Synthesis
The general procedure for the synthesis of pyridine 4-bromo-2,6-dicarboxylic acid methyl ester from 4-oxo-1,4-dihydro-2,6-pyridinedicarboxylic acid was as follows: compound 1 was prepared by a modified method from literature [29]. Tribenzoic acid monohydrate (2.20 g, 10.9 mmol) and phosphorus pentabromide (23.4 g, 54.3 mmol, 5 eq.) were heated to 90 °C under nitrogen protection and the reaction was maintained for 2 hours. Upon completion of the reaction, the dark red melt was cooled to room temperature and dissolved by addition of chloroform (25 mL). The reaction mixture was filtered and the filtrate was cooled in an ice bath (0 °C) and methanol (90 mL) was added slowly to promote crystallization. Crystallization was induced by scraping and the resulting crystalline solid was collected by vacuum filtration and dried under vacuum to afford compound 1 as a white crystalline solid (2.82 g, 86% yield).1H NMR (300 MHz, CDCl3) δ 8.45 (s, 2H), 4.02 (s, 6H).
References
[1] Journal of Inorganic Biochemistry, 2016, vol. 162, p. 253 - 262
[2] Organic Letters, 2011, vol. 13, # 3, p. 442 - 445
[3] Chemical Communications, 2012, vol. 48, # 80, p. 10025 - 10027
[4] Chemical Communications, 2014, vol. 50, # 68, p. 9665 - 9668
[5] Dalton Transactions, 2017, vol. 46, # 16, p. 5229 - 5239
