Palladium-catalyzed ligand-regulated divergent synthesis of pyrrole[2,3-b]indoles and ureas from 2-ethynylanilines and isocyanides

Herein, a palladium-catalyzed and ligand-controlled protocol for the divergent synthesis of pyrrole[2,3-b]indole and urea derivatives has been described. Pyrrole[2,3-b]indoles ("cyclization on" products) via tandem cyclization of o-alkynylanilines with isocyanides in the absence of a ligand and ureas ("cyclization off" products) via oxidative amination of anilines with isocyanides in the presence of a ligand were obtained both in moderate to good yields with high selectivity. In this chemistry, cyclic and acyclic products were easily accessed with the same starting materials under the regulation of the ligand.