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Special Issue "Development of New Methods of Synthesis of Heterocycles"

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

Deadline for manuscript submissions: 31 October 2020.

Special Issue Editors

Prof. Dr. Paula Sério Branco
Website
Guest Editor
LAQV-REQUIMTE, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
Interests: organic synthesis; heterocyclic compounds; natural products synthesis; dye-sensitized-solar-cells; catalytic sustainable procedures; new synthetic methods
Dr. Filipa Siopa
Website
Guest Editor
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
Interests: C-H Activation; flow chemistry; total synthesis; heterocyclic compounds; organocatalysis

Special Issue Information

Dear Colleagues,

Heterocyclic compounds, cyclic compounds that have atoms of at least two different elements as members of their ring, are unavoidable structures due to the wide diversity of their applications. Nature is prodigious and creative in offering a huge amount of diverse heterocyclic compounds, such as nucleic acids, antibiotics, anticancer agents, agrochemicals, pharmaceuticals, pigments and others, that chemists use as the lead compounds to create even more diversity. Interest in this type of structure comes from the proprieties they impart to materials due to their polarity, solubility, and electronic properties. “Development of New Methods of Synthesis of Heterocycles” is a Special Issue of Molecules accepting manuscripts addressing the synthesis of natural and unnatural heterocyclic compounds with potential biological applications or heterocyclic new materials with singular proprieties. Original research articles or reviews that discuss alternative, new and innovative sustainable organic reactions and methodologies and employing alternative energy sources are welcome.

Prof. Paula Branco
Dr. Filipa Siopa
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

  • heterocycles
  • synthetic methods
  • annulations
  • C–H activation
  • cross-coupling reactions
  • multicomponent reactions
  • condensation reactions
  • ring-closing reactions
  • solvent-free reactions
  • non-conventional reaction media
  • microwaves
  • sonication
  • electrosynthesis
  • photochemical and photocatalysis
  • metal–organocatalysis
  • biocatalysis and biotransformations
  • mechanochemical mixing
  • high-speed ball milling
  • Flow chemistry

Published Papers (8 papers)

