Iridium Complexes with Phosphine−Phosphite Ligands. Structural Aspects and Application in the Catalytic Asymmetric Hydrogenation of N-Aryl Imines
Citations Over TimeTop 10% of 2006 papers
Abstract
A family of modularly designed phosphine−phosphites (P−OP), possessing a C−C−O backbone, has been synthesized and evaluated in the iridium-catalyzed asymmetric hydrogenation of N-aryl imines. The enantioselectivity of this reaction is highly dependent on the nature of the ligand, and catalysts bridged by an oxyethylene fragment have produced significantly higher enantiomeric excesses (Δee > 20%) than their o-oxyphenylene counterparts. Structural studies by X-ray crystallography and NMR spectroscopy of complexes with the formulation [Ir(COD)(P−OP)]BF4 and Ir(Cl)(CO)(P−OP), complemented by DFT calculations of model compounds of the chlorocarbonyls, have shown important differences between complexes bridged by an aliphatic or an aromatic bridge, regarding the iridacycle conformation and the location of phosphine substituents. Catalyst optimization has afforded enantioselectivities from 72 to 85% ee in the hydrogenation of several N-aryl imines.
Related Papers
- → Iridium catalysts for the asymmetric hydrogenation of olefins with nontraditional functional substituents(2007)236 cited
- → The synthesis of new chiral phosphine–phosphinites, phosphine–phosphoramidite, and phosphine–phosphite ligands and their applications in asymmetric hydrogenation(2004)64 cited
- → Recent Advances in Iridium-Catalyzed Asymmetric Hydrogenation: New Catalysts, Substrates and Applications in Total Synthesis(2012)11 cited
- → Asymmetric iridium-catalyzed hydrogenation of 2-methylindole using phosphite ligands(2014)14 cited
- → The crystal structure of [Ir4(CO)9{Ph2P3CH}];a phosphine substituted iridium cluster with all-terminal CO ligands(1984)23 cited