Regioselective Cobalt(II) Catalyzed C–H Functionalization and [3 + 2] Annulation of N‑Arylguanidines with 1,3-Diynes

8-Quinolinyl directed N-arylguanidines were subjected to cobalt­(II) catalyzed C–H functionalization/1,3-diyne annulation under mild conditions to afford 40 alkynylated indole guanidines in 34% to 92% yields. The scope of the substrates was explored. The reported procedure is mostly regioselective and tolerates various functional groups in the substrates. The regioselectivity of the reactions was assessed with the aid of multinuclear NMR spectroscopy and X-ray crystallography. Competition and labeling experiments were carried out to support the proposed mechanism.