[CH3:1][O:2][C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][C:4]=1B(O)O.[Br:12][C:13]1[CH:14]=[CH:15][CH:16]=[C:17](Br)[CH:18]=1.C(=O)(O)[O-].[Na+]>COCCOC.O.Cl[Pd](Cl)([P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[P](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1>[Br:12][C:13]1[CH:18]=[C:17]([C:4]2[CH:5]=[CH:6][CH:7]=[CH:8][C:3]=2[O:2][CH3:1])[CH:16]=[CH:15][CH:14]=1
A mixture of 2-methoxyphenylboronic acid (4.3 g, 28.3 mmol), 3,5-dibromobenzene (20 g, 85.5 mmol, 3 equiv.) and bis(triphenylphosphine)palladium(II) dichloride (100 mg) in ethyleneglycol dimethylether (25 mL) and a solution of sodium bicarbonate (8.2 g, 0.098 mol) in water (140 mL) were kept at reflux under nitrogen with good stirring overnight. After cooling, the reaction mixture was partitioned between ethyl acetate (600 mL) and water (300 mL). The organic phase was washed with water (2×300 mL), dried over sodium sulfate and filtered. The solvent was removed in vacuo and the crude product was purified by chromatography on silica (150 g) with heptane (6 L) to afford pure 21 (14.2 g, 58%).
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