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

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).

1. temperatureThe resulting solution was cooled to 0° C.
2. customThe layers were separated
3. extractionthe aqueous layer was extracted with dichloromethane (3×50 mL)
4. washThe combined organic layers were washed with brine (30 mL)
5. dry with materialdried over magnesium sulfate
6. filtrationThe resulting mixture was filtered
7. concentrationconcentrated in vacuo
8. customThe crude material was purified by flash chromatography (silica gel, SF40-240 g, 15% to 40% EtOAc in hexanes)

ORD record

ord-2a4d2659462a49c5b000d0b46cb7b7bd

Source dataset

uspto-grants-2014_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08889682B2