反应详情

温度

-78 °C

To a solution of the title compound of Preparation 1f (5.4 grams, 22.1 mmol) in tetrahydrofuran (500 mL) at −78° C. was added phenyltrimethylammonium bromide tribromide (8.31 grams, 22.1 mmol) in portions. The mixture was allowed to stir at −78° C. for 1 hour and then allowed to slowly warm to 0° C. over 1.5 hours. After stirring at 0° C. for a further 3 hours, the mixture was poured into water and extracted twice with ethyl acetate. The combined extracts were dried (MgSO4) and concentrated to give an orange oil that was passed through a pad of silica gel washing with ethyl acetate. Concentration provided crude title product as an orange foam. 1H NMR (CDCl3) selected signals: δ 4.78 (dd, J=5.7, 13.5 Hz, 1 H), 3.28 (dd, J=5.7, 13.0 Hz, 1 H), 2.94–2.91 (m, 2 H).

1. temperatureto slowly warm to 0° C. over 1.5 hours
2. stirringAfter stirring at 0° C. for a further 3 hours
3. extractionextracted twice with ethyl acetate
4. dry with materialThe combined extracts were dried (MgSO4)
5. concentrationconcentrated
6. customto give an orange oil that
7. concentrationConcentration