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Special Issue "Enantioselective Catalysis"

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

Deadline for manuscript submissions: 31 August 2018

Special Issue Editors

Guest Editor
Prof. Dr. Laura Palombi

Dipartimento di Chimica e Biologia, Università di Salerno, Via GiovanniPaolo II, 132, 84084-Fisciano, SA, Italy
Website | E-Mail
Interests: stereoselective synthesis; heterocycles; electrosynthesis; electrocatalysis; organocatalysis
Guest Editor
Prof. Dr. Antonio Massa

Dipartimento di Chimica e Biologia, Università di Salerno, Via Giovanni Paolo II, 132, 84084-Fisciano, SA, Italy
Website | E-Mail
Phone: +39 089 969565
Interests: asymmetric synthesis; synthesis of bioactive compounds; organocatalysis; heterocycles; scale-up and development

Special Issue Information

Dear Colleagues,

Asymmetric Catalysis is one of the most powerful methods for the achievement of optically-active organic compounds, entities with a central role in synthetic, medicinal and material chemistry. Given the continuous advancements in this area and, as a consequence, the new challenges to be faced, a focus on this matter is highly desirable. The main aim of this Special Issue is to highlight strategies, methodologies and techniques recently implemented to promote chiral induction. Original research papers and reviews encompassing the various aspects of asymmetric catalysis, such as the designing of tailored catalysts, development of new catalytic systems, synthetic applications and mechanistic studies dealing with stereo-controlled catalytic reactions are welcome.

Prof. Dr. Laura Palombi
Prof. Dr. Antonio Massa
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 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

  • Chiral catalysts
  • Stereoselective processes
  • Phase transfer catalysis
  • Organocatalysis

Published Papers (6 papers)

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Research

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Open AccessArticle General Method for the Synthesis of (−)-Conduritol C and Analogs from Chiral Cyclohexadienediol Scaffolds
Molecules 2018, 23(7), 1653; https://doi.org/10.3390/molecules23071653
Received: 31 May 2018 / Revised: 29 June 2018 / Accepted: 1 July 2018 / Published: 6 July 2018
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Abstract
An efficient and facile general method for the synthesis of conduritol C analogs, taking advantage of an enantioselective biocatalysis process of monosubstituted benzenes, is described. The absolute stereochemical patterns of the target molecules (−)-conduritol C, (−)-bromo-conduritol C, and (−)-methyl-conduritol C were achieved by
[...] Read more.
An efficient and facile general method for the synthesis of conduritol C analogs, taking advantage of an enantioselective biocatalysis process of monosubstituted benzenes, is described. The absolute stereochemical patterns of the target molecules (−)-conduritol C, (−)-bromo-conduritol C, and (−)-methyl-conduritol C were achieved by means of chemoenzymatic methods. The stereochemistry present at the homochiral cyclohexadiene-cis-1,2-diols derived from the arene biotransformation and the enantioselective ring opening of a non-isolated vinylepoxide derivative permitted the absolute configuration of the carbon bearing the hydroxyl groups at the target molecules to be established. All three conduritols and two intermediates were crystallized, and their structures were confirmed by X-ray diffraction. The three conduritols and intermediates were isostructural. The versatility of our methodology is noteworthy to expand the preparation of conduritol C analogs starting from toluene dioxygenase (TDO) monosubstituted arene substrates. Full article
(This article belongs to the Special Issue Enantioselective Catalysis)
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Open AccessFeature PaperArticle Towards an Asymmetric Organocatalytic α-Azidation of β-Ketoesters
Molecules 2018, 23(5), 1142; https://doi.org/10.3390/molecules23051142
Received: 20 April 2018 / Revised: 4 May 2018 / Accepted: 10 May 2018 / Published: 11 May 2018
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Abstract
Detailed investigations concerning the organocatalytic (asymmetric) α-azidation of prochiral β-ketoesters were carried out. It was shown that the racemic version of such a reaction can either be carried out under oxidative conditions using TMSN3 as the azide-source with quaternary ammonium iodides as
[...] Read more.
Detailed investigations concerning the organocatalytic (asymmetric) α-azidation of prochiral β-ketoesters were carried out. It was shown that the racemic version of such a reaction can either be carried out under oxidative conditions using TMSN3 as the azide-source with quaternary ammonium iodides as the catalysts, or by using hypervalent iodine-based electrophilic azide-transfer reagents with different organocatalysts. In addition, the latter strategy could also be carried out with modest enantioselectivities when using simple cinchona alkaloid catalysts, albeit with relatively low yields. Full article
(This article belongs to the Special Issue Enantioselective Catalysis)
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Graphical abstract

