O[C:2]1[N:6]([C:7]2[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=2)[N:5]=[C:4]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[CH:3]=1.O(Br)[Br:19].[P].CN([CH:25]=[O:26])C>ClCCCl>[Br:19][C:2]1[N:6]([C:7]2[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=2)[N:5]=[C:4]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:3]=1[CH:25]=[O:26]To a solution of ethyl 5-hydroxy-1-phenyl-1H-pyrazole-3-carboxylate (6.47 g, 27.52 mmol) in DCE (70 mL) is added phosphorus oxy bromide (13.86 g, 48.16 mmol) and DMF (4 mL, 51.46 mmol). The reaction mixture is refluxed at 90° C. for 3 h. Phosphorus oxy bromide (34.8 g, 121.38 mmol) is added again and the reaction mixture is refluxed at 90° C. for 20 h. The reaction mixture is poured over ice and extracted with DCM twice. The organic layer is dried over Na2SO4 and concentrated. The crude is purified by column chromatography to afford the title compound. 1H NMR (DMSO-d6, 400 MHz): δ 10.30 (s, 1H), 7.63-7.61 (m, 5H), 4.38 (q, J=3.6 Hz, 2H), 1.32 (t, J=7.1 Hz, 3H). MS (ESI+): 325.0, HPLC (max plot) 97.37%, Rt 4.42 min.
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