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Advances in Cycloadditions: Theory, Practice, and Applications

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 19784

Special Issue Editors


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Guest Editor
Istituto di Scienze e Tecnologie Chimiche "Giulio Natta" - SCITEC, Consiglio Nazionale delle Ricerche, via C. Golgi 19, 20133 Milano, Italy
Interests: Density Functional Theory; post-SCF methods; chemical reactivity; catalysis
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Guest Editor
University of Milan, Milan, Italy
Interests: synthetic aspects of heterocyclic chemistry; 1,3-dipolar cycloadditions (enantiopure tricyclic benzodiazepines and β-lactam-based molecules); mechanistic and theoretical aspects of inter- and intra-molecular 1,3-dipolar cycloadditions; catalysis of cycloadditions by metal-oxide nanoparticles; behaviour of 1,3-dipolar species in aqueous medium

Special Issue Information

Dear Colleagues,

Cycloaddition reactions occupy a prominent place in both synthetic and mechanistic organic chemistry. The ever-growing number of papers, from the 100 papers published 50 years ago to the present-day 800+ papers published per year, witnesses the richness and diversity of this field.

Our current understanding of cycloaddition reactions relies upon the interplay between experimental, mechanistic, and theoretical results.

The synthetic effectiveness of cycloaddition reactions relies upon several key points. First, cycloadditions in both the inter- and intra-molecular version lead to products much more complex than the reactants. Next, a number of cycloadditions are able to generate carbo- or heterocyclic rings containing several contiguous stereocenters. As an intriguing topic, the absolute configuration of such newly formed stereocenters can now be controlled by the asymmetric version of cycloadditions in several ways, namely by metal-catalyzed or organo-catalyzed processes. Moreover, following the paradigm of green chemistry, a number of cycloadditions can be performed in water or aqueous media as an environmentally friendly approach. Finally, thanks to the latent array of functionalities of the cycloadducts, the latter can be transformed into a variety of other molecules, including many natural products.

Physical organic chemistry concepts and methods are widely used to elucidate the variety of cycloaddition mechanisms. The stereoconservativity (or not) of the reaction, solvent and isotope effects, and the kinetic determination of activation parameters are of great help to establish the degree of cycloaddition synchronicity and concertedness, the intermediacy of zwitterionic species, and so on.

Cycloaddition reactions have been a favorite playground for theoretical chemists for many decades since their rationalization by the orbital-based Woodward–Hoffman rules in the 1960s. Modern approaches to understanding the reactivity of cycloadditions range from ab initio calculations (based on both the wavefunction ansatz and density functional theory) to conceptual approaches exploiting calculated reactivity indices.

This Special Issue aims to present recent advances in the theory, practice, and applications of cycloadditions. It is our pleasure to invite you to submit a manuscript to this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Alessandro Ponti
Dr. Giorgio Molteni
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Cycloaddition
  • Diels–Alder cycloaddition
  • 1,3-dipolar cycloaddition
  • Staudinger cycloaddition
  • Higher-order cycloadditions
  • "click" chemistry
  • Metal-catalyzed cycloadditions
  • Organo-catalyzed cycloadditions
  • Asymmetric catalysis
  • Mechanistic analysis
  • Ab initio calculation
  • Density functional theory (DFT)
  • Reactivity indices

Published Papers (5 papers)

