Synthesis of 3-(3-thienyl)benzaldehyde (2a): 3.11 g (0.024 mol) of 3-thiopheneboronic acid was added to 80 mL of 1,2-dimethoxyethane solution containing 3 g (0.016 mol) of m-bromobenzaldehyde. Subsequently 5.15 g (0.048 mol) of aqueous 2N sodium carbonate solution and 0.56 g (4.9 x 10^-4 mol) of tetrakis(triphenylphosphine)palladium were added as catalyst. The reaction mixture was heated to reflux at 80 °C for 16 hours. After completion of the reaction, it was cooled to room temperature and the mixture was poured into water. The aqueous phase was extracted with ethyl acetate and the combined organic phases were washed with saturated aqueous sodium chloride solution. The organic phase was dried over anhydrous magnesium sulfate and filtered and concentrated under reduced pressure to remove the solvent. The product was purified by silica gel column chromatography with the eluent cyclohexane/ethyl acetate (90/10, v/v) to give 2.61 g of light yellow solid product in 86% yield. Melting point: 59 °C. 1H NMR (CDCl3) δ: 7.46 (s, 2H), 7.53-7.59 (m, 2H), 7.79 (d, J = 7.68 Hz, 1H), 7.86 (d, J = 8.88 Hz, 1H).
