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

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Reaction Conditions

Reaction Steps

To a mixture of 2,2,6,6-tetramethylpyran-3,5-dione (2.78 g, 16.3 mmol) and N,N-dimethylaminopyridine (9.97 g, 81.6 mmol) is added anhydrous chloroform (120 ml). To this solution is added anhydrous toluene (30 ml), followed by 5-bromo-2-chlorophenyllead triacetate (10.32 g, 18 mmol) in one portion and the reaction mixture is heated at 80° C. overnight. The mixture is allowed to cool to room temperature, then diluted with dichloromethane (120 ml) and 2M aqueous hydrochloric acid (250 ml), followed by filtration through diatomaceous earth to remove inorganic residues. The filter cake is washed with dichloromethane, and all organic fractions are combined, washed with 2M hydrochloric acid, water and brine, dried over anhydrous magnesium sulfate then concentrated in vacuo. This material is finally purified by flash column chromatography on silica gel to afford 4-(5-bromo-2-chlorophenyl)-2,2,6,6-tetramethylpyran-3,5-dione (0.44 g) of sufficient purity to use directly in the next step.

Provenance & Evidence