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Research

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Open AccessCommunication
Triazolopyridopyrimidine: A New Scaffold for Dual-Target Small Molecules for Alzheimer’s Disease Therapy
Molecules 2020, 25(14), 3190; https://doi.org/10.3390/molecules25143190 - 13 Jul 2020
Abstract
Alzheimer’s disease (AD) is multifactorial disease characterized by the accumulation of abnormal extracellular deposits of amyloid-beta (Aβ) peptide, and intracellular neurofibrillary tangles (NFTs), along with dramatic neuronal death and decreased levels of choline acetyltransferase. Given the limited therapeutic success of available drugs, it [...] Read more.
Alzheimer’s disease (AD) is multifactorial disease characterized by the accumulation of abnormal extracellular deposits of amyloid-beta (Aβ) peptide, and intracellular neurofibrillary tangles (NFTs), along with dramatic neuronal death and decreased levels of choline acetyltransferase. Given the limited therapeutic success of available drugs, it is urgent to explore all the opportunities available to combat this illness. Among them, the discovery of new heterocyclic scaffolds binding different receptors involved in AD should offer structural diversity and new therapeutic solutions. In this context, this work describes new triazolopyridopyrimidine easily prepared in good yields showing anticholinesterase inhibition and strong antioxidant power, particularly the most balanced: 6-amino-5-(4-methoxyphenyl)-2-phenyl-[1,2,4]triazolo[1′,5′:1,6] pyrido[2,3-d]pyrimidine-4-carbonitrile(3c) with IC50 equal to 1.32 μM against AChE and oxygen radical absorbance capacity (ORAC) value equal to 4.01 Trolox equivalents (TE); thus representing a new and very promising hit-triazolopyridopyrimidine for AD therapy. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Open AccessFeature PaperArticle
Deep Eutectic Solvents as Effective Reaction Media for the Synthesis of 2-Hydroxyphenylbenzimidazole-Based Scaffolds en Route to Donepezil-Like Compounds
Molecules 2020, 25(3), 574; https://doi.org/10.3390/molecules25030574 - 28 Jan 2020
Cited by 1
Abstract
An unsubstituted 2-hydroxyphenylbenzimidazole has recently been included as a scaffold in a series of hybrids (including the hit compound PZ1) based on the framework of the acetylcholinesterase (AChE) inhibitor Donepezil, which is a new promising multi-target ligand in Alzheimer’s disease (AD) treatment. Building [...] Read more.
An unsubstituted 2-hydroxyphenylbenzimidazole has recently been included as a scaffold in a series of hybrids (including the hit compound PZ1) based on the framework of the acetylcholinesterase (AChE) inhibitor Donepezil, which is a new promising multi-target ligand in Alzheimer’s disease (AD) treatment. Building upon these findings, we have now designed and completed the whole synthesis of PZ1 in the so-called deep eutectic solvents (DESs), which have emerged as an unconventional class of bio-renewable reaction media in green synthesis. Under optimized reaction conditions, the preparation of a series of 2-hydroxyphenylbenzimidazole-based nuclei has also been perfected in DESs, and comparison with other routes which employ toxic and volatile organic solvents (VOCs) provided. The functionalization of the aromatic ring can have implications on some important biological properties of the described derivatives and will be the subject of future studies of structure-activity relationships (SARs). Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Open AccessArticle
Dialkylation of Indoles with Trichloroacetimidates to Access 3,3-Disubstituted Indolenines
Molecules 2019, 24(22), 4143; https://doi.org/10.3390/molecules24224143 - 15 Nov 2019
Abstract
2-Substituted indoles may be directly transformed to 3,3-dialkyl indolenines with trichloroacetimidate electrophiles and the Lewis acid TMSOTf. These reactions provide rapid access to complex indolenines which are present in a variety of complex natural products and medicinally relevant small molecule structures. This method [...] Read more.
2-Substituted indoles may be directly transformed to 3,3-dialkyl indolenines with trichloroacetimidate electrophiles and the Lewis acid TMSOTf. These reactions provide rapid access to complex indolenines which are present in a variety of complex natural products and medicinally relevant small molecule structures. This method provides an alternative to the use of transition metal catalysis. The indolenines are readily transformed into spiroindoline systems which are privileged scaffolds in medicinal chemistry. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Open AccessCommunication
Synthesis, Physicochemical Properties, and Biological Activities of 4-(S-Methyl-N-(2,2,2-Trifluoroacetyl)Sulfilimidoyl) Anthranilic Diamide
Molecules 2019, 24(19), 3451; https://doi.org/10.3390/molecules24193451 - 23 Sep 2019
Abstract
Novel anthranilic diamides with sulfilimidoyl and sulfoximidoyl functionalities were successfully prepared. Among newly-prepared organosulfur compounds, 3-bromo-1-(3-chloropyridin-2-yl)-N-(2-methyl-6-(methylcarbamoyl)-4-(methylthio)phenyl)-1H-pyrazole-5-carboxamide and (S,E)-3-bromo-1-(3-chloropyridin-2-yl)-N-(2-methyl-4-(S-methyl-N-(2,2,2-trifluoroacetyl)sulfinimidoyl)-6-(methylcarbamoyl)phenyl)-1H-pyrazole-5-carboxamide showed good levels of efficacy and a strong correlation between insecticidal [...] Read more.
Novel anthranilic diamides with sulfilimidoyl and sulfoximidoyl functionalities were successfully prepared. Among newly-prepared organosulfur compounds, 3-bromo-1-(3-chloropyridin-2-yl)-N-(2-methyl-6-(methylcarbamoyl)-4-(methylthio)phenyl)-1H-pyrazole-5-carboxamide and (S,E)-3-bromo-1-(3-chloropyridin-2-yl)-N-(2-methyl-4-(S-methyl-N-(2,2,2-trifluoroacetyl)sulfinimidoyl)-6-(methylcarbamoyl)phenyl)-1H-pyrazole-5-carboxamide showed good levels of efficacy and a strong correlation between insecticidal activities and physical properties, respectively. In particular, available data indicated that the N-trifluoroacetyl sulfilimine moiety could be an appealing structural scaffold for the discovery of a new crop-protecting agent. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Open AccessArticle
Synthesis of 6,12-Disubstituted Methanodibenzo[b,f][1,5]dioxocins: Pyrrolidine Catalyzed Self-Condensation of 2′-Hydroxyacetophenones
Molecules 2019, 24(13), 2405; https://doi.org/10.3390/molecules24132405 - 29 Jun 2019
Abstract
The preparation of unprecedented 6,12-disubstituted methanodibenzo[b,f][1,5]dioxocins from pyrrolidine catalyzed self-condensation of 2′-hydroxyacetophenones is herein described. This method provides easy access to this highly bridged complex core, resulting in construction of two C–O and two C–C bonds, a methylene bridge [...] Read more.
The preparation of unprecedented 6,12-disubstituted methanodibenzo[b,f][1,5]dioxocins from pyrrolidine catalyzed self-condensation of 2′-hydroxyacetophenones is herein described. This method provides easy access to this highly bridged complex core, resulting in construction of two C–O and two C–C bonds, a methylene bridge and two quaternary centers in a single step. The intricate methanodibenzo[b,f][1,5]dioxocin compounds were obtained in up to moderate yields after optimization of the reaction conditions concerning solvent, reaction times and the use of additives. Several halide substituted methanodibenzo[b,f][1,5]dioxocins could be prepared from correspondent 2′-hydroxyacetophenones. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Review

