反应详情

To a mixture of 2,2,6,6-tetramethylpyran-3,5-dione (3.57 g, 21.00 mmol) and N,N-dimethylaminopyridine (13.50 g, 111.00 mmol) is added anhydrous chloroform (120 ml), followed by stirring at room temperature until dissolution. To this solution is added anhydrous toluene (37 ml), followed by 5-bromo-2-ethylphenyllead triacetate (10.69 g, 24.00 mmol) in one portion and the reaction mixture is heated at 80° C. for 2 hours, then allowed to stand overnight at room temperature. The mixture is diluted with dichloromethane (185 ml) and dilute aqueous hydrochloric acid (185 ml), followed by swirling for 5 minutes and filtration to remove inorganic residues (additional washing with dichloromethane). All organic fractions are combined, washed with brine, dried over anhydrous magnesium sulfate, then concentrated in vacuo to afford a crude oil which is further purified by flash column chromatography (hexane/ethyl acetate 5:1 ratio) to give the product as a yellow solid (4.47 g). Lead residues are removed by dissolving this solid in chloroform (50 ml) and stirring with 3-mercaptopropyl-functionalized silica gel (5.50 g, 1.20 mmol/g loading) overnight. After filtration and concentration 4-(5-bromo-2-ethylphenyl)-2,2,6,6-tetramethylpyran-3,5-dione (4.36 g) is afforded as a cream powder.

1. temperaturethe reaction mixture is heated at 80° C. for 2 hours
2. waitby swirling for 5 minutes
3. filtrationfiltration
4. customto remove inorganic
5. washresidues (additional washing with dichloromethane)
6. washwashed with brine
7. dry with materialdried over anhydrous magnesium sulfate
8. concentrationconcentrated in vacuo
9. customto afford a crude oil which
10. customis further purified by flash column chromatography (hexane/ethyl acetate 5:1 ratio)