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Special Issue "Stereochemistry in Action"

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

Deadline for manuscript submissions: closed (31 December 2019).

Special Issue Editors

Prof. Dr. Zbigniew Czarnocki
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Guest Editor
Laboratory of Natural Products Chemistry, The Faculty of Chemistry, University of Warsaw, Warsaw, Poland
Interests: synthetic organic chemistry; stereochemistry; asymmetric synthesis; chemistry of natural products
Dr. Joanna Szawkało
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Assistant Guest Editor
Laboratory of Natural Products Chemistry, The Faculty of Chemistry,University of Warsaw, Warsaw, Poland
Interests: organic synthesis; heterocyclic compounds; asymmetric reactions; organocatalysis

Special Issue Information

Dear Colleagues,

Stereochemistry is an important area of chemistry which started with the fundamental contribution of Louis Pasteur in 1848, and in 1874, it acquired three-dimensional spatial characteristics with the hypothesis of Le Bel and vant’t Hoff. Another important landmark in the development of stereochemistry was set by Sir Derek Barton and Odd Hassel in 1950, through the introduction of conformational analysis, and in 1951 by Johannes Martin Bijvoet, with his study on anomalous X-ray scattering that allowed absolute configuration assignment. In later years, several phases of development were observed, being greatly accelerated by the emergence of modern instrumentation methods like nuclear resonance spectroscopy, circular dichroism, optical rotary dispersion, and X-ray crystallography. Soon after the thalidomide tragedy in the 1950s/1960s, it became obvious that stereodifferentiation in a living system is a general rule, not an exemption, which had enormous consequences for science. This therefore resulted in a significant increase in interest in dynamic stereochemistry, asymmetric synthesis, topicity and prostereoisomerism, as well as chemical topology and cyclostereoisomerism. Stereochemistry is no longer an isolated field of fundamental science and has become tightly linked with many branches of chemistry, medicinal chemistry, polimer science, new materials engineering, and many others. Over the last decades, an impressive development has been made in the area of stereocontrolled organic synthesis. Scientists now have a wide range of tools for effective optical activation, among them chiral catalysts or organocatalysts for the creation of the desired spatial arrangement of the molecule.

This Special Issue aimes to invite contributions on all aspects of organic stereochemistry, including its dynamic aspects studied by various physicochemical methods (X-ray, VT NMR, ECD, VCD, etc.) as well as being important in asymmetric synthesis.

Prof. Dr. Zbigniew Czarnocki
Dr. Joanna Szawkało
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 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 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 2000 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

  • Absolute stereochemistry assignment of important molecules
  • Dynamic stereochemistry
  • Quantum-chemical modeling of transition states in the asymmetric synthesis
  • Asymmetric transformations and optical activation
  • Supramolecular stereochemistry (static and dynamic)
  • Stereochemistry in polymer systems

Published Papers (5 papers)

