Nickel-catalyzed [3 + 2 + 2] cycloaddition of ethyl cyclopropylideneacetate and heteroatom-substituted alkynes: application to selective three-component reaction with 1,3-diynes.

Heteroatom-substituted alkynes such as ynol ethers and ynamines turned out to be decent substrates for the Ni-catalyzed [3 + 2 + 2] cocyclization of ethyl cyclopropylideneacetate (1). The three-component cocyclization of 1, 1,3-diynes, and heteroatom-substituted alkynes also proceeded selectively. The study provided an efficient method for the synthesis of heteroatom-substituted cycloheptadiene and related compounds.

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.