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Special Issue "Stereogenic Centers"

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

Deadline for manuscript submissions: 30 July 2018

Special Issue Editor

Guest Editor
Dr. Alejandro Baeza Carratalá

Universitat d'Alacant, Institute of Organic Synthesis, Alicante, Spain
Website | E-Mail
Interests: asymmetric catalysis; green chemistry; organocatalysis; metal catalysis

Special Issue Information

Dear Colleagues,

The importance of having access to chiral molecules is a well-known fact for the scientific community. This is due to the fact that most of the biological activity that some molecules possess is associated to one of the all-possible enantiomers, which can interact differentially with chiral recognition entities, triggering distinct biochemical responses.

It is not surprising then that different methodologies have been developed in the last century, within the frame of so-called asymmetric synthesis, in order to tackle the challenging task of constructing such chiral compounds, as most of these strategies are based on the construction of stereogenic centers starting from racemic and/or pro-chiral compounds.

Thus, the aim of this Special Issue is to gather recent developments in the establishment of stereogenic centers in organic molecules. Therefore, asymmetric synthesis, kinetic resolutions, asymmetric catalysis (metal-, organo- and biocatalysis), among other strategies, as well as studies that help in the understanding of the mechanism behind these processes will be covered in this Special Issue.

Dr. Alejandro Baeza Carratalá
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 papers will be 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 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 1800 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

  • Chirality
  • Stereogenic Centers
  • Asymmetric Synthesis
  • Asymmetric Catalysis
  • Enantiomers

Published Papers (4 papers)

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Research

Open AccessArticle One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination
Molecules 2018, 23(7), 1785; https://doi.org/10.3390/molecules23071785
Received: 21 June 2018 / Revised: 13 July 2018 / Accepted: 17 July 2018 / Published: 20 July 2018
PDF Full-text (877 KB) | HTML Full-text | XML Full-text
Abstract
The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of
[...] Read more.
The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons. Full article
(This article belongs to the Special Issue Stereogenic Centers)
Figures

Graphical abstract

Open AccessArticle Chiral 2-Aminobenzimidazole as Bifunctional Catalyst in the Asymmetric Electrophilic Amination of Unprotected 3-Substituted Oxindoles
Molecules 2018, 23(6), 1374; https://doi.org/10.3390/molecules23061374
Received: 9 May 2018 / Revised: 4 June 2018 / Accepted: 5 June 2018 / Published: 6 June 2018
PDF Full-text (3100 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The use of readily available chiral trans-cyclohexanediamine-benzimidazole derivatives as bifunctional organocatalysts in the asymmetric electrophilic amination of unprotected 3-substituted oxindoles is presented. Different organocatalysts were evaluated; the most successful one contained a dimethylamino moiety (5). With this catalyst under optimized
[...] Read more.
The use of readily available chiral trans-cyclohexanediamine-benzimidazole derivatives as bifunctional organocatalysts in the asymmetric electrophilic amination of unprotected 3-substituted oxindoles is presented. Different organocatalysts were evaluated; the most successful one contained a dimethylamino moiety (5). With this catalyst under optimized conditions, different oxindoles containing a wide variety of substituents at the 3-position were aminated in good yields and with good to excellent enantioselectivities using di-tert-butylazodicarboxylate as the aminating agent. The procedure proved to be also efficient for the amination of 3-substituted benzofuranones, although with moderate results. A bifunctional role of the catalyst, acting as Brønsted base and hydrogen bond donor, is proposed according to the experimental results observed. Full article
(This article belongs to the Special Issue Stereogenic Centers)
Figures

Figure 1

Open AccessFeature PaperCommunication Catalytic Enantioselective Addition of Organozirconium Reagents to Aldehydes
Molecules 2018, 23(4), 961; https://doi.org/10.3390/molecules23040961
Received: 6 April 2018 / Revised: 17 April 2018 / Accepted: 17 April 2018 / Published: 20 April 2018
PDF Full-text (3684 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A catalytic enantioselective addition reaction of alkylzirconium species to aromatic aldehydes is reported. The reaction, facilitated by a chiral nonracemic diol ligand complex with Ti(OiPr)4, proceeds under mild and convenient conditions, and no premade organometallic reagents are required since
[...] Read more.
A catalytic enantioselective addition reaction of alkylzirconium species to aromatic aldehydes is reported. The reaction, facilitated by a chiral nonracemic diol ligand complex with Ti(OiPr)4, proceeds under mild and convenient conditions, and no premade organometallic reagents are required since the alkylzirconium nucleophiles are generated in situ by hydrozirconation of alkenes with the Schwartz reagent. The methodology is compatible with functionalized nucleophiles and a broad range of aromatic aldehydes. Full article
(This article belongs to the Special Issue Stereogenic Centers)
Figures

Graphical abstract

Open AccessArticle Asymmetric Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes Organocatalyzed by Chiral Monosalicylamides from trans-Cyclohexane-1,2-Diamines
Molecules 2018, 23(1), 141; https://doi.org/10.3390/molecules23010141
Received: 25 December 2017 / Revised: 8 January 2018 / Accepted: 9 January 2018 / Published: 11 January 2018
PDF Full-text (1803 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Primary amine-salicylamides derived from chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room
[...] Read more.
Primary amine-salicylamides derived from chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room temperature. The corresponding enantioenriched γ-nitroaldehydes are obtained with enantioselectivities up to 95%. Theoretical calculations are used to justify the reasons of the stereoinduction. Full article
(This article belongs to the Special Issue Stereogenic Centers)
Figures

Graphical abstract

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Author: Dr. Wei Zhang
Affiliation: Department of Chemistry, University of Massachusetts, , Boston, MA, USA
Tentative title: "Recyclable Fluorous Organocatalyst-Promoted Asymmetric Michael/Michael Additions for Asymmetric Synthesis of Substituted Cyclohexanones"

Author: Xiang Wu
Affiliation: Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, China
Tentative tile: Asymmetric Oxidative Formal Aza-Diels-Alder Reaction for the Synthesis of Indoloquinolizidines.

Author: Yasuhiro Kawnami
Affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan
Tentative title: "Practical enantioselective reduction of ketones using an oxazaborolidin catalyst generated in situ from a chiral lactam alcohol and borane"


Tentative title: "One Dimensional 13C NMR is a Simple and Highly Quantitative Method for Enantiodiscrimination."
Author: Peter P. Lankhorst, Joep van Rijn, Alexander L.L. Duchateau
Abstract: The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol is presented. It is shown that 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The method is validated by preparing artificial mixtures of the (R)-enantiomer and the (R/S) mixture, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained. Furthermore, the method is very linear, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative amount of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons.

Tentative title: "Stereoselective Synthesis of 6-Desmethyl-N-methylfluvirucinine A1 Aglycon via Conformationally-controlled Diastereoselective Lactam-ring Expansion"
Author: Young-Ger Suh
Affiliation: College of Pharmacy, Seoul National University, Korea

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