Rhodium-Catalyzed Cyclization of 2-Ethynylanilines in the Presence of Isocyanates: Approach toward Indole-3-carboxamides.

Catalytic synthesis of indole-3-carboxamides from 2-ethynylanilines and isocyanates was achieved in the presence of a rhodium catalyst through a tandem-type, cyclization-addition sequence. This tandem-type process can be performed under mild reaction conditions, affording 2,3-disubstituted indoles in a one-pot manner generally in good to excellent yields. The broad substrate scope and good functional group compatibility make the method highly efficient and widely applicable, providing a facile and entirely novel route toward variously substituted indole-3-carboxamides.