2023

Jump to: 2022

14 pages, 1571 KiB

Open AccessArticle

Synthesis of an Electrodeficient Dipyridylbenzene-like Terdentate Ligand: Cyclometallating Ligand for Highly Emitting Iridium(III) and Platinum(II) Complexes

by Pierre-Henri Lanoë, Christian Philouze and Frédérique Loiseau

Organics 2023, 4(3), 403-416; https://doi.org/10.3390/org4030029 - 14 Jul 2023

Viewed by 934

Abstract

Cyclometallated iridium(III) and platinum(II) complexes are intensely used in optoelectronics for their photophysical properties and ability to convert excitons from singlet to triplet state, thus improving the device efficiency. In this contribution, we report the multi-steps synthesis of an electrodeficient dipyridylbenzene-like terdentate ligand [...] Read more.

Cyclometallated iridium(III) and platinum(II) complexes are intensely used in optoelectronics for their photophysical properties and ability to convert excitons from singlet to triplet state, thus improving the device efficiency. In this contribution, we report the multi-steps synthesis of an electrodeficient dipyridylbenzene-like terdentate ligand [N^C^N], namely 2′,6′-dimethyl-2,3′:5′,2″-terpyridine (6), with 18% overall yield. Compound 6 has been employed to synthesize two phosphorescent complexes of platinum(II) and iridium(III), namely compounds 7 and 8, respectively. Both complexes have been characterized by NMR and high resolution mass spectrometry, and demonstrate high luminescence quantum yields in a deaerated solution at room temperature, with 18% and 61% for 7 and 8, respectively. If the iridium(III) complex displays similar emission properties to [Ir(dpyx)(ppy)Cl] (dpyx = 3,5-dimethyl-2,6-dipyridylbenzene and ppy = 2- phenylpyridine), the platinum(II) derivative, with λ_em = 470 nm, is a rare example of a fluorine atom-free blue emitting [N^C^N]PtCl complex. Full article

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22 pages, 2652 KiB

Open AccessArticle

Synthesis and Biological Evaluation of Substituted Fused Dipyranoquinolinones

by Evangelia-Eirini N. Vlachou, Eleni Pontiki, Dimitra J. Hadjipavlou-Litina and Konstantinos E. Litinas

Organics 2023, 4(3), 364-385; https://doi.org/10.3390/org4030027 - 10 Jul 2023

Cited by 1 | Viewed by 953

Abstract

New methyl-substituted, and diphenyl-substituted fused dipyranoquinolinones are prepared in excellent yields via the triple bond activation and 6-endo-dig cyclization of propargyloxycoumarin derivatives by gold nanoparticles supported on TiO₂ in chlorobenzene under microwave irradiation. In the absence of gold nanoparticles, the methyl-substituted propargyloxycoumarin [...] Read more.

New methyl-substituted, and diphenyl-substituted fused dipyranoquinolinones are prepared in excellent yields via the triple bond activation and 6-endo-dig cyclization of propargyloxycoumarin derivatives by gold nanoparticles supported on TiO₂ in chlorobenzene under microwave irradiation. In the absence of gold nanoparticles, the methyl-substituted propargyloxycoumarin derivatives resulted in fused furopyranoquinolinones through Claisen rearrangement and 5-exo-dig cyclization. The intermediate propargyloxy-fused pyridocoumarins are prepared by propargylation of the corresponding hydroxy-fused pyridocoumarins. The methyl-substituted derivatives of the latter are synthesized in excellent yield by the three-component reaction of amino hydroxycoumarin with n-butyl vinyl ether under iodine catalysis. The diphenyl-substituted derivatives of hydroxy-fused pyridocoumarins are obtained, also, by the three-component reaction of amino hydroxycoumarin with benzaldehyde and phenyl acetylene catalyzed by iron (III) chloride. Preliminary biological tests of the title compounds indicated lipoxygenase (LOX) (EC 1.13.11.12) inhibitory activity (60–100 μM), whereas compound 28a, with IC₅₀ = 10 μM, was found to be a potent LOX inhibitor and a possible lead compound. Only compounds 10b and 28b significantly inhibited lipid peroxidation. Full article

