Cobalt(III)-Catalyzed C2-Selective C-H Alkynylation of Indoles

A cobalt(III)-catalyzed C-2 selective C-H alkynylation of indoles using hypervalent iodine-alkyne reagents is described. A broad range of synthetically useful functional groups (-F, -Cl, -Br, -CO2Me, -CN) were tolerated, providing an efficient and robust protocol for the synthesis of C-2 alkynylated indoles. The pyrimidyl and silyl protecting groups could be easily removed to give the corresponding 2-ethynyl-1H-indole.