反应详情

A cold solution (5° C.) of compound 5 (40 g, 149 mmol, 1 equiv), dimethyl sulfoxide (400 mL) and water (5 mL) was treated in one portion with N-bromosuccinimide (39.8 g, 224 mmol, 1.5 equiv). The bath was removed and the reaction allowed to stir at room temperature overnight. The reaction was poured into water (1 L) and extracted with ethyl acetate (2×500 mL). The combined organic layers were washed with saturated brine (1 L), dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was dissolved in 500 mL of toluene and p-toluenesulfonic acid (5.6 g, 29.4 mmol, 0.2 equiv) was added. This mixture was refluxed for 20 hours while removing water with a Dean-Stark trap. The reaction was cooled to room temperature and concentrated under reduced pressure. The resulting residue was purified over silica gel (1 Kg), eluting with heptanes to give compound 6 (39 g, 75% yield) as a light yellow solid.

1. customThe bath was removed
2. additionThe reaction was poured into water (1 L)
3. extractionextracted with ethyl acetate (2×500 mL)
4. washThe combined organic layers were washed with saturated brine (1 L)
5. dry with materialdried over sodium sulfate
6. concentrationconcentrated under reduced pressure
7. dissolutionThe resulting residue was dissolved in 500 mL of toluene
8. temperatureThis mixture was refluxed for 20 hours
9. customwhile removing water with a Dean-Stark trap
10. temperatureThe reaction was cooled to room temperature
11. concentrationconcentrated under reduced pressure
12. customThe resulting residue was purified over silica gel (1 Kg)
13. washeluting with heptanes