Efficient Copper(II)-Catalyzed Addition of Activated Methylene Compounds to Alkenes

Abstract
Efficient regioselective addition of β-diketones to styrenes, norbornene, cyclic enol ether, and diene has been realized by means of copper(II) triflate as the catalyst. The solvent effect is prominent on the reactions, and the desired addition products were obtained in good to excellent yields only in dioxane or ionic liquid [bmim]PF6. The mechanism suggests that copper(II) triflate activates the enolic O−H bond of a β-diketone substrate to initiate the addition reaction.
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