5-Bromo-2-pyridinecarboxaldehyde was synthesized according to General Method C using 2,5-dibromopyridine and N,N-dimethylformamide (DMF) as raw materials. The specific operation was as follows: 2,5-dibromopyridine (237 mg, 1 mmol) was mixed with DMF (115 μL, 1.5 mmol) for the reaction. After completion of the reaction, the crude product was purified by fast column chromatography (eluent: hexane/ethyl acetate = 10:1) to afford the target compound 5-bromo-2-pyridinecarboxaldehyde (27b) as a brown solid (149 mg, 80% yield). Thin layer chromatography (TLC) analysis showed an Rf value of 0.45 (Expander: hexane/ethyl acetate = 8:1). Nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 400 MHz, CDCl3) data were as follows: δ 10.03 (1H, s), 8.85 (1H, dd, J = 0.8, 2.0 Hz), 8.02 (1H, ddd, J = 0.8, 2.0, 8.0 Hz), 7.85 (1H, dd, J = 0.8, 8.0 Hz). The nuclear magnetic resonance carbon spectrum (13C NMR, 100 MHz, CDCl3) data were as follows: δ 192.4, 151.7, 151.3, 140.0, 126.3, 122.8. The spectral data obtained were in agreement with literature reports.
