反应详情

温度

-78 °C

Under nitrogen atmosphere, n-butyllithium 1.6M in hexane (6.5 mL, 10.42 mmol) was added dropwise to a solution of 3,5-dibromo-1-methyl-1H-pyrazole (11d) (2.00 g, 8.34 mmol) in anhydrous tetrahydrofuran (40 mL) at −78° C. After 30 minutes stirring at the same temperature, copper iodide (5.56 g, 29.18 mmol) was added. The temperature was allowed to reach 0° C. for 40 minutes, then cooled to −78° C. Ethyl chlorooxoacetate (2.80 mL, 25.01 mmol) was dropwise added. The mixture was stirred at room temperature for 2 hours. Water (20 mL) was added and the mixture was extracted with ethyl acetate (2×30 mL). The organic layer was washed with a saturated solution of sodium hydrogenocarbonate (20 mL), dried over sodium sulfate and concentrated in vacuo. The residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate: 100/0 to 80/20) to provide ethyl 2-(3-bromo-1-methyl-1H-pyrazol-5-yl)-2-oxoacetate (11e) (1.36 g, 5.21 mmol, 62%).

1. additionwas added
2. extractionthe mixture was extracted with ethyl acetate (2×30 mL)
3. washThe organic layer was washed with a saturated solution of sodium hydrogenocarbonate (20 mL)
4. dry with materialdried over sodium sulfate
5. concentrationconcentrated in vacuo
6. customThe residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate: 100/0 to 80/20)