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Catalysts
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Organocatalysis: Mechanistic Investigations, Design, and Applications
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Organocatalysis: Mechanistic Investigations, Design, and Applications

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalysis in Organic and Polymer Chemistry".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 20702

Special Issue Editor

Dr. Cristina Trujillo

E-Mail Website
Guest Editor
Trinity Biomedical Sciences Institute, School of Chemistry, Trinity Dublin College, D02 R590 Dublin 2, Ireland
Interests: computationally led catalyst design within asymmetric organocatalysis

Special Issue Information

Dear Colleagues,

Catalysis remains one of the most challenging topics in contemporary organic chemistry. Because of the absence of transition metals, organocatalytic methods are attractive for the preparation of pharmaceutical compounds where levels of certain metal-ion contamination are tightly controlled. While the asymmetric organocatalysis field is currently growing exponentially, an understanding of the mechanistic details involved in most of these reactions has often lagged far behind the pace of catalyst development, which retards catalyst design. However, over the last two decades, computational methods have become a cost-effective treatment of large chemical systems with reasonable accuracy. Remarkably, density functional theory (DFT) has been especially useful in the field of organic chemistry in order to elucidate the mechanisms behind chemical reactions.

This Special Issue focuses on synthetic and computational organic chemistry and their contributions to enlarge and enhance our understanding of organocatalysis. This will include studying, predicting, understanding, and validating chemical reactivity in catalytic systems.

Dr. Cristina Trujillo
Guest Editor

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. Catalysts is an international peer-reviewed open access monthly 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

  • Computational chemistry
  • Organocatalysis
  • Chemical reactivity and mechanism
  • Organic chemistry

Published Papers (6 papers)

