Реакция #1455199

Уравнение реакции

7-Chloro-2-ethyl-5-fluoro-4-nitrobenzoxazole

7-Chloro-2-ethyl-5-fluorobenzoxazole

sulfuric acid

nitric acid

→

7-chloro-2-ethyl-5-fluoro-6-nitrobenzoxazole

desired product

4-Amino-7-chloro-2-ethyl-5-fluorobenzoxazole

Условия реакции

Обработка

1. 1
   ДругоеThe dryice-acetone bath was removed
2. 2
   workup.ADDITIONIce-water was added
3. 3
   Экстракцияthe mixture was extracted with ether
4. 4
   СушкаThe organic phase was dried over anhydrous sodium sulfate
5. 5
   Концентрированиеconcentrated to an oil under reduced pressure
6. 6
   ДругоеThe residue was purified by column chromatography on silica gel using 5% ether in hexane

Методика

Step 4 Preparation of 7-Chloro-2-ethyl-5-fluoro-4-nitrobenzoxazole as an Intermediate 7-Chloro-2-ethyl-5-fluorobenzoxazole (0.9 g) was slowly added to a mixture of sulfuric acid (9 ml) and nitric acid (0.6 ml) at −40° C. The dryice-acetone bath was removed and the mixture stirred for 2 hours. Ice-water was added and the mixture was extracted with ether. The organic phase was dried over anhydrous sodium sulfate and concentrated to an oil under reduced pressure. The residue was purified by column chromatography on silica gel using 5% ether in hexane. The desired product was obtained as a white solid [0.35 g, 1H-NMR (CDCl3, 300 MHz): 1.48(3H, t, J=7.6 Hz), 3.07(2H, q, J=7.6 Hz), 7.27(1H, d, J=10.5 Hz) ppm], along with a by-product, 7-chloro-2-ethyl-5-fluoro-6-nitrobenzoxazole (0.49 g).

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