We have reported the synthesis of seven-membered rings by the nickel-catalyzed [3+2+2] cycloaddition of electron-deficient alkylidenecyclopropanes with alkynes. Herein, we examined the [3+2+2] cycloaddition of ethyl cyclopropylideneacetate with conjugated enynes in the presence of a nickel catalyst and vinylcycloheptadiene derivatives were isolated in good yields. The products were useful substrates for the Diels-Alder reaction with various dienophiles, and the reaction proceeded smoothly to give the corresponding polycyclic compounds. Furthermore, the one-pot [3+2+2]/[4+2] cycloaddition was carried out successfully.
