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Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review

An increasing interest in the synthesis and use of optically active pyridine N-oxides as chiral controllers for asymmetric reactions has been observed in the last few years. Chiral heteroaromatic N-oxides can work as powerful electron-pair donors, providing suitable electronic environments in the tr...

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Autores principales: Wrzeszcz, Zuzanna, Siedlecka, Renata
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7024222/
https://www.ncbi.nlm.nih.gov/pubmed/31947566
http://dx.doi.org/10.3390/molecules25020330
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author Wrzeszcz, Zuzanna
Siedlecka, Renata
author_facet Wrzeszcz, Zuzanna
Siedlecka, Renata
author_sort Wrzeszcz, Zuzanna
collection PubMed
description An increasing interest in the synthesis and use of optically active pyridine N-oxides as chiral controllers for asymmetric reactions has been observed in the last few years. Chiral heteroaromatic N-oxides can work as powerful electron-pair donors, providing suitable electronic environments in the transition state formed within the reaction. The nucleophilicity of the oxygen atom in N-oxides, coupled with a high affinity of silicon to oxygen, represent ideal properties for the development of synthetic methodology based on nucleophilic activation of organosilicon reagents. The application of chiral N-oxides as efficient organocatalysts in allylation, propargylation, allenylation, and ring-opening of meso-epoxides, as well as chiral ligands for metal complexes catalyzing Michael addition or nitroaldol reaction, can also be found in the literature. This review deals with stereoselective applications of N-oxides, and how the differentiating properties are correlated with their structure. It contains more recent results, covering approximately the last ten years. All the reported examples have been divided into five classes, according to the chirality elements present in their basic molecular frameworks.
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spelling pubmed-70242222020-03-19 Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review Wrzeszcz, Zuzanna Siedlecka, Renata Molecules Review An increasing interest in the synthesis and use of optically active pyridine N-oxides as chiral controllers for asymmetric reactions has been observed in the last few years. Chiral heteroaromatic N-oxides can work as powerful electron-pair donors, providing suitable electronic environments in the transition state formed within the reaction. The nucleophilicity of the oxygen atom in N-oxides, coupled with a high affinity of silicon to oxygen, represent ideal properties for the development of synthetic methodology based on nucleophilic activation of organosilicon reagents. The application of chiral N-oxides as efficient organocatalysts in allylation, propargylation, allenylation, and ring-opening of meso-epoxides, as well as chiral ligands for metal complexes catalyzing Michael addition or nitroaldol reaction, can also be found in the literature. This review deals with stereoselective applications of N-oxides, and how the differentiating properties are correlated with their structure. It contains more recent results, covering approximately the last ten years. All the reported examples have been divided into five classes, according to the chirality elements present in their basic molecular frameworks. MDPI 2020-01-14 /pmc/articles/PMC7024222/ /pubmed/31947566 http://dx.doi.org/10.3390/molecules25020330 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Review
Wrzeszcz, Zuzanna
Siedlecka, Renata
Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
title Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
title_full Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
title_fullStr Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
title_full_unstemmed Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
title_short Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
title_sort heteroaromatic n-oxides in asymmetric catalysis: a review
topic Review
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7024222/
https://www.ncbi.nlm.nih.gov/pubmed/31947566
http://dx.doi.org/10.3390/molecules25020330
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