反应详情

1.7 g of magnesium shavings were covered with 10 ml of ether. A solution of 7.7 g of benzyl chloride in 80 ml of ether was added dropwise thereto under slight reflux and the mixture was subsequently held at boiling for an additional hour until the magnesium had dissolved completely. After cooling to room temperature, a solution of 7 g of 3,4-dihydro-4,4-dimethyl-7-acetyl-2H-1-benzopyran in 50 ml of ether was added dropwise and the reaction mixture was heated under reflux for an additional 2.5 hours. After cooling, the mixture was poured on to ice/2N hydrochloric acid and extracted with ether. The organic phase was washed with water and dilute sodium bicarbonate solution, dried and evaporated. The thus-obtained slightly yellow oil was dissolved in 10 ml of acetic acid and, after the addition of 0.5 g of p-toluenesulfonic acid, heated under reflux for 2 hours. The reaction solution obtained was diluted with water and extracted several times with ether. The combined extracts were diluted with water, washed with sodium bicarbonate solution and water, dried and evaporated. The crude product was chromatographed (silica gel, eluting agent hexane/0.5% ethyl acetate) and recrystallized from hexane. There were obtained 4.8 g of 3,4-dihydro-4,4-dimethyl-7-(α-methylstyryl)-2H-1-benzopyran, melting point 44°-46° C.

1. temperatureunder slight reflux
2. dissolutionhad dissolved completely
3. temperaturethe reaction mixture was heated
4. temperatureunder reflux for an additional 2.5 hours
5. temperatureAfter cooling
6. extractionextracted with ether
7. washThe organic phase was washed with water and dilute sodium bicarbonate solution
8. customdried
9. customevaporated
10. customThe thus-obtained slightly yellow oil
11. temperatureheated
12. temperatureunder reflux for 2 hours
13. customThe reaction solution obtained
14. extractionextracted several times with ether
15. additionThe combined extracts were diluted with water
16. washwashed with sodium bicarbonate solution and water
17. customdried
18. customevaporated
19. customThe crude product was chromatographed
20. wash(silica gel, eluting agent hexane/0.5% ethyl acetate)
21. customrecrystallized from hexane