[Br:1][C:2]1[C:3]([OH:13])=[C:4]([CH:7]=[C:8]([Br:12])[C:9]=1[O:10][CH3:11])[CH:5]=O.C(=O)([O-])[O-].[K+].[K+].Br[CH2:21][C:22]([O:24][CH2:25][CH3:26])=[O:23]>CN(C=O)C>[Br:12][C:8]1[C:9]([O:10][CH3:11])=[C:2]([Br:1])[C:3]2[O:13][C:21]([C:22]([O:24][CH2:25][CH3:26])=[O:23])=[CH:5][C:4]=2[CH:7]=116 g (51,6 mmol) of 3,5-dibromo-2-hydroxy-4-methoxybenzaldehyde (Biorg. Med. Chem. 1998, 6, 1153–1162) and 17.84 g (129 mmol) of potassium carbonate are initially introduced in DMF and 8.62 g (51.6 mmol) of ethyl bromoacetate are then added dropwise to the mixture. The latter is stirred at 80° C. for 6 hours and then poured onto ice water after having been cooled; the precipitate is filtered off with suction. The precipitate is washed with water and dried. 15.47 g (79%) of ethyl 5,7-dibromo-6-methoxy-1-benzofuran-2-carboxylate are obtained.
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