C[O:2][C:3]1[CH:8]=[CH:7][C:6]([C:9]2[CH:14]=[C:13]([O:15]C)[CH:12]=[CH:11][C:10]=2[O:17]C)=[CH:5][N:4]=1.C([O-])(O)=O.[Na+]>Br.O>[OH:17][C:10]1[CH:11]=[CH:12][C:13]([OH:15])=[CH:14][C:9]=1[C:6]1[CH:7]=[CH:8][C:3](=[O:2])[NH:4][CH:5]=1A solution of 502 mg (2.05 mmol) of 2-methoxy-5-(2,5-dimethoxyphenyl)pyridine in 20 mL of 48% hydrobromic acid (aqueous) is refluxed for 6 hours, cooled to ca. 25° C. and diluted with 150 mL of water. The mixture is neutralized with solid NaHCO3, cooled to 0° C. and the resulting solid product collected by filtration. The solid is washed well with water, collected by centrifugation, then further purified by recrystalization in methanol to obtain 5-(2,5-dihydroxyphenyl)-2(1H)-pyridone m.p. 303°-306° C. dec).
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