反应详情

A mixture of 1.53 g (15 mmoles) of 2-ketobutyric acid, 1.54 g (10 mmoles) of 2,2-dichlorocyclopropanecarboxamide and 10 ml of toluene was heated under reflux for 12 hrs. with removal of H2O by a modified Dean-Stark trap containing molecular sieves (4A). An additional 0.7 g of 2-ketobutyric acid was added and the reaction mixture was heated under reflux for an additional 12 hrs. The mixture was cooled, diluted with 20 ml of toluene and extracted with saturated sodium bicarbonate (3×10 ml). The extracts were combined, washed with ether and acidified to pH 3 (pH meter) with concentrated hydrochloric acid. A gum precipitated which soon solidified. It was filtered, washed with water, dried and recrystallized from nitromethane to give 423 mg of Z-2-(2,2-dichlorocyclopropanecarboxamido)-2-butenoic acid, m.p. 188°-189.5° C. The NMR spectrum was in accord with the desired structure.

1. temperaturewas heated
2. temperatureunder reflux for 12 hrs
3. customwith removal of H2O by a modified Dean-Stark trap
4. additioncontaining molecular sieves (4A)
5. additionAn additional 0.7 g of 2-ketobutyric acid was added
6. temperaturethe reaction mixture was heated
7. temperatureunder reflux for an additional 12 hrs
8. temperatureThe mixture was cooled
9. additiondiluted with 20 ml of toluene
10. extractionextracted with saturated sodium bicarbonate (3×10 ml)
11. washwashed with ether
12. customA gum precipitated which
13. filtrationIt was filtered
14. washwashed with water
15. customdried
16. customrecrystallized from nitromethane