Utility of Ligand Effect in Homogenous Gold Catalysis: Enabling Regiodivergent π‑Bond-Activated Cyclization

Abstract

Comprehensive utilization of both electronic and steric properties of ligands in homogeneous gold catalysis is achieved in the regio­divergent intra­molecular hydroarylation of alkynes. A flexible electron-deficient phosphite ligand, combined with the readily transformable directing group methoxyl amide, is attached to a cationic Au­(I) center in three-coordinate mode, affording sterically hindered <i>ortho</i>-position cyclization. Meanwhile, <i>para</i>-position cyclization is exclusively achieved with the assistance of a rigid electron-abundant phosphine ligand-based Au­(I) catalyst, in which ligands manifest the compensating effect for cyclization through steric hindrance and electronic properties. By combining gold with silver catalysts, tetrahydro­pyrrolo­quinolinones possessing a congested tricyclic structure are obtained via a proven Au/Ag relay catalytic process