Synthesis
General procedure for the synthesis of 4-bromo-3-phenylpyridine from iodobenzene and 4-bromopyridine hydrochloride: 4-bromopyridine hydrochloride (1-BA-2, 1 g, 5.14 mmol) was dissolved in 5.1 mL of tetrahydrofuran (THF), and the resulting solution was cooled to -78 °C. Lithium diisopropylammonium (LDA, 10.28 mL of 1 M THF solution) was added slowly over 10 min and the reaction mixture changed color to brown. After stirring for 30 minutes, zinc chloride (ZnCl2, 10.3 mL of a 0.5 M THF solution) was added over 10 minutes and the resulting mixture was stirred for 10 minutes and then slowly warmed to room temperature. Subsequently, iodobenzene (0.229 mL, 2.06 mmol) and tetrakis(triphenylphosphine)palladium (Pd(PPh3)4, 593 mg, 0.514 mmol) were added, and the reaction mixture was stirred under reflux conditions for 2 hours. After completion of the reaction, the reaction mixture was diluted with saturated aqueous ammonium chloride solution and extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: hexane/ethyl acetate) to afford the target product 4-bromo-3-phenylpyridine (2-BA-2, 741 mg, 62% yield); LCMS detection showed the molecular ion peak m/z of 234.0 ([M+H]+).
References
[1] Patent: WO2011/79114, 2011, A1. Location in patent: Page/Page column 113; 114
[2] Synlett, 2002, # 5, p. 808 - 810
