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Synthesis and Catalytic Properties of Pseudo-Cs-Symmetric Heterometallic Bissalen Complexes

Li, Yutang LU (2017) KEMR31 20171
Department of Chemistry
Abstract
Asymmetric synthesis has been an active research topic for the past decades since it can lead to enantiopure compounds that are of great importance in biology and medicinal chemistry. Among all the synthetic strategies that have been developed, asymmetric ring-opening of epoxides received much attention for their ability to providing precursors for β-amino alcohols. Efforts have been made to achieve high enantioselectivity in this class of reaction, and chiral metal-salen complexes are found to be highly effective catalysts.

In this project, two novel bimetallic bissalen complexes 9a and 9b with pseudo-Cs-symmetry have been synthesized to be aimed to give better enantioselectivity in asymmetric ring-opening of epoxides. Characterization... (More)
Asymmetric synthesis has been an active research topic for the past decades since it can lead to enantiopure compounds that are of great importance in biology and medicinal chemistry. Among all the synthetic strategies that have been developed, asymmetric ring-opening of epoxides received much attention for their ability to providing precursors for β-amino alcohols. Efforts have been made to achieve high enantioselectivity in this class of reaction, and chiral metal-salen complexes are found to be highly effective catalysts.

In this project, two novel bimetallic bissalen complexes 9a and 9b with pseudo-Cs-symmetry have been synthesized to be aimed to give better enantioselectivity in asymmetric ring-opening of epoxides. Characterization of 9a and 9b have been done by MS and visible spectroscopy. Catalytic properties of 9a and 9b with respect to the asymmetric ring-opening of epoxides were investigated with variation of reaction conditions, catalyst loading, epoxides and nucleophiles. Comparison with previously reported pseudo-C2-symmetric bissalen complexes indicated a less favored transition state when 9a and 9b were applied in catalysis of asymmetric ring-opening of epoxides. (Less)
Popular Abstract
Modern pharmaceutical industry relies very much on the development of asymmetric catalysts. This is because many drug molecules are chiral. A chiral molecule always has a “twin brother” that looks like its mirror image, also known as its enantiomer. During a chemical reaction, if no special condition is applied, a chiral molecule tends to be produced together with its enantiomer in equal amount. However, in pharmaceutical industry, people often favor only one of the enantiomers, thus asymmetric catalysts were developed. Asymmetric catalysts are a class of complexes with chiral ligands coordinated by transition metal cations. During a reaction, they can interact with a certain configuration and therefore increase the ratio of this... (More)
Modern pharmaceutical industry relies very much on the development of asymmetric catalysts. This is because many drug molecules are chiral. A chiral molecule always has a “twin brother” that looks like its mirror image, also known as its enantiomer. During a chemical reaction, if no special condition is applied, a chiral molecule tends to be produced together with its enantiomer in equal amount. However, in pharmaceutical industry, people often favor only one of the enantiomers, thus asymmetric catalysts were developed. Asymmetric catalysts are a class of complexes with chiral ligands coordinated by transition metal cations. During a reaction, they can interact with a certain configuration and therefore increase the ratio of this enantiomer in products. To synthesize more types of chiral molecules with high selectivity, efforts have been made to design different kinds of asymmetric catalysts for various reactions.

Here in this project, we designed and synthesized the first asymmetric catalyst based on an achiral ligand. As it shows in Fig 1, the ligand that we synthesized is achiral, just like the balance on the left. It is superposable on its mirror image. But when we coordinate this ligand with two different metal ions, the symmetry is broken and a weak chirality is generated in the formed complex. And to our delight, with such small modification to an achiral ligand, the new class of bimetallic catalysts show good enantioselectivity when applied to the asymmetric ring-opening of epoxides. This project provide an alternative thinking on the design of asymmetric catalysts. (Less)
Please use this url to cite or link to this publication:
author
Li, Yutang LU
supervisor
organization
course
KEMR31 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
organic chemistry, organisk kemi
language
English
id
8919357
date added to LUP
2017-07-13 11:26:29
date last changed
2017-07-13 11:26:29
@misc{8919357,
  abstract     = {Asymmetric synthesis has been an active research topic for the past decades since it can lead to enantiopure compounds that are of great importance in biology and medicinal chemistry. Among all the synthetic strategies that have been developed, asymmetric ring-opening of epoxides received much attention for their ability to providing precursors for β-amino alcohols. Efforts have been made to achieve high enantioselectivity in this class of reaction, and chiral metal-salen complexes are found to be highly effective catalysts.

In this project, two novel bimetallic bissalen complexes 9a and 9b with pseudo-Cs-symmetry have been synthesized to be aimed to give better enantioselectivity in asymmetric ring-opening of epoxides. Characterization of 9a and 9b have been done by MS and visible spectroscopy. Catalytic properties of 9a and 9b with respect to the asymmetric ring-opening of epoxides were investigated with variation of reaction conditions, catalyst loading, epoxides and nucleophiles. Comparison with previously reported pseudo-C2-symmetric bissalen complexes indicated a less favored transition state when 9a and 9b were applied in catalysis of asymmetric ring-opening of epoxides.},
  author       = {Li, Yutang},
  keyword      = {organic chemistry,organisk kemi},
  language     = {eng},
  note         = {Student Paper},
  title        = {Synthesis and Catalytic Properties of Pseudo-Cs-Symmetric Heterometallic Bissalen Complexes},
  year         = {2017},
}