General procedure for the synthesis of 6-bromobenzo[d]oxazol-2(3H)-ones from 2-benzoxazolidinones: 3H-1,3-benzoxazol-2-one (5.00 g, 37.00 mmol) was dissolved in acetic acid (50 mL), and bromine (1.9 mL, 37.0 mmol) was slowly added dropwise. The reaction mixture was stirred at 20°C for 4 hours. After completion of the reaction, the mixture was poured into ice water, the precipitate was collected by filtration, washed with water and dried over air to give a pink solid product (7.48 g, 34.8 mmol, 94% yield). The melting point of the product was 191.6-192.3 °C. 1H NMR (300 MHz, DMSO-d6): δ 11.81 (s, 1H), 7.57 (dd, J=1.9 Hz, 0.3 Hz, 1H), 7.30 (dd, J=8.3 Hz, 1.9 Hz, 1H), 7.04 (dd, J=8.3 Hz, 0.3 Hz, 1H) .13C NMR (75MHz, DMSO-d6): δ154.5, 144.5, 130.3, 126.9, 113.5, 113.2, 111.7.LCMS m/z calculated values [M-H]+: 211.9, 213.9; measured values: 211.8, 213.8.