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Research

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18 pages, 1254 KiB  
Article
The Azide-Allene Dipolar Cycloaddition: Is DFT Able to Predict Site- and Regio-Selectivity?
by Giorgio Molteni and Alessandro Ponti
Molecules 2021, 26(4), 928; https://doi.org/10.3390/molecules26040928 - 10 Feb 2021
Cited by 6 | Viewed by 2275
Abstract
The site- and regio-selectivity of thermal, uncatalysed 1,3-dipolar cycloadditions between arylazides and mono- or tetra-substituted allenes with different electronic features have been investigated by both conceptual (reactivity indices) and computational (M08-HX, ωB97X-D, and B3LYP) DFT approaches. Both approaches show that these cycloadditions follow [...] Read more.
The site- and regio-selectivity of thermal, uncatalysed 1,3-dipolar cycloadditions between arylazides and mono- or tetra-substituted allenes with different electronic features have been investigated by both conceptual (reactivity indices) and computational (M08-HX, ωB97X-D, and B3LYP) DFT approaches. Both approaches show that these cycloadditions follow a nonpolar one-step mechanism. The experimental site- and regio-selectivity of arylazides towards methoxycarbonyl- and sulfonyl-allenes as well as tetramethyl- and tetrafluoro-allenes was calculated by DFT transition state calculations, achieving semiquantitative agreement to both previous and novel experimental findings. From the mechanistic standpoint, 1H-NMR evidence of a methylene-1,2,3-triazoline intermediate reinforces the reliability of the computational scheme. Full article
(This article belongs to the Special Issue Advances in Cycloadditions: Theory, Practice, and Applications)
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12 pages, 2744 KiB  
Article
Microwave-Assisted Synthesis of Fluorescent Pyrido[2,3-b]indolizines from Alkylpyridinium Salts and Enaminones
by Ekaterina A. Sokolova, Alexey A. Festa, Karthikeyan Subramani, Victor B. Rybakov, Alexey V. Varlamov, Leonid G. Voskressensky and Erik V. Van der Eycken
Molecules 2020, 25(18), 4059; https://doi.org/10.3390/molecules25184059 - 05 Sep 2020
Cited by 6 | Viewed by 3006
Abstract
Pyridinium ylides are well recognized as dipoles for cycloaddition reactions. In its turn, the microwave-assisted interaction of N-(cyanomethyl)-2-alkylpyridinium salts with enaminones unexpectedly proceeds as a domino sequence of cycloisomerization and cyclocondensation reactions, instead of a 1,3-dipolar cycloaddition. The reaction takes place in [...] Read more.
Pyridinium ylides are well recognized as dipoles for cycloaddition reactions. In its turn, the microwave-assisted interaction of N-(cyanomethyl)-2-alkylpyridinium salts with enaminones unexpectedly proceeds as a domino sequence of cycloisomerization and cyclocondensation reactions, instead of a 1,3-dipolar cycloaddition. The reaction takes place in the presence of sodium acetate as base and employs benign solvents. The optical properties of the resulting pyrido[2,3-b]indolizines were studied, showing green light emission with high fluorescence quantum yields. Full article
(This article belongs to the Special Issue Advances in Cycloadditions: Theory, Practice, and Applications)
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26 pages, 5122 KiB  
Article
Unveiling the Lewis Acid Catalyzed Diels–Alder Reactions Through the Molecular Electron Density Theory
by Luis R. Domingo, Mar Ríos-Gutiérrez and Patricia Pérez
Molecules 2020, 25(11), 2535; https://doi.org/10.3390/molecules25112535 - 29 May 2020
Cited by 32 | Viewed by 4356
Abstract
The effects of metal-based Lewis acid (LA) catalysts on the reaction rate and regioselectivity in polar Diels–Alder (P-DA) reactions has been analyzed within the molecular electron density theory (MEDT). A clear linear correlation between the reduction of the activation energies and the increase [...] Read more.
The effects of metal-based Lewis acid (LA) catalysts on the reaction rate and regioselectivity in polar Diels–Alder (P-DA) reactions has been analyzed within the molecular electron density theory (MEDT). A clear linear correlation between the reduction of the activation energies and the increase of the polar character of the reactions measured by analysis of the global electron density transfer at the corresponding transition state structures (TS) is found, a behavior easily predictable by analysis of the electrophilicity ω and nucleophilicity N indices of the reagents. The presence of a strong electron-releasing group in the diene changes the mechanism of these P-DA reactions from a two-stage one-step to a two-step one via formation of a zwitterionic intermediate. However, this change in the reaction mechanism does not have any chemical relevance. This MEDT study makes it possible to establish that the more favorable nucleophilic/electrophilic interactions taking place at the TSs of LA catalyzed P-DA reactions are responsible for the high acceleration and complete regioselectivity experimentally observed. Full article
(This article belongs to the Special Issue Advances in Cycloadditions: Theory, Practice, and Applications)
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Review

