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.