[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([C:8](=[O:18])[CH:9]([CH3:17])[C:10](=O)[C:11]([O:13][CH2:14][CH3:15])=[O:12])=[CH:4][CH:3]=1.Cl.[NH2:20]O>C(O)C>[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[O:18][N:20]=[C:10]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[C:9]=2[CH3:17])=[CH:4][CH:3]=1The lithium enolate of ethyl 4-(4-chlorophenyl)-3-methyl-2,4-dioxobutanoate (1.5 g, 5.5 mmol) and hydroxylamine hydrochloride (0.46 g, 6.6 mmol) in absolute ethanol (30 mL) were heated to reflux for 17 hours, cooled to room temperature, then cooled to 0° C. for 3 hours. The resulting white crystals were collected and dried under vacuum to obtain ethyl 5-(4-chlorophenyl)-4-methylisoxazole-3-carboxylate (0.55 g, 0.20 mmol).
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