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31 pages, 14087 KiB

Open AccessReview

Indole-Based Macrocyclization by Metal-Catalyzed Approaches

by Subba Rao Cheekatla, Debashis Barik, Geethanjali Anand, Rakhi Mol K. M. and Mintu Porel

Organics 2023, 4(3), 333-363; https://doi.org/10.3390/org4030026 - 04 Jul 2023

Cited by 2 | Viewed by 2121

Abstract

This review is dedicated to the different varieties of macrocycles synthesis bearing indole units in their architecture by metal-catalyzed strategies. The progress of the new macrocyclization approaches is persisted be a keen area of research. Macrocycles contain a wide variety of molecules, and [...] Read more.

This review is dedicated to the different varieties of macrocycles synthesis bearing indole units in their architecture by metal-catalyzed strategies. The progress of the new macrocyclization approaches is persisted be a keen area of research. Macrocycles contain a wide variety of molecules, and among those, heteroaryl motifs are valuable constituents that provide an attractive feature to macrocyclic systems. Indole represents one of the privileged pharmacophores against a variety of targets with various biological applications. Among the nitrogen-based heterocycles, indole plays a prominent role in organic synthesis, medicinal chemistry, pharmaceuticals, natural products synthesis, agrochemicals, dye and fragrances, and drug design. These scaffolds are widely distributed in several bioactive natural products and synthetic macrocycles constructed against a specific biochemical target and the most common constituents of naturally occurring molecules. Due to its immense importance, the progress of novel approaches for the synthesis of indole-based scaffolds has increased steadily. The majority of the macrocycles synthesis proceeds through the macrolactamization and macrolactonization, as well as the C–C bond macrocyclization process described by metal-catalyzed ring-closing metathesis (RCM) and coupling reactions. Among macrocyclizations, metal-catalyzed approaches are considered one of the most powerful tools for synthetic chemists in the design of a variety of macrocycles. This review aims to give a comprehensive insight into the synthesis of varieties of macrocycles bearing indole scaffold catalyzed by various transition metals that emerged in the literature over the last two decades. We hope that this review will persuade synthetic chemists to search for novel strategies for the C–C bond macrocyclization by metal-catalyzed protocols. Full article

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16 pages, 2366 KiB

Open AccessArticle

Structural and Dynamic Behaviour of Heterocycles Derived from Ethylenediamines with Formaldehyde: 1,3,5-Triazinanes and Bis(imidazolidinyl)methanes

by Raúl Colorado-Peralta, Sonia Araceli Sánchez-Ruiz and Angelina Flores-Parra

Organics 2023, 4(2), 297-312; https://doi.org/10.3390/org4020024 - 15 Jun 2023

Viewed by 1003

Abstract

Formaldehyde is a simple chemical compound that is used as a building block in obtaining a wide range of products. The versatility of formaldehyde in chemical synthesis becomes evident when it is reacted with N-alkylethylenediamines. Therefore, this paper reports the structure and [...] Read more.

Formaldehyde is a simple chemical compound that is used as a building block in obtaining a wide range of products. The versatility of formaldehyde in chemical synthesis becomes evident when it is reacted with N-alkylethylenediamines. Therefore, this paper reports the structure and reactivity of a series of compounds derived from easily accessible molecules, such as formaldehyde, sodium hydrosulphide, and N-alkylethylenediamines. The 1,3,5-triazines (1a-1d) and bis(3-alkyl-imidazolidin-1-yl)methanes (2a-2d) were obtained by simple reaction conditions. Additionally, different proportions of sodium hydrosulphide and formaldehyde were used with N-benzylamine to obtain N-benzyltriazinane (3), N-benzylthiadiazinane (4) and N-benzyldithiazinane (5). All these compounds were characterized by analytical, spectroscopic, and spectrometric techniques, such as melting point, solubility, one-dimensional and two-dimensional nuclear magnetic resonance (¹³C, ¹H, ¹⁵N, COSY, HETCOR, NOESY, COLOC), elemental analysis, high- and low-resolution mass spectrometry, among others. The structures of compounds 4 and 5 were obtained by single-crystal X-ray diffraction. The results show that small variations in the stoichiometry and the reaction conditions significantly influence the products obtained. Full article

