反应详情

温度

-5 °C

To a 3 L round bottom flask was added (r)-Pulegone (300 g, 1.97 mol), anhydrous NaHCO3 (82 g, 0.99 mol) and Ether (1.5 L). The mixture was cooled to −5° C. ice-salt bath under N2. Then bromine (101 mL, 1.97 mol) was added dropwise over 45 minutes. The mixture was filtered and carefully added dropwise (addition is exothermic in nature) to NaOEt (20 wt %, 4.3 mol) cooled at 0° C. The reaction was allowed to stir with warming to ambient temperature overnight. Then 1 L of 5% HCl and 300 mL of ether was added. The aqueous phase was extracted with ether and the combined organic layers washed with brine, dried with MgSO4 and concentrated. The resulting brown oil diluted with EtOH was added to a warm solution of semicarbazide HCl (150 g, 1.3 mol), NaOAc (150 g, 1.8 mol) and H2O (2 L) to give a brownish solution. The mixture was then refluxed for 3 hours and stirred at ambient temperature overnight. The mixture was treated with 1 L of water and 500 mL of ether. The aqueous phase was extracted with ether. The combined organic layers were dried with MgSO4 and concentrated to give a brown oil. The oil was subject to vacuum distillation, and the title compound (247 g, 64% yield) was collected at 73-76° C.

1. filtrationThe mixture was filtered
2. additioncarefully added dropwise
3. temperaturecooled at 0° C
4. temperaturewith warming to ambient temperature overnight
5. extractionThe aqueous phase was extracted with ether
6. washthe combined organic layers washed with brine
7. dry with materialdried with MgSO4
8. concentrationconcentrated
9. additionThe resulting brown oil diluted with EtOH
10. customto give a brownish solution
11. temperatureThe mixture was then refluxed for 3 hours
12. stirringstirred at ambient temperature overnight
13. extractionThe aqueous phase was extracted with ether
14. dry with materialThe combined organic layers were dried with MgSO4
15. concentrationconcentrated
16. customto give a brown oil
17. distillationThe oil was subject to vacuum distillation