Phosphorus tribromide → 1-(2-bromoethyl)-5-(bromomethyl)-3-nitro-1H-pyrazole

Participants

Reaction Steps

To as solution of (1-(2-bromoethyl)-3-nitro-1H-pyrazol-5-yl)methanol (4.24 g, 17 mmol) in chloroform (100 mL), cooled to 0° C., was added phosphorus tribromide (4.59 g, 1.6 mL, 17 mmol) drop wise. The resulting solution was warmed to room temperature and stirred for 2 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 was (20 mL). The layers were separated, and the aqueous layer was extracted with dichloromethane (3×50 mL). The combined organic layers were washed with brine (30 mL), dried over magnesium sulfate. The resulting mixture was filtered and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, SF40-240 g, 15% to 40% EtOAc in hexanes) to give 1-(2-bromoethyl)-5-(bromomethyl)-3-nitro-1H-pyrazole (3.58 g, 67%) as a white solid. 1H NMR (300 MHz, DMSO-d6) 8 ppm 3.92 (t, J=6.23 Hz, 2 H) 4.69 (t, J=6.23 Hz, 2 H) 4.89 (s, 2 H) 7.19 (s, 1 H).

Provenance & Evidence