反应详情

To a suspension of 3-hydroxyanthranilic acid (0.300 g, 1.96 mmol) in toluene (10 mL) was added benzoyl chloride (0.830 g, 5.90 mmol) followed by pyridine (0.545 g, 6.92 mmol) at room temperature. The resulting mixture was stirred at room temperature for 30 min then heated to 80° C. for 1 hr. After this time the reaction was cooled and poured into a mixture of ethyl acetate (50 mL) and 5% aqueous hydrochloric acid (50 mL). Subsequent separation of the layers, drying the organic over MgSO4 and filtration afforded an orange solution. This solution was concentrated to an orange solid which was directly re-dissolved in xylenes (20 mL) and the solution treated with p-toluenesulfonic acid (0.800 g, 4.20 mmol). The reaction mixture was then heated to reflux for 6 hrs. After this time the reaction was cooled and poured into water (50 mL), the organic layer separated then washed with water (3×50 mL). The organic was dried over MgSO4, filtered and concentrated to an orange/brown solid. Re-crystallization of this solid from ethyl acetate afforded 0.412 g (88% yield) of 2-phenylbenzoxazole-4-carboxylic acid as a light yellow solid: 1H NMR (300 MHz, CD3OD) δ 11.58 (br s, 1H), 8.30 (m, 2H), 8.17 (dd, J=7.8, 0.8 Hz, 1H), 7.83 (dd, J=8.2, 0.8 Hz, 1H), 7.69-7.45 (m, 4H); MS (APCI) m/z 240 [M+H]+.

1. temperaturethen heated to 80° C. for 1 hr
2. temperatureAfter this time the reaction was cooled
3. customSubsequent separation of the layers
4. customdrying the
5. filtrationorganic over MgSO4 and filtration
6. customafforded an orange solution
7. concentrationThis solution was concentrated to an orange solid which
8. dissolutionwas directly re-dissolved in xylenes (20 mL)
9. temperatureThe reaction mixture was then heated
10. temperatureto reflux for 6 hrs
11. temperatureAfter this time the reaction was cooled
12. customthe organic layer separated
13. washthen washed with water (3×50 mL)
14. dry with materialThe organic was dried over MgSO4
15. filtrationfiltered
16. concentrationconcentrated to an orange/brown solid