Salts, organic, carbene complex synthesis

Very recently, transition metal complexes were reported where 1,2,3-triazolium salts served as precursors for 1,2,3-triazolylidene ligands (Mathew, Neels et al. 2008). However, application of these carbene complexes as catalysts in organic synthesis has not been reported so far. We tried to apply an in situ procedure in Suzuki reaction using Pd2(dba)3,... 

Kantchev EAB, O Brien CJ, Organ MG (2007) Palladium complexes of A-heterocyclic carbenes as catalysts for cross-coupling reactions - a synthetic chemist s perspective. Angew Chem Int Ed 46 2768-2813 Kerr MS, Rovis T (2004) Enantio selective synthesis of quaternary stereocenters via a catalytic asymmetric Stetter reaction. J Am Chem Soc 126 8876-8877 Kerr MS, Read de Alaniz J, Rovis T (2002) A highly enantio selective catalytic intramolecular Stetter reaction. J Am Chem Soc 124 10298-1029 Kerr MS, Read de Alaniz J, Rovis T (2005) An efficient synthesis of achiral and chiral 1,2,4-triazolium salts bench stable precursors for A-heterocyclic carbenes. J Org Chem 70 5725-5728... 

Recently, Peris and coworkers reported the synthesis of highly stable orthometallated Cp -Ir NHC complexes and a catalytic application in the deuteration of organic molecules. Complexes (227) were synthesized from imidazolium salt (225) and [IrCp Cl2]2 as metal precursor either by a one-step procedure with sodium iodide to minimize the mixture I versus Cl or by transmetallation from the corresponding silver carbene affording (226) followed by the C-H activation of the phenyl ring by the iridium... 

The aim of this Chapter is to examine the application of well-defined N-hetero-cyclic carbene (NHC) complexes as well as the systems prepared in situ which involve free NHCs or the precursor salt for the reduction of imsaturated organic molecules such as alkynes, alkenes and carbonyl compounds. The most active complexes for such reductions contain electron-rich, late transition metals in low oxidation states. Herein, reductions useful for organic synthesis will be classified into four types aeeording to reductants used (i) hydrogenations, (ii) transfer hydrogenation, (iii) hydrosilylation and (iv) hydroboration. For examples of reduction reactions with systems containing non-classical NHC ligands, the reader is referred to Chapter 5. 

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