反应详情

A 1000-mL 3-necked round-bottom flask was charged with a solution of methyl 2-amino-4-methoxybenzo[d]thiazole-6-carboxylate (5 g, 21.01 mmol, 1.00 equiv) and H3PO4 (40 mL). To this is added of a solution of NaNO2 (4.5 g, 65.22 mmol, 3.00 equiv) in water (10 mL) dropwise at 0°C. The resulting solution was stirred fo(1 h at 0°C. A solution of CuSO4 (10 g, 62.50 mmol, 5.00 equiv) in water (10 mL) was then added dropwise at 0°C., followed by a solution of NaCl (18.5 g, 318.97 mmol, 15.00 equiv) in water (10 mL) dropwise at 0°C. The resulting solution was stirred fo(1 h at room temperature, and then diluted with 100 mL of water. The aqueous solution was extracted with dichloromethane (2×50 mL) and the combined organic layer was concentrated under vacuum. The residue was purified by silica gel chromatography eluting with ethyl acetate/petroleum ether (3:1) to give methyl 2-chloro-4-methoxybenzo[d]thiazole-6-carboxylate as a white solid. (ES, m/z): Calc'd for C10H8ClNO3S [M+1]+=258, found 258. 1H-NMR (CDCl3, ppm): 3.98(s, 1H), 4.10(s, 1H), 7.28(s, 1H), 7.60(d, 1H, J=1.2), 8.12(d, 1H, J=1.2).

1. custom1 h
2. customat 0°C
3. stirringThe resulting solution was stirred
4. custom1 h
5. customat room temperature
6. extractionThe aqueous solution was extracted with dichloromethane (2×50 mL)
7. concentrationthe combined organic layer was concentrated under vacuum
8. customThe residue was purified by silica gel chromatography
9. washeluting with ethyl acetate/petroleum ether (3:1)