81721-87-1

The general procedure for the synthesis of 6-nitro-2H-1,4-benzoxazin-3(4H)-one from chloroacetyl chloride and 2-amino-4-nitrophenol was as follows: 1. 2-Amino-4-nitrophenol (6.0 g, 38.93 mmol) was dissolved in dichloromethane (200 mL) and the solution was cooled to 0°C. 2. To the cooled solution, triethylamine (16.3 mL, 116.9 mmol) and chloroacetyl chloride (3.42 mL, 42.8 mmol) were added sequentially with stirring, noting that the chloroacetyl chloride had to be added in small batches to avoid violent reaction. 3. After the addition of chloroacetyl chloride, the reaction mixture was gradually warmed up to room temperature and stirred for 18 hours to ensure complete reaction. 4. After completion of the reaction, the reaction mixture is diluted with additional dichloromethane and the organic phase is subsequently washed with water to remove water soluble impurities. 5. The organic phase was dried over anhydrous magnesium sulfate, filtered to remove the desiccant, and the filtrate was concentrated under reduced pressure to afford 6-nitro-4H-benzo[1,4]oxazin-3-one as 7.5 g solid in 100% yield.

[1] Patent: US2010/160373, 2010, A1. Location in patent: Page/Page column 30
[2] Patent: US2007/93477, 2007, A1. Location in patent: Page/Page column 20
[3] Bioorganic and Medicinal Chemistry, 2013, vol. 21, # 13, p. 3821 - 3830
[4] Journal of Medicinal Chemistry, 2015, vol. 58, # 1, p. 222 - 236
[5] Patent: WO2018/19252, 2018, A1. Location in patent: Page/Page column 37