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 4 N 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