Cobalt(II)-Catalyzed [4 + 2] Annulation of Picolinamides with Alkynes via C-H Bond Activation.

A cobalt(II)-catalyzed [4+2] annulation of picolinamides with alkynes via C-H bond activation has been developed. The operationally simple annulation reaction allows for the synthesis of acyl-substituted 1H-benzoquinoline bearing multiple aromatic rings (up to 96 % yield) without co-oxidant or other oxidation factors under mild conditions. Several control experiments were carried out. This practical [4+2] annulation provides an efficient route to access highly functionalized compounds.