[(NHC)Pd(OAc)2]: Highly Active Carboxylate Pd(II)–NHC (NHC = N-Heterocyclic Carbene) Precatalysts for Suzuki–Miyaura and Buchwald–Hartwig Cross-Coupling of Amides by N–C(O) Activation

Abstract

In the past eight years, the selective cross-coupling of amides by N–C(O) bond activation has emerged as a highly attractive manifold for the manipulation of traditionally unreactive amide bonds. In this Special Issue on Next-Generation Cross-Coupling Chemistry, we report the Suzuki–Miyaura and Buchwald–Hartwig cross-coupling of amides by selective N–C(O) cleavage catalyzed by bench-stable, well-defined carboxylate Pd(II)–NHC (NHC = N-heterocyclic carbene) catalysts {[(NHC)Pd(O₂CR)₂]}. This class of Pd(II)–NHCs promotes cross-coupling under exceedingly mild room-temperature conditions owing to the facile dissociation of the carboxylate ligands to form the active complex. These readily accessible Pd(II)–NHC precatalysts show excellent functional group tolerance and are compatible with a broad range of amide activating groups. Considering the mild conditions for the cross-coupling and the facile access to carboxylate Pd(II)–NHC complexes, we anticipate that this class of bench-stable complexes will find wide application in the activation of amide N–C(O) and related acyl X–C(O) bonds.