反应详情

To 0.8 g of magnesium shavings activated with methyl iodide was added dropwise a solution of 7.77 g of 1-bromo-2,5-dimethoxy-3,4,6-trimethylbenzene in 20 ml of absolute tetrahydrofuran at a rate such that the solvent was brought just to boiling. Subsequently, the reaction mixture was boiled under reflux for an additional hour. To this Grignard solution, cooled down to 0°, were added dropwise 5.0 g of (S)-2,2,4-trimethyl-1,3-dioxolan-4-acetaldehyde. Subsequently, the reaction mixture was stirred at room temperature for a further 4 hours and under reflux for 15 minutes. For the working-up, the reaction mixture was cooled down to 0°, it was treated with 10 ml of saturated ammonium chloride solution followed by 10 ml of 2-N sulfuric acid and extracted with a total of 0.5 l of ether. The organic phase was washed neutral with water and dried over magnesium sulfate. After removal of the solvent on a rotary evaporator and drying of the residue in a high vacuum, there were obtained 10.5 g of a highly viscous oil, which, for purification, was chromatographed on 450 g of Kieselgel with ether/hexane/acetic ester (4:4:1 parts by volume). The yield of α-(2,5-dimethoxy-3,4,6-trimethylphenyl)-2,2,4-(S)-trimethyl-1,3-dioxolan-4-ethanol amounted to 8.83 g; [α]D20 =-5.5° (c=1.20; CHCl3).

1. temperatureunder reflux for an additional hour
2. temperatureTo this Grignard solution, cooled down to 0°
3. temperatureunder reflux for 15 minutes
4. temperaturethe reaction mixture was cooled down to 0°
5. extractionextracted with a total of 0.5 l of ether
6. washThe organic phase was washed neutral with water
7. dry with materialdried over magnesium sulfate
8. customAfter removal of the solvent
9. customon a rotary evaporator
10. customdrying of the residue in a high vacuum
11. customthere were obtained 10.5 g of a highly viscous oil, which
12. customfor purification
13. customwas chromatographed on 450 g of Kieselgel with ether/hexane/acetic ester (4:4:1 parts by volume)
14. custom[α]D20 =-5.5° (c=1.20; CHCl3)