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12 pages, 4352 KiB

Open AccessArticle

The Use of a Natural Polysaccharide as a Solidifying Agent and Color-Fixing Agent on Modern Paper and Historical Materials

by Lucia Emanuele, Tanja Dujaković, Graziella Roselli, Simone Campanelli and Giulia Bellesi

Organics 2023, 4(2), 265-276; https://doi.org/10.3390/org4020021 - 02 Jun 2023

Cited by 1 | Viewed by 1101

Abstract

This article presents results on the use of a new material as a solidifying agent and/or color-fixing agent. A special polysaccharide material extracted from the prickly pear cactus (Opuntia ficus indica) was tested on historical materials and modern papers. An old book from [...] Read more.

This article presents results on the use of a new material as a solidifying agent and/or color-fixing agent. A special polysaccharide material extracted from the prickly pear cactus (Opuntia ficus indica) was tested on historical materials and modern papers. An old book from the 18th century was chosen as historical material. From the mentioned book 42 pages were taken, on which a conservation and restoration pretreatment was performed before applying the polysaccharide material: sampling, fiber analysis, dry cleaning, ink solubility, pH test, thickness measurement and wet cleaning. The paper sheets provided for the test were divided into 4 groups, 3 of which were treated with gel and one left untreated as a reference. The division into groups is not only due to the different method of application, but also due to the process of gel extraction. The effect of the treatment was analyzed using FTIR-ATR. To test the mucilage as color-fixing agent 2 samples were prepared using watercolor papers colored with 6 different watercolors applied to 2.5 cm² samples for each color in two rows of different intensity. One of the 2 samples was treated with gel, but both were immersed for 3 times in a water-ethanol solution for approximately 20 min as is standard practice in conservation and restoration. After washing, both specimens were subjected to colorimetric analysis to assess their differences. The results provided satisfactory evidence for the protection of paints sensitive to aqueous treatments and suggest the use of mucilage as a new material in cleaning method for water-soluble media. Full article

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14 pages, 10416 KiB

Open AccessArticle

Facile Photochemical/Thermal Assisted Hydration of Alkynes Catalysed under Aqueous Media by a Chalcogen Stabilized, Robust, Economical, and Reusable Fe₃Se₂(CO)₉ Cluster

by Munsaf Ali, Avinash K. Srivastava, Nitinkumar Satyadev Upadhyay, Naveen Satrawala and Raj K. Joshi

Organics 2023, 4(2), 251-264; https://doi.org/10.3390/org4020020 - 25 May 2023

Cited by 2 | Viewed by 1939

Abstract

In this report, the catalytic potential of chalcogen-stabilized iron carbonyl clusters [Fe₃E₂(CO)₉ (E = S, Se, Te)] for the photolytic hydration of alkynes has been explored. The iron chalcogenide clusters bring excellent transformations of terminal and internal alkynes [...] Read more.

In this report, the catalytic potential of chalcogen-stabilized iron carbonyl clusters [Fe₃E₂(CO)₉ (E = S, Se, Te)] for the photolytic hydration of alkynes has been explored. The iron chalcogenide clusters bring excellent transformations of terminal and internal alkynes to their respective keto products in just 25 min photolysis at −5 °C in inert free and aqueous conditions. After the completion of the reaction, the product can be extracted from organic solvent, and due to the lower solubility of the catalyst in water, it can also be isolated and further reused several times prior to any activation. The catalyst was also found to be active in thermal conditions and bring about the desired transformations with average to good catalytic efficiency. Moreover, during the thermal reaction, the catalyst decomposed and formed the nanoparticles of iron selenides, which worked as a single-source precursor for FeSe nanomaterials. The presented photolysis methodology was found to be most feasible, economical, instantly produce the desired product, and work for a wide range of internal and terminal alkynes; hence, all these features made this method superior to the other reported ones. This report also serves as the first catalytic report of chalcogen-stabilized iron carbonyl clusters for alkyne hydrations. Full article

