General procedure for the synthesis of ethyl 4-(3-bromo-4-formylphenoxy)benzoate from ethyl nipagin (ethyl 4-hydroxybenzoate) and 2-bromo-4-fluorobenzaldehyde: 2-bromo-4-fluorobenzaldehyde (10 g, 49.26 mmol) and ethyl 4-hydroxybenzoate (8.19 g, 49.26 mmol) were dissolved in N,N-dimethylformamide (DMF , 50 mL) in N,N-dimethylformamide (DMF). To this solution was added potassium carbonate (10.21 g, 73.89 mmol). The reaction mixture was stirred in an oil bath at 100 °C for 17 h under nitrogen protection. After completion of the reaction, it was cooled to room temperature and extracted by adding a mixture of ethyl acetate and water. After stirring for 30 minutes, the mixture was concentrated by rotary evaporator to remove most of the organic solvent. The resulting solid was filtered, washed with water and dried to afford the target compound ethyl 4-(3-bromo-4-formylphenoxy)benzoate (17 g, 98.8% yield) as a white solid.1H NMR (DMSO-d6, 300 MHz) δppm: 10.13 (s, 1H), 8.03 (d, 2H, J = 8.7Hz), 7.89 (d, 1H, J = 8.7Hz). J = 8.7Hz), 7.45 (m, 1H), 7.26 (d, 2H, J = 8.7Hz), 7.19 (m, 1H), 4.30 (q, 2H), 1.30 (t, 3H).