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Research

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14 pages, 3051 KiB  
Article
Kinetic Resolution in Transannular Morita-Baylis-Hillman Reaction: An Approximation to the Synthesis of Sesquiterpenes from Guaiane Family
by Raquel Mato, Rubén Manzano, Efraím Reyes, Liher Prieto, Uxue Uria, Luisa Carrillo and Jose L. Vicario
Catalysts 2022, 12(1), 67; https://doi.org/10.3390/catal12010067 - 08 Jan 2022
Cited by 1 | Viewed by 1834
Abstract
An approximation to the synthesis of several sesquiterpenes from the Guaiane family is described in which the core structure was obtained through a transannular Morita-Baylis-Hillman reaction performed under kinetic resolution. Several manipulations of the obtained MBH adduct have been carried out directed towards [...] Read more.
An approximation to the synthesis of several sesquiterpenes from the Guaiane family is described in which the core structure was obtained through a transannular Morita-Baylis-Hillman reaction performed under kinetic resolution. Several manipulations of the obtained MBH adduct have been carried out directed towards the total synthesis of γ-Gurjunene, to the formal synthesis of Clavukerin A, to the synthesis of a non-natural isomer of isoguaiane and to the synthesis of an advanced intermediate in the total synthesis of Palustrol. Full article
(This article belongs to the Special Issue Organocatalysis: Mechanistic Investigations, Design, and Applications)
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14 pages, 3375 KiB  
Article
Organocatalytic Asymmetric Michael Addition in Aqueous Media by a Hydrogen-Bonding Catalyst and Application for Inhibitors of GABAB Receptor
by Jae Ho Shim, Yeonsun Hong, Ji Hae Kim, Hyeon Soo Kim and Deok-Chan Ha
Catalysts 2021, 11(9), 1134; https://doi.org/10.3390/catal11091134 - 21 Sep 2021
Cited by 6 | Viewed by 3146
Abstract
Catalysts based on (R, R)-1,2-diphenylethylenediamine are, as chiral organic catalysts, applied to the asymmetric Michael addition to α, β-unsaturated nitroalkenes under neutral conditions. The role of an aqueous medium for organic catalytic activity can be reversed concerning hydrophilic-hydrophobic [...] Read more.
Catalysts based on (R, R)-1,2-diphenylethylenediamine are, as chiral organic catalysts, applied to the asymmetric Michael addition to α, β-unsaturated nitroalkenes under neutral conditions. The role of an aqueous medium for organic catalytic activity can be reversed concerning hydrophilic-hydrophobic function depending on the reaction conditions. In this study, to provide an environmentally friendly system, the thiourea-based catalyst substituted with 3,5-(CF3)2-Ph was used in water solvents. The hydrophobic effect of the substituent provided fast reaction, high chemical yield, and mirror-image selectivity. This reaction allowed the preparation of GABAB agonists in an optically pure manner. Additionally, GABA (γ-aminobutyric acid) analogs such as baclofen and phenibut were synthesized as R-type S-type with high optical purity. Full article
(This article belongs to the Special Issue Organocatalysis: Mechanistic Investigations, Design, and Applications)
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17 pages, 2780 KiB  
Article
Triazolium Salt Organocatalysis: Mechanistic Evaluation of Unusual Ortho-Substituent Effects on Deprotonation
by Peter Quinn, Matthew S. Smith, Jiayun Zhu, David R. W. Hodgson and AnnMarie C. O’Donoghue
Catalysts 2021, 11(9), 1055; https://doi.org/10.3390/catal11091055 - 30 Aug 2021
Cited by 2 | Viewed by 2965
Abstract
Organocatalysis by N-heterocyclic carbenes is normally initiated by the deprotonation of precursor azolium ions to form active nucleophilic species. Substituent effects on deprotonation have an impact on catalytic efficiency and provide insight into general catalytic mechanisms by commonly used azolium systems. Using an [...] Read more.
Organocatalysis by N-heterocyclic carbenes is normally initiated by the deprotonation of precursor azolium ions to form active nucleophilic species. Substituent effects on deprotonation have an impact on catalytic efficiency and provide insight into general catalytic mechanisms by commonly used azolium systems. Using an NMR kinetic method for the analysis of C(3)-H/D exchange, we determined log kex–pD profiles for three ortho-substituted N-aryl triazolium salts, which enables a detailed analysis of ortho-substituent effects on deprotonation. This includes N-5-methoxypyrid-2-yl triazolium salt 7 and di-ortho-methoxy and di-ortho-isopropoxyphenyl triazolium salts 8 and 9, and we acquired additional kinetic data to supplement our previously published analysis of N-pyrid-2-yl triazolium salt 6. For 2-pyridyl triazoliums 6 and 7, novel acid catalysis of C(3)-H/D exchange is observed under acidic conditions. These kinetic data were supplemented by DFT analyses of the conformational preferences of 6 upon N-protonation. A C(3) deprotonation mechanism involving intramolecular general base deprotonation by the pyridyl nitrogen of the N(1)-deuterated dicationic triazolium salt is most consistent with the data. We also report kDO values (protofugalities) for deuteroxide-catalyzed exchange for 6–9. The protofugalities for 8 and 9 are the lowest values to date in the N-aryl triazolium series. Full article
(This article belongs to the Special Issue Organocatalysis: Mechanistic Investigations, Design, and Applications)
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10 pages, 1909 KiB  
Article
Organocatalysis for the Asymmetric Michael Addition of Cycloketones and α, β-Unsaturated Nitroalkenes
by Jae Ho Shim, Byung Kook Ahn, Ji Yeon Lee, Hyeon Soo Kim and Deok-Chan Ha
Catalysts 2021, 11(8), 1004; https://doi.org/10.3390/catal11081004 - 20 Aug 2021
Cited by 6 | Viewed by 3783
Abstract
Michael addition is one of the most important carbon–carbon bond formation reactions. In this study, an (R, R)-1,2-diphenylethylenediamine (DPEN)-based thiourea organocatalyst was applied to the asymmetric Michael addition of nitroalkenes and cycloketones to produce a chiral product. The primary amine [...] Read more.
Michael addition is one of the most important carbon–carbon bond formation reactions. In this study, an (R, R)-1,2-diphenylethylenediamine (DPEN)-based thiourea organocatalyst was applied to the asymmetric Michael addition of nitroalkenes and cycloketones to produce a chiral product. The primary amine moiety in DPEN reacts with the ketone to form an enamine and is activated through the hydrogen bond formation between the nitro group in the α, β-unsaturated nitroalkene and thiourea. Here, the aim was to obtain an asymmetric Michael product through the 1,4-addition of the enamine to an alkene to form a new carbon–carbon bond. As a result, the primary amine of the chiral diamine was converted into an enamine. The reaction proceeded with a relatively high level of enantioselectivity achieved using double activation through the hydrogen bonding of the nitro group and thiourea. Michael products with high levels of enantioselectivity (76–99% syn ee) and diastereoselectivity (syn/anti = 9/1) were obtained with yields in the range of 88–99% depending on the ketone. Full article
(This article belongs to the Special Issue Organocatalysis: Mechanistic Investigations, Design, and Applications)
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10 pages, 3220 KiB  
Article
Visible-Light Radical–Radical Coupling vs. Radical Addition: Disentangling a Mechanistic Knot
by Fernando Aguilar-Galindo, Ricardo I. Rodríguez, Leonardo Mollari, José Alemán and Sergio Díaz-Tendero
Catalysts 2021, 11(8), 922; https://doi.org/10.3390/catal11080922 - 29 Jul 2021
Cited by 2 | Viewed by 2332
Abstract
A highly enantioselective protocol has been recently described as allowing the synthesis of five-membered cyclic imines harnessing the selective generation of a β-Csp3-centered radical of acyl heterocyclic derivatives and its subsequent interaction with diverse NH-ketimines. The overall transformation represents a novel [...] Read more.
A highly enantioselective protocol has been recently described as allowing the synthesis of five-membered cyclic imines harnessing the selective generation of a β-Csp3-centered radical of acyl heterocyclic derivatives and its subsequent interaction with diverse NH-ketimines. The overall transformation represents a novel cascade process strategy crafted by individual well-known steps; however, the construction of the new C-C bond highlights a crucial knot from a mechanistically perspective. We believe that the full understanding of this enigmatic step may enrich the current literature and expand latent future ideas. Therefore, a detailed mechanistic study of the protocol has been conducted. Here, we provide theoretical insight into the mechanism using quantum chemistry calculations. Two possible pathways have been investigated: (a) imine reduction followed by radical–radical coupling and (b) radical addition followed by product reduction. In addition, investigations to unveil the origin behind the enantioselectivity of the 1-pyrroline derivatives have been conducted as well. Full article
(This article belongs to the Special Issue Organocatalysis: Mechanistic Investigations, Design, and Applications)
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Review

