反应详情

(Z)-Phenyl 2-(4-bromo-3-chlorophenyl)-1-(hydroxyimino)ethylcarbamate (Intermediate 23-2; 2 g, 5.21 mmol) was dissolved in anhydrous toluene (65.2 mL). The resulting solution was stirred at reflux for 16 hours. The cooled reaction mixture was evaporated to dryness and redissolved in DCM (50 mL) and extracted with saturated NaHCO3 (50 mL). The aqueous layer was acidified with 2M HCl and extracted with EtOAc (3×50 mL). The organic layers were combined and dried over MgSO4, filtered and evaporated to afford crude product. The crude product was purified by flash silica chromatography {CombiFlash Companion—Presearch Ltd}, column size=120 g, flow rate=85 mL/min, elution gradient 0 to 10% MeOH in DCM}. Pure fractions were evaporated to dryness to afford 3-(4-bromo-3-chlorobenzyl)-1,2,4-oxadiazol-5(4H)-one (1.240 g, 82%) as a colourless solid.

1. temperatureat reflux for 16 hours
2. customThe cooled reaction mixture
3. customwas evaporated to dryness
4. dissolutionredissolved in DCM (50 mL)
5. extractionextracted with saturated NaHCO3 (50 mL)
6. extractionextracted with EtOAc (3×50 mL)
7. dry with materialdried over MgSO4
8. filtrationfiltered
9. customevaporated
10. customto afford crude product
11. customThe crude product was purified by flash silica chromatography {CombiFlash Companion—Presearch Ltd}, column size=120 g, flow rate=85 mL/min, elution gradient 0 to 10% MeOH in DCM
12. customPure fractions were evaporated to dryness