Carbamoyl-Substituted N-Heterocyclic Carbene Complexes of Palladium(II):  Application to Sonogashira Cross-Coupling Reactions

[reaction: see text]. The first examples of N-carbamoyl-substituted heterocyclic carbene Pd(II) complexes are described. These thermal and hydrolytically stable complexes are readily prepared from carbamoyl imidazolium salts and efficiently promote Sonogashira cross-coupling reactions under mild conditions. Cesium carbonate is also shown to be an effective base for the coupling of aryl bromides.