Axial chirale Phosphite als Liganden in der enantioselektiven Rhodium-katalysierten Hydrierung

In the pharmaceutical and agrochemical industry enantiomerically pure substances become more and more important as drugs or chiral building blocks. The Rhodium-catalyzed hydrogenation is a very effective way to produce such enantiomerically pure substances. Activity and selectivity of the Rhodium-catalyst are mainly influenced by the bounded chiral ligands. For optimizing the catalyst to different substrates, modification of the steric and electronic properties of the ligand (ligand tuning) should be easy to make. Also both optical antipodes of the ligand should be available. In order to achieve a good appreciation, the sythesis of the ligand should be easy and of low costs. As part of this work new monodentate, axially chiral phosphite-ligands with Cl-MeOBiphenyl-backbone were synthesized. The route to the key intermediate ClMeOBiphenol was improved essentially and both optical antipodes are accessable now with ee´s > 99%. In contrary to the corresponding bisphosphines the monodentate phosphites are much easier to sythesize and they are less sensitive towards oxidation. It is also easier to perform ligand tuning. These phosphite-ligands were tested in the Rhodium-catalized hydrogenation with different olefins. In the hydrogenation of dimethylitaconate, ee´s up to 99% and turnoverfrequencies higher than 5600 1/h were achieved with a hydrogen pressure of only 1.5 bar at a catalyst/substrate ratio of 1/10000. By increasing the hydrogen pressure to 10 bar the turnover frequency could be improved up to 35000 1/h without loss in enantioselectivity. It was also possible to hydrogenate 2-acetamidomethylacrylate with ee´s up to 94%. Investigations with further substrates showed, that triple substitution of the olefin and additional electron-donating atoms have a negativ impact on activity and selectivity.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Agel, Friederike

Contributors dc:contributor

• Drießen-Hölscher, Birgit

• info:eu-repo/classification/ddc/540
• Alkene
• Katalytische Hydrierung
• Asymmetrische Reaktion
• Rhodiumkomplexe
• Phosphite
• Axiale Chiralität
• Ligand
• Asymmetrische Synthese
• Chemie
• enantioselektive Hydrierung
• Rhodium Katalyse
• monodentate Phosphite
• axial chirale Biphenyle

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121666%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59926