Catalytic cross-coupling reactions mediated by palladium/nucleophilic carbene systems

Heck Reaction—State of the Art

“…Hillier et al [17] have reviewed the catalytic cross-coupling reactions mediated by palladium with nucleophilic NHC as ancillary ligands of diazabutadienes 38-40 ( Figure 6) mostly based on their own work.…”

The crystal structure of 1,3-bis(2,6-diiso-propylphenyl)imidazol-2-ylidene)-dibromido-(1-methyl-1H-imidazole-κ1N)palladium(II) – ethyl acetate – water (1/1/1), C31H42Br2N4Pd

“…During the past years, N-heterocyclic carbene-palladium complexes have been proven e cient catalysts in the traditional cross-coupling reactions [6][7][8][9][10]. For instance, the synthesis of [1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-2(3H)-ylidene]palladium complex, from easily available starting materials in a one-pot procedure was reported [1].…”

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“…In particular, the imidazol-2-ylidenes, which can be considered phosphine mimics, have been regarded as possible alternatives for the widely used phosphine ligands in homogeneous catalysis. [98][99][100] In fact, several successful applications of palladium catalyst systems in which these carbenes are used as supporting ligands have been reported in the literature. The success of these ligands is due to the fact that they coordinate tightly to palladium, thus disfavouring the formation of Pd black, 101 and that the thermal stability of the Pd-NHC bond avoids the necessity for excess ligand.…”