Rhodium-Catalyzed Synthesis of Unsymmetric Di(heteroaryl)ureas Involving an Equilibrium Shift

Abstract

Unsymmetric di­(heteroaryl)­ureas such as HetAr1-NHCONH-HetAr2 are efficiently synthesized from two symmetric ureas, HetAr1-NHCONH-HetAr1 and HetAr2-NHCONH-HetAr2, by rhodium-catalyzed exchange reactions. The equilibrium in some of the reactions can be shifted to the formation of unsymmetric ureas by the aggregation of the dimers formed by inter- and intramolecular hydrogen bonding.