Reaktion #7792

Reaktionsgleichung

tert-butylcyanoacetate

HCl

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

K2CO3

p-toluenesulfonic acid

→

[4-(1,3-benzoxazol-2-yl)-2-nitrophenyl]acetonitrile

Lösungsmittel

H2O

H2O

DMSO

toluene

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe dark red mixture was heated to 65° C. for 30 min
2. 2
   Temperaturcooled to rt
3. 3
   Extraktionwas extracted with EtOAc (3×)
4. 4
   Waschenwashed with brine (2×)
5. 5
   Trocknendried over Na2SO4
6. 6
   Sonstigeevaporated to dryness
7. 7
   Temperaturthe mixture was refluxed for 20 h
8. 8
   TemperaturAfter cooling to rt
9. 9
   Sonstigethe two layers were separated
10. 10
    ExtraktionThe aqueous was extracted with EtOAc (3×)
11. 11
    Trocknendried over Na2SO4
12. 12
    Sonstigeevaporated to dryness
13. 13
    SonstigePurification of the residue by flash chromatography on silica gel eluting with EtOAc:hexanes (3:7 to 2:3 to 1:1)

Vorschrift

2-(4-fluoro-3-nitrophenyl)-1,3-benzoxazole (200 mg, 0.77 mmol) was dissolved in DMSO (5 mL) and K2CO3 (267 mg, 1.94 mmol) was added. The resulting yellow mixture was warmed to 65° C. and tert-butylcyanoacetate (137 mg, 0.97 mmol) was added dropwise. The dark red mixture was heated to 65° C. for 30 min, cooled to rt, and poured into H2O. The aqueous layer was acidified to pH 3 (with a 10% aqueous HCl solution) and it was extracted with EtOAc (3×). The organics were combined, washed with brine (2×), dried over Na2SO4, and evaporated to dryness. The yellow residue and p-toluenesulfonic acid (29.5 mg, 0.15 mmol) were dissolved in toluene (15 mL) and the mixture was refluxed for 20 h. After cooling to rt, the mixture was poured in H2O and the two layers were separated. The aqueous was extracted with EtOAc (3×), the organics were combined, dried over Na2SO4, and evaporated to dryness. Purification of the residue by flash chromatography on silica gel eluting with EtOAc:hexanes (3:7 to 2:3 to 1:1) afforded the desired [4-(1,3-benzoxazol-2-yl)-2-nitrophenyl]acetonitrile as an orange solid (M.p. 203° C.). 1H NMR (CDCl3, 300 MHz) δ 8.79 (s, 1H), 8.57 (dd, 1H), 7.97 (d, 1H), 7.86 (m, 2H), 7.54–7.44 (m, 2H), 4.50 (s, 2H). MS (ESI) 280 (M+H)+.

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