Reaktion #41145

Reaktionsgleichung

2-dimethylaminomethylene-3-oxo-butyric acid methyl ester

tert-butylhydrazine hydrochloride

sodium acetate

dichloromethane

→

1-tert-butyl-5-methyl-1H-pyrazole-4-carboxylic acid methyl ester

Ausbeute 71.0%

Lösungsmittel

ethanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturAt this time, the reaction was cooled to 25° C
2. 2
   workup.ADDITIONThe reaction was poured onto ice
3. 3
   SonstigeThe mixture was transferred to a separatory funnel at which time
4. 4
   Sonstigeseparated
5. 5
   ExtraktionThe aqueous layer was further extracted with dichloromethane (1×50 mL)
6. 6
   WaschenThe combined organics were washed with a saturated aqueous sodium bicarbonate solution (1×50 mL), water (1×50 mL)
7. 7
   Trocknena saturated aqueous sodium chloride solution (1×50 mL), dried over magnesium sulfate
8. 8
   Filtrationfiltered
9. 9
   Einengenconcentrated in vacuo

Vorschrift

A solution of 2-dimethylaminomethylene-3-oxo-butyric acid methyl ester (7.43 g, 43.40 mmol) in absolute ethanol (70 mL) was treated with tert-butylhydrazine hydrochloride (5.52 g, 44.29 mmol) and sodium acetate (4.42 g, 53.88 mmol). The resulting mixture was heated to 90° C. for 18 h. At this time, the reaction was cooled to 25° C. The reaction was poured onto ice using dichloromethane to assist the transfer (50 mL). The mixture was transferred to a separatory funnel at which time the layers were shaken and separated. The aqueous layer was further extracted with dichloromethane (1×50 mL). The combined organics were washed with a saturated aqueous sodium bicarbonate solution (1×50 mL), water (1×50 mL) and a saturated aqueous sodium chloride solution (1×50 mL), dried over magnesium sulfate, filtered and concentrated in vacuo. ISCO CombiFlash (120 g column; 0-10% ethyl acetate/hexanes) afforded 1-tert-butyl-5-methyl-1H-pyrazole-4-carboxylic acid methyl ester (6.04 g, 71%) as a yellow oil.

Quelle