ethyl 4-methyl-5-oxo-4H-1,2-oxazole-3-carboxylate

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Ethyl 4-methyl-5-oxo-4,5-dihydroisoxazole-3-carboxylate (42.5 g, 248 mmol) and phosphorous oxybromide (199 g, 695 mmol) were stirred together and heated to 80° C. Triethylamine (34.6 mL, 248 mmol) was added dropwise over 15 mins and the reaction mixture was stirred at 80° C. for 3 hours. The resulting mixture was cooled to room temperature. DCM (400 mL) was added and the mixture was poured into ice (˜400 mL) with stirring. 2M NaOH (aq) (1250 mL) was added until pH 7 and the resulting layers were separated. The aqueous layer was extracted with DCM (2×300 mL) and the resulting organic extracts were combined, washed with water (400 mL), sodium thiosulfate (5% w/v solution, 400 mL), water (400 mL) and brine (400 mL). The organics were dried over MgSO4 and charcoal, filtered and the solvent removed under reduced pressure. The crude material was adsorbed onto silica and purification by chromatography eluting with 0-30% EtOAc in iso-hexane afforded the title compound; The resulting mixture was cooled to room temperature with stirring the resulting layers were separated The aqueous layer was extracted with DCM (2×300 mL) washed with water (400 mL), sodium thiosulfate (5% w/v solution, 400 mL), water (400 mL) and brine (400 mL) The organics were dried over MgSO4 and charcoal filtered the solvent removed under reduced pressure The crude material was adsorbed onto silica and purification by chromatography eluting with 0-30% EtOAc in iso-hexane