反应详情

To a solution of (E)-N′-hydroxy-4-(trifluoromethoxy)benzimidamide (3.0 g, 13.6 mmol) and pyridine (1.6 g, 20.4 mmol) in CHCl3 (20 mL), ethyl 2-chloro-2-oxoacetate (2.2 g, 16.4 mmol) was added slowly at 0° C. The mixture was stirred at reflux for 3 h, and then concentrated to give the crude product, which was purified by silica gel column chromatography (Petroleum ether:EtOAc=10:1) to give ethyl 3-(4-(trifluoromethoxy)phenyl)-1,2,4-oxadiazole-5-carboxylate as a white solid (4.5 g, 82%). MS (ES+) C12H9F3N2O4 requires: 302 found: 303[M+H]+.

1. temperatureat reflux for 3 h
2. concentrationconcentrated
3. customto give the crude product, which
4. customwas purified by silica gel column chromatography (Petroleum ether:EtOAc=10:1)