6-Bromo-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one

Application

6-Bromo-3-hydroxy-2-nitropyridine is a pyridine derivative and an important organic chemical intermediate that can be widely used in pesticides, pharmaceuticals, dyes, fragrances, and other fields.

Synthesis

Compound 3.1 (2.7 g, 8.85 mmol) was used as raw material and mixed with iron powder (2.48 g, 44.3 mmol) in acetic acid (40 mL). The reaction mixture was stirred at 100 °C for 2 hours. After the reaction was completed, it was cooled to room temperature and the reaction solution was filtered through diatomaceous earth. Water (100 mL) was added to the filtrate and extracted with dichloromethane (20 mL x 3). The organic phases were combined, dried over anhydrous sodium sulfate and concentrated. The residue was purified by silica gel column chromatography (petroleum ether/ethyl acetate= 3/1) to afford the target product, 6-bromo-2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one (Compound 3.2, 1.9 g, Yield: 95%) as a pale yellow liquid.

References

[1] Patent: CN108623615, 2018, A. Location in patent: Paragraph 0362; 0363; 0366
[2] Tetrahedron Letters, 2010, vol. 51, # 38, p. 5035 - 5037
[3] Synthetic Communications, 2013, vol. 43, # 24, p. 3315 - 3321
[4] Patent: EP2341052, 2011, A1. Location in patent: Page/Page column 35-36
[5] Patent: WO2017/199265, 2017, A1. Location in patent: Paragraph 000134