Synthesis
General procedure for the synthesis of 2,4-dichloro-6-methyl-3-nitropyridine from 4-hydroxy-6-methyl-3-nitro-2-pyridone: (1) 4-hydroxy-6-methyl-3-nitro-2-pyridone (1.7 g, 10 mmol) was dissolved in 10 mL of phosphorus oxychloride (POCl3), heated to 95 °C, and the reaction was stirred for 1.5 hours. Upon completion of the reaction, excess POCl3 was removed by centrifugation.Subsequently, the reaction was quenched by slow addition of 100 mL of ice water. The reaction mixture was extracted with ethyl acetate (80 mL x 3). The organic phases were combined, washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to give 1.773 g of yellow powdery product in 85.7% yield.
References
[1] Journal of Medicinal Chemistry, 2005, vol. 48, # 16, p. 5104 - 5107
[2] Patent: US2012/289497, 2012, A1. Location in patent: Page/Page column 40
[3] Patent: EP2524917, 2012, A1. Location in patent: Page/Page column 43-44
[4] Patent: WO2008/119713, 2008, A1. Location in patent: Page/Page column 65
[5] Journal of Medicinal Chemistry, 2008, vol. 51, # 22, p. 7273 - 7286
