Phosphorus tribromide → 5-(Bromomethyl)-1-methyl-3-nitro-1H-pyrazole

Participants

Reaction Steps

To a solution of (1-methyl-3-nitro-1H-pyrazol-5-yl)methanol (496 mg, 3.16 mmol) in chloroform (10 mL) at 0° C. was added phosphorus tribromide (854 mg, 0.30 mL, 3.16 mmol) drop wise via syringe. The resulting solution was warmed to room temperature and stirred for 1 h. The resulting solution was cooled to 0° C. and diluted with dichloromethane (50 ml). The resulting solution was made basic (pH 8.5) with saturated aqueous sodium bicarbonate (20 mL). The layers were separated, and the aqueous layer was extracted with dichloromethane (3×20 mL). The combined organic layers were dried over magnesium sulfate. The resulting mixture was filtered and concentrated in vacuo and the residue purified by flash chromatography (silica gel, 40 g, 20% to 40% ethyl acetate in hexanes) to give 5-(bromomethyl)-1-methyl-3-nitro-1H-pyrazole (436 mg, 63%) as a white solid. 1H NMR (300 MHz, DMSO-d6) 8 ppm 3.94 (s, 3 H) 4.85 (s, 2 H) 7.14 (s, 1 H).

Provenance & Evidence