Water → Methyl 4-(benzoxazol-2-yl)benzoate

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A solution of (2-hydroxyphenyl)-terephthalamic acid methyl ester (0.35 g, 1.3 mmol) in polyphosphoric acid (˜5 mL) was heated to reflux for 3 h. The solution was cooled to 0° C., water added (100 mL) and solid K2CO3 introduced until pH 7–9 was attained. The residue was diluted with ethyl acetate (2×100 mL) and the organic extract dried (MgSO4), filtered and concentrated to give cyclized methyl 4-(benzoxazol-2-yl)-benzoate (0.15 g, 45%) as a beige powder. 1H NMR (CDCl3) δ 3.98 (s, 3H), 7.40 (m, 2H), 7.61 (m, 1H), 7.81 (m, 1H), 8.20 (d, 2H, J=7.8 Hz), 8.34 (d, 2H, J=7.8 Hz).

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