反应详情

温度

11.5 °C

Urea (19.39 g, 0.32 mol) (J. T. Baker) was added over 20 minutes to fuming sulfuric acid (26–29.5% free SO3, 135 mL, 2.65 mol) (Aldrich) with cooling in an ice water bath maintaining the reaction temperature between 8 to 15° C. After stirring for an additional 30 minutes, ethyl 2-formylbutyrate (46.55 g, 0.32 mol) (from Example 1c, supra) was added over 18 minutes keeping the reaction at the same temperature. After stirring for another 30 minutes, a second portion of urea (15.07 g, 0.25 mol) was added over 10 minutes at the same temperature. The reaction mixture was then stirred at room temperature for 65 hours, and at 90–100° C. for 2 hours (gas evolution was observed, and reaction was exothermic, with reaction temperature rising to 110° C.). The mixture was cooled to 30° C. with an ice-water bath. Ice (270 g) was added slowly keeping the reaction below 35° C. The mixture was then cooled to 5° C. and stirred for 20 minutes. The solid formed was collected by filtration, washed with cold water, hexanes, and diethyl ether and dried by suction to give 5-ethyl uracil. (Yield 38.85 g, 85.9%).

1. temperaturewith cooling in an ice water bath
2. customthe reaction at the same temperature
3. stirringAfter stirring for another 30 minutes
4. stirringThe reaction mixture was then stirred at room temperature for 65 hours
5. customat 90–100° C. for 2 hours (gas evolution was observed, and reaction was exothermic, with reaction temperature rising to 110° C.)
6. temperatureThe mixture was cooled to 30° C. with an ice-water bath
7. customthe reaction below 35° C
8. temperatureThe mixture was then cooled to 5° C.
9. stirringstirred for 20 minutes
10. customThe solid formed
11. filtrationwas collected by filtration
12. washwashed with cold water, hexanes, and diethyl ether
13. customdried by suction