Reaktion #7791

Reaktionsgleichung

p-toluenesulfonic acid

4-fluoro-3-nitrobenzoic acid

thionyl chloride

2-aminophenol

diisopropylethylamine

→

2-(4-fluoro-3-nitrophenyl)-1,3-benzoxazole

Lösungsmittel

toluene

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturwas refluxed for 3 h
2. 2
   SonstigeThe excess thionyl chloride was removed
3. 3
   workup.DISSOLUTIONthe residue dissolved in 10 mL of THF
4. 4
   workup.ADDITIONwas added to
5. 5
   TemperaturThe resulting mixture was refluxed for 4 h
6. 6
   Temperaturcooled to rt
7. 7
   SonstigeThe solvent was removed
8. 8
   Sonstigeto afford a dark mixture that
9. 9
   Temperaturwas refluxed overnight
10. 10
    SonstigeThe solvent was removed
11. 11
    Sonstigethe crude was purified by flash chromatography on silica gel eluting with hexanes:CH2Cl2 (1:5)

Vorschrift

A mixture of 4-fluoro-3-nitrobenzoic acid (2.1 g, 11.3 mmol) and thionyl chloride (20 mL) was refluxed for 3 h and then cooled to rt. The excess thionyl chloride was removed and the residue dissolved in 10 mL of THF was added to a cooled (0° C.) solution of 2-aminophenol (1.24 g, 11.3 mmol) and diisopropylethylamine (2.4 mL, 13.6 mmol) in anhydrous THF (20 mL). The resulting mixture was refluxed for 4 h and then cooled to rt. The solvent was removed and p-toluenesulfonic acid (8.63 g, 45.4 mmol) and toluene (50 mL) were added to afford a dark mixture that was refluxed overnight. The solvent was removed and the crude was purified by flash chromatography on silica gel eluting with hexanes:CH2Cl2 (1:5) to afford 2-(4-fluoro-3-nitrophenyl)-1,3-benzoxazole as a colorless solid.

Quelle