Cobalt-Catalyzed Intramolecular Reactions between a Vinylcyclopropane and an Alkyne: Switchable [5+2] Cycloaddition and Homo-Ene Pathways.

Cobalt-diphosphine catalysts have been found to promote intramolecular reactions between a vinylcyclopropane and an alkyne to selectively afford either the [5+2] cycloaddition product or the homo-ene reaction product under solvent control. The former product is exclusively formed in noncoordinating 1,2-dichloroethane, whereas the latter is dominant in coordinating solvents, such as acetonitrile and dimethylacetamide. Furthermore, a highly enantioselective variant of the homo-ene reaction afforded chiral tetrahydrofuran, pyrrolidine, and cyclopentane derivatives bearing 1,3-diene and alkylidene substituents.