A toluene/Water (175 mL+25 mL) mixture was degassed with nitrogen for 30 minutes. Cesium carbonate (14.9 g, 43.55 mmol) was added followed by 4-bromo-2,3,5,6-tetrafluoro-benzoic acid methyl ester (5.0 g, 17.42 mmol), 4-formyl boronic acid (3.4 g, 22.64 mmol) and dichlorobis(triphenylphosphine)-palladium(II) catalyst (0.611 g, 0.87 mmol). The reaction mixture was refluxed for 15 h. TLC shows completion of the reaction. The reaction mixture was cooled to room temperature and was extracted with ethyl acetate. The combined organic layers were dried over sodium sulphate and concentrated. The obtained residue was purified by column chromatography using 5% ethyl acetate in hexane to get colorless solid (3.0 g, 55.24%).
