Hexane → 3,5-Dibromo-1-(2'-hydroxyethyl)-4-nitropyrazole

Temperatur

80 °C

A solution of 3,5-dibromo-4-nitropyrazole (2) (11.0 g, 41 mmol) in DMF (52 ml) was added dropwise over 20 min to a stirred solution of NaH (1.76 g, 46 mmol; 60% dispersion in oil, prewashed with hexane under an inert atmosphere) in DMF (88 ml). After stirring for 10 minutes, a solution of 2-bromoethanol (6.4 g, 49 mmol) in DMF (14 ml) was added dropwise over 10 minutes. The reaction mixture was heated to 80° C. for 2 hours and then the DMF was evaporated off under reduced pressure. A mixture of DCM/water (100 ml, 1/1) is added to the residue and the organic phase is washed with water (50 ml). The organic phase was dried over Na2SO4 and the solvent was evaporated off under reduced pressure. The crude brown solid obtained was subsequently purified by column chromatography (5%/95% EtOAc/hexane). The yellow solid product (3.4 g) was recrystallized from a mixture of toluene/hexane (20 ml, 55%/45%) to give the 2-(3,5-dibromo-4-nitropyrazol-1-yl)ethanol (3) in the form of a white solid (2.8 g, 22%).

1. customthe DMF was evaporated off under reduced pressure
2. additionA mixture of DCM/water (100 ml, 1/1)
3. additionis added to the residue
4. washthe organic phase is washed with water (50 ml)
5. dry with materialThe organic phase was dried over Na2SO4
6. customthe solvent was evaporated off under reduced pressure
7. customThe crude brown solid obtained
8. customwas subsequently purified by column chromatography (5%/95% EtOAc/hexane)
9. customThe yellow solid product (3.4 g) was recrystallized from a mixture of toluene/hexane (20 ml, 55%/45%)

ORD-Eintrag

ord-2a84430a84bb465c92f452a6b69a439a

Quelldatensatz

uspto-grants-2006_08

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US07091350B2