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Synthesis of Heterocyclic Compounds

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

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 17137

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Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell'Insubria, via Valleggio 9, 22100 Como, Italy
Interests: organic synthesis; indoles; biindole compounds, natural products; nitrosoarenes; alkynes; bioactive compounds; annulations; cycloaddition, material science
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Special Issue Information

Dear Colleagues,

Heterocyclic compounds play a relevant role in many different aspects of our daily lives and in the current facets and features of research in synthetic organic chemistry. Most of the chemicals that have interesting functions in hereditary information, food, energetics, drugs and pharmaceuticals, photosynthesis, agriculture, supramolecular chemistry, and health are also characterized by the presence of at least one heterocyclic ring in their molecular structure. In recent decades, heterocycles have become fundamental in chemistry, and their peculiarities have emerged in many varied fields with interesting developments occurring in industry, technology, and materials science. Heterocyclic compounds are certainly the basis of the majority of building blocks and fine chemicals discovered and synthesized over two centuries, attesting to an exponential growth in chemical synthesis. Both academic and industrial chemists work continuously to develop novel methodologies, innovative preparation techniques, environmentally friendly approaches, and new synthetic protocols for the preparation of interesting heterocyclic derivatives or their optimization. Molecules is a peer-reviewed scientific journal that in the recent years has been receiving ever-growing interest and attention both from the community of chemists and other scientists that work in cooperation with the chemists.

Prof. Dr. Andrea Penoni
Guest Editor

Manuscript Submission Information

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Keywords

  • nitrogen-containing heterocycles;
  • oxygen-containing heterocycles;
  • sulfur-containing heterocycles;
  • natural products;
  • synthetic compounds;
  • spectroscopic characterization;
  • organic synthesis;
  • materials science; NMR;
  • mass spectrometry;
  • macrocycles; ligands;
  • synthetic methodologies;
  • annulation; cycloaddition;
  • total synthesis

Published Papers (5 papers)

