[CH2:1]([O:3][C:4](=[O:18])[C:5]([C:10]([C:12]1[CH:16]=[C:15]([CH3:17])[O:14][N:13]=1)=O)=[CH:6][N:7](C)C)C.Cl.[C:20]([NH:24]N)([CH3:23])([CH3:22])[CH3:21].C([O-])(=O)C.[Na+]>C(O)C.O>[CH3:1][O:3][C:4]([C:5]1[CH:6]=[N:7][N:24]([C:20]([CH3:23])([CH3:22])[CH3:21])[C:10]=1[C:12]1[CH:16]=[C:15]([CH3:17])[O:14][N:13]=1)=[O:18]
A solution of 3-dimethylamino-2-(5-methyl-isoxazole-3-carbonyl)-acrylic acid ethyl ester (27.53 mmol) in absolute ethanol (41.7 mL) was treated with tert-butylhydrazine hydrochloride (3.57 g, 28.63 mmol) and sodium acetate (2.80 g, 34.13 mmol). The resulting mixture was heated to 90° C. for 18 h. At this time, the reaction was cooled to 25° C. The reaction was diluted with water (200 mL) and was then extracted with dichloromethane (3×150 mL). The combined organics were dried over sodium sulfate, filtered and concentrated in vacuo to afford 1-tert-butyl-5-(5-methyl-isoxazol-3-yl)-1H-pyrazole-4-carboxylic acid methyl ester (7.37 g, 96%) as a black solid. The material was used without further purification.
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