Cl.[NH2:2]O.[C:4]([C:8]1[CH:13]=[CH:12][C:11]([C:14](=[O:23])[CH2:15][C:16](=O)[C:17]([O:19][CH2:20][CH3:21])=[O:18])=[CH:10][CH:9]=1)([CH3:7])([CH3:6])[CH3:5]>C(O)C>[C:4]([C:8]1[CH:13]=[CH:12][C:11]([C:14]2[O:23][N:2]=[C:16]([C:17]([O:19][CH2:20][CH3:21])=[O:18])[CH:15]=2)=[CH:10][CH:9]=1)([CH3:7])([CH3:6])[CH3:5]Hydroxylamine hydrochloride (6.14 g, 88.0 mmol) was added to a suspension of ethyl 4-(4-tert-butylphenyl)-2,4-dioxobutanoate (20.4 g, 73.7 mmol) in absolute ethanol (300 mL) and the reaction was heated to reflux for 3 hours. After cooling to room temperature, the organics were removed in vacuo and the resulting residue was purified by silica gel chromatography, eluting with heptane to 10% methanol in dichloromethane, to obtain afford the title compound white solid was filtered, washed with water and cold ethanol and dried in vacuo to obtain ethyl 5-(4-tert-butylphenyl)isoxazole-3-carboxylate (15.9 g, 58.0 mmol).
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