A Sustainable, User‐Friendly Protocol for the Pd‐Free Sonogashira Coupling Reaction

Abstract

We herein present a new catalytic system for the palladium‐free Sonogashira coupling reaction. The catalytically active moiety is formed in situ, in a straightforward and user‐friendly manner, by combining a widely available low‐cost copper salt and an N‐heterocyclic carbene precursor. A series of N‐heterocyclic carbene ligand precursors with variable structural features, some of which are novel, were tested and the reaction conditions were optimized. Using the catalytic system with the optimum performance, the scopes of the alkyne and the aryl halide were probed. Aryl iodides readily react with terminal alkynes, providing the coupling products in high to excellent yields. The protocol is highly efficient with alkynes bearing either alkyl or aryl substituents, the latter having either electron‐donating or electron‐withdrawing groups.