, 29 mmol) was dissolved in a reaction system at 0°C with trifluoroacetic acid (TFA, 11 mL. 140 mmol) were co-dissolved in the reaction system. Subsequently, the reaction mixture was stirred continuously at room temperature overnight. Upon completion of the reaction, the solvent was removed by concentration under reduced pressure and the resulting residue was diluted with ethyl acetate (EtOAc, 50 mL) and washed with water (50 mL). The aqueous layer was further extracted with ethyl acetate (2 x 50 mL). All organic phases were combined, dried with anhydrous sodium sulfate (Na2SO4), filtered into a round bottom flask and finally concentrated under reduced pressure to afford the target product 5-chloro-3-trifluoromethyl-1H-pyrazole (5.0 g, 29 mmol, 100% yield). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6) with chemical shift δppm 6.97 (s, 1H).
