反应详情

A quantity (3.04 gm., 0.01 mole) of 3,4,5-tribromopyrazole was dissolved in 70 ml. acetone and 2.76 gm. (0.02 mole) solid anhydrous potassium carbonate was added. The mixture was heated at the reflux temperature with stirring for 10 minutes and, after cooling, 2.0 gm. (0.011 mole) ethyl 2-bromopropionate was added. This reaction mixture was heated at the reflux temperature for 11/2 hrs. After cooling, an aqueous solution of sodium hydroxide (0.5 gm. in 90 ml. water) was added. The acetone was distilled off and the remaining aqueous solution was heated at the reflux temperature for 2 hrs. The clear solution thus obtained was cooled and acidified to about pH 2 with 2 N hydrochloric acid. A white precipitate that formed was collected on a filter, washed with water, and dried. There was thus obtained 3.55 gm. (95% yield) of 3,4,5-tribromo-α-methylpyrazole-1-acetic acid having a melting point at 162° to 164° C., identical with the product of Example 5.

1. temperatureThe mixture was heated at the reflux temperature
2. temperatureafter cooling
3. temperatureThis reaction mixture was heated at the reflux temperature for 11/2 hrs
4. temperatureAfter cooling
5. distillationThe acetone was distilled off
6. temperaturethe remaining aqueous solution was heated at the reflux temperature for 2 hrs
7. customThe clear solution thus obtained
8. temperaturewas cooled
9. customA white precipitate that formed
10. customwas collected on a filter
11. washwashed with water
12. customdried