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Research

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Open AccessArticle
Regioselective and Stereodivergent Synthesis of Enantiomerically Pure Vic-Diamines from Chiral β-Amino Alcohols with 2-Pyridyl and 6-(2,2′-Bipyridyl) Moieties
Molecules 2020, 25(3), 727; https://doi.org/10.3390/molecules25030727 - 07 Feb 2020
Cited by 1
Abstract
In this report, we describe the synthetic elaboration of the easily available enantiomerically pure β-amino alcohols. Attempted direct substitution of the hydroxyl group by azido-functionality in the Mitsunobu reaction with hydrazoic acid was inefficient or led to a diastereomeric mixture. These outcomes resulted [...] Read more.
In this report, we describe the synthetic elaboration of the easily available enantiomerically pure β-amino alcohols. Attempted direct substitution of the hydroxyl group by azido-functionality in the Mitsunobu reaction with hydrazoic acid was inefficient or led to a diastereomeric mixture. These outcomes resulted from the participation of aziridines. Intentionally performed internal Mitsunobu reaction of β-amino alcohols gave eight chiral aziridines in 45–82% yield. The structural and configuration identity of products was confirmed by NMR data compared to the DFT calculated GIAO values. For 1,2,3-trisubstituted aziridines slow configurational inversion at the endocyclic nitrogen atom was observed by NMR at room temperature. Moreover, when aziridine was titrated with Zn(OAc)2 under NMR control, only one of two N-epimers directly participated in complexation. The aziridines underwent ring opening with HN3 to form the corresponding azido amines as single regio- and diastereomers in 90–97% yield. Different results were obtained for 1,2-disubstituted and 1,2,3-trisubstituted aziridines. For the later aziridines ring closure and ring opening occurred at different carbon stereocenters, thus yielding products with two inverted configurations, compared to the starting amino alcohol. The 1,2-disubstituted aziridines produced azido amines of the same configuration as the starting β-amino alcohols. To obtain a complete series of diastereomeric vic-diamines, we converted the amino alcohols into cyclic sulfamidates, which reacted with sodium azide in SN2 reaction (25–58% overall yield). The azides obtained either way underwent the Staudinger reduction, giving a series of six new chiral vic-diamines of defined stereochemistries. Full article
(This article belongs to the Special Issue Stereochemistry in Action)
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Open AccessArticle
Trityl-Containing Alcohols—An Efficient Chirality Transmission Process from Inductor to the Stereodynamic Propeller and their Solid-State Structural Diversity
Molecules 2020, 25(3), 707; https://doi.org/10.3390/molecules25030707 - 06 Feb 2020
Cited by 2
Abstract
The cascade process of a dynamic chirality transmission from the permanent chirality center to the stereodynamic triphenylmethyl group has been studied for series of optically active trityl derivatives. The structural analysis, carried out with the use of complementary methods, enabled us to determine [...] Read more.
The cascade process of a dynamic chirality transmission from the permanent chirality center to the stereodynamic triphenylmethyl group has been studied for series of optically active trityl derivatives. The structural analysis, carried out with the use of complementary methods, enabled us to determine the mechanism of chirality transfer. The process of chirality transmission involves a set of weak but complementary electrostatic interactions. The induction of helicity in a trityl propeller is revealed by rising non-zero cotton effects in the area of trityl UV-absorption. The presence of an additional stereogenic center in close proximity to the trityl-containing stereogenic center significantly affects the sign and, to a lesser extent, magnitude of the respective cotton effects. Despite the bulkiness of the trityl, in the crystalline phase, the molecules under study strictly fill the space. In the crystal, molecules form aggregates stabilized by OH•••O hydrogen bonds. However, the presence of two trityl groups precludes formation of OH•••O hydrogen bonding. Additionally, the trityl group seems to be responsible for the formation of the solid solutions by e.g., racemates of trans- and cis-2-tritylcyclohexanol. Therefore, the trityl group acts as a supramolecular protective group, which in turn can be used in the crystal engineering. Full article
(This article belongs to the Special Issue Stereochemistry in Action)
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Open AccessArticle
2-Unsubstituted Imidazole N-Oxides as Novel Precursors of Chiral 3-Alkoxyimidazol-2-ylidenes Derived from trans-1,2-Diaminocyclohexane and Other Chiral Amino Compounds
Molecules 2019, 24(23), 4398; https://doi.org/10.3390/molecules24234398 - 02 Dec 2019
Cited by 2
Abstract
‘Desymmetrization’ of trans-1,2-diaminocyclohexane by treatment with α,ω-dihalogenated alkylation reagents leads to mono-NH2 derivatives (‘primary-tertiary diamines’). Upon reaction with formaldehyde, these products formed monomeric formaldimines. Subsequently, reactions of the formaldimines with α-hydroxyiminoketones led to the corresponding 2-unsubstituted imidazole N-oxide derivatives, which [...] Read more.
‘Desymmetrization’ of trans-1,2-diaminocyclohexane by treatment with α,ω-dihalogenated alkylation reagents leads to mono-NH2 derivatives (‘primary-tertiary diamines’). Upon reaction with formaldehyde, these products formed monomeric formaldimines. Subsequently, reactions of the formaldimines with α-hydroxyiminoketones led to the corresponding 2-unsubstituted imidazole N-oxide derivatives, which were used here as new substrates for the in situ generation of chiral imidazol-2-ylidenes. Upon O-selective benzylation, new chiral imidazolium salts were obtained, which were deprotonated by treatment with triethylamine in the presence of elemental sulfur. Under these conditions, the intermediate imidazol-2-ylidenes were trapped by elemental sulfur, yielding the corresponding chiral non-enolizable imidazole-2-thiones in good yields. Analogous reaction sequences, starting with imidazole N-oxides derived from enantiopure primary amines, amino alcohols, and amino acids, leading to the corresponding 3-alkoxyimidazole-2-thiones were also studied. Full article
(This article belongs to the Special Issue Stereochemistry in Action)
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Review

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Open AccessReview
Chiral Thioureas—Preparation and Significance in Asymmetric Synthesis and Medicinal Chemistry
Molecules 2020, 25(2), 401; https://doi.org/10.3390/molecules25020401 - 18 Jan 2020
Cited by 5
Abstract
For almost 20 years, thioureas have been experiencing a renaissance of interest with the emerged development of asymmetric organocatalysts. Due to their relatively high acidity and strong hydrogen bond donor capability, they differ significantly from ureas and offer, appropriately modified, great potential as [...] Read more.
For almost 20 years, thioureas have been experiencing a renaissance of interest with the emerged development of asymmetric organocatalysts. Due to their relatively high acidity and strong hydrogen bond donor capability, they differ significantly from ureas and offer, appropriately modified, great potential as organocatalysts, chelators, drug candidates, etc. The review focuses on the family of chiral thioureas, presenting an overview of the current state of knowledge on their synthesis and selected applications in stereoselective synthesis and drug development. Full article
(This article belongs to the Special Issue Stereochemistry in Action)
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Open AccessReview
Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review
Molecules 2020, 25(2), 330; https://doi.org/10.3390/molecules25020330 - 14 Jan 2020
Cited by 5
Abstract
An increasing interest in the synthesis and use of optically active pyridine N-oxides as chiral controllers for asymmetric reactions has been observed in the last few years. Chiral heteroaromatic N-oxides can work as powerful electron-pair donors, providing suitable electronic environments in [...] Read more.
An increasing interest in the synthesis and use of optically active pyridine N-oxides as chiral controllers for asymmetric reactions has been observed in the last few years. Chiral heteroaromatic N-oxides can work as powerful electron-pair donors, providing suitable electronic environments in the transition state formed within the reaction. The nucleophilicity of the oxygen atom in N-oxides, coupled with a high affinity of silicon to oxygen, represent ideal properties for the development of synthetic methodology based on nucleophilic activation of organosilicon reagents. The application of chiral N-oxides as efficient organocatalysts in allylation, propargylation, allenylation, and ring-opening of meso-epoxides, as well as chiral ligands for metal complexes catalyzing Michael addition or nitroaldol reaction, can also be found in the literature. This review deals with stereoselective applications of N-oxides, and how the differentiating properties are correlated with their structure. It contains more recent results, covering approximately the last ten years. All the reported examples have been divided into five classes, according to the chirality elements present in their basic molecular frameworks. Full article
(This article belongs to the Special Issue Stereochemistry in Action)
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