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Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa

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

Deadline for manuscript submissions: closed (31 July 2021) | Viewed by 20279

Special Issue Editors

Prof. Dr. Scott K. Bur

E-Mail Website
Guest Editor
Department of Chemistry, Gustavus Adolphus College, St. Peter, MN 56028, USA
Interests: synthetic methodology; natural products synthesis; chemical biology; bromodomains; fragment-based ligand discovery
Dr. Qiu Wang

E-Mail Website
Guest Editor
Department of Chemistry, Duke University, 124 Science Drive, Durham, NC 27708, USA
Interests: organic chemistry and chemical biology; catalysis; heterocyclic compounds; molecular imaging; methodology and synthesis

Special Issue Information

Dear Colleagues,

Heterocyclic structures play important roles in fields such as medicinal chemistry and materials science because of their diverse and important biological and physical properties. Accordingly, efficient methods for the synthesis of heterocyclic molecules are highly valued in the synthetic organic community. For over 50 years, Dr. Al Padwa has been a central figure in the development of new synthetic methods for heterocyclic molecules. His influence on chemists in the pharmaceutical industry and academia is hard to overstate. In combination, the 800+ articles he has published and his work on the editorial boards of many journals demonstrate the broad impact Dr. Padwa has had on the discipline.

Dr. Padwa (born, New York, 1937) holds a PhD from Columbia University and has worked with Howard Zimmerman at the University of Wisconsin as a National Science Foundation Postdoctoral Fellow. He started his academic career at the Ohio State University in 1963, then moved to the State University of New York, Buffalo in 1969. In 1979, he accepted the position of William Patterson Timmie Professor of Chemistry at Emory University, where he has remained since. His body of work spans from understanding the mechanisms of photochemical transformations involving small-ring heterocyclic molecules to the development of cascade reactions to generate natural product-like structures. He is probably most well-known for using dipolar- and Diels–Alder-cycloaddition reactions as key strategic steps in the construction of complex heterocycles. For his various contributions, he has been honored with numerous awards, including a Sloan Fellowship, a John S. Guggenheim Foundation Fellowship, the Senior Scholar Award of the International Society of Heterocyclic Chemsitry (1999), and an Arthur C. Cope award (2000) from the American Chemical Society.

Dr. Padwa’s influence on heterocyclic synthesis will be felt for many years. In honor of all the contributions Dr. Padwa has made and the tremendous impact his work has had on the field, we invite you to submit a publication for this Special Edition.

Prof. Dr. Scott K. Bur
Dr. Qiu Wang
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 submissions that pass pre-check are 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 2700 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
  • Natural product synthesis
  • Alkaloids
  • Cycloadditions
  • Synthesis
  • Synthetic methodology

Published Papers (7 papers)

