Synthesis
Step 1. Synthesis of 3-bromo-5-nitropyridin-4-ol
To a suspension of 4-hydroxy-3-nitropyridine (7.00 g, 50 mmol) in water (50 mL), bromine (3.23 mL, 63 mmol) was added slowly and dropwise at room temperature. The reaction mixture was stirred at room temperature for 1 hour, followed by heating to 50 °C and maintained for 2 hours. Upon completion of the reaction, the mixture was cooled to room temperature and stirring was continued for 1 hour. The solid product was collected by filtration, washed well with water and dried under vacuum for 2 days to afford 3-bromo-5-nitropyridin-4-ol 9.54 g in 87% yield.
References
[1] Patent: WO2005/37198, 2005, A2. Location in patent: Page/Page column 26
[2] Patent: WO2006/38773, 2006, A1. Location in patent: Page/Page column 57
[3] Tetrahedron Letters, 2012, vol. 53, # 4, p. 377 - 379
[4] Journal of Medicinal Chemistry, 2014, vol. 57, # 6, p. 2462 - 2471
