67-56-1

100-26-5

881-86-7

Oxalyl chloride (60.96 g, 480 mmol) was slowly added dropwise over 20 min to a suspension of 2,5-pyridinedicarboxylic acid (20 g, 120 mmol) in dichloromethane (396 mL) and N,N-dimethylformamide (DMF, 6.6 mL). The reaction mixture was stirred at room temperature for 16 h. The reaction mixture was concentrated under reduced pressure by rotary evaporator and the residue was azeotroped with toluene to remove residual water. The residue was dissolved in methanol (276 mL) pre-cooled to 0 °C and stirred for 15 min. Upon completion of the reaction, the solution was concentrated under reduced pressure and the residue was dissolved in ethyl acetate. The organic phase was washed sequentially with saturated aqueous sodium bicarbonate solution, deionized water and saturated brine. Some of the product was collected as a white precipitate. The organic phase was separated, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give methyl 2,5-pyridinedicarboxylate as a white solid (Yield: 22.93 g, 98% yield). It was analyzed by liquid chromatography-mass spectrometry (LCMS, Method B) with a retention time (R t) of 2.48 min and a molecular ion peak [M + H] + = 196.