Synthesis
In a 250 mL round-bottomed flask under nitrogen protection, 2-amino-6-chlorobenzoic acid (11.69 g, 68 mmol) was dissolved in 100 mL of 1,4-dioxane. After cooling the reaction system to 0°C, phosgene (36 mL, 68 mmol) was slowly added through a dropping funnel. The reaction mixture was stirred at 0°C for 24 h, followed by natural warming to 23°C (room temperature). Upon completion of the reaction, the resulting white solid product was collected by filtration and washed sequentially with 1,4-dioxane and ether to afford 5-chloro-1H-benzo[d][1,3]oxazine-2,4-dione (12.5 g, 93% yield).
References
[1] Organic Process Research and Development, 2007, vol. 11, # 4, p. 674 - 680
[2] Patent: US2007/249605, 2007, A1. Location in patent: Page/Page column 8
[3] Patent: US2004/162285, 2004, A1
[4] Patent: US2004/87577, 2004, A1. Location in patent: Page 65
[5] Patent: US2004/167123, 2004, A1. Location in patent: Page/Page column 98
