反应详情

2-Bromo-7-chloro-9H-xanthen-9-one (prepared as described in example 1 using 4-bromophenol and 2-bromo-5-chlorobenzoic acid) (12.78 g, 41 mmol) was treated with 100 ml of dry THF. The mixture was stirred for 10 min at room temperature and the resulting suspension was placed in water-ice bath for another 10 min. MeMgBr (23 ml, 70 mmol) (3M in THF) was added dropwise under argon using syringe. As addition progressed major amount of solid dissolved to form red solution. The mixture was stirred another 5 min at 0° C. then was removed from the bath and allowed to reach room temperature. The flask was recooled to 0° C. and ˜20 ml of saturated ammonium chloride solution was added dropwise slowly (CAREFUL: gas evolution!). The mixture was diluted with ether, organic layer was separated, washed with brine, dried and concentrated to afford an oil. The oil was dissolved in 100 ml of DCM, PPTS (0.2 g, 0.8 mmol) was added and the mixture was heated to reflux for 5 min and left overnight at room temperature. The precipitate was filtered and rinsed with ether, the filtrate was concentrated in vacuo and treated with hot methanol (˜30 ml) and allowed to crystallize at room temperature. The crystalline material was filtered off and dried in vacuo. These two batches gave 2-bromo-7-chloro-9-methylene-9H-xanthene (8.69 g, 68% yield). m/z=307.5 [M+H]+. Calc'd for C14H8BrClO: 307.5

1. customfor another 10 min
2. additionAs addition
3. dissolutiondissolved
4. customto form red solution
5. stirringThe mixture was stirred another 5 min at 0° C.
6. customthen was removed from the bath
7. customto reach room temperature
8. customwas recooled to 0° C.
9. addition˜20 ml of saturated ammonium chloride solution was added dropwise slowly (CAREFUL: gas evolution!)
10. additionThe mixture was diluted with ether, organic layer
11. customwas separated
12. washwashed with brine
13. customdried
14. concentrationconcentrated
15. customto afford an oil
16. temperaturethe mixture was heated
17. temperatureto reflux for 5 min
18. waitleft overnight at room temperature
19. filtrationThe precipitate was filtered
20. washrinsed with ether
21. concentrationthe filtrate was concentrated in vacuo
22. additiontreated with hot methanol (˜30 ml)
23. customto crystallize at room temperature
24. filtrationThe crystalline material was filtered off
25. customdried in vacuo