General procedure for the synthesis of 2-amino-3-nitro-5-bromopyridine from 2-amino-5-bromopyridine: 2-amino-5-bromopyridine (0.020 mol) was slowly added to concentrated sulfuric acid that was pre-cooled to 0 °C, maintaining the temperature of the reaction system in the 0-5 °C range. Concentrated nitric acid (1.09 mL, 0.024 mol) was slowly added dropwise with continuous stirring, and the rate of dropwise acceleration was controlled to maintain the reaction temperature in the range of 0-5 °C. After the dropwise addition was completed, the reaction mixture was continued to be stirred at 0-5 °C for 1 hour. Subsequently, the reaction system was slowly warmed to room temperature and stirred overnight at room temperature. Upon completion of the reaction, the mixture was carefully poured into crushed ice and the pH was adjusted to 7-8 with 10% aqueous sodium hydroxide solution. the resulting precipitate was collected by filtration, washed well with cold water and finally dried under vacuum at 60 °C overnight to obtain high purity 2-amino-3-nitro-5-bromopyridine.
[1] Chemical Communications, 2013, vol. 49, # 72, p. 7929 - 7931
[2] Tetrahedron, 2003, vol. 59, # 43, p. 8555 - 8570
[3] Tetrahedron, 2014, vol. 70, # 5, p. 1077 - 1083
[4] Patent: US6025366, 2000, A
[5] Journal of the Chemical Society, 1948, p. 1389,1392
