Toluene → 4-(5-Bromo-2-ethylphenyl)-2,2,6,6-tetramethylpyran-3,5-dione

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Reaction Steps

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.

Provenance & Evidence