Isolation of Cp*Co III -Alkenyl Intermediate in Efficient Cobalt-Catalyzed C-H Alkenylation with Alkynes.

A general and efficient procedure for C-H alkenylation of arenes with a broad substrate scope catalyzed by Cp*CoIII was demonstrated with alkynes. A highly selective mono-alkenylation and sequential bis-C-H bond functionalization was displayed to exemplify the versatility of the cobalt catalyst. Isolation of cationic Cp*CoIII -alkenyl intermediate was achieved under identical catalytic conditions to further establish the proposed pathway.