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-48b2f903935a4e6486724c9ba2f9769c

Source dataset

uspto-grants-2015_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08940741B2