Phosphorus pentachloride → 2-Chloro-5-phenylbenzoxazole

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5-Phenyl-3H-benzooxazole-2-thione (227 mg, 1.0 mmol) was dissolved in phosphorus oxychloride (1.6 mL). Phosphorus pentachloride (208 mg, 1.0 mmol) was added and the mixture was placed in an oil bath at 100° C. for 3 h. The mixture was allowed to cool to RT and concentrated. The crude residue was concentrated from CH2Cl2 (3×). The crude reaction product was triturated with hexanes (40 mL), and the resulting solids were collected by filtration. The solids were washed with hexanes (20 mL×3) and dried to afford 1.47 g (73%) of the title compound: 1H NMR (CDCl3, 400 MHz) δ 7.86 (d, 1H, J=1.3 Hz), 7.60-7.56 (m, 3H), 7.55-7.52 (m, 1H), 7.49-7.44 (m, 2H), 7.40-7.36 (m, 1H); 13C NMR (CDCl3, 100 MHz) δ 151.6, 151.4, 141.9, 140.7, 139.3, 129.2, 127.8, 127.7, 125.2, 118.4, 110.7; MS (Cl) m/z 230.1 (M+1); HPLC retention time=5.41 min.

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