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. 1H NMR (300 MHz, DMSO-d6) 8 ppm 3.94 (s, 3 H) 4.85 (s, 2 H) 7.14 (s, 1 H).

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-939f376c0b3948668ae1dbd6d7417d95

Source dataset

uspto-grants-2014_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08889682B2