反应详情

A mixture of methyl 2-amino-3-hydroxybenzoate from Step A (2.04 g, 12.2 mmol) and potassium O-ethylxanthate (1.37 g, 8.56 mmol) in pyridine (8 mL) was heated to reflux for 2 h, then cooled to room temperature and poured into a mixture of ice-water (45 mL) and conc. HCl (4.8 mL). The resulting precipitate was collected by filtration and washed with water, dried on vacuum to give methyl 2-thioxo-2,3-dihydrobenzoxazole-4-carboxylate (1.33 g, 52%) as a light brown solid: 1H NMR (500 MHz, CDCl3) δ 10.40 (br s, 1H), 7.82 (dd, J 8.0, 1.0 Hz, 1H), 7.49 (dd, J 8.0, 1.0 Hz, 1H), 7.28 (t, J=8.0 Hz, 1H), 4.01 (s, 3H); MS (ESI+) m/z 210 (M+H).

1. temperaturewas heated
2. temperatureto reflux for 2 h
3. filtrationThe resulting precipitate was collected by filtration
4. washwashed with water
5. customdried on vacuum