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Special Issue "25th Anniversary of Molecules—Recent Advances in Organic Synthesis"

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

Deadline for manuscript submissions: 31 December 2020.

Special Issue Editors

Prof. Dr. M. Graça P. M. S. Neves
Website1 Website2
Guest Editor
Department of Chemistry and LAQV-REQUIMTE , University of Aveiro, 3810-193 Aveiro, Portugal
Interests: Organic synthesis; tetrapyrrolic macrocycles; functionalization of porphyrins and analogues via metal-catalyzed processes and cycloaddition reactions; development of molecules with structural features to be considered as sensors, catalysts, dyes for photovoltaic cells and for medicinal and environmental applications
Special Issues and Collections in MDPI journals
Prof. Dr. Gianfranco Favi
Website
Guest Editor
School of Farmacy, Department of Biomolecular Sciences, University of Urbino "Carlo Bo", Urbino, Italy
Interests: organic synthesis; synthetic methodologies; sustainable chemistry; heterocyclic chemistry; chemistry of azoalkenes; indole based molecules; cyclizations; cycloadditions; C–H activation
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

In 2020, we are celebrating the 25th anniversary of our journal Molecules. To date, the journal has published more than 20,000 papers, and the journal website attracts 115,000 monthly visits and more than 395,000 monthly page-views. Our sincerest thanks go to our readers, innumerable authors, anonymous peer reviewers, editors, and all the people working in some way for the journal who have joined their efforts for years. Without your help, we would never have achieved this.
To mark this important milestone, a Special Issue entitled “Recent Advances in Organic Synthesis” is being launched. This Special Issue collects communications, full papers, and high-quality review papers in the organic synthesis research fields. We kindly encourage all research groups covering various organic areas to make contributions to this Special Issue.

Prof. Dr. M. Graça P. M. S. Neves
Prof. Dr. Gianfranco Favi
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.

Published Papers (6 papers)

