Chiral metal complexes transfer hydrogenation

Arylation, olefins, 187, 190 Arylketimines, iridium hydrogenation, 83 Arylpropanoic acid, Grignard coupling, 190 Aspartame, 8, 27 Asymmetric catalysis characteristics, 11 chiral metal complexes, 122 covalently bound intermediates, 323 electrochemistry, 342 hydrogen-bonded associates, 328 industrial applications, 8, 357 optically active compounds, 2 phase-transfer reactions, 333 photochemistry, 341 polymerization, 174, 332 purely organic compounds, 323 see also specific complexes Asymmetric induction, 71, 155 Attractive interaction, 196, 216 Autoinduction, 330 Axial chirality, 18 Aza-Diels-Alder reaction, 220 Azetidinone, 44, 80 Aziridination, olefins, 207... 

BINAP, 127, 171, 191, 194, 196 olefin reaction, 126, 167, 169, 191 organic halides, 191 Pancreatic lipase inhibitors, 357 Pantoyl lactone, 56, 59 para-hydrogen, 53 Peptides, matrix structure, 350 Perhydrotriphenylene, crystal lattice, 347 Pericyclic reactions, 212 chiral metal complexes, 212 Claisen rearrangement, 222 Diels-Alder, 212, 291 ene reaction, 222, 291 olefin dihydroxylation, 150 Phase-transfer reactions asymmetric catalysis, 333... 

Y. Wang, J. Yu, Y. Li, and R. Xu, Chirality Transfer from Guest Chiral Metal Complexes to Inorganic Framework The Role of Hydrogen Bonding. Chem.-Eur. J., 2003, 9, 5048-5055. 

Transition metal complexes with chiral phosphorous and nitrogen ligands have also been used for promoting asymmetric transfer hydrogenation. Moderate to good results have been obtained.114... 

In summary, the asymmetric hydrogenation of olefins or functionalized ketones catalysed by chiral transition metal complexes is one of the most practical methods for preparing optically active organic compounds. Ruthenium and rhodium-diphosphine complexes, using molecular hydrogen or hydrogen transfer, are the most common catalysts in this area. The hydrogenation of simple ketones has proved to be difficult with metallic catalysts. However,... 

Asymmetric transfer hydrogenation of imines catalyzed by chiral arene-Ru complexes achieves high enantioselectivity (Figure 1.34). Formic acid in aprotic dipolar solvent should be used as a hydride source. The reaction proceeds through the metal-ligand bifunctional mechanism as shown in the carbonyl reduction (Figure 1.24). 

A wide range of metals and ligand combinations have been demonstrated to effect the ATH reaction and in this book we concentrate on the systems that have demonstrated high activities and ees that would be the requirement of an industrial application. The initial breakthrough in this area came in 1995 with the report from Ohkuma et alP on the use of chiral monotosylated diamine complexes for asymmetric transfer hydrogenation. 

Blacker, A.J. and MeUor, B. J. Preparation of Chiral Arylalkanols by Transfer Hydrogenation using Chiral Metal Cyclopentadiene Complex Catalysts. PCT Int. Appl. 1998, WO 9842643 Al. 

In conclusion, we have found a convenient and practical method for the selective reduction of C=0 bond of a wide spectrum of a-keto-)S, -unsaturated esters with Ru(p-cymene)(TsDPEN) as catalyst. The transition metal catalyzed transfer hydrogenation reaction with good selectivity and high efficiency offers possibilities to provide the optically active a-hydroxy-/l, y-unsaturated esters with chiral catalysts. Table 3.8 gives different substrates that can be reduced with Ru(p-cymene) (TsDPEN) complex in isopropyl alcohol. 

Transfer hydrogenation of ketones using metal complexes with a chiral water-soluble [97,98] and a dendritic ligand [99] was investigated for use in recycling catalysts. The reaction with immobilized catalysts has also been reported [100]. 

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