Regio- and Stereoselectivity in Cycloaddition Reactions

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (30 August 2022) | Viewed by 6808

Special Issue Editor


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Guest Editor
Institute of Organic Chemistry & Technology, Cracow University of Technology, Warszawska 24, 31‐155 Krakow, Poland
Interests: cycloaddition reactions; nitrocompounds; cycloaddition; heterocycles; reaction mechanisms; organic reactivity; DFT calculations
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Special Issue Information

Cycloaddition reactions are the most universal protocol for the preparation of a wide range of carbo- and heterocyclic molecular systems. In this way, it is possible to synthesize three-, four-, five-, six- (etc.) membered cyclic molecules, including almost any combination of heteroatoms. Most of these types of processes proceed with high yields and selectivity. Additionally, cycloaddition reactions are realized with full atomic economy. Therefore, this class of organic processes is valuable from the point of view of green chemistry.

The latest discoveries shed new insight into the mechanisms of cycloaddition processes, as well as the factors that stimulate chemo-, regio-, and stereoselectivity. It should be noted that in the case of reactions involving functionalized addents, the cycloaddition process can take place on two regioisomeric paths, within which two stereoisomeric forms are possible. Sometimes there is a perfect symmetry between the yields of the individual pair of isomers. This symmetry may be broken due to the occurrence of certain electronic and steric effects. Further symmetry breakdown in the regio- and stereochemistry of cycloaddition can take place when the one-step mechanism gives way to the stepwise mechanism with a biradical or zwitterionic intermediate. So, this issue should attract significant attention from organic chemists.

This Special Issue is especially dedicated to the presentation of new, important discoveries in the mentioned field. In particular, we invite short laboratory notes, including rare cases of the reaction course, full papers with comprehensive studies, kinetic considerations about substituent and/or solvent effects, as well as activation parameters, preparation of analogs of natural products, mechanistic experimental and/or theoretical studies, prediction of the reactivity and selectivity on the basis of modern organic theories. Review articles by experts in the field are also welcome.

Prof. Dr. Radomir Jasiński
Guest Editor

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Keywords

  • Cycloaddition
  • Regio- and stereoselectivity
  • Reaction mechanisms
  • Zwitterions and biradicals
  • Quantum-chemical computational study
  • Molecular electron density theory

Published Papers (2 papers)

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Review

17 pages, 4728 KiB  
Review
On the Question of Stepwise [4+2] Cycloaddition Reactions and Their Stereochemical Aspects
by Radomir Jasiński
Symmetry 2021, 13(10), 1911; https://doi.org/10.3390/sym13101911 - 11 Oct 2021
Cited by 20 | Viewed by 3564
Abstract
Even at the end of the twentieth century, the view of the one-step [4+2] cycloaddition (Diels-Alder) reaction mechanism was widely accepted as the only possible one, regardless of the nature of the reaction components. Much has changed in the way these reactions are [...] Read more.
Even at the end of the twentieth century, the view of the one-step [4+2] cycloaddition (Diels-Alder) reaction mechanism was widely accepted as the only possible one, regardless of the nature of the reaction components. Much has changed in the way these reactions are perceived since then. In particular, multi-step mechanisms with zwitterionic or diradical intermediates have been proposed for a number of processes. This review provided a critical analysis of such cases. Full article
(This article belongs to the Special Issue Regio- and Stereoselectivity in Cycloaddition Reactions)
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21 pages, 51532 KiB  
Review
Acyl(imidoyl)ketenes: Reactive Bidentate Oxa/Aza-Dienes for Organic Synthesis
by Ekaterina A. Lystsova, Ekaterina E. Khramtsova and Andrey N. Maslivets
Symmetry 2021, 13(8), 1509; https://doi.org/10.3390/sym13081509 - 17 Aug 2021
Cited by 9 | Viewed by 2499
Abstract
Polyfunctional building blocks are essential for the implementation of diversity-oriented synthetic strategies, highly demanded in small molecule libraries’ design for modern drug discovery. Acyl(imidoyl)ketenes are highly reactive organic compounds, bearing both oxa- and aza-diene moieties, conjugated symmetrically to the ketene fragment, enabling synthesis [...] Read more.
Polyfunctional building blocks are essential for the implementation of diversity-oriented synthetic strategies, highly demanded in small molecule libraries’ design for modern drug discovery. Acyl(imidoyl)ketenes are highly reactive organic compounds, bearing both oxa- and aza-diene moieties, conjugated symmetrically to the ketene fragment, enabling synthesis of various skeletally diverse heterocycles on their basis. The highlights of reactions utilizing acyl(imidoyl)ketenes are high yields, short reaction time (about several minutes), high selectivity, atom economy, and simple purification procedures, which benefits the drug discovery. The present review focuses on the approaches to thermal generation of acyl(imidoyl)ketenes, patterns of their immediate transformations via intra- and intermolecular reactions, including the reactions of cyclodimerization, in which either symmetric or dissymmetric heterocycles can be formed. Recent advances in investigations on mechanisms, identifications of intermediates, and chemo- and regioselectivity of reactions with participation of acyl(imidoyl)ketenes are also covered. Full article
(This article belongs to the Special Issue Regio- and Stereoselectivity in Cycloaddition Reactions)
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Scheme 1

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