C[O:2][C:3]1[CH:12]=[C:11]([O:13][CH3:14])[CH:10]=[C:9]2[C:4]=1[C:5](=[O:15])[NH:6][CH:7]=[N:8]2.[Mg+2].[Br-].[Br-]>N1C=CC=CC=1>[OH:2][C:3]1[CH:12]=[C:11]([O:13][CH3:14])[CH:10]=[C:9]2[C:4]=1[C:5](=[O:15])[NH:6][CH:7]=[N:8]2To a mixture of 5,7-dimethoxyquinazolin-4(3H)-one (4.80 g, 23.3 mmol) in pyridine (50 mL) at room temperature was slowly added MgBr2 (4.29 g, 23.3 mmol). It was heated to reflux for 1.5 hour. After solvent was evaporated under reduced pressure, to the residue was added a solution of AcOH (10 mL) in water (50 mL). A solid was precipitated. It was filtered, washed with water, and dried under vacuum with P2O5 to afford 5-hydroxy-7-methoxyquinazolin-4(3H)-one as solid (4.398 g, 98%). 1H NMR (300 MHz, DMSO-d6) δ 11.95 (br, 1H), 8.08 (s, 1H), 6.63 (s, 1H), 6.50 (s, 1H), 3.85 (s, 3H); LC-MS (ESI) m/z 193 (M+H)+.
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