Rational Exploration of N-Heterocyclic Carbene (NHC) Palladacycle Diversity: A Highly Active and Versatile Precatalyst for Suzuki-Miyaura Coupling Reactions of Deactivated Aryl and Alkyl Substrates

As less attention has been focussed on the design of highly efficient palladium precatalysts to ensure the smooth formation of the active catalyst for metal-mediated cross coupling reactions, we herein demonstrate that combining the bulky N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) with cyclopalladated acetanilide as the optimal palladium precatalyst leads to superior catalytic activity compared with the state-of-the-art NHC-Pd catalysts. The complex was discovered through the evaluation of a small, rationally designed library of NHC-palladacycles prepared by a novel, practical and atom-economic method, the direct reaction of IPr center dot HCl with palladacycle acetate dimers.