[C:1](Cl)(=[O:8])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[NH2:10][C:11](=[N:17]O)[C:12]([O:14][CH2:15][CH3:16])=[O:13].C(N(CC)C(C)C)(C)C.O>ClCCl>[C:2]1([C:1]2[O:8][N:17]=[C:11]([C:12]([O:14][CH2:15][CH3:16])=[O:13])[N:10]=2)[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1Benzoyl chloride (0.219 mL; 1.89 mmol) was added to a mixture of ethyl 2-amino-2-(hydroxyimino)acetate (0.250 g; 1.89 mmol) and N,N diisopropylethylamine (0.527 mL; 3.03 mmol) in dichloromethane (18 mL) at −15° C. The reaction mixture was stirred at room temperature overnight and poured into a mixture of ice and water. The aqueous layer was extracted with dichloromethane, and the combined organic extracts were dried and concentrated under reduced pressure. The residue was refluxed in a sealed tube with pyridine (6 mL) for 20 hours and concentrated under reduced pressure. The crude material was purified by flash chromatography on silica (eluent 20 to 100% ethyl acetate in heptane) to yield 0.239 (60%) of ethyl 5-phenyl-1,2,4-oxadiazole-3-carboxylate as a yellow solid.
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