An aqueous 2N NaOH solution (5 mL) was slowly added dropwise to a stirred solution of methyl 6-chloro-3-methylpyridine-2-carboxylate (0.500 g, 2.702 mmol) in tetrahydrofuran (THF, 10 mL) at 0 °C. The reaction mixture was then warmed to 50 °C with continuous stirring for 2 hours. Upon completion of the reaction, the mixture was acidified to pH < 7 with aqueous citric acid and subsequently extracted with ethyl acetate (EtOAc, 2 × 10 mL). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford 6-chloro-3-methylpyridine-2-carboxylic acid as an off-white solid (0.45 g, 97% yield). The resulting product could be used in the subsequent reaction without further purification. Mass spectrometry (MS) analysis showed the molecular ion peak (m/z) of the target compound: 172.0 ([M+H]+).
