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Special Issue "Recent Advances in Nitrogen-Containing Aromatic Heterocycles"

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

Deadline for manuscript submissions: closed (21 December 2018).

Special Issue Editor

Prof. Dr. Fawaz Aldabbagh
Website
Guest Editor
Department of Pharmacy, School of Life Sciences, Pharmacy & Chemistry, Kingston University, Penrhyn Road, Kingston upon Thames, KT1 2EE, UK
Interests: free radical organic and polymer chemistry; heterocyclic and medicinal chemistry
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to aromatic organic compounds containing one or more nitrogen atoms. These are five or six-membered rings, fused or not fused onto other rings, and containing nitrogen only or in combination with oxygen or sulfur. A surfeit of such compounds occurs in the chemical literature, including many natural substances and bioactive synthetic compounds. I am therefore looking forward to receiving timeless research articles, communications and reviews detailing the latest advances in synthetic methods, target oriented synthesis, applications, and biological evaluation of such small molecule heterocycles.    

Prof. Dr. Fawaz Aldabbagh
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 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

  • heterocyclic chemistry
  • medicinal chemistry
  • natural products
  • organic synthesis
  • reactive intermediates
  • synthetic methods

Published Papers (7 papers)

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Research

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Open AccessFeature PaperArticle
New Quinoline-Based Heterocycles as Anticancer Agents Targeting Bcl-2
Molecules 2019, 24(7), 1274; https://doi.org/10.3390/molecules24071274 - 02 Apr 2019
Cited by 5
Abstract
The Bcl-2 protein has been studied as an anticancer drug target in recent years, due to its gatekeeper role in resisting programmed cancer cell death (apoptosis), and the design of BH3 domain mimetics has led to the clinical approval of Venetoclax (ABT-199) for [...] Read more.
The Bcl-2 protein has been studied as an anticancer drug target in recent years, due to its gatekeeper role in resisting programmed cancer cell death (apoptosis), and the design of BH3 domain mimetics has led to the clinical approval of Venetoclax (ABT-199) for the treatment of chronic lymphocytic leukaemia. In this work we extend our previous studies on the discovery of indole-based heterocycles as Bcl-2 inhibitors, to the identification of quinolin-4-yl based oxadiazole and triazole analogues. Target compounds were readily synthesized via a common aryl-substituted quinolin-4-carbonyl-N-arylhydrazine-1-carbothioamide (5a–b) intermediate, through simple variation of the basic cyclisation conditions. Some of the quinoline-based oxadiazole analogues (e.g. compound 6i) were found to exhibit sub-micromolar anti-proliferative activity in Bcl-2-expressing cancer cell lines, and sub-micromolar IC50 activity within a Bcl2-Bim peptide ELISA assay. The Bcl-2 targeted anticancer activity of 6i was further rationalised via computational molecular modelling, offering possibilities to extend this work into the design of further potent and selective Bcl-2 inhibitory heteroaromatics with therapeutic potential. Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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Open AccessFeature PaperArticle
Regioselective Fluorination of 7-Oxo-1,2,4-benzotriazines Using Selectfluor
Molecules 2019, 24(2), 282; https://doi.org/10.3390/molecules24020282 - 14 Jan 2019
Cited by 4
Abstract
7-Oxo-1,2,4-benzotriazines (benzo[1,2,4]triazin-7-ones) are reversible thioredoxin reductase inhibitors that exhibit very strong correlations to pleurotin. In this article, we provide the first synthesis of fluorinated derivatives. Fluorination using Selectfluor of benzo[1,2,4]triazin-7-ones occurs regioselectively and in high yield at the enamine-activated position. This electron N-lone [...] Read more.
7-Oxo-1,2,4-benzotriazines (benzo[1,2,4]triazin-7-ones) are reversible thioredoxin reductase inhibitors that exhibit very strong correlations to pleurotin. In this article, we provide the first synthesis of fluorinated derivatives. Fluorination using Selectfluor of benzo[1,2,4]triazin-7-ones occurs regioselectively and in high yield at the enamine-activated position. This electron N-lone pair activation overrides the activation/deactivation effects of some other substituents. The reaction time was significantly reduced with the use of microwave irradiation at 120 °C and 7 bar. The cytotoxicity and cyclic voltammetry measurements for 8-fluoro-1,3-diphenylbenzo[e][1,2,4]triazin-7(1H)-one (2) are presented and compared with its synthetic precursor, 1,3-diphenylbenzo[e][1,2,4]triazin-7(1H)-one (1a). Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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Open AccessArticle
Synthesis and Antifungal Potential of Some Novel Benzimidazole-1,3,4-Oxadiazole Compounds
Molecules 2019, 24(1), 191; https://doi.org/10.3390/molecules24010191 - 06 Jan 2019
Cited by 10
Abstract
Discovery of novel anticandidal agents with clarified mechanisms of action, could be a rationalist approach against diverse pathogenic fungal strains due to the rise of resistance to existing drugs. In support to this hypothesis, in this paper, a series of benzimidazole-oxadiazole compounds were [...] Read more.
