Synthesis of Vinylcycloheptadienes by the Nickel-Catalyzed Three-Component [3 + 2 + 2] Cocyclization. Application to the Synthesis of Polycyclic Compounds

The nickel-catalyzed [3 + 2 + 2] cycloaddition of ethyl cyclopropylideneacetate and conjugated enynes proceeded smoothly and divinylcycloheptadienes were isolated in high yields. The three-component cocyclization of ethyl cyclopropylideneacetate, conjugated enynes, and (trimethylsilyl)acetylene also proceeded in a highly selective manner to afford vinylcycloheptadienes, which were reacted with various dienophiles. This study provided a new, short-step synthesis of polycyclic compounds with cycloheptane skeleton.