Hydrochloric Acid → 3-(5-Bromo-2-ethylphenyl)-1,8,8-trimethylbicyclo[3.2.1]octane-2,4-dione

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Reaction Conditions

Reaction Steps

A solution of 1,8,8-trimethylbicyclo[3.2.1]octane-2,4-dione (0.22 g, 1.22 mmol) (preparation described by H. Favre et al., Can. J. Chem. (1956), 34 1329-39.) in dry chloroform (10 ml) is stirred at room temperature then thoroughly flushed with nitrogen. To this mixture is then added 4-dimethylaminopyridine (0.744 g, 6.15 mmol) and anhydrous toluene (3 ml), followed by heating to 80° C. 5-Bromo-2-ethylphenyllead triacetate (0.673 g, 1.18 mmol) is added portionwise over 10 minutes, and the mixture is further heated at this temperature for a further 4 hours then left to stand overnight. 2M hydrochloric acid (10 ml) is added, and the resulting biphasic mixture is filtered to remove any inorganic salts (washing with additional dichloromethane, 10 ml). The organic phase separated, and the aqueous phase is extracted again with dichloromethane (10 ml×2). All organic fractions are combined, dried over magnesium sulfate, filtered and the filtrate concentrated under reduced pressure to give an orange gum. This crude product is purified by flash column chromatography on silica gel (100% to 40% hexane/ethyl acetate eluant ratio) to afford rac-3-(5-bromo-2-ethylphenyl)-1,8,8-trimethylbicyclo[3.2.1]octane-2,4-dione as a colourless gum.

Provenance & Evidence