Br[C:2]1[CH:7]=[C:6]([Br:8])[CH:5]=[C:4]([Br:9])[CH:3]=1.[CH2:10]([O:17][C:18]1[CH:23]=[CH:22][C:21](B(O)O)=[CH:20][CH:19]=1)[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1>O.C1COCC1.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>[CH2:10]([O:17][C:18]1[CH:23]=[CH:22][C:21]([C:2]2[CH:7]=[C:6]([Br:8])[CH:5]=[C:4]([Br:9])[CH:3]=2)=[CH:20][CH:19]=1)[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=19.0 g (32 mmol) of sodium metaborate octahydrate and 1.3 g (1.82 mmol) of bis(triphenylphosphine)palladium(II) chloride are initially introduced in 200 ml of water and 40 ml of THF, a solution of 55 g (171 mmol) of 1,3,5-tribromobenzene in 80 ml of THF is added, and a solution of 10 g (45.5 mmol) of 4-benzyloxybenzeneboronic acid is added dropwise under reflux. The batch is heated under reflux for 16 h, added to water and extracted three times with MTB ether. The combined org. phases are washed with sat. sodium chloride soln. and dried over sodium sulfate. The solvent is removed in vacuo, and the residue is chromatographed on silica gel with heptane/ethyl acetate (19:1) and recrystallised from ethanol, giving 4′-benzyloxy-3,5-dibromobiphenyl as colourless crystals.
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