反应详情

To a solution of 1 (12.6 g, 49.75 mmol) in THF (200 mL) is added KOTMS (6.38 g, 49.75 mmol). The mixture is stirred overnight at room temperature. The mixture is concentrated and the residue dissolved in dichloromethane (200 mL) and cooled to 0° C. Trimethylacetyl chloride (5.94 g, 49.25 mmol) is added slowly and the mixture is warmed to room temperature over 2 hours. The mixture is cooled to −78° C., 2 (8.63 g, 49.25 mmol) is added and stirring continued at −78° C. for 1.5 h. Saturated sodium bicarbonate (100 mL) is added and the mixture is allowed to warm to rt. The mixture is extracted with EtOAc (4×100 mL) and the organic extracts are combined, dried and concentrated under vacuum. The residue is purified by flash chromatography (silica gel; Hexane/EtOAc 1:8) to provide 15 g (76%) of the title compound as a mixture of two diastereomers in an equimolecular ratio. M+H+=399.37.

1. concentrationThe mixture is concentrated
2. dissolutionthe residue dissolved in dichloromethane (200 mL)
3. temperaturecooled to 0° C
4. temperaturethe mixture is warmed to room temperature over 2 hours
5. temperatureThe mixture is cooled to −78° C.
6. stirringstirring
7. waitcontinued at −78° C. for 1.5 h
8. temperatureto warm to rt
9. extractionThe mixture is extracted with EtOAc (4×100 mL)
10. customdried
11. concentrationconcentrated under vacuum
12. customThe residue is purified by flash chromatography (silica gel; Hexane/EtOAc 1:8)