反应详情

A mixture of 60 g (0.16 mol) of the compound of Example 11, and 450 ml. of 2 N aqueous HBr was heated under N2 at 95° for 30 hours. The solution was concentrated in vacuo and the residual salt was taken up in 300 ml of water. The solution was brought to pH 5.5 with 4N NaOH and the mixture was chilled in an icebath for 1 hour. The precipitate was collected, washed with cold water and dried to give 34.8 g of product. Crystallization from glacial acetic acid (360 ml.) afforded, after drying at 100°/0.2 mmHg, 30.8 g (82%) of white crystals, m.p. 280° (dec.) (lit. m.p. 285°-286°), which was identical with an authentic sample.

1. concentrationThe solution was concentrated in vacuo
2. temperaturethe mixture was chilled in an icebath for 1 hour
3. customThe precipitate was collected
4. washwashed with cold water
5. customdried