Methyl iodide → Methyl 2,4-dichloropyridine-3-carboxylate

To a solution of 2,4-dichloronicotinic acid (500 mg, 2.60 mmol) in acetonitrile (10 mL) cooled to 0° C. was added DBU (0.981 mL, 6.51 mmol) followed by methyl iodide (0.814 mL, 13.0 mmol). The reaction mixture was stirred at RT overnight (14 h). After the reaction completion, the solvent was removed under reduced pressure. The residue was taken up in ethyl acetate (10 mL) and washed with water (1×5 mL), dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (EtOAc-hexane) to afford methyl 2,4-dichloronicotinate (260 mg, 1.262 mmol, 49% yield) as pale yellow oil. LC/MS, (ESI) m/z 206.1 [(M+H)+, calcd for C7H6Cl2NO2 205.97]; LC/MS retention time (method D): tR=0.85 min. 1H NMR (300 MHz, CD3OD) δ ppm 8.42 (d, J=5.4 Hz, 1H), 7.59 (d, J=5.4 Hz, 1H), 3.99 (s, 3H).