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] cyclo-addition 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 dimethylucetamide. Furthermore, a highly enantioselective variant of the homo-ene reaction afforded chiral tetrahydrofuran, pyrrolidine, and cyclopent ne derivatives bearing 1,3 dime and alkylidene substituents.