反应详情

温度

-78 °C

(R)-8-Bromo-3-(N,N-dibenzylamino)-5-methoxy-3,4-dihydro-2H-1-benzopyran (4.35 g, 9.9 mmol) was dissolved in 45 mL of anhydrous THF and cooled to -78° C. To this was a 1.6M n-BuLi solution (6.8 mL, 10.9 mmol) added dropwise and the mixture was allowed to stir at -78° C. for 1 h. N-Fluorobenzenesulfonimide (3.8 g, 11.9 mmol), dissolved in 30 mL anhydrous THF, was added dropwise over 45 min and allowed to stir at -78° C. for 1 h. The reaction was stopped by adding 3 mL saturated NH4Cl followed by 9 mL of a solution comprised of 2 g of NH2OH×HCl and 8 g of Na2CO3 in 100 mL of H2O and allowing the reaction to warm to room temperature. A 2M NH3 solution was added and the reaction was extracted twice with ether, treated with brine, dried (Na2SO4), filtered, and evaporated in vacuo to give the crude product. Purification of the 8-fluoro (desired) from the 8-hydrogen (15 %) compound was carried out by a crude chromatography (eluent: 25% CH2Cl2 /hexane) to give 1.78 g. The crude product was rechromatographed on silica (eluent: 3% acetone/hexane) to give 1.50 g (40% yield) of the title compound as a clear oil. [α]21D =-112.1° (C=0.1, CHCl3). GC-MS (70 eV) M=377 (37%).

1. additionadded dropwise
2. additionwas added dropwise over 45 min
3. stirringto stir at -78° C. for 1 h
4. customthe reaction
5. temperatureto warm to room temperature
6. extractionthe reaction was extracted twice with ether
7. additiontreated with brine
8. dry with materialdried (Na2SO4)
9. filtrationfiltered
10. customevaporated in vacuo
11. customto give the crude product
12. customPurification of the 8-fluoro (desired) from the 8-hydrogen (15 %) compound
13. customto give 1.78 g
14. customThe crude product was rechromatographed on silica (eluent: 3% acetone/hexane)