phenyl N-[(Z)-C-[(4-bromo-3-chlorophenyl)methyl]-N-hydroxycarbonimidoyl]carbamate → 3-(4-bromo-3-chlorobenzyl)-1,2,4-oxadiazol-5(4H)-one

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Reaction Steps

(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.

Provenance & Evidence