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50 pages, 45389 KiB  
Review
Diels–Alder Cycloaddition to the Bay Region of Perylene and Its Derivatives as an Attractive Strategy for PAH Core Expansion: Theoretical and Practical Aspects
by Aneta Kurpanik, Marek Matussek, Piotr Lodowski, Grażyna Szafraniec-Gorol, Michał Krompiec and Stanisław Krompiec
Molecules 2020, 25(22), 5373; https://doi.org/10.3390/molecules25225373 - 17 Nov 2020
Cited by 10 | Viewed by 5877
Abstract
PAHs (polycyclic aromatics hydrocarbons), the compound group that contains perylene and its derivatives, including functionalized ones, have attracted a great deal of interest in many fields of science and modern technology. This review presents all of the research devoted to modifications of PAHs [...] Read more.
PAHs (polycyclic aromatics hydrocarbons), the compound group that contains perylene and its derivatives, including functionalized ones, have attracted a great deal of interest in many fields of science and modern technology. This review presents all of the research devoted to modifications of PAHs that are realized via the Diels–Alder (DA) cycloaddition of various dienophiles to the bay regions of PAHs, leading to the π-extension of the starting molecule. This type of annulative π-extension (APEX) strategy has emerged as a powerful and efficient synthetic method for the construction of polycyclic aromatic hydrocarbons and their functionalized derivatives, nanographenes, and π-extended fused heteroarenes. Then, [4 + 2] cycloadditions of ethylenic dienophiles, -N=N-, i.e., diazo-dienophiles and acetylenic dienophiles, are presented. This subject is discussed from the organic synthesis point of view but supported by theoretical calculations. The possible applications of DA cycloaddition to PAH bay regions in various science and technology areas, and the prospects for the development of this synthetic method, are also discussed. Full article
(This article belongs to the Special Issue Advances in Cycloadditions: Theory, Practice, and Applications)
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23 pages, 3841 KiB  
Review
The Application of Biomass-Based Catalytic Materials in the Synthesis of Cyclic Carbonates from CO2 and Epoxides
by Li Guo, Ran Zhang, Yuge Xiong, Dandan Chang, Haoran Zhao, Wenbo Zhang, Wei Zheng, Jialing Chen and Xiaoqin Wu
Molecules 2020, 25(16), 3627; https://doi.org/10.3390/molecules25163627 - 10 Aug 2020
Cited by 17 | Viewed by 3481
Abstract
The synthesis of cyclic carbonates from carbon dioxide (CO2) and epoxides is a 100% atom economical reaction and an attractive pathway for CO2 utilisation. Because CO2 is a thermodynamically stable molecule, the use of catalysts is mandatory in reducing [...] Read more.
The synthesis of cyclic carbonates from carbon dioxide (CO2) and epoxides is a 100% atom economical reaction and an attractive pathway for CO2 utilisation. Because CO2 is a thermodynamically stable molecule, the use of catalysts is mandatory in reducing the activation energy of the CO2 conversion. Considering environmental compatibility and the high-efficiency catalytic conversion of CO2, there is the strong need to develop green catalysts. Biomass-based catalysts, a type of renewable resource, have attracted considerable attention due to their unique properties—non-toxic, low-cost, pollution-free, etc. In this review, recent advances in the development of biomass-based catalysts for the synthesis of cyclic carbonates by CO2 and epoxides coupling are summarized and discussed in detail. The effect of biomass-based catalysts, functional groups, reaction conditions, and co-catalysts on the catalytic efficiency and selectivity of synthesizing cyclic carbonates process is discussed. We intend to provide a comprehensive understanding of recent experimental and theoretical progress of CO2 and epoxides coupling reaction and pave the way for both CO2 conversion and biomass unitization. Full article
(This article belongs to the Special Issue Advances in Cycloadditions: Theory, Practice, and Applications)
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