Synthesis
4-Methyl-3-nitropyridin-2-amine (compound 8, 11 g, 0.072 mol) was added to 150 mL of water, concentrated sulfuric acid (11 mL) was added slowly with stirring and cooled to 0 °C in an ice bath. Sodium nitrite (9 g, 0.130 mol) was dissolved in 20 mL of water and added slowly dropwise through a long-necked funnel to just below the reaction solution level. The reaction was stirred continuously for 2 h at room temperature and then heated to boiling until the reaction was complete, during which no brown gas escaped. After completion of the reaction, the reaction solution was cooled and the solid product was collected by filtration and dried to give 2-keto-3-nitro-4-methylpyridine (Compound 9, 10.8 g, 97.6% yield). The melting points of the product were 222.3-222.6 °C (aqueous phase) and 231.6-231.8 °C (ethanol phase), which were in agreement with literature reports.
References
[1] Patent: EP2366691, 2011, A1. Location in patent: Page/Page column 7
[2] Journal of the American Chemical Society, 1950, vol. 72, p. 2806
[3] Journal of Organic Chemistry, 1955, vol. 20, p. 1729,1731
[4] Chemical and Pharmaceutical Bulletin, 2008, vol. 56, # 6, p. 775 - 780
[5] Chemical and Pharmaceutical Bulletin, 2017, vol. 65, # 1, p. 66 - 81
