Br[C:2]1[CH:3]=[CH:4][C:5]([CH2:10][CH3:11])=[C:6]([CH:9]=1)[CH:7]=[O:8].[Cl:12][C:13]1[CH:18]=[C:17]([Cl:19])[CH:16]=[CH:15][C:14]=1B(O)O.C(=O)([O-])[O-].[Na+].[Na+]>C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.Cl[Pd]Cl.[Fe+2].COCCOC>[Cl:12][C:13]1[CH:18]=[C:17]([Cl:19])[CH:16]=[CH:15][C:14]=1[C:2]1[CH:3]=[CH:4][C:5]([CH2:10][CH3:11])=[C:6]([CH:7]=[O:8])[CH:9]=1
A suspension of 5-bromo-2-ethylbenzaldehyde (1.0 g, 4.7 mmol), 2,4-dichlorophenyl boronic acid (1.34 g, 7.0 mmol) and sodium carbonate (0.99 g, 7.98 mmol) in a mixed solvent system of 1,2-dimethoxyethane (12 ml) and distilled water (4 ml) is stirred under a nitrogen atmosphere, then flushed with nitrogen (×2). [1,1′-Bis(diphenylphosphino)ferrocene]palladium(II)chloride (1.15 g, 1.41 mmol) is then added in one portion and the suspension is again flushed with nitrogen, then heated at reflux overnight. After cooling to room temperature the reaction mixture is diluted with distilled water (10 ml) and extracted with dichloromethane (10 ml). The aqueous phase is extracted again with dichloromethane (×2), and the combined organic fractions are finally washed with brine then dried over magnesium sulfate. The crude product is purified by flash column chromatography (isohexane to 75:25 isohexane/ethyl acetate ratio eluant) to afford 2′,4′-dichloro-4-ethylbiphenyl-3-carbaldehyde as a yellow oil.
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