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Research

15 pages, 1081 KiB  
Article
Regioselective Reduction of 1H-1,2,3-Triazole Diesters
by Christopher R. Butler, Justin Bendesky and Allen Milton Schoffstall
Molecules 2021, 26(18), 5589; https://doi.org/10.3390/molecules26185589 - 15 Sep 2021
Cited by 3 | Viewed by 3186
Abstract
Regioselective reactions can play pivotal roles in synthetic organic chemistry. The reduction of several 1-substituted 1,2,3-triazole 4,5-diesters by sodium borohydride has been found to be regioselective, with the C(5) ester groups being more reactive towards reduction than the C(4) ester groups. The amount [...] Read more.
Regioselective reactions can play pivotal roles in synthetic organic chemistry. The reduction of several 1-substituted 1,2,3-triazole 4,5-diesters by sodium borohydride has been found to be regioselective, with the C(5) ester groups being more reactive towards reduction than the C(4) ester groups. The amount of sodium borohydride and reaction time required for reduction varied greatly depending on the N(1)-substituent. The presence of a β-hydroxyl group on the N(1)-substituent was seen to have a rate enhancing effect on the reduction of the C(5) ester group. The regioselective reduction was attributed to the lower electron densities of the C(5) and the C(5) ester carbonyl carbon of the 1,2,3-triazole, which were further lowered in cases involving intramolecular hydrogen bonding. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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13 pages, 3180 KiB  
Article
Challenges in the Highly Selective [3 + 1]-Cycloaddition of an Enoldiazoacetamide to Form a Donor–Acceptor Cis-Cyclobutenecarboxamide
by Sipak Joyasawal, Donghui Ma and Michael P. Doyle
Molecules 2021, 26(12), 3520; https://doi.org/10.3390/molecules26123520 - 9 Jun 2021
Cited by 1 | Viewed by 2209
Abstract
A substituted donor–acceptor cyclobutenecarboxamide is synthesized with modest enantiocontrol through a chiral copper(I) complex catalyzed [3 + 1]-cycloaddition reaction of α-acyl diphenylsulfur ylides with 3-siloxy-2-diazo-3-butenamides. With a methyl substituent on the 4-position of the 3-butenamide, the cis-vicinal-3,4-disubstituted cyclobutenecarboxamide is formed with >20:1 [...] Read more.
A substituted donor–acceptor cyclobutenecarboxamide is synthesized with modest enantiocontrol through a chiral copper(I) complex catalyzed [3 + 1]-cycloaddition reaction of α-acyl diphenylsulfur ylides with 3-siloxy-2-diazo-3-butenamides. With a methyl substituent on the 4-position of the 3-butenamide, the cis-vicinal-3,4-disubstituted cyclobutenecarboxamide is formed with >20:1 diastereocontrol. Donor-acceptor 3-methyl-2-siloxycyclopropenecarboxamide is rapidly formed from the reactant enoldiazoamide and undergoes catalytic ring opening to give only the Z-γ-substituted metallo-enolcarbene. Elimination from 3-siloxy-2-diazo-3-pentenamide to form the conjugated 3-siloxy-2,4-pentadienamide is competitive but minimized at low temperature. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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12 pages, 3375 KiB  
Article
Xylochemical Synthesis and Biological Evaluation of Shancigusin C and Bletistrin G
by Leander Geske, Ulrich Kauhl, Mohamed E. M. Saeed, Anja Schüffler, Eckhard Thines, Thomas Efferth and Till Opatz
Molecules 2021, 26(11), 3224; https://doi.org/10.3390/molecules26113224 - 27 May 2021
Cited by 4 | Viewed by 3736
Abstract
The biological activities of shancigusin C (1) and bletistrin G (2), natural products isolated from orchids, are reported along with their first total syntheses. The total synthesis of shancigusin C (1) was conducted by employing the Perkin [...] Read more.
The biological activities of shancigusin C (1) and bletistrin G (2), natural products isolated from orchids, are reported along with their first total syntheses. The total synthesis of shancigusin C (1) was conducted by employing the Perkin reaction to forge the central stilbene core, whereas the synthesis of bletistrin G (2) was achieved by the Wittig olefination followed by several regioselective aromatic substitution reactions. Both syntheses were completed by applying only renewable starting materials according to the principles of xylochemistry. The cytotoxic properties of shancigusin C (1) and bletistrin G (2) against tumor cells suggest suitability as a starting point for further structural variation. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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16 pages, 2462 KiB  
Communication
Synthesis of New Functionally Substituted 9-Azabicyclo[4.2.1]nona-2,4,7-trienes by Cobalt(I)-Catalyzed [6π + 2π]-Cycloaddition of N-Carbocholesteroxyazepine to Alkynes
by Gulnara N. Kadikova, Vladimir A. D’yakonov and Usein M. Dzhemilev
Molecules 2021, 26(10), 2932; https://doi.org/10.3390/molecules26102932 - 14 May 2021
Cited by 7 | Viewed by 1951
Abstract
Catalytic [6π + 2π]-cycloaddition of N-carbocholesteroxyazepine with functionally substituted terminal alkynes and 1,4-butynediol was performed for the first time under the action of the Co(acac)2(dppe)/Zn/ZnI2 three-component catalytic system. The reaction gave previously undescribed but promising 9-azabicyclo[4.2.1]nona-2,4,7-trienes (in 79–95% yields), [...] Read more.
