Synthesis
A suspension of 2-bromo-4-methyl-5-nitropyridine (XIV) (200 g, 921 mmol, 1.00 eq.) was formed with NH4Cl (240 g, 4.49 mol, 4.87 eq.) in EtOH (3.50 L) and water (150 mL). The mixture was heated to 50 °C with stirring. Subsequently, Fe (120 g, 2.15 mol, 2.33 eq.) and HCl (10.2 g, 279 mmol, 0.30 eq.) were added to the mixture. The suspension was heated to 80 °C and kept for 3 hours. After completion of the reaction, the mixture was cooled to 25 °C and filtered through a diatomaceous earth plug. The filtrate was concentrated under reduced pressure to give a residue. The residue was dissolved in EtOAc (1L x 3) and washed with brine. The organic layer was dried with sodium sulfate, filtered and concentrated under reduced pressure to give 6-bromo-4-methylpyridin-3-amine (XV) as a brown solid (167.9 g, 898 mmol, 97.4% yield), which could be used for the next reaction without further purification.1H NMR (CDCl3,400 MHz) δ ppm 2.15 (s, 3H), 3.44 (br s 2H), 7.14 (s, 1H), 7.78 (s, 1H); ESIMS m/z 186.8 ([M + H]+).
References
[1] Patent: WO2017/23975, 2017, A1. Location in patent: Paragraph 0610; 0611
[2] Patent: WO2017/24026, 2017, A1. Location in patent: Paragraph 0614; 0615
[3] Bioorganic and Medicinal Chemistry Letters, 2016, vol. 26, # 15, p. 3441 - 3446
[4] Bioorganic and Medicinal Chemistry Letters, 2015, vol. 25, # 22, p. 5258 - 5264
[5] Bioorganic and Medicinal Chemistry, 2007, vol. 15, # 6, p. 2441 - 2452
