Metal–Ligand Binding Interactions in Rhodium/Palladium-Catalyzed Synthesis of Dihydroquinolines

A domino Rh- and Pd-catalyzed synthesis of dihydroquinolines is disclosed. Two metals and two ligands are placed in one reaction vessel along with the two reactive reagents to afford selective sequential coupling despite the potential for side reactions. In this report, we describe mechanistic investigations attempting to discern the catalyst–ligand interactions occurring in this domino reaction. Through these studies, the reactivity and relative catalyst ligand loadings were successfully tuned to efficiently access the heterocyclic products.