[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8](=O)[CH2:9][C:10](=[O:22])[CH2:11][C:12]2[CH:17]=[CH:16][C:15]([O:18][CH3:19])=[C:14]([O:20][CH3:21])[CH:13]=2)=[CH:4][CH:3]=1.O>P(=O)(O)(O)O>[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[C:17]3[C:12](=[CH:13][C:14]([O:20][CH3:21])=[C:15]([O:18][CH3:19])[CH:16]=3)[CH:11]=[C:10]([OH:22])[CH:9]=2)=[CH:4][CH:3]=11-(4-Bromophenyl)-4-(3,4-dimethoxyphenyl)butane-1,3-dione (3 g, 8 mmol) in 85% phosphoric acid was heated at 70° C. for 20 h. The resulting solution was cooled, poured into water (150 ml) and filtered. The residue was dissolved in dichloromethane (50 ml), washed with water (50 ml), dried (MgSO4) and the solvent was removed under reduced pressure to give the title compound (2.56 g, 90%) as a brown powder.
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