反応 #1455199

反応方程式

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

反応条件

後処理

1. 1
   その他The dryice-acetone bath was removed
2. 2
   workup.ADDITIONIce-water was added
3. 3
   抽出the mixture was extracted with ether
4. 4
   乾燥The organic phase was dried over anhydrous sodium sulfate
5. 5
   濃縮concentrated to an oil under reduced pressure
6. 6
   その他The residue was purified by column chromatography on silica gel using 5% ether in hexane

実験手順

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).

出典