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Advances in Organocatalysts: Synthesis and Applications

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Catalytic Materials".

Deadline for manuscript submissions: closed (15 November 2021) | Viewed by 17972

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Special Issue Editors

Dr. Erika Bálint

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Guest Editor

Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budapest, Hungary
Interests: heterocyclic chemistry; multicomponent synthesis; microwave chemistry; continuous flow synthesis; cyclodextrin chemistry
Special Issues, Collections and Topics in MDPI journals

Dr. József Kupai

E-Mail Website
Guest Editor

Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budapest, Hungary
Interests: organocatalysis; cinchona catalysts; hydrogen–bond donors; recycling; organic solvent nanofiltration; immobilization

Special Issue Information

Dear Colleagues,

Organocatalysis represents one of the most exciting and rapidly developing research fields in organic chemistry, becoming the third pillar after transition metal catalysis and biocatalysis. Using nonmetal catalysts in organic syntheses presents a lot of advantages, such as less toxicity and pollution, ease of handling, less sensitivity to air and moisture, lower cost, thus making this option more economical and less harmful to the environment than applying traditional organometallic catalysts. In this regard, low-cost and environmentally benign organocatalysis may be an effective tool for the synthesis of complex organic molecules. Moreover, using chiral organocatalysts can make asymmetric syntheses possible.
In addition, electrochemical and photochemical reactions applying organic molecules as mediators and catalysts can offer mild, alternative methodological strategies towards green chemistry.
This Special Issue aims to cover recent research and advances in the field of metal-free catalysts, photoredox- and electrocatalysis. Novel mechanistic and investigatory studies on catalysis, design and synthesis of organocatalysts, their applications in the preparation of products important in the pharmaceutical or material sciences, as well as recycling are welcomed in this issue as full papers, communications, and mini-reviews.

Dr. Erika Bálint
Dr. József Kupai
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. Materials 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 2600 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

Organocatalysis
Nonmetal catalysis
Photocatalysis
Electrocatalysis
Recycling
Asymmetric synthesis
Enantioselectivity
Multicomponent reactions
Green chemistry
Hydrogen–bond donors
Bifunctional catalysis
Catalyst immobilization

Published Papers (6 papers)

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Research

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18 pages, 4010 KiB

Open AccessEditor’s ChoiceArticle

Theoretical Study of N-Heterocyclic-Carbene–ZnX₂ (X = H, Me, Et) Complexes

by Mirosław Jabłoński

Materials 2021, 14(20), 6147; https://doi.org/10.3390/ma14206147 - 16 Oct 2021

Cited by 12 | Viewed by 1632

Abstract

This article discusses the properties of as many as 30 carbene–ZnX

_{2}

(X = H, Me, Et) complexes featuring a zinc bond C⋯Zn. The group of carbenes is represented by imidazol-2-ylidene and its nine derivatives (labeled as IR), in which both hydrogen atoms [...] Read more.

This article discusses the properties of as many as 30 carbene–ZnX

_{2}

^{i}

Pr,

^{t}

Bu through Ph, Tol, and Xyl to the bulkiest Mes, Dipp, and Ad. The main goal is to study the relationship between type and size of R and X and both the strength of C⋯Zn and the torsional angle of the ZnX

_{2}

plane with respect to the plane of the imidazol-2-ylidene ring. Despite the considerable diversity of R and X, the range of

d_{C \dots Zn}

is quite narrow: 2.12–2.20 Å. On the contrary,

D_{0}

is characterized by a fairly wide range of 18.5–27.4 kcal/mol. For the smallest carbenes, the ZnX

_{2}

molecule is either in the plane of the carbene or is only slightly twisted with respect to it. The twist angle becomes larger and more varied with the bulkier R. However, the value of this angle is not easy to predict because it results not only from the presence of steric effects but also from the possible presence of various interatomic interactions, such as dihydrogen bonds, tetrel bonds, agostic bonds, and hydrogen bonds. It has been shown that at least some of these interactions may have a non-negligible influence on the structure of the IR–ZnX2 complex. This fact should be taken into account in addition to the commonly discussed R⋯X steric repulsion. Full article

(This article belongs to the Special Issue Advances in Organocatalysts: Synthesis and Applications)

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13 pages, 1361 KiB

Open AccessArticle

Study of the Three-Component Reactions of 2-Alkynylbenzaldehydes, Aniline, and Dialkyl Phosphites—The Significance of the Catalyst System

by Nóra Popovics-Tóth, Kármen Emőke Szabó and Erika Bálint

Materials 2021, 14(20), 6015; https://doi.org/10.3390/ma14206015 - 13 Oct 2021

Cited by 1 | Viewed by 1378

Abstract

New, practical approaches for the synthesis of α-amino (2-alkynylphenyl)-methylphosphonates and 1,2-dihydroisoquinolin-1-ylphosphonates were developed. By the propylphosphonic anhydride (T₃P^®)-mediated Kabachnik–Fields reaction of 2-alkynylbenzaldehydes, aniline, and dialkyl phosphites, α-amino (2-alkynylphenyl)-methylphosphonates were obtained selectively in high yields. The method developed is a simple operation and did not require a chromatographic separation since the products could be isolated from the reaction mixture by a simple extraction. At the same time, 2,3-disubstituted-1,2-dihydroisoquinolin-1-ylphosphonates could be prepared effectively from the same kinds of starting materials (2-alkynylbenzaldehydes, aniline, and dialkyl phosphites) at 60 °C in a short reaction time by changing the catalyst for CuCl. Therefore, it was proved that the catalyst system applied played a crucial role with respect to the reaction outcome. Full article

