General procedure for the synthesis of methyl 2,6-dichloronicotinate from methanol and 2,6-dichloronicotinic acid: to a solution of 2,6-dichloronicotinic acid (5.0 g, 26 mmol) in methanol (100 mL) was slowly added thionyl chloride (0.1 mL). The reaction mixture was heated to reflux and kept reacting overnight. Upon completion of the reaction, the solvent was removed by rotary evaporator. The residue was dissolved in ethyl acetate and washed sequentially with saturated sodium bicarbonate solution and saturated sodium chloride solution. The organic phase was dried with anhydrous sodium sulfate, filtered and concentrated to give methyl 2,6-dichloronicotinate (5.37 g, 100% yield) as a white solid.1H NMR (300 MHz, CDCl3) δ 8.13 (d, J=8.1 Hz, 1H), 7.33 (d, J=8.1 Hz, 1H), 3.94 (s, 3H).