Open AccessArticle Stereoselective Syntheses and Application of Chiral Bi- and Tridentate Ligands Derived from (+)-Sabinol
Molecules 2018, 23(4), 771; https://doi.org/10.3390/molecules23040771
Received: 13 February 2018 / Revised: 21 March 2018 / Accepted: 22 March 2018 / Published: 27 March 2018
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Abstract
A library of bidentate diols, as well as tridentate triols and aminodiols, derived from (+)-sabinol, was synthesized in a stereoselective manner. Sabinol was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. After changing the protecting group to Boc, the enamine
[...] Read more.
A library of bidentate diols, as well as tridentate triols and aminodiols, derived from (+)-sabinol, was synthesized in a stereoselective manner. Sabinol was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. After changing the protecting group to Boc, the enamine was subjected to stereospecific dihydroxylation with OsO4/NMO, resulting in the (1R,2R,3R,5R)-aminodiol diastereomer. The obtained primary aminodiol was transformed to a secondary analogue. The ring closure of the N-benzyl-substituted aminodiol with formaldehyde was investigated and regioselective formation of the spiro-oxazolidine ring was observed. Hydroboration or dihydroxylation of sabinol or its benzyl ether with OsO4/NMO resulted in the formation of sabinane-based diols and triols following a highly stereospecific reaction. Treatment of sabinol with m-CPBA afforded O-benzoyl triol as a diastereoisomer of the directly dihydroxylated product, instead of the expected epoxy alcohol. The resulting aminodiols, diol, and triols were applied as chiral catalysts in the reaction of diethylzinc and benzaldehyde from moderate to good selectivity. Full article
(This article belongs to the Special Issue Enantioselective Catalysis)
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Graphical abstract

Open AccessFeature PaperArticle Economy of Catalyst Synthesis—Convenient Access to Libraries of Di- and Tetranaphtho Azepinium Compounds
Molecules 2018, 23(4), 750; https://doi.org/10.3390/molecules23040750
Received: 22 February 2018 / Revised: 14 March 2018 / Accepted: 20 March 2018 / Published: 24 March 2018
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Abstract
Efficient optimization procedures in chiral catalysis are usually linked to a straightforward strategy to access groups of structurally similar catalysts required for fine-tuning. The ease of building up such ligand libraries can be increased when the structure-modifying step (introduction of a substituent) is
[...] Read more.
Efficient optimization procedures in chiral catalysis are usually linked to a straightforward strategy to access groups of structurally similar catalysts required for fine-tuning. The ease of building up such ligand libraries can be increased when the structure-modifying step (introduction of a substituent) is done at a later stage of the synthesis. This is demonstrated for the extended family of di- and tetranaphtho azepinium compounds, widely used as chiral phase transfer catalysts (PTC). Using 2,6-diiodo-4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′-e]azepine and 4,8-diiodo-6,7-dihydro-5H-dibenzo[c,e]azepine, respectively, as key intermediates, 18 spiro-azepinium compounds were synthesized in a total yield of 25–42% over 6–7 steps from 1,1′-binaphthyl-2,2′-dicarboxylic acid or diphenic acid, respectively. The replacement of iodo groups with aryl substituents was performed as the last or the penultimate step of the synthesis. Full article
(This article belongs to the Special Issue Enantioselective Catalysis)
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Graphical abstract

Open AccessArticle Asymmetric Synthesis of Spirooxindoles via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts
Molecules 2018, 23(2), 438; https://doi.org/10.3390/molecules23020438
Received: 5 February 2018 / Revised: 12 February 2018 / Accepted: 12 February 2018 / Published: 16 February 2018
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Abstract
Taking into account the postulated reaction mechanism for the organocatalytic epoxidation of electron-poor olefins developed by our laboratory, we have investigated the key factors able to positively influence the H-bond network installed inside the substrate/catalyst/oxidizing agent. With this aim, we have: (i) tested
[...] Read more.
Taking into account the postulated reaction mechanism for the organocatalytic epoxidation of electron-poor olefins developed by our laboratory, we have investigated the key factors able to positively influence the H-bond network installed inside the substrate/catalyst/oxidizing agent. With this aim, we have: (i) tested a few catalysts displaying various effects that noticeably differ in terms of steric hindrance and electron demand; (ii) employed α-alkylidene oxindoles decorated with different substituents on the aromatic ring (11ag), the exocylic double bond (11hl), and the amide moiety (11mv). The observed results suggest that the modification of the electron-withdrawing group (EWG) weakly conditions the overall outcomes, and conversely a strong influence is unambiguously ascribable to either the N-protected or N-unprotected lactam framework. Specifically, when the NH free substrates (11mu) are employed, an inversion of the stereochemical control is observed, while the introduction of a Boc protecting group affords the desired product 12v in excellent enantioselectivity (97:3 er). Full article
(This article belongs to the Special Issue Enantioselective Catalysis)
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Review

Jump to: Research

Open AccessReview Whole Cells as Biocatalysts in Organic Transformations
Molecules 2018, 23(6), 1265; https://doi.org/10.3390/molecules23061265
Received: 8 April 2018 / Revised: 21 May 2018 / Accepted: 22 May 2018 / Published: 25 May 2018
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Abstract
Currently, the power and usefulness of biocatalysis in organic synthesis is undeniable, mainly due to the very high enantiomeric excess reached using enzymes, in an attempt to emulate natural processes. However, the use of isolated enzymes has some significant drawbacks, the most important
[...] Read more.
Currently, the power and usefulness of biocatalysis in organic synthesis is undeniable, mainly due to the very high enantiomeric excess reached using enzymes, in an attempt to emulate natural processes. However, the use of isolated enzymes has some significant drawbacks, the most important of which is cost. The use of whole cells has emerged as a useful strategy with several advantages over isolated enzymes; for this reason, modern research in this field is increasing, and various reports have been published recently. This review surveys the most recent developments in the enantioselective reduction of carbon-carbon double bonds and prochiral ketones and the oxidation of prochiral sulfides using whole cells as biocatalytic systems. Full article
(This article belongs to the Special Issue Enantioselective Catalysis)
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Scheme 1

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