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19 pages, 6801 KiB

Open AccessReview

Synthetic Organic Molecules as Metallic Corrosion Inhibitors: General Aspects and Trends

by Renato Corrêa da Silva Lessa

Organics 2023, 4(2), 232-250; https://doi.org/10.3390/org4020019 - 17 May 2023

Cited by 2 | Viewed by 2161

Abstract

Organic molecules are gaining special attention over the last years in the corrosion area thanks to their general low achievable cytotoxicity, structural versatility, and environmentally friendly obtainment methods. Under those approaches, synthetic organic motifs have attracted the interest of researchers due to their [...] Read more.

Organic molecules are gaining special attention over the last years in the corrosion area thanks to their general low achievable cytotoxicity, structural versatility, and environmentally friendly obtainment methods. Under those approaches, synthetic organic motifs have attracted the interest of researchers due to their variated methods of obtention through molecular manipulation via diverse chemical reactions, allowing the production of adequately planned structures or repurposing their original application in the case of drugs. This review summarizes general aspects that are desired in organic molecules as corrosion inhibitors, presenting selected works published in the 2022–2023 period and emphasizing the importance of finding novel and different organic corrosion inhibitors. Patents were not considered in this review. Scifinder, Google Scholar, and Web of Science were employed as databases. Mathematical and analytical methods involved in the search for corrosion inhibitors are out of this review’s scope. Full article

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13 pages, 3227 KiB

Open AccessArticle

A Novel Class of Functionally Tuneable Star-Shaped Molecules for Interaction with Multiple Proteins

by Debashis Barik, Geethanjali Anand, Subba Rao Cheekatla and Mintu Porel

Organics 2023, 4(2), 219-231; https://doi.org/10.3390/org4020018 - 16 May 2023

Viewed by 1396

Abstract

Molecules with tuneable properties are well known for their applications in the material and bio-medical fields; nevertheless, the structural and functional tunability makes them more significant in diverse applications. Herein, we designed and synthesized a novel class of star-shaped molecules via incorporating two [...] Read more.

Molecules with tuneable properties are well known for their applications in the material and bio-medical fields; nevertheless, the structural and functional tunability makes them more significant in diverse applications. Herein, we designed and synthesized a novel class of star-shaped molecules via incorporating two important functional groups, i.e., triazole and dithiocarbamate (DTC). The rationale behind selecting these two key functional groups is their diverse applications, e.g., DTC having applications for therapeutics, pesticides, and vulcanizing agents, and triazole having applications for anti-cancer, fungicides, anti-microbials, inhibitors, etc. The structure of the molecules was strategically designed in such a way that their overall structures are the same (central tertiary-amine and peripheral hydroxy groups), except the key functional group (DTC and triazole) in the respective molecules was different. Following synthesis and characterization, the influence of DTC and triazole groups on their bioactivity was compared via interacting with the most abundant proteins present in the blood, including serum albumin, trypsin, haemoglobin, and ribonuclease. From both the experimental and molecular docking studies, it was confirmed that the triazole molecule has a higher binding affinity towards these proteins as compared to the DTC molecule. In summary, two star-shaped DTC- and triazole-based molecules were synthesized and their bioactivity was compared via binding with blood plasma proteins. Full article

