Acid chlorides palladium complex catalysis

Another interesting approach to an NHC ligand with a chiral, bridging wingtip group was introduced by Perry et al. [45] and uses enantiomerically pure 1,2-diamino-cyclohexane as the scaffold. Reaction with chloroacetic acid chloride and subsequently with DIPP-imidazole yields the imidazolium salt that can be reacted with silver(I) oxide [46] to the respective silver(I) NHC complex. Subsequent carbene transfer to palladium(II) renders the chiral palladium(II) carbene transfer that can be used in catalysis (see Figure 5.9). 

Many other types of organometallics which are not acylated directly acid chlorides and which do not undergo addition to ketones may still transmetallate into the acylpalladiumfll) complex. Simple alkyl organomercurials have been acylated in this fashion to give moderate to good yields of ketones. " Larock has studied the palladium-catalyzed acylation of vinylmercury(II) compounds with acyl halides (equation 104). The reaction was only modestly productive and could not compare to the yield provided by aluminum chloride catalysis. 

As carboxylic acid additives increased the efficiency of palladium catalysts in direct arylations through a cooperative deprotonation/metallation mechanism (see Chapter 11) [45], their application to ruthenium catalysis was tested. Thus, it was found that a ruthenium complex modified with carboxylic acid MesC02H (96) displayed a broad scope and allowed for the efficient directed arylation of triazoles, pyridines, pyrazoles or oxazolines [44, 46). With respect to the electrophile, aryl bromides, chlorides and tosylates, including ortho-substituted derivatives, were found to be viable substrates. It should be noted here that these direct arylations could be performed at a lower reaction temperatures of 80 °C (Scheme 9.34). 

Mixed phosphorus compounds, bearing at least two different tervalent phosphorus moieties have been developed and have found several applications in catalysis. Iri li described the synthesis of aminophosphine-phosphinite ligands 149 and 150, from the commercially available 3-piperidinemethanol and 3-(methylamino) pro-pan-l-ol. Their palladium and platinum complexes 151 and 152, containing metallocyclic rings, were obtained as air-stable compounds with high yields, and characterized by P, and NMR spectroscopy, FTIR spectroscopy and X-ray crystallography. The Pd complexes were effective catalysts on Suzuki-Miyaura cross-coupling reactions of various aryl chlorides and atyl bromides with phe-nylboronic acid. 

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