Ruthenium-Catalyzed [3 + 2] Intramolecular Cycloaddition of Alk-5-ynylidenecyclopropanes Promoted by the “First-Generation” Grubbs Carbene Complex.

The well-known "first generation" Grubbs metathesis complex is capable of catalyzing the intramolecular [3 + 2] cycloaddition of alk-5-ynylidenecyclopropanes. It appears that the species responsible for the catalysis is a ruthenium complex generated in situ from the Grubbs carbene in the presence of the substrate.