GENERAL STEPS: 2,4,6-Trichloropyridine (5 g, 27.4 mmol) was dissolved in anhydrous THF (100 ml) and the solution was cooled to -78 °C. N-butyllithium (22.27 ml, 28.8 mmol, 1.6 M hexane solution) was slowly added at -78 °C and stirred for 30 min. Subsequently, ethyl formate (10.15 g, 137 mmol) was added, ensuring that the internal temperature was maintained below -74 °C. The reaction mixture was stirred continuously at -78 °C until the feedstock was completely consumed (9:1 unfolding agent ratio of heptane/EtOAc monitored by TLC). Upon completion of the reaction, the reaction was quenched with saturated ammonium chloride solution (50 ml) and 0.5 N HCl solution at -78 °C. The mixture was warmed to room temperature and extracted with EtOAc. The organic phase was washed with brine, dried over MgSO4 and concentrated. The crude product (light yellow solid) was purified by rapid chromatography on silica gel with 0-20% EtOAc/heptane as eluent to give 5.1 g (88% yield) of the target product 2,4,6-trichloronicotinaldehyde as a white solid.1H NMR (400 MHz, chloroform-d3) δppm= 10.42 (s, 1H), 7.45 (s, 1H).
