反应详情

温度

-78 °C

In a 250 mL round-bottomed flask was (S)-4-benzyloxazolidin-2-one (5 g, 28.2 mmol) and THF (30 mL) to give a colorless solution. Cooled in −78° C. bath. 2.5M BuLi in hexane (11.29 mL, 28.2 mmol) was added slowly to the oxazolidinone. Initially a thick white precipitate formed, added another 10 mL THF. At the end of the addition the reaction mixture became light orange and contained white solid material. The reaction mixture was stirred at −78° C. for 1 h, and then pent-4-enoyl chloride (3.11 mL, 28.2 mmol) was added dropwise to the oxazolidinone anion at −78° C. The orange color immediately discharged and the reaction became a pale yellow color. Still several large white chunks in the reaction. After 30 min. The reaction mixture was removed from −78° C. bath and let warm to room temperature. All the white chunks have dissolved. The reaction mixture was then stirred at room temperature for 4 h. The reaction was quenched with saturated NH4Cl. The reaction mixture was diluted with 10% aqueous LiCl and Et2O. The organic layer was separated and washed with saturated aqueous NaHCO3 and then washed with brine. The organic layer was dried over MgSO4, filtered and concentrated to give a crude material. This crude material was purified on silica gel column (120 g ISCO) eluting with a gradient from 100% hexane/EtOAc to 50% hexane/EtOAc. The product came off ˜20% EtOAc/hexane. The product was collected in tubes and concentrated to afford (S)-4-benzyl-3-(pent-4-enoyl)oxazolidin-2-one, Intermediate S8A (4.35 g, 16.78 mmol, 59.5% yield) as thick colorless oil. 1H NMR (400 MHz, chloroform-d) δ 7.43-7.22 (m, 5H), 6.01-5.81 (m, 1H), 5.20-5.02 (m, 2H), 4.78-4.62 (m, 1H), 4.29-4.16 (m, 2H), 3.34 (dd, J=13.4, 3.3 Hz, 1H), 3.19-3.02 (m, 2H), 2.80 (dd, J=13.3, 9.6 Hz, 1H), 2.50 (d, J=7.3 Hz, 2H).

1. customInitially a thick white precipitate formed
2. additionAt the end of the addition the reaction mixture
3. customStill several large white chunks in the reaction
4. waitAfter 30 min
5. customThe reaction mixture was removed from −78° C. bath
6. temperaturelet warm to room temperature
7. dissolutionAll the white chunks have dissolved
8. stirringThe reaction mixture was then stirred at room temperature for 4 h
9. customThe reaction was quenched with saturated NH4Cl
10. additionThe reaction mixture was diluted with 10% aqueous LiCl and Et2O
11. customThe organic layer was separated
12. washwashed with saturated aqueous NaHCO3
13. washwashed with brine
14. dry with materialThe organic layer was dried over MgSO4
15. filtrationfiltered
16. concentrationconcentrated
17. customto give a crude material
18. customThis crude material was purified on silica gel column (120 g ISCO)
19. washeluting with a gradient from 100% hexane/EtOAc to 50% hexane/EtOAc
20. customThe product was collected in tubes
21. concentrationconcentrated