反应详情

Methanesulfonic acid 3-[4-((R)-2,2-dimethyl[1,3]dioxolan-4-ylmethoxy)-phenyl]-propylester (11.8 g, 34.2 mmol) in acetone (200 ml) is treated with lithium bromide (8.9 g, 100 mmol) and then heated at reflux for 5 h. After cooling to room temperature, the mixture is concentrated in vacuo. The resulting residue is dissolved in EtOAc (150 ml), washed with water (2×50 ml), brine, dried (MgSO4), filtered and concentrated in vacuo to give an oil. Purification by chromatography on silica eluting with 4:1 iso-hexane/EtOAc gives (R)-4-[4-(3-Bromo-propyl)-phenoxymethyl]-2,2-dimethyl-[1,3]dioxolane as a colourless oil which solidifies; 1H NMR (CDCl3): 1.39 (3H, s), 1.43 (3H, s), 2.02 (2H, pent, J=6.9 Hz), 2.63 (2H, tr, J=6.9 Hz), 3.38 (2H, tr, J=6.9 Hz), 3.90 (2H, m), 4.02 (1H, m), 4.15 (1H, m), 4.46 (1H, pent, J=6.9 Hz), 6.82 (2H, d, J=7.4 Hz), 7.10 (2H, d, J=7.4 Hz).

1. temperatureheated
2. temperatureat reflux for 5 h
3. concentrationthe mixture is concentrated in vacuo
4. dissolutionThe resulting residue is dissolved in EtOAc (150 ml)
5. washwashed with water (2×50 ml), brine
6. dry with materialdried (MgSO4)
7. filtrationfiltered
8. concentrationconcentrated in vacuo
9. customto give an oil
10. customPurification by chromatography on silica eluting with 4:1 iso-hexane/EtOAc