Synthesis
Ethyl 2-nitro-5-fluorophenoxyacetate (50 mmol) was added to 50 mL of glacial acetic acid. It was heated to reflux under stirring conditions and iron powder (100 mmol) was added in three batches. After addition, the reaction was continued to reflux for 3 hours. Upon completion of the reaction, the filtrate was filtered through a diatomaceous earth pad while hot to remove the iron powder. The filtrate was cooled to room temperature and then slowly poured into 200 mL of water with vigorous stirring for 30 minutes. The precipitated solid was collected by filtration, washed with deionized water and dried under vacuum to give 7.18 g of white solid product 7-fluoro-2H-1,4-benzoxazin-3(4H)-one in 86% yield.
References
[1] Patent: CN108727367, 2018, A. Location in patent: Paragraph 0138; 0142; 0143
[2] Patent: WO2014/122674, 2014, A1. Location in patent: Paragraph 00065
[3] Patent: WO2011/151361, 2011, A1. Location in patent: Page/Page column 40-41
[4] Patent: WO2013/153539, 2013, A1. Location in patent: Page/Page column 47
[5] Journal of Agricultural and Food Chemistry, 2017, vol. 65, # 26, p. 5278 - 5286
