反应详情

A solution of the compound from example 14 b) (8.73 g; 0.042 mol.) in water (300 mL) was treated with 2M aqu. sulfuric acid (60.0 mL) to precipitate the free acid as a fine powder. This suspension was then stirred and cooled to 10° then slowly treated dropwise with a solution of sodium nitrite (3.03 g; 0.044 mol.) in water (30.0 mL). After 30 min. at 10° the solution was added very slowly dropwise to a refluxing solution of 40% aqu. sulfuric acid (1 L). Complete addition took ˜1 h. After complete addition the mixture was heated under reflux for a further 15 min. then quickly hot-filtered through a plug of glass wool to remove insoluble, charred material. The filtrate was allowed to cool depositing the title compound (5.85 g; 74%) as yellow crystals. mp 210-212°. MS(ES) m/z 187 [M−H].

1. customsulfuric acid (60.0 mL) to precipitate the free acid as a fine powder
2. temperaturecooled to 10°
3. additionAfter 30 min. at 10° the solution was added very slowly dropwise to a refluxing solution of 40% aqu
4. additionComplete addition
5. additionAfter complete addition the mixture
6. temperaturewas heated
7. temperatureunder reflux for a further 15 min.
8. filtrationthen quickly hot-filtered through a plug of glass wool
9. customto remove insoluble
10. temperatureto cool