Catalytic [6π + 2π]-cycloaddition of N-carbocholesteroxyazepine with functionally substituted terminal alkynes and 1,4-butynediol was performed for the first time under the action of the Co(acac)2(dppe)/Zn/ZnI2 three-component catalytic system. The reaction gave previously undescribed but promising 9-azabicyclo[4.2.1]nona-2,4,7-trienes (in 79–95% yields), covalently bound to a natural metabolite, cholesterol. The structure of the synthesized azabicycles was confirmed by analysis of one- and two-dimensional (1H, 13C, DEPT 13C, COSY, NOESY, HSQC, HMBC) NMR spectra. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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15 pages, 1567 KiB  
Article
Efficient Synthesis of a New Family of 2,6-Disulfanyl-9-selenabicyclo[3.3.1]nonanes
by Maxim V. Musalov, Vladimir A. Potapov and Svetlana V. Amosova
Molecules 2021, 26(10), 2849; https://doi.org/10.3390/molecules26102849 - 11 May 2021
Cited by 4 | Viewed by 1960
Abstract
The efficient synthesis of a new family of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonanes in high yields has been developed based on 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion generated from bis-isothiouronium salt of 2,6-dibromo-9-selenabicyclo[3.3.1]nonane. The derivatives of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonane containing alkyl, allyl and benzyl moieties have been prepared in 90–99% yields by nucleophilic [...] Read more.
The efficient synthesis of a new family of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonanes in high yields has been developed based on 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion generated from bis-isothiouronium salt of 2,6-dibromo-9-selenabicyclo[3.3.1]nonane. The derivatives of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonane containing alkyl, allyl and benzyl moieties have been prepared in 90–99% yields by nucleophilic substitution of 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion with alkyl, allyl and benzyl halides. The reaction of nucleophilic addition of 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion to alkyl propiolates afforded 2,6-di(vinylsulfanyl)-9-selenabicyclo[3.3.1]nonanes. The conditions for regio- and stereoselective addition of 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion to a triple bond of alkyl propiolates have been found. To date, not a single representative of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonanes has been described in the literature. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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23 pages, 900 KiB  
Article
Synthesis and Antibacterial Activity of New Azole, Diazole and Triazole Derivatives Based on p-Aminobenzoic Acid
by Birutė Sapijanskaitė-Banevič, Vykintas Palskys, Rita Vaickelionienė, Jūratė Šiugždaitė, Povilas Kavaliauskas, Birutė Grybaitė and Vytautas Mickevičius
Molecules 2021, 26(9), 2597; https://doi.org/10.3390/molecules26092597 - 29 Apr 2021
Cited by 17 | Viewed by 3513
Abstract
The p-aminobenzoic acid was applied for the synthesis of substituted 1-phenyl-5-oxopyrrolidine derivatives containing benzimidazole, azole, oxadiazole, triazole, dihydrazone, and dithiosemicarbazide moieties in the structure. All the obtained compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Bacillus cereus [...] Read more.
The p-aminobenzoic acid was applied for the synthesis of substituted 1-phenyl-5-oxopyrrolidine derivatives containing benzimidazole, azole, oxadiazole, triazole, dihydrazone, and dithiosemicarbazide moieties in the structure. All the obtained compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Salmonella enteritidis, Escherichia coli, and Pseudomonas aeruginosa by using MIC and MBC assays. This study showed a good bactericidal activity of γ-amino acid and benzimidazoles derivatives. The antimicrobial activity of the most promising compounds was higher than ampicillin. Furthermore, two benzimidazoles demonstrated good antimicrobial activity against L. monocytogenes (MIC 15.62 µg/mL) that was four times more potent than ampicillin (MIC 65 µg/mL). Further studies are needed to better understand the mechanism of the antimicrobial activity as well as to generate antimicrobial compounds based on the 1-phenyl-5-oxopyrrolidine scaffold. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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17 pages, 1522 KiB  
Article
Three-Component Reactions of 3-Arylidene-3H-Indolium Salts, Isocyanides and Amines
by Hung M. Nguyen, Nikita E. Golantsov, Alexandra S. Golubenkova, Victor B. Rybakov and Leonid G. Voskressensky
Molecules 2021, 26(9), 2402; https://doi.org/10.3390/molecules26092402 - 21 Apr 2021
Cited by 2 | Viewed by 2677
Abstract
A multicomponent reaction of isocyanides with aryl(indol-3-yl)methylium salts and amines has been found. A series of aryl(indol-3-yl)acetimidamides was obtained in up to 96% yields. In the case of ethyl isocyanoacetate, the reaction is followed by cyclization to form 3,5-dihydro-4H-imidazol-4-one derivatives. Full article
(This article belongs to the Special Issue Heterocycles in Organic Synthesis: A Theme Issue in Honor of Prof. Dr. Albert Padwa)
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