C[O:2][C:3]1[CH:4]=[C:5]([C:9]2[N:13]3[CH:14]=[CH:15][C:16]([CH3:18])=[N:17][C:12]3=[N:11][CH:10]=2)[CH:6]=[CH:7][CH:8]=1.[OH-].[Na+]>Br.C(O)(=O)C>[CH3:18][C:16]1[CH:15]=[CH:14][N:13]2[C:9]([C:5]3[CH:4]=[C:3]([OH:2])[CH:8]=[CH:7][CH:6]=3)=[CH:10][N:11]=[C:12]2[N:17]=1A mixture of 3-(3-methoxyphenyl)-7-methylimidazo[1,2-a]pyrimidine (5.02 g, 21 mmol) in hydrogen bromide (25 ml of a 30 wt. % solution in acetic acid) was heated at 130° C. for 8 h. A further portion of hydrogen bromide solution was added (25 ml) and heating continued for 16 h. The reaction was cooled to ambient temperature and diluted with ice-cold water (200 ml). The aqueous phase was made neutral with 4N sodium hydroxide then extracted with dichloromethane (2×250 ml). The organics were combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and evaporated to dryness. The residue was triturated with ether to afford 3-(7-methylimidazo[1,2-a]pyrimidin-3-yl)-phenol as a light-grey solid (4.4 g, 93%): m/z (ES+) 226 (M++H).
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