3-BROMO-1H-PYRAZOLE

500011-84-7

14521-80-3

General procedure for the synthesis of 3-bromopyrazole from 1-(dimethylaminosulfonyl)-3-bromopyrazole: 3-bromo-N,N-dimethyl-1H-pyrazole-1-sulfonamide (5.83 g) obtained in step B was mixed with trifluoroacetic acid (9.0 mL) and the reaction was stirred for 2 hours at room temperature. Upon completion of the reaction, ethyl acetate was added to the mixture, followed by neutralization of the reaction solution with saturated aqueous sodium bicarbonate and washing with saturated aqueous sodium chloride. The organic layer was separated, dried with anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The resulting crude product was purified by silica gel column chromatography (eluent: ethyl acetate/hexane) to give the final target compound 3-bromopyrazole (2.92 g). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 6.37 (1H, d, J=2.4 Hz), 7.57 (1H, d, J=2.4 Hz).