Discovery of novel anticandidal agents with clarified mechanisms of action, could be a rationalist approach against diverse pathogenic fungal strains due to the rise of resistance to existing drugs. In support to this hypothesis, in this paper, a series of benzimidazole-oxadiazole compounds were synthesized and subjected to antifungal activity evaluation. In vitro activity assays indicated that some of the compounds exhibited moderate to potent antifungal activities against tested Candida species when compared positive control amphotericin B and ketoconazole. The most active compounds 4h and 4p were evaluated in terms of inhibitory activity upon ergosterol biosynthesis by an LC-MS-MS method and it was determined that they inhibited ergosterol synthesis concentration dependently. Docking studies examining interactions between most active compounds and lanosterol 14-α-demethylase also supported the in vitro results. Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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Open AccessFeature PaperArticle
Further Studies on the Pyrolytic Domino Cyclization of Stabilized Phosphonium Ylides Bearing an Ortho-Aminophenyl Group
Molecules 2018, 23(9), 2153; https://doi.org/10.3390/molecules23092153 - 27 Aug 2018
Cited by 2
Abstract
Four new, stabilized phosphonium ylides containing a 2-(benzyl(methyl)amino)phenyl group have been prepared and characterized and are found, upon pyrolysis under gas-phase flow conditions, to lose Ph3PO and benzyl radicals to afford new heterocyclic products resulting from domino cyclization of both C [...] Read more.
Four new, stabilized phosphonium ylides containing a 2-(benzyl(methyl)amino)phenyl group have been prepared and characterized and are found, upon pyrolysis under gas-phase flow conditions, to lose Ph3PO and benzyl radicals to afford new heterocyclic products resulting from domino cyclization of both C- and N-centered radicals. Most products arise from processes of the former type and have quinoline, phenanthridine, or ring-fused phenanthridine structures, while in one case, a process of the latter type leads to a benzocarbazole product. The X-ray structure of a 2-(methyl(tosyl)amino)phenyl ylide is also reported. Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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Open AccessCommunication
Suzuki-Type Cross-Coupling Reaction of Unprotected 3-Iodoindazoles with Pinacol Vinyl Boronate: An Expeditive C-3 Vinylation of Indazoles under Microwave Irradiation
Molecules 2018, 23(8), 2051; https://doi.org/10.3390/molecules23082051 - 16 Aug 2018
Cited by 4
Abstract
Herein we report an expeditive C-3 vinylation of unprotected 3-iodoindazoles under microwave irradiation. Ten C-5 substituted 3-vinylindazole derivatives, nine of them novel, were synthesized through this method, which proceeds in moderate to excellent yields starting from C-5 substituted 3-iodoindazole derivatives. In all cases, [...] Read more.
Herein we report an expeditive C-3 vinylation of unprotected 3-iodoindazoles under microwave irradiation. Ten C-5 substituted 3-vinylindazole derivatives, nine of them novel, were synthesized through this method, which proceeds in moderate to excellent yields starting from C-5 substituted 3-iodoindazole derivatives. In all cases, the C-3 vinylated derivative was the only isolated product. This methodology allows access to 3-vinylated indazoles selectively and directly without the need of N-protection. 3-Vinylindazoles could be interesting synthetic intermediates allowing access to biologically active molecules. Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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Open AccessFeature PaperArticle
The Conversion of 5,5′-Bi(1,2,3-dithiazolylidenes) into Isothiazolo[5,4-d]isothiazoles
Molecules 2018, 23(6), 1257; https://doi.org/10.3390/molecules23061257 - 24 May 2018
Cited by 3
Abstract
Thermolysis of 4,4′-dichloro-, 4,4′-diaryl-, and 4,4′-di(thien-2-yl)-5,5′-bi(1,2,3-dithiazol-ylidenes) affords the respective 3,6-dichloro-, 3,6-diaryl- and 3,6-di(thien-2-yl)isothiazolo[5,4-d]-isothiazoles in low to high yields. The transformation of the 4,4′-diaryl- and 4,4′-di(thien-2-yl)-5,5′-bi(1,2,3-dithiazolylidenes) occurs at lower temperatures in the presence of the thiophiles triphenylphosphine or tetraethylammonium iodide. Optimized reaction [...] Read more.
Thermolysis of 4,4′-dichloro-, 4,4′-diaryl-, and 4,4′-di(thien-2-yl)-5,5′-bi(1,2,3-dithiazol-ylidenes) affords the respective 3,6-dichloro-, 3,6-diaryl- and 3,6-di(thien-2-yl)isothiazolo[5,4-d]-isothiazoles in low to high yields. The transformation of the 4,4′-diaryl- and 4,4′-di(thien-2-yl)-5,5′-bi(1,2,3-dithiazolylidenes) occurs at lower temperatures in the presence of the thiophiles triphenylphosphine or tetraethylammonium iodide. Optimized reaction conditions and a mechanistic rationale for the thiophile-mediated ring transformation are presented. Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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Review

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Open AccessFeature PaperReview
Recent Advances in Indazole-Containing Derivatives: Synthesis and Biological Perspectives
Molecules 2018, 23(11), 2783; https://doi.org/10.3390/molecules23112783 - 26 Oct 2018
Cited by 25
Abstract
Indazole-containing derivatives represent one of the most important heterocycles in drug molecules. Diversely substituted indazole derivatives bear a variety of functional groups and display versatile biological activities; hence, they have gained considerable attention in the field of medicinal chemistry. This review aims to [...] Read more.
Indazole-containing derivatives represent one of the most important heterocycles in drug molecules. Diversely substituted indazole derivatives bear a variety of functional groups and display versatile biological activities; hence, they have gained considerable attention in the field of medicinal chemistry. This review aims to summarize the recent advances in various methods for the synthesis of indazole derivatives. The current developments in the biological activities of indazole-based compounds are also presented. Full article
(This article belongs to the Special Issue Recent Advances in Nitrogen-Containing Aromatic Heterocycles)
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