Synthese von planar chiralen Imidazoliumsalzen, ihren Metall-Carbenkomplexen und deren Verwendung in der asymmetrischen Katalyse

In addition to the properties of central and axial chirality, planar chirality plays a significant role in many asymmetric catalytic processes. The concept of planar chirality is often implemented by the application of metallocenes such as ferrocene derivatives. Some industrially important syntheses are amongst those processes, including the preparation of the herbicide (S)-metolachlor, which is obtained through an asymmetric hydrogenation reaction mediated by a ferrocenyldiphosphane. [2.2]Paracyclophanes constitute another important class of planar chiral substances, which are also established as ligands in asymmetric catalysis. In this thesis, the planar chirality of the paracyclophanes was combined with the concept of N-heterocyclic carbenes, in order to develop new ligands for asymmetric catalysis. N-heterocyclic carbenes have been investigated since the early 90s to identify their potential as ligands in homogenous catalysis, and thus represent at present an interesting alternative to the commonly used phosphanes. Starting from enantiopure pseudo-ortho-dibromo[2.2]paracyclophane, different paracyclophanylimidazolium salts were synthesized, and either subsequently transformed to their metal complexes or directly used in catalytic reactions. Hence, various paracyclophanyliridium complexes with N-heterocyclic carbene ligands and oxazolino- or phosphinoligands, respectively, were prepared and used as catalysts in the asymmetric hydrogenation of functionalized and unfunctionalized olefins. Furthermore, new palladium allylcomplexes with carbene-oxazolinyl-paracyclophanylligands were isolated and tested for their catalytic properties in the palladium-catalyzed allylic substitution. Finally, the application of paracyclophanylimidazolium salts in the rhodium-catalyzed, asymmetric addition of arylboronic acids to aromatic aldehydes to give diarylmethanols was investigated.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2003

Author dc:creator

• Focken, Thilo

Contributors dc:contributor

• Bolm, Carsten

• info:eu-repo/classification/ddc/540
• Übergangsmetallkomplexe
• Carbene
• Imidazoliumsalze
• Paracyclophane
• Asymmetrische Synthese
• Katalyse
• Chemie
• Hydrierung

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123551%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61943