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Research

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Open AccessArticle
Antioxidant and Anticancer Activity of Novel Derivatives of 3-[(4-Methoxyphenyl)amino]propanehydrazide
Molecules 2020, 25(13), 2980; https://doi.org/10.3390/molecules25132980 - 29 Jun 2020
Abstract
Series of novel 3-[(4-methoxyphenyl)amino]propanehydrazide derivatives bearing semicarbazide, thiosemicarbazide, thiadiazole, triazolone, triazolethione, thiophenyltriazole, furan, thiophene, naphthalene, pyrrole, isoindoline-1,3-dione, oxindole, etc. moieties were synthesized and their molecular structures were confirmed by IR, 1H-, 13C-NMR spectroscopy and mass spectrometry data. The antioxidant activity of [...] Read more.
Series of novel 3-[(4-methoxyphenyl)amino]propanehydrazide derivatives bearing semicarbazide, thiosemicarbazide, thiadiazole, triazolone, triazolethione, thiophenyltriazole, furan, thiophene, naphthalene, pyrrole, isoindoline-1,3-dione, oxindole, etc. moieties were synthesized and their molecular structures were confirmed by IR, 1H-, 13C-NMR spectroscopy and mass spectrometry data. The antioxidant activity of the synthesized compounds was screened by DPPH radical scavenging method. The antioxidant activity of N-(1,3-dioxoisoindolin-2-yl)-3-((4-methoxyphenyl)amino)propanamide and 3-((4-methoxyphenyl)amino)-N’-(1-(naphthalen-1-yl)-ethylidene)propanehydrazide has been tested to be ca. 1.4 times higher than that of a well-known antioxidant ascorbic acid. Anticancer activity was tested by MTT assay against human glioblastoma U-87 and triple-negative breast cancer MDA-MB-231 cell lines. In general, the tested compounds were more cytotoxic against U-87 than MDA-MB-231 cell line. 1-(4-Fluorophenyl)-2-((5-(2-((4-methoxyphenyl)amino)ethyl)-4-phenyl-4H-1,2,4-triazol-3-yl)thio)ethanone has been identified as the most active compound against the glioblastoma U-87 cell line. Full article
(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Organic Synthesis)
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Open AccessArticle
Stereodivergent Synthesis of Camphor-Derived Diamines and Their Application as Thiourea Organocatalysts
Molecules 2020, 25(13), 2978; https://doi.org/10.3390/molecules25132978 - 29 Jun 2020
Abstract
A series of 18 regio- and stereo-chemically diverse chiral non-racemic 1,2-, 1,3-, and 1,4-diamines have been synthesized from commercial (1S)-(+)-ketopinic acid and (1S)-(+)-10-camphorsulfonic acid. The structures of the diamines are all based on the d-(+)-camphor scaffold and feature [...] Read more.
A series of 18 regio- and stereo-chemically diverse chiral non-racemic 1,2-, 1,3-, and 1,4-diamines have been synthesized from commercial (1S)-(+)-ketopinic acid and (1S)-(+)-10-camphorsulfonic acid. The structures of the diamines are all based on the d-(+)-camphor scaffold and feature isomeric diversity in terms of regioisomeric attachment of the primary and the tertiary amine function and the exo/endo-isomerism. Diamines were transformed into the corresponding noncovalent bifunctional thiourea organocatalysts, which have been evaluated for catalytic activity in the conjugative addition of 1,3-dicarbonyl nucleophiles (dimethyl malonate, acetylacetone, and dibenzoylmethane) to trans-β-nitrostyrene. The highest enantioselectivity was achieved in the reaction with acetylacetone as nucleophile using endo-1,3-diamine derived catalyst 52 (91.5:8.5 er). All new organocatalysts 4863 have been fully characterized. The structures and the absolute configurations of eight intermediates and thiourea derivative 52 were also determined by X-ray diffraction. Full article
(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Organic Synthesis)
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Open AccessArticle
Chiral Phase Transfer Catalysis in the Asymmetric Synthesis of a 3,3-Disubstituted Isoindolinone and Determination of Its Absolute Configuration by VCD Spectroscopy
Molecules 2020, 25(10), 2272; https://doi.org/10.3390/molecules25102272 - 12 May 2020
Abstract
In this work we report our endeavors toward the development of an asymmetric synthesis of a 3,3-disubstituted isoindolinone, dimethyl 2-(1-methyl-3-oxoisoindolin-1-yl)malonate, via asymmetric cascade reaction of 2-acetylbenzonitrile with dimethylmalonate and the determination of its absolute configuration (AC) by vibrational circular dichroism (VCD). Bifunctional ammonium [...] Read more.
In this work we report our endeavors toward the development of an asymmetric synthesis of a 3,3-disubstituted isoindolinone, dimethyl 2-(1-methyl-3-oxoisoindolin-1-yl)malonate, via asymmetric cascade reaction of 2-acetylbenzonitrile with dimethylmalonate and the determination of its absolute configuration (AC) by vibrational circular dichroism (VCD). Bifunctional ammonium salts, derived from trans-1,2-cyclohexanediamine in combination with inorganic bases under phase transfer conditions, were the most effective catalytic systems, leading to the target in high yields and moderate enantioselectivity. An efficient process of heterochiral crystallization allowed the increase of the enantiopurity up to 96% ee and in an acceptable overall yield. An important aim of the present work is the comparison of different VCD methodologies for AC determination of the target compound. Full article
(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Organic Synthesis)
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Open AccessArticle
Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation
Molecules 2020, 25(7), 1694; https://doi.org/10.3390/molecules25071694 - 07 Apr 2020
Cited by 2
Abstract
New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi [...] Read more.
New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands attributed to the presence of intermolecular H-bond interactions were confirmed by FT–IR spectroscopy. All prepared complexes possessed an enantiotropic nematic phase with a broad temperature nematogenic range. Phases were confirmed by miscibility with a standard nematic (N) compound. A comparison was constructed to investigate the influence of the incorporation of the azophenyl moiety on the mesomeric behavior of corresponding five-membered complexes. It was found that the present complexes observed induced a wide nematic phase with relatively higher temperature ranges than the five aromatic systems. Density functional theory (DFT) suggested the nonlinear geometry of the formed complex. The results of the DFT explained the nematic mesophase formation. Moreover, the π–π stacking of the aromatic moiety in the phenylazo acid plays an effective role in the mesomorphic thermal stability. The energy difference between the frontier molecular orbitals, HOMO (highest occupied) and LUMO (lowest occupied), and the molecular electrostatic potential (MEP) of the prepared complexes were estimated by DFT calculations. The results were used to illustrate the observed nematic phase for all H-bonded supramolecular complexes. Finally, photophysical studies were discussed which were carried out by UV spectroscopy connected to a hot stage. Full article
(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Organic Synthesis)
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Open AccessArticle
2,3-Diaminopropanols Obtained from d-Serine as Intermediates in the Synthesis of Protected 2,3-l-Diaminopropanoic Acid (l-Dap) Methyl Esters
Molecules 2020, 25(6), 1313; https://doi.org/10.3390/molecules25061313 - 13 Mar 2020
Abstract
A synthetic strategy for the preparation of two orthogonally protected methyl esters of the non-proteinogenic amino acid 2,3-l-diaminopropanoic acid (l-Dap) was developed. In these structures, the base-labile protecting group 9-fluorenylmethyloxycarbonyl (Fmoc) was paired to the p-toluensulfonyl (tosyl, Ts) or [...] Read more.
A synthetic strategy for the preparation of two orthogonally protected methyl esters of the non-proteinogenic amino acid 2,3-l-diaminopropanoic acid (l-Dap) was developed. In these structures, the base-labile protecting group 9-fluorenylmethyloxycarbonyl (Fmoc) was paired to the p-toluensulfonyl (tosyl, Ts) or acid-labile tert-butyloxycarbonyl (Boc) moieties. The synthetic approach to protected l-Dap methyl esters uses appropriately masked 2,3-diaminopropanols, which are obtained via reductive amination of an aldehyde prepared from the commercial amino acid Nα-Fmoc-O-tert-butyl-d-serine, used as the starting material. Reductive amination is carried out with primary amines and sulfonamides, and the process is assisted by the Lewis acid Ti(OiPr)4. The required carboxyl group is installed by oxidizing the alcoholic function of 2,3-diaminopropanols bearing the tosyl or benzyl protecting group on the 3-NH2 site. The procedure can easily be applied using the crude product obtained after each step, minimizing the need for chromatographic purifications. Chirality of the carbon atom of the starting d-serine template is preserved throughout all synthetic steps. Full article
(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Organic Synthesis)
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Review

