反应详情

Into a dry flask fitted with dropping funnel reflux condenser, drying tube and mechanical stirrer was placed 51 g of magnesium turnings, followed by the addition of 200 ml of dry ether. A small portion of bromobenzene was added to initiate the reaction, followed by the remainder of 330 g (2.1 mole) of bromobenzene in 1 liter of dry ether at a rate sufficient to maintain reflux. The mixture was cooled in an ice-salt bath to which was added dropwise the cold ethereal solution of 2,3-dichlorotetrahydropyran. After completing the addition, the slurry was refluxed for 3 hours, cooled in an ice-water bath and 300 ml of cold 20 percent hydrochloric acid added slowly to the stirred mixture. The addition of 500 ml of water dissolved the precipitated salts, the layers were separated, the aqueous phase extracted with ether (2×200 ml) and the combined ethereal layers washed with brine (200 ml) and dried over anhydrous potassium carbonate. In vacuo removal of solvent left an amber liquid which was distilled through a 20 cm Vigreux column, whereby 256 g was collected at 77°-90°/0.25 mm Hg. The product was redistilled at 153-154/16 mm Hg, the distillate crystallizing to give needles m.p. 39.5°-40.5°. The crude yield was 256 g (93% yield based on dihydropyran).

1. customInto a dry flask fitted
2. temperaturereflux condenser
3. customdrying tube and mechanical stirrer
4. additionfollowed by the addition of 200 ml of dry ether
5. additionA small portion of bromobenzene was added
6. customthe reaction
7. temperatureto maintain
8. temperaturereflux
9. temperatureThe mixture was cooled in an ice-salt bath to which
10. additionthe addition
11. temperaturethe slurry was refluxed for 3 hours
12. temperaturecooled in an ice-water bath
13. dissolutiondissolved the precipitated salts
14. customthe layers were separated
15. extractionthe aqueous phase extracted with ether (2×200 ml)
16. washthe combined ethereal layers washed with brine (200 ml)
17. dry with materialdried over anhydrous potassium carbonate
18. customIn vacuo removal of solvent
19. waitleft an amber liquid which
20. distillationwas distilled through a 20 cm Vigreux column, whereby 256 g
21. customwas collected at 77°-90°/0.25 mm Hg
22. distillationThe product was redistilled at 153-154/16 mm Hg
23. customthe distillate crystallizing