(This article belongs to the Special Issue Advances in Organocatalysts: Synthesis and Applications)

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13 pages, 3487 KiB

Open AccessEditor’s ChoiceArticle

Novel Selenoureas Based on Cinchona Alkaloid Skeleton: Synthesis and Catalytic Investigations

by Mariola Zielińska-Błajet and Joanna Najdek

Materials 2021, 14(3), 600; https://doi.org/10.3390/ma14030600 - 28 Jan 2021

Cited by 4 | Viewed by 2016

Abstract

An efficient approach to the synthesis of chiral selenoureas consisting of Cinchona alkaloid scaffolds was described. The new selenoureas were assessed as bifunctional organocatalysts in the asymmetric Michael addition reactions under mild conditions. The best results were obtained for selenoureas bearing the 4-fluorophenyl group. These catalysts promoted the reactions with enantioselectivities of up to 96% ee. Additionally, the catalytic performance of the thiourea and selenourea counterpart was compared. Full article

(This article belongs to the Special Issue Advances in Organocatalysts: Synthesis and Applications)

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15 pages, 2654 KiB

Open AccessArticle

Comparison of Cinchona Catalysts Containing Ethyl or Vinyl or Ethynyl Group at Their Quinuclidine Ring

by Sándor Nagy, Zsuzsanna Fehér, Gergő Dargó, Júlia Barabás, Zsófia Garádi, Béla Mátravölgyi, Péter Kisszékelyi, Gyula Dargó, Péter Huszthy, Tibor Höltzl, György Tibor Balogh and József Kupai

Materials 2019, 12(18), 3034; https://doi.org/10.3390/ma12183034 - 18 Sep 2019

Cited by 6 | Viewed by 3943

Abstract

Numerous cinchona organocatalysts with different substituents at their quinuclidine unit have been described and tested, but the effect of those saturation has not been examined before. This work presents the synthesis of four widely used cinchona-based organocatalyst classes (hydroxy, amino, squaramide, and thiourea) with different saturation on the quinuclidine unit (ethyl, vinyl, ethynyl) started from quinine, the most easily available cinchona derivative. Big differences were found in basicity of the quinuclidine unit by measuring the pK_a values of twelve catalysts in six solvents. The effect of differences was examined by testing the catalysts in Michael addition reaction of pentane-2,4-dione to trans-β-nitrostyrene. The 1.6–1.7 pK_a deviation in basicity of the quinuclidine unit did not result in significant differences in yields and enantiomeric excesses. Quantum chemical calculations confirmed that the ethyl, ethynyl, and vinyl substituents affect the acid-base properties of the cinchona-thiourea catalysts only slightly, and the most active neutral thione forms are the most stable tautomers in all cases. Due to the fact that cinchonas with differently saturated quinuclidine substituents have similar catalytic activity in asymmetric Michael addition application of quinine-based catalysts is recommended. Its vinyl group allows further modifications, for instance, recycling the catalyst by immobilization. Full article

(This article belongs to the Special Issue Advances in Organocatalysts: Synthesis and Applications)

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Review

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19 pages, 4907 KiB

Open AccessReview

Recent Advances in Imidazolium-Based Dicationic Ionic Liquids as Organocatalysts: A Mini-Review

by Fabiana Pandolfi, Martina Bortolami, Marta Feroci, Anastasia Fornari, Vincenzo Scarano and Daniele Rocco

Materials 2022, 15(3), 866; https://doi.org/10.3390/ma15030866 - 23 Jan 2022

Cited by 14 | Viewed by 3855

Abstract

Imidazolium-based dicationic ionic liquids (DILs) are gaining considerable space in the field of organocatalysis mainly due to the opportunities in offering new possible applicable structural variations. In addition to the well-known variables which made the ionic liquids (ILs) famous as the type of cation and anion used, the nature of the molecular spacer moiety turns out a further possibility to improve some physicochemical properties, for example, solubility, acidity, electrochemical behavior, and so on. For this reason, this class of ionic liquids has been considered as possible competitors to their corresponding monocationic salts in replacing common catalysts in organic synthesis, particularly in cases in which their bidentate nature could positively affect the catalytic activity. This mini-review is intended to highlight the progress carried out in the last six years in the field of organocatalysis, including DILs as such and as hybrids with polymers, nanomaterials, and composites. Full article

(This article belongs to the Special Issue Advances in Organocatalysts: Synthesis and Applications)

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30 pages, 14602 KiB

Open AccessReview

Organocatalytic Name Reactions Enabled by NHCs

by Krzysztof Dzieszkowski, Izabela Barańska, Karina Mroczyńska, Michał Słotwiński and Zbigniew Rafiński

Materials 2020, 13(16), 3574; https://doi.org/10.3390/ma13163574 - 13 Aug 2020

Cited by 12 | Viewed by 3748

Abstract

Giving reactions the names of their discoverers is an extraordinary tradition of organic chemistry. Nowadays, this phenomenon is much rarer, although already named historical reactions are still often developed. This is also true in the case of a broad branch of N‑heterocyclic carbenes catalysis. NHCs allow many unique synthetic paths, including commonly known name reactions. This article aims to gather this extensive knowledge and compare historical reactions with current developed processes. Furthermore, this review is a great opportunity to highlight some of the unique applications of these procedures in the total synthesis of biologically active compounds. Hence, this concise article may also be a source of knowledge for scientists just starting their adventure with N‑heterocyclic carbene chemistry. Full article

(This article belongs to the Special Issue Advances in Organocatalysts: Synthesis and Applications)

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