Neue chirale Triazoliumsalze in der Carben-katalysierten intramolekularen gekreuzten Benzoin-Reaktion
type: CreativeWork
description: In nature many metal free catalytic reactions are accomplished in enzymes. The broad facilities of organocatalysis as a selective and environment-friendly synthetic method has only been recognized recently by chemists. This thesis deals with the synthesis of novel chiral polycylic triazolim salts as pre-catalysts for N-heterocyclic carbenes. Their application was shown in the first asymmetric intramolecular aldehyde-ketone benzoin reaction. Different alpha-hydroxy-tetralone, - indanone- and -chromanone-derivatives could be obtained with generation of a quaternary stereogenic center with high enantioselectivities. This alpha-hydroxy-ketones are structural motifs of many bioactive natural products. Thus, synthetic concepts for the synthesis of (S)-eucomol and (S)-lacinilen C methylether have been followed. Furthermore, an efficient proline-catalyzed asymmetric intramolecular 5-enolexo aldol reaction for the cis-selective synthesis of 3-hydroxy-2,3-dihydrobenzofuranes has been developed. After a simple 1,2-addition the corresponding tertiary alcohols can be obtained which are structural motifs in many bioactive natural products such as the coumarins smyrindiol and vaginidiol.
abstract: In nature many metal free catalytic reactions are accomplished in enzymes. The broad facilities of organocatalysis as a selective and environment-friendly synthetic method has only been recognized recently by chemists. This thesis deals with the synthesis of novel chiral polycylic triazolim salts as pre-catalysts for N-heterocyclic carbenes. Their application was shown in the first asymmetric intramolecular aldehyde-ketone benzoin reaction. Different alpha-hydroxy-tetralone, - indanone- and -chromanone-derivatives could be obtained with generation of a quaternary stereogenic center with high enantioselectivities. This alpha-hydroxy-ketones are structural motifs of many bioactive natural products. Thus, synthetic concepts for the synthesis of (S)-eucomol and (S)-lacinilen C methylether have been followed. Furthermore, an efficient proline-catalyzed asymmetric intramolecular 5-enolexo aldol reaction for the cis-selective synthesis of 3-hydroxy-2,3-dihydrobenzofuranes has been developed. After a simple 1,2-addition the corresponding tertiary alcohols can be obtained which are structural motifs in many bioactive natural products such as the coumarins smyrindiol and vaginidiol.
author: Niemeier, Oliver
language: ger
keywords: info:eu-repo/classification/ddc/540, Katalyse, Organische Chemie, Naturstoff, Wirkstoff, Stereoselektive Synthese, Organische Synthese, Asymmetrische Synthese, Chemie, Organokatalyse, Carben, Benzoin-Reaktion, intramolekular, asymmetrisch, organocatalysis, carbene, natural product, benzoin reaction, intramolecular
date published: 2007
date modified: 2026-07-30T19:43:10Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Mainz