[CH3:1][N:2]1[C:7](=[O:8])[C:6]([C:9]2[CH2:13][CH:12]([C:14]3[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=3)[O:11][N:10]=2)=[CH:5][C:4]([C:20]([O:22]C)=[O:21])=[N:3]1.[OH-].[Li+]>CO.C1COCC1.O>[CH3:1][N:2]1[C:7](=[O:8])[C:6]([C:9]2[CH2:13][CH:12]([C:14]3[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=3)[O:11][N:10]=2)=[CH:5][C:4]([C:20]([OH:22])=[O:21])=[N:3]1
To a solution of methyl 1-methyl-6-oxo-5-(5-phenyl-4,5-dihydroisoxazol-3-yl)-1,6-dihydropyridazine-3-carboxylate (200 mg, 0.638 mmol, Preparation #33) in a mixture of methanol (2 mL) and THF (4 mL) was added lithium hydroxide (30.6 mg, 1.277 mmol, Spectrochem) dissolved in water (2 mL). The reaction mixture was stirred at RT for about 3 h. The reaction mixture was concentrated under vacuum and dissolved in water (10 mL). Further it was acidified to pH 2 with 2N HCl and the solids obtained were collected by filtration to afford 1-methyl-6-oxo-5-(5-phenyl-4,5-dihydroisoxazol-3-yl)-1,6-dihydropyridazine-3-carboxylic acid 0.150 g (79%) as light brown solids. 1H NMR (400 MHz, DMSO) δ 13.8 (br s, 1H), 8.122 (s, 1H), 7.405-7.331 (m, 5H), 5.806-5.757 (m, 1H), 3.958-3.886 (m, 1H) 3.762 (s, 3H), 3.506-3.441 (m, 1H). MS m/z: 298.0 (M−H)−
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