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Research

10 pages, 1389 KiB  
Article
Base-Promoted Annulation of Amidoximes with Alkynes: Simple Access to 2,4-Disubstituted Imidazoles
by Hina Mehmood, Muhammad Asif Iqbal, Le Lu and Ruimao Hua
Molecules 2020, 25(16), 3621; https://doi.org/10.3390/molecules25163621 - 09 Aug 2020
Cited by 6 | Viewed by 3033
Abstract
An efficient construction of imidazole ring by a Cs2CO3-promoted annulation of amidoximes with terminal alkynes in DMSO has been developed. This protocol provides a simple synthetic route with high atom-utilization for the synthesis of 2,4-disubstituted imidazoles in good yields [...] Read more.
An efficient construction of imidazole ring by a Cs2CO3-promoted annulation of amidoximes with terminal alkynes in DMSO has been developed. This protocol provides a simple synthetic route with high atom-utilization for the synthesis of 2,4-disubstituted imidazoles in good yields under transition-metal-free and ligand-free conditions. Internal alkynes can also undergo the annulation to give 2,4,5-trisubstituted imidazoles. Full article
(This article belongs to the Special Issue Synthesis of Heterocyclic Compounds)
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14 pages, 2416 KiB  
Article
Synthesis and Antibacterial Evaluation of N-phenylacetamide Derivatives Containing 4-Arylthiazole Moieties
by Hui Lu, Xia Zhou, Lei Wang and Linhong Jin
Molecules 2020, 25(8), 1772; https://doi.org/10.3390/molecules25081772 - 12 Apr 2020
Cited by 15 | Viewed by 3508
Abstract
A series of new N-phenylacetamide derivatives containing 4-arylthiazole moieties was designed and synthesized by introducing the thiazole moiety into the amide scaffold. The structures of the target compounds were confirmed by 1H-NMR, 13C-NMR and HRMS. Their in vitro antibacterial activities [...] Read more.
A series of new N-phenylacetamide derivatives containing 4-arylthiazole moieties was designed and synthesized by introducing the thiazole moiety into the amide scaffold. The structures of the target compounds were confirmed by 1H-NMR, 13C-NMR and HRMS. Their in vitro antibacterial activities were evaluated against three kinds of bacteria—Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac) and X.oryzae pv. oryzicola (Xoc)—showing promising results. The minimum 50% effective concentration (EC50) value of N-(4-((4-(4-fluoro-phenyl)thiazol-2-yl)amino)phenyl)acetamide (A1) is 156.7 µM, which is superior to bismerthiazol (230.5 µM) and thiodiazole copper (545.2 µM). A scanning electron microscopy (SEM) investigation has confirmed that compound A1 could cause cell membrane rupture of Xoo. In addition, the nematicidal activity of the compounds against Meloidogyne incognita (M. incognita) was also tested, and compound A23 displayed excellent nematicidal activity, with mortality of 100% and 53.2% at 500 μg/mL and 100 μg/mL after 24 h of treatment, respectively. The preliminary structure-activity relationship (SAR) studies of these compounds are also briefly described. These results demonstrated that phenylacetamide derivatives may be considered as potential leads in the design of antibacterial agents. Full article
(This article belongs to the Special Issue Synthesis of Heterocyclic Compounds)
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20 pages, 4209 KiB  
Article
Unsymmetrically Substituted Dibenzo[b,f][1,5]-diazocine-6,12(5H,11H)dione—A Convenient Scaffold for Bioactive Molecule Design
by Bartosz Bieszczad, Damian Garbicz, Damian Trzybiński, Damian Mielecki, Krzysztof Woźniak, Elżbieta Grzesiuk and Adam Mieczkowski
Molecules 2020, 25(4), 906; https://doi.org/10.3390/molecules25040906 - 18 Feb 2020
Cited by 8 | Viewed by 3432
Abstract
A novel approach for the synthesis of unsymmetrically substituted dibenzo[b,f][1,5]diazocine-6,12(5H,11H)diones has been developed. This facile three-step method uses variously substituted 1H-benzo[d][1,3]oxazine-2,4-diones (isatoic anhydrides) and 2-aminobenzoic acids as a starting materials. The obtained products [...] Read more.
A novel approach for the synthesis of unsymmetrically substituted dibenzo[b,f][1,5]diazocine-6,12(5H,11H)diones has been developed. This facile three-step method uses variously substituted 1H-benzo[d][1,3]oxazine-2,4-diones (isatoic anhydrides) and 2-aminobenzoic acids as a starting materials. The obtained products were further transformed into N-alkyl-, N-acetyl- and dithio analogues. Developed procedures allowed the synthesis of unsymmetrical dibenzo[b,f][1,5]diazocine-6,12(5H,11H)diones and three novel heterocyclic scaffolds: benzo[b]naphtho[2,3-f][1,5]diazocine-6,14(5H,13H)dione, pyrido[3,2-c][1,5]benzodiazocine-5,11(6H,12H)-dione and pyrazino[3,2-c][1,5]benzodiazocine-6,12(5H,11H)dione. For 11 of the compounds crystal structures were obtained. The preliminary cytotoxic effect against two cancer (HeLa, U87) and two normal lines (HEK293, EUFA30) as well as antibacterial activity were determined. The obtained dibenzo[b,f][1,5]diazocine(5H,11H)6,12-dione framework could serve as a privileged structure for the drug design and development. Full article
(This article belongs to the Special Issue Synthesis of Heterocyclic Compounds)
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13 pages, 1689 KiB  
Article
General Synthesis of 1-Aryl-6-azaisocytosines and Their Utilization for the Preparation of Related Condensed 1,2,4-Triazines
by František Zálešák, Jan Slouka and Jakub Stýskala
Molecules 2019, 24(19), 3558; https://doi.org/10.3390/molecules24193558 - 01 Oct 2019
Cited by 3 | Viewed by 3018
Abstract
A simple general synthesis of 1-aryl-6-azaisocytosine-5-carbonitriles 4 is described. This method is based on coupling diazonium salts with cyanoacetylcyanamide 2 and then cyclization of the formed 2-arylhydrazono-2-cyanoacetylcyanamides 3. The 6-azaisocytosines 4 were studied with respect to tautomeric equilibrium and the transformation of [...] Read more.
A simple general synthesis of 1-aryl-6-azaisocytosine-5-carbonitriles 4 is described. This method is based on coupling diazonium salts with cyanoacetylcyanamide 2 and then cyclization of the formed 2-arylhydrazono-2-cyanoacetylcyanamides 3. The 6-azaisocytosines 4 were studied with respect to tautomeric equilibrium and the transformation of functional groups, and used in the synthesis of the condensed heterocyclic compounds: Purine isosteric imidazo[2,1-c]-[1,2,4]triazine 8 and the 1,2,4-triazino[2,3-a]quinazolines 912. Full article
(This article belongs to the Special Issue Synthesis of Heterocyclic Compounds)
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11 pages, 4195 KiB  
Article
4H-Benzo[d][1,3]oxazin-4-ones and Dihydro Analogs from Substituted Anthranilic Acids and Orthoesters
by Joel K. Annor-Gyamfi and Richard A. Bunce
Molecules 2019, 24(19), 3555; https://doi.org/10.3390/molecules24193555 - 01 Oct 2019
Cited by 6 | Viewed by 3050
Abstract
A one-pot route to 2-alkyl and 2-aryl-4H-benzo[d][1,3]oxazin-4-ones (also known as 4H-3,1-benzoxazin-4-ones) has been developed and studied. The method involves the reaction of aryl-substituted anthranilic acids with orthoesters in ethanol catalyzed by acetic acid. Additionally, we have also [...] Read more.
A one-pot route to 2-alkyl and 2-aryl-4H-benzo[d][1,3]oxazin-4-ones (also known as 4H-3,1-benzoxazin-4-ones) has been developed and studied. The method involves the reaction of aryl-substituted anthranilic acids with orthoesters in ethanol catalyzed by acetic acid. Additionally, we have also investigated the reaction under microwave conditions. Not all of the substrates were successful in yielding the target heterocycles as some of the reactions failed to undergo the final elimination. This process led to the isolation of (±)-2-alkyl/aryl-2-ethoxy-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-ones. The formation of the dihydro analogs correlated with the electron density on the aromatic ring: Electron-donating groups favored the 4H- benzo[d][1,3]oxazin-4-ones, while electron-withdrawing groups tended to favor the dihydro product. Substituting a pyridine ring for the benzene ring in the substrate acid suppressed the reaction. Full article
(This article belongs to the Special Issue Synthesis of Heterocyclic Compounds)
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