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

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.

1. temperatureThe resulting solution was cooled to 0° C.
2. customThe layers were separated
3. extractionthe aqueous layer was extracted with dichloromethane (3×20 mL)
4. dry with materialThe combined organic layers were dried over magnesium sulfate
5. filtrationThe resulting mixture was filtered
6. concentrationconcentrated in vacuo
7. customthe residue purified by flash chromatography (silica gel, 40 g, 20% to 40% ethyl acetate in hexanes)

ORD record

ord-2a746e58ff6c4d01a4508342611598c8

Source dataset

uspto-grants-2013_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08481540B2