Hydrochloric Acid → 3-(5-Bromo-2-ethylphenyl)bicyclo[3.2.2]non-6-ene-2,4-dione

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A solution of bicyclo[3.2.2]non-6-ene-2,4-dione (0.835 g, 5.58 mmol), prepared by the method of R. Beaudegnies et al., WO2005/123667, in dry chloroform (30 ml) is stirred at room temperature then thoroughly flushed with nitrogen. To this mixture is added 4-dimethylaminopyridine (3.41 g, 28 mmol) and anhydrous toluene (5 ml), followed by heating to 80° C. 5-Bromo-2-ethylphenyllead triacetate (4.75 g, 8.36 mmol) is added portionwise over 20 minutes, and the mixture is further heated at this temperature for a further 4 hours then left to stand overnight. 2M hydrochloric acid (40 ml) is added, and the suspension is vigorously stirred for 30 minutes then filtered through diatomaceous earth (washing with additional dichloromethane, 40 ml). The organic phase is separated, and the aqueous phase is extracted with dichloromethane (40 ml×2). All organic fractions are combined, dried over magnesium sulfate, filtered and the filtrate concentrated under reduced pressure to give a brown oil. The crude product is purified by flash column chromatography on silica gel (100% to 40% hexane/ethyl acetate eluant ratio) to afford 3-(5-bromo-2-ethylphenyl)bicyclo[3.2.2]non-6-ene-2,4-dione (0.400 g, 22%) as a yellow gum.

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