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Dienes with a twist - New ligands for asymmetric catalysis

Rolim Alves da Silva, Bianca LU (2017) KEMR31 20171
Department of Chemistry
Abstract
Chirality of organic molecules plays a big role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form remains a challenge. Asymmetric synthesis is a key process in modern chemistry and allows us to achieve the selective synthesis of one enantiomer over the other. The design and development of new chiral ligands for metals is an exciting area that offers new opportunities in the field of asymmetric catalysis. Well-designed new ligands could not only improve enantioselectivity in known reactions, but also help in the discovery of novel enantioselective process and allow access to previously inaccessible molecules. Herein, we present the design and synthesis of a new chiral diene... (More)
Chirality of organic molecules plays a big role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form remains a challenge. Asymmetric synthesis is a key process in modern chemistry and allows us to achieve the selective synthesis of one enantiomer over the other. The design and development of new chiral ligands for metals is an exciting area that offers new opportunities in the field of asymmetric catalysis. Well-designed new ligands could not only improve enantioselectivity in known reactions, but also help in the discovery of novel enantioselective process and allow access to previously inaccessible molecules. Herein, we present the design and synthesis of a new chiral diene ligand and its use in the Rh-catalyzed 1,4-addition of phenylboronic acid to cyclohexanone. The enantioselectivity obtained was below the one predicted by DFT calculations. A mechanistic study shows results that support the hypothesis of intramolecular isomerization of the ligand during the catalytic process. A change from diphenyl to dibenzyl substitution on the diene ligand has prevented this isomerization during the reaction and allowed for a high enantioselectivity to be obtained. (Less)
Popular Abstract
The universe is chiral. Chirality is the property of shapes and objects, our hands being a good example, to exist as different and non-superposable mirror-images. The two distinct forms that a chiral molecule can have are called enantiomers. Despite having the same connectivity, enantiomers might present different properties in chiral environments. One form might be the cause of therapeutic effects in a drug while the other is less active or even the cause of adverse effects on a person. That’s why the selective synthesis of one form over the other, also called asymmetric synthesis, is so important when it comes to obtaining natural products and pharmaceuticals.
One strategy commonly employed to achieve the selective synthesis of an... (More)
The universe is chiral. Chirality is the property of shapes and objects, our hands being a good example, to exist as different and non-superposable mirror-images. The two distinct forms that a chiral molecule can have are called enantiomers. Despite having the same connectivity, enantiomers might present different properties in chiral environments. One form might be the cause of therapeutic effects in a drug while the other is less active or even the cause of adverse effects on a person. That’s why the selective synthesis of one form over the other, also called asymmetric synthesis, is so important when it comes to obtaining natural products and pharmaceuticals.
One strategy commonly employed to achieve the selective synthesis of an enantiomer is asymmetric catalysis. Catalysts are substances that speed up reactions without being consumed during the process. The benefits of using catalysts in a reaction may range from decrease of energy demand to less pollution and decrease in costs of a certain product. These catalysts usually consist of a metal connected to an organic molecule, which is then able to influence the chirality of its ligand to the product. The development of new chiral ligands is therefore fundamental for its advance. Great efforts have been employed in designing and synthesizing new ligands that can improve the catalytic activity and enantioselectivity of different reactions. This work summarizes the endeavor of design, synthesis, and application of a novel twisted ligand in asymmetric catalysis. (Less)
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author
Rolim Alves da Silva, Bianca LU
supervisor
organization
course
KEMR31 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
organic chemisty, organisk kemi
language
English
id
8921723
date added to LUP
2017-08-18 13:12:06
date last changed
2017-08-18 13:12:06
@misc{8921723,
  abstract     = {Chirality of organic molecules plays a big role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form remains a challenge. Asymmetric synthesis is a key process in modern chemistry and allows us to achieve the selective synthesis of one enantiomer over the other. The design and development of new chiral ligands for metals is an exciting area that offers new opportunities in the field of asymmetric catalysis. Well-designed new ligands could not only improve enantioselectivity in known reactions, but also help in the discovery of novel enantioselective process and allow access to previously inaccessible molecules. Herein, we present the design and synthesis of a new chiral diene ligand and its use in the Rh-catalyzed 1,4-addition of phenylboronic acid to cyclohexanone. The enantioselectivity obtained was below the one predicted by DFT calculations. A mechanistic study shows results that support the hypothesis of intramolecular isomerization of the ligand during the catalytic process. A change from diphenyl to dibenzyl substitution on the diene ligand has prevented this isomerization during the reaction and allowed for a high enantioselectivity to be obtained.},
  author       = {Rolim Alves da Silva, Bianca},
  keyword      = {organic chemisty,organisk kemi},
  language     = {eng},
  note         = {Student Paper},
  title        = {Dienes with a twist - New ligands for asymmetric catalysis},
  year         = {2017},
}