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Open AccessReview
Advances in Synthesis of π-Extended Benzosilole Derivatives and Their Analogs
Molecules 2020, 25(3), 548; https://doi.org/10.3390/molecules25030548 - 27 Jan 2020
Abstract
Benzosiloles and their π-extended derivatives are present in many important advanced materials due to their excellent physical properties. Especially, they have found many potential applications in the development of novel electronic materials such as OLEDs, semiconductors and solar cells. In this review, we [...] Read more.
Benzosiloles and their π-extended derivatives are present in many important advanced materials due to their excellent physical properties. Especially, they have found many potential applications in the development of novel electronic materials such as OLEDs, semiconductors and solar cells. In this review, we have summarized several main approaches to construct (di)benzosilole derivatives and (benzo)siloles fused to aromatic five- and six-membered heterocycles. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Open AccessReview
Revisiting the Structure and Chemistry of 3(5)-Substituted Pyrazoles
Molecules 2020, 25(1), 42; https://doi.org/10.3390/molecules25010042 - 20 Dec 2019
Cited by 5
Abstract
Pyrazoles are known as versatile scaffolds in organic synthesis and medicinal chemistry, often used as starting materials for the preparation of more complex heterocyclic systems with relevance in the pharmaceutical field. Pyrazoles are also interesting compounds from a structural viewpoint, mainly because they [...] Read more.
Pyrazoles are known as versatile scaffolds in organic synthesis and medicinal chemistry, often used as starting materials for the preparation of more complex heterocyclic systems with relevance in the pharmaceutical field. Pyrazoles are also interesting compounds from a structural viewpoint, mainly because they exhibit tautomerism. This phenomenon may influence their reactivity, with possible impact on the synthetic strategies where pyrazoles take part, as well as on the biological activities of targets bearing a pyrazole moiety, since a change in structure translates into changes in properties. Investigations of the structure of pyrazoles that unravel the tautomeric and conformational preferences are therefore of upmost relevance. 3(5)-Aminopyrazoles are largely explored as precursors in the synthesis of condensed heterocyclic systems, namely pyrazolo[1,5-a]pyrimidines. However, the information available in the literature concerning the structure and chemistry of 3(5)-aminopyrazoles is scarce and disperse. We provide a revision of data on the present subject, based on investigations using theoretical and experimental methods, together with the applications of the compounds in synthesis. It is expected that the combined information will contribute to a deeper understanding of structure/reactivity relationships in this class of heterocycles, with a positive impact in the design of synthetic methods, where they take part. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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Open AccessReview
Current Advances in the Synthesis of Valuable Dipyrromethane Scaffolds: Classic and New Methods
Molecules 2019, 24(23), 4348; https://doi.org/10.3390/molecules24234348 - 28 Nov 2019
Cited by 1
Abstract
This review presents the most recent developments on the synthesis of dipyrromethanes, covering classical synthetic strategies, using acid catalyzed condensation of pyrroles and aldehydes or ketones, and recent breakthroughs which allow the synthesis of these type of heterocycles with new substitution patterns. Full article
(This article belongs to the Special Issue Development of New Methods of Synthesis of Heterocycles)
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