2-(4-Bromo-2,6-dimethylphenyl)-3-methoxy-cyclopent-2-enone → 2-(2,6-Dimethyl-4-prop-1-ynylphenyl)-3-methoxycyclopent-2-enone

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Reaction Steps

To a solution of anhydrous zinc bromide (1.41 g, 6.3 mmol) in anhydrous tetrahydrofuran (8.0 ml) under nitrogen at 0°C., is added propynylmagnesium bromide (15.7 ml, 6.3 mmol, 0.4 M solution in tetrahydrofuran) dropwise. The reaction mixture is then allowed to warm to room temperature and stir for 10 minutes, then cooled again to 0°C. To this mixture is then added [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.102 g, 0.13 mmol), followed by a solution of 2-(4-bromo-2,6-dimethylphenyl)-3-methoxycyclopent-2-enone (0.370 g, 1.25 mmol) in anhydrous tetrahydrofuran (4.0 ml). The reaction mixture is heated at reflux for 4.5 hours, then allowed to cool to room temperature followed by quenching with saturated aqueous ammonium chloride (10 ml). Ethyl acetate is added, and the mixture is filtered through a bed of diatomaceous earth and the phases separated. The aqueous phase is extracted again with ethyl acetate (×3) and combined organics are washed with brine, dried over magnesium sulfate, filtered and the filtrate concentrated in vacuo. The residue is purified by flash column chromatography (ethyl acetate and isohexane as eluant) to afford 2-(2,6-dimethyl-4-prop-1-ynylphenyl)-3-methoxycyclopent-2-enone.

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