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53 pages, 11647 KiB  
Review
Non-Covalent Interactions in Enantioselective Organocatalysis: Theoretical and Mechanistic Studies of Reactions Mediated by Dual H-Bond Donors, Bifunctional Squaramides, Thioureas and Related Catalysts
by Ana Maria Faisca Phillips, Martin H. G. Prechtl and Armando J. L. Pombeiro
Catalysts 2021, 11(5), 569; https://doi.org/10.3390/catal11050569 - 29 Apr 2021
Cited by 29 | Viewed by 5348
Abstract
Chiral bifunctional dual H-bond donor catalysts have become one of the pillars of organocatalysis. They include squaramide, thiosquaramide, thiourea, urea, and even selenourea-based catalysts combined with chiral amines, cinchona alkaloids, sulfides, phosphines and more. They can promote several types of reactions affording products [...] Read more.
Chiral bifunctional dual H-bond donor catalysts have become one of the pillars of organocatalysis. They include squaramide, thiosquaramide, thiourea, urea, and even selenourea-based catalysts combined with chiral amines, cinchona alkaloids, sulfides, phosphines and more. They can promote several types of reactions affording products in very high yields and excellent stereoselectivities in many cases: conjugate additions, cycloadditions, the aldol and Henry reactions, the Morita–Baylis–Hilman reaction, even cascade reactions, among others. The desire to understand mechanisms and the quest for the origins of stereoselectivity, in attempts to find guidelines for developing more efficient catalysts for new transformations, has promoted many mechanistic and theoretical studies. In this review, we survey the literature published in this area since 2015. Full article
(This article belongs to the Special Issue Organocatalysis: Mechanistic Investigations, Design, and Applications)
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