Tunable Diastereoselective Desymmetrization of Cyclohexadienones Triggered by Copper-Catalyzed Three-Component Coupling Reaction.

Catalytic tandem diastereoselective desymmetrization of cyclohexadienone-containing 1,6-enynes has been achieved through copper-catalyzed [3 + 2]-cycloaddition followed by ketenimine formation and subsequent intramolecular conjugate addition. The cascade reaction provides cis-hydrobenzofurans in good yields with excellent diastereoselectivity. The exo- or endo-selectivity of bicyclic scaffolds depends on the selection of the base in the reaction. In addition, N-tethered bicyclic products further transformed into tricyclic compounds via intramolecular Michael addition.