Boron trifluoride etherate → 3-Acetoxy-6-fluoropyridine

Temperatur

5 °C

A solution of 3-amino-6-fluoropyridine (5.0 g, 45 mmol, from Step 8c above) dissolved in DME (30 mL) was added to a cooled solution (-15° C.) of boron trifluoride etherate (12.2 mL, 99 mmol). tert-Butyl nitrite (6.3 mL, 54 mmol) was then added at a rate which maintained the temperature below 0° C. After 10 minutes at -10° C. the reaction was warmed to 5° C. and stirred for 30 min. Pentane (150 mL) was then added to the reaction mixture, and the resultant solid was collected by suction filtration, washed with cold ether, air dried, and dissolved in acetic anhydride (75 mL). The solution was heated to 105° C. until nitrogen evolution ceased. The solvent was removed in vacuo, and the residue was suspended in saturated aqueous Na2CO3 (200 mL) and extracted with ethyl ether (2×150 mL). The combined organic extracts were dried (MgSO4) and concentrated. Purification by chromatography (silica gel; hexane/EtOAc, 9:1 to 7:3) afforded the title compound (2.25 g, 33%): 1H NMR (CDCl3 300 MHz) δ 2.32 (s, 3H), 6.96 (d, J=3, 9 Hz, 1H), 7.59 (m, 1H), 8.03 (dd, J=0.5, 1 Hz, 1H); MS (CI/NH3) m/z 156 (M+H)+, 171 (M+NH4)+.

1. temperaturemaintained the temperature below 0° C
2. filtrationthe resultant solid was collected by suction filtration
3. washwashed with cold ether, air
4. customdried
5. dissolutiondissolved in acetic anhydride (75 mL)
6. temperatureThe solution was heated to 105° C. until nitrogen evolution
7. customThe solvent was removed in vacuo
8. extractionextracted with ethyl ether (2×150 mL)
9. dry with materialThe combined organic extracts were dried (MgSO4)
10. concentrationconcentrated
11. customPurification by chromatography (silica gel; hexane/EtOAc, 9:1 to 7:3)

ORD-Eintrag

ord-e8e9642b97c8461eb142aaa19421fc0f

Quelldatensatz

uspto-grants-2000_10

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US06133253