To a stirred solution of 5-bromopyrimidine (1 eq.), 4-formylphenylboronic acid (1.3-3.0 eq.), and sodium carbonate monohydrate (1.3-3.0 eq.) in a mixed solvent of dimethoxyethane/water (4:1, v/v) (concentration of about 0.05-0.2 M) was added tetrakis(triphenylphosphine)palladium (Pd(PPh3)4, 0.1 eq.). The reaction mixture was stirred at 90 °C for about 18 h and subsequently quenched with water. The mixture was extracted with dichloromethane (CH2Cl2) according to standard post-treatment steps and the organic layer was dried over anhydrous sodium sulfate (Na2SO4) or anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. The crude product was purified by fast column chromatography or silica gel radial chromatography. According to the above general method, 4-(5-pyrimidinyl)benzaldehyde (162 mg, 99% yield) was obtained from 5-bromopyrimidine (199 mg, 1.25 mmol) and 4-formylphenylboronic acid (469 mg, 3.13 mmol).
