Reaktion #9854

Reaktionsgleichung

hexane

2-bromoethanol

3,5-dibromo-4-nitropyrazole

NaH

→

2-(3,5-dibromo-4-nitropyrazol-1-yl)ethanol

Lösungsmittel

DMF

DMF

DMF

Reaktionsbedingungen

Aufarbeitung

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

Vorschrift

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%).

Quelle