Nickel-Catalyzed Intramolecular [3 + 2 + 2] Cycloadditionsof Alkylidenecyclopropanes. A Straightforward Entry to Fused 6,7,5-TricyclicSystems.

A highly diastereo- and chemoselectiveintramolecular nickel-catalyzedcycloaddition of alkene- and alkyne-tethered alkynylidenecyclopropanesis reported. The method constitutes the first fully intramolecular[3 + 2 + 2] alkylidenecyclopropropane cycloaddition occurring viaa proximal cleavage of the cyclopropane and makes it possible to buildrelevant 6,7,5-tricyclic frameworks in a single-pot reaction. Importantly,the reaction outcome is highly dependent on the characteristics ofthe nickel ligands. [ABSTRACT FROM AUTHOR]