Synthesis
General procedure for the synthesis of 5-bromo-2(3H)-benzoxazolone from 2-amino-4-bromophenol and N,N'-carbonyldiimidazole: Referring to Example 2, to a solution of 2-amino-4-bromophenol (3.50 g, 18.6 mmol) in tetrahydrofuran (100 mL) was slowly added N,N'-carbonyldiimidazole (3.62 g, 22.3 mmol). The reaction mixture was heated to reflux for 1.5 hours. Upon completion of the reaction, the reaction solution was cooled to 20-25 °C, acidified by addition of 2N aqueous hydrochloric acid and subsequently extracted with ethyl acetate. The organic layers were combined and washed sequentially with saturated aqueous sodium bicarbonate and saturated aqueous sodium chloride, then dried with anhydrous sodium sulfate. The desiccant was removed by filtration and the filtrate was concentrated under reduced pressure to give 5-bromo-1,3-benzoxazol-2(3H)-one (3.89 g, quantitative yield).IR (cm-1): 960, 1149, 1474, 1622, 1751.
References
[1] Patent: EP1719761, 2006, A1. Location in patent: Page/Page column 26
[2] Bioorganic and Medicinal Chemistry, 2012, vol. 20, # 18, p. 5568 - 5582
[3] Journal of Medicinal Chemistry, 2013, vol. 56, # 20, p. 8191 - 8195
[4] Synthesis (Germany), 2013, vol. 45, # 23, p. 3269 - 3275
[5] Patent: WO2013/64984, 2013, A1. Location in patent: Page/Page column 125
