反应详情

温度

50 °C

A suspension of 5-(3,4-dichloro-phenyl)-oxazole-4-carboxylic acid methyl ester (1.5 g, 5.51 mmol), 3 N HCl (10 mL), and MeOH (15 mL) was heated at 50° C. for 4 h. The mixture was concentrated, diluted with water, and washed with Et2O. The aqueous layer was concentrated and Et2O was added, causing precipitation of a white solid. The precipitate was collected by filtration to provide 1.0 g (63%) of the desired product as an apparent 10:1 mixture of keto-enol tautomers. MS (ESI+): mass calcd. for C10H9Cl2NO3, 261.00; m/z found, 262/264 [M+H]+. Major tautomer: 1H NMR (500 MHz, CDCl3): 8.32 (d, J=2.1, 1H), 8.09 (dd, J=8.4, 2.1, 1H), 7.79 (d, J=8.5, 1H), 3.80 (s, 3H). Minor tautomer: 1H NMR (500 MHz, CDCl3): 8.19 (d, J=2.0, 1H), 7.96 (dd, J=8.4, 2.1, 1H), 7.76 (d, J=8.4, 1H), 6.18 (s, 1H).

1. concentrationThe mixture was concentrated
2. additiondiluted with water
3. washwashed with Et2O
4. concentrationThe aqueous layer was concentrated
5. additionEt2O was added
6. customprecipitation of a white solid
7. filtrationThe precipitate was collected by filtration