151049-87-5

1904-31-0

151049-87-5

General procedure for the synthesis of 3-bromo-1-methylpyrrole from N-methyl-3-aminopyrazole: A) Synthesis of 3-bromo-1-methyl-1H-pyrazole: To a solution of 1-methyl-1H-pyrazol-3-amine (2.00 g) in hydrobromic acid (14.0 mL) was added slowly and dropwise to an aqueous solution (2.06 mL) of sodium nitrite (1.56 g) under the cooling of an ice bath. The reaction mixture was stirred under ice bath cooling for 30 minutes before a solution of copper(I) bromide (7.39 g) in hydrobromic acid (14.0 mL) was slowly added. The reaction mixture was continued to be stirred under ice bath cooling for 30 hours. Upon completion of the reaction, the reaction solution was neutralized with saturated aqueous sodium bicarbonate and diluted with dichloromethane. The insoluble material was removed by filtration, and the filtrate was washed sequentially with water and saturated brine and dried over anhydrous magnesium sulfate. After evaporation of the solvent under reduced pressure, the residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane) to afford 3-bromo-1-methylpyrrole (818 mg). The product was characterized by 1H NMR (400 MHz, CDCl3): δ3.88 (3H, s), 6.25 (1H, d, J=2.4 Hz), 7.25 (1H, d, J=2.0 Hz).