Publikationsserver der RWTH Aachen University
Synthese neuer C 1-symmetrischer Monosulfoximine und deren Anwendung als Liganden in der asymmetrischen Katalyse
Abstract
dc:descriptionThis PhD thesis describes the development of a new class of C1-symmetric monosulfoximines and their application as ligands in asymmetric catalysis. The main question, with which the research was concerned, is whether a ligand which does not possess C2-symmetry and has only one chiral sulfoximine unit can transfer chirality during catalysis. The structures of existing aryl- and ethylene-bridged C2-symmetric bissulfoximines served as inspiration for the design of C1-symmetric structures in which one of the two sulfoximine units was replaced by an achiral N-donor group. The availability of a multitude of chiral sulfoximines, which can be prepared in enantiopure form using established procedures, as well as the possibility of attaching various groups to the sulfoximine nitrogen, allowed the synthesis of a broad range of C1-symmetric compounds with different steric and electronic characteristics. The new C1-symmetric monosulfoximines were shown to chelate copper(II) salts and the resulting complexes were used as chiral Lewis acids in several asymmetrical catalyses. Extensive investigations into their use in the hetero-Diels-Alder reaction of electron deficient aldehydes and ketones with various dienes showed that the cycloaddition products could be obtained in enantiomeric excesses of up to 96%. X-ray crystallography of the copper-catalyst allowed its structure to be determined. Based on this, an explanation of the origin of the observed asymmetric inductions could be proposed and possible modifications for improvement determined. Accordingly, an optimized ligand was synthesized which increased the enantioselectivity of the hetero-Diels-Alder reaction of ethylglyoxylate with 1,3-cyclohexadiene. Use of the monosulfoximines as ligands in Cu(II)-catalyzed Mukaiyama aldol reactions between various silylenolethers and Alpha-ketoesters gave better results than the corresponding C2-symmetric bissulfoximines (giving the addition product in up to 85% ee, compared with 58% for the bissulfoximines). Overall, the new C1-symmetric monosulfoximines have been shown to act as efficient ligands in asymmetric catalysis and it has been proven that structures which have only one chiral sulfoximine unit are comparable with, and in some cases an improvement on, their C2-symmetric bissulfoximine analogues. Finally, during this work a novel synthesis of sulfoximine-based heterocycles was developed which involves palladium-catalyzed intramolecular Alpha-arylation of N-(2-bromobenzyl)- and N-(2-bromobenzoyl)sulfoximines. This protocol expands the current repertoire of conversions which the sulfoximine unit can undergo and lays the basis for the construction of new ligand structures.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2004
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Verrucci, Marinella
- Contributors dc:contributor
-
- Bolm, Carsten
Subjects
dc:subject × 11Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger