Cobalt-catalyzed regioselective (4+2)-annulation of benzamides with allenyl carbinol acetates: access to 3-vinylisoquinolinones

Herein, we disclose a Co-catalyzed regioselective (4+2)-annulation of aryl-, heteroaryl- and acrylamides with allenyl acetates to access a diverse array of heterocyclic derivatives in high yields with excellent regioselectivity. The protocol employs inexpensive cobalt(II) salts and exhibits broad functional group tolerance. Solvent plays a crucial role in governing regioselective migratory insertion, facilitating the selective formation of the elusive Co-alkenyl intermediate. Preliminary mechanistic experiments were performed to elucidate the plausible reaction pathway.