20348-09-8

A reaction mixture was prepared by mixing a solution of 2-amino-3-hydroxypyridine (45 mmol) and sodium bicarbonate (51 mmol) in water (30 mL) with 2-butanone (30 mL). A solution of 2-butanone (10 mL) with chloroacetyl chloride (51 mmol) was slowly added dropwise under ice-bath cooling conditions, and the rate of dropwise acceleration was controlled to keep the reaction temperature from exceeding 10°C. The reaction was carried out at room temperature. After dropwise addition, stirring was continued at room temperature for 30 min, and then the reaction was warmed up to 75°C for 1 hr. Upon completion of the reaction, the reaction solution was concentrated and purified by recrystallization (methanol/water=1:1) to afford 4.3 g of the target product 2H-pyrido[3,2-b][1,4]oxazin-3(4H)-one.

[1] Bioorganic and Medicinal Chemistry, 1998, vol. 6, # 2, p. 133 - 142
[2] Helvetica Chimica Acta, 1976, vol. 59, p. 1593 - 1612
[3] Patent: CN103130792, 2016, B. Location in patent: Paragraph 0605-0607