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Open AccessReview
Empowering the Medicinal Applications of Bisphosphonates by Unveiling their Synthesis Details
Molecules 2020, 25(12), 2821; https://doi.org/10.3390/molecules25122821 - 18 Jun 2020
Abstract
Bisphosphonates (BPs), well-known medicinal compounds used for osteoporosis management, are currently the target of intensive research, from basic pre-formulation studies to more advanced stages of clinical practice. The high demand by the pharmaceutical industry inherently requires an easy, efficient and quick preparation of [...] Read more.
Bisphosphonates (BPs), well-known medicinal compounds used for osteoporosis management, are currently the target of intensive research, from basic pre-formulation studies to more advanced stages of clinical practice. The high demand by the pharmaceutical industry inherently requires an easy, efficient and quick preparation of BPs. Current synthetic procedures are, however, still far from ideal. This work presents a comprehensive compilation of reports on the synthesis of the commercially available bisphosphonates that are pharmaceutical active ingredients. Current limitations to the conventional synthesis are assessed, and paths towards their improvement are described, either through the use of alternative solvents and/or by selecting appropriate ratios of the reactants. Innovative processes, such as microwave-assisted synthesis, are presented as more environmental-friendly and effective methods. The main advantages and setbacks of all syntheses are provided as a way to clarify and promote the development of simpler and improved procedures. Only in this way one will be able to efficiently respond to the future high demand of BPs, mostly due to the increase in life span in occidental countries. Full article
(This article belongs to the Special Issue 25th Anniversary of Molecules—Recent Advances in Organic Synthesis)
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