反应详情

温度

0 °C

Intermediate (1u) (0.25 g, 1.03 mmol) and NH4BF4 (0.22 g, 2.06 mmol) were dissolved in 10 mL of mixed solvent of AcOH/water (2:1) and cooled to 0° C., and followed by addition of concentrated HCl (0.43 mL, 5.16 mmol) and NaNO2 (0.078 g, 1.13 mmol) to the solution at 0° C. The color of the solution immediately turned into yellow as sodium nitrate was added. The reaction mixture was then allowed to warm to room temperature. After stirring 2 hours, the solvent was removed under reduced pressure and azeotroped with toluene three times to removed the water, to give a pale yellow crude solid. The solid was dissolved in 10 mL of EtOAc and KOAc was added to the solution. The color of suspension turned into deep orange in 30 minutes and then stirred an additional hour. The white inorganic salt was removed by filtration and washed with EtOAc. The combined filtrate was diluted with EtOAc to 100 mL of total volume and transferred to a separatory funnel, washed with sat. NaHCO3 (10 mL) and brine, dried over MgSO4, filtered and evaporated to obtain a deep orange colored solid. The crude solid was purified on silica gel with EtOAc/hexane (2:3) to afford an orange yellow colored solid (2u) (0.23 g, 88% yield over 2 steps). 1H NMR (400 MHz, CDCl3) δ 8.65 (s, 1H), 8.15 (s, 1H), 7.30-7.34 (m, 2H), 7.32-7.22 (m, 2H), 7.12 (dd, J=9.4, 4.7 Hz, 1H) ppm.

1. additionwas added
2. temperatureto warm to room temperature
3. customthe solvent was removed under reduced pressure
4. customazeotroped with toluene three times
5. customto removed the water
6. customto give a pale yellow crude solid
7. customdeep orange in 30 minutes
8. stirringstirred an additional hour
9. customThe white inorganic salt was removed by filtration
10. washwashed with EtOAc
11. additionThe combined filtrate was diluted with EtOAc to 100 mL of total volume
12. customtransferred to a separatory funnel
13. washwashed with sat. NaHCO3 (10 mL) and brine
14. dry with materialdried over MgSO4
15. filtrationfiltered
16. customevaporated
17. customto obtain a deep orange colored solid
18. customThe crude solid was purified on silica gel with EtOAc/hexane (2:3)