Synthesis
2,3-Pyridinedicarboxylic acid (80 g, 0.48 mol) was dissolved in methanol (400 ml) and stirred at room temperature for 30 minutes. Concentrated sulfuric acid (94.1 g, 0.96 mol) was then added slowly dropwise for about 1 hour. The reaction mixture was heated to 60°C and the reaction was stirred overnight. After completion of the reaction, methanol was removed by distillation under reduced pressure. The concentrate was slowly poured into aqueous sodium carbonate solution during which a large amount of gas was produced. The pH was adjusted to 7-8 and extracted with dichloromethane (1000 ml × 2). The organic phase was dried with anhydrous sodium sulfate and concentrated under reduced pressure to give dimethyl 2,3-pyridinedicarboxylate as a pale yellow solid (89.7 g, 99% purity, 95.8% yield).
References
[1] Patent: CN105566319, 2016, A. Location in patent: Paragraph 0185; 0186; 0187; 0188
[2] Australian Journal of Chemistry, 1984, vol. 37, # 1, p. 87 - 94
[3] Patent: EP3252059, 2017, A1. Location in patent: Paragraph 0686; 0686-0688
[4] European Journal of Medicinal Chemistry, 2018, vol. 157, p. 397 - 404
[5] Bioorganic and Medicinal Chemistry, 2003, vol. 11, # 3, p. 433 - 450
