Synthesis
General procedure for the synthesis of 4-amino-6-chloro-3-pyridinecarboxaldehyde from (4-amino-6-chloropyridin-3-yl)methanol: Compound 4 ((4-amino-6-chloropyridin-3-yl)methanol, 600 mg, 3.77 mmol) was dissolved in tetrahydrofuran (THF, 50 mL). Manganese dioxide (MnO2, 3.32 g, 37.7 mmol) was added all at once to this solution. The reaction mixture was stirred at room temperature for 5 h. The progress of the reaction was monitored by thin layer chromatography (TLC). After completion of the reaction, the solid manganese dioxide was removed by filtration. The filtrate was concentrated to give compound 5 (4-amino-6-chloro-3-pyridinecarboxaldehyde, 3.7 g, yield: 86.5%) as a white solid.
References
[1] Patent: WO2014/52365, 2014, A1. Location in patent: Page/Page column 180-181
[2] Patent: US2012/184562, 2012, A1. Location in patent: Page/Page column 21
[3] Patent: WO2013/134298, 2013, A1. Location in patent: Page/Page column 40
[4] Journal of Medicinal Chemistry, 2015, vol. 58, # 10, p. 4165 - 4179
[5] Patent: WO2015/120049, 2015, A1. Location in patent: Page/Page column 218
