A new chiral multidentate ligand for asymmetric catalysis
作者:Achim Kless、Renat Kadyrov、Armin Börner、Jens Holz、Henri B Kagan
DOI:10.1016/0040-4039(95)00844-3
日期:1995.6
The synthesis of enantiomerically pure (R,R)-N,N′-bis(3-diphenylphosphino-2-hydroxybenzylidene)-1,2-diphenyl-1,2-ethanediamine (1) is described. This multidentate salentype ligand offers several possibilities for the construction of chiral mono-nuclear or bi-nuclear metal complexes, which may be useful in bifunctional asymmetriccatalysis.
The synthesis of new chiral salenophos-type ligands bearing 'hard' and 'soft' coordination sites is described. The polyfunctionalised ligands are used for the construction of monometallic and early-late heterobimetallic complexes. In the reaction with titanium(IV) reagents the salen subunit selectively coordinated to the 'hard' metal. The phosphine groups in turn can be coordinated to rhodium(I). The coordination geometry of the diphosphine-Rh subunit is strongly influenced by the counter ligands COD or CO and Cl, respectively. In the asymmetric hydroformylation of vinyl acetate with one of the Rh-Ti-complexes, the branched aldehyde is predominantly formed with 30% ee. (C) 1999 Elsevier Science Ltd. All rights reserved.