Indole Synthesis via Cobalt(III)-Catalyzed Oxidative Coupling of N-Arylureas and Internal Alkynes

A mild Co(III)-catalyzed oxidative annulation of N-arylureas and internal alkynes has been developed. The use of less electrophilic ureas other than acetamides as directing groups is crucial for the reaction. A broad range of synthetically useful functional groups are compatible with this reaction, thus providing a new opportunity for the synthesis of diverse indoles.