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10 pages, 1530 KiB

Open AccessArticle

Computational Modeling of the Feasibility of Substituted [1.1.1]Propellane Formation from Anionic Bridgehead Bromide Precursors

by Katherine E. Gates, Caitlin Herring, Andrew T. Lumpkin, Robert J. Maraski, Elizabeth G. Perry, Madelen G. Prado, Sarah L. Quigley, Jazmine V. Ridlehoover, Edith Salazar, Kynslei Sims, Kaitlin R. Stephenson, Emma A. Stewart, Mackenzie E. Sullivan, James R. Tucker and Gary W. Breton

Organics 2023, 4(2), 196-205; https://doi.org/10.3390/org4020016 - 04 May 2023

Cited by 1 | Viewed by 1206

Abstract

[1.1.1]Propellane, a compound whose structure includes two saturated carbons in which all four bonds are directed into a single hemisphere, is of theoretical interest, but has also seen recent practical applications. Mono-, di-, and trisubstituted derivatives of this propellane (by substitution of its [...] Read more.

[1.1.1]Propellane, a compound whose structure includes two saturated carbons in which all four bonds are directed into a single hemisphere, is of theoretical interest, but has also seen recent practical applications. Mono-, di-, and trisubstituted derivatives of this propellane (by substitution of its CH₂ bridges with O, S, NH, CF₂, CO, SO, and SO₂) remain unknown despite several computational studies that have suggested some may be stable. In this study, we show that, in several cases, substituted propellanes are spontaneously formed upon the attempted computational optimization of the geometries of anionic bridgehead bromide precursors using the ωB97X-D/aug-cc-pVDZ DFT method. Spontaneous formation suggests that these propellanes are at lower energy relative to the precursors and, therefore, are promising synthetic targets. The success or failure to spontaneously form the propellane is considered in relation to the length and strain energy of the central bridgehead-bridgehead bond, as well as the total strain energy of each propellane. Full article

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13 pages, 6299 KiB

Open AccessReview

Advance in the Synthesis of Sulfoxides and Sulfinamides from β-Sulfinyl Esters

by Xianjie Yin, Qiaoling Zhang and Qingle Zeng

Organics 2023, 4(2), 173-185; https://doi.org/10.3390/org4020014 - 19 Apr 2023

Viewed by 1346

Abstract

Sulfoxides and sulfinamides play important roles in the pharmaceutical industry, organic synthesis and fine chemicals. This review will demonstrate that, under catalysis by transition metals, β-sulfinyl esters, as nucleophilic reagents, react with a variety of electrophilic reagents to produce sulfoxides and sulfinamides. [...] Read more.

Sulfoxides and sulfinamides play important roles in the pharmaceutical industry, organic synthesis and fine chemicals. This review will demonstrate that, under catalysis by transition metals, β-sulfinyl esters, as nucleophilic reagents, react with a variety of electrophilic reagents to produce sulfoxides and sulfinamides. The important prospect of the asymmetric catalytic synthesis of chiral sulfur-containing molecules in this field is described. Full article

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11 pages, 3271 KiB

Open AccessArticle

Cell Viability Study of ZnCuInS/ZnS–TPPS₄ Conjugates against Different Cell Lines as a Promising Fluorescent Probe

by Ncediwe Tsolekile, Sundararajan Parani, Thabang Calvin Lebepe, Rodney Maluleke, Vuyelwa Ncapayi, Mangaka Clara Matoetoe, Sandile Phinda Songca and Oluwatobi Samuel Oluwafemi

Organics 2023, 4(1), 126-136; https://doi.org/10.3390/org4010010 - 17 Mar 2023

Viewed by 1266

Abstract

In the present work, we report a simple synthetic strategy for fabricating ZnCuInS/ZnS–TPPS₄ conjugates and study its cytotoxicity as a promising material for imaging and phototherapy applications. The quaternary QDs were synthesized using eco-friendly materials such as glutathione and water as a [...] Read more.

In the present work, we report a simple synthetic strategy for fabricating ZnCuInS/ZnS–TPPS₄ conjugates and study its cytotoxicity as a promising material for imaging and phototherapy applications. The quaternary QDs were synthesized using eco-friendly materials such as glutathione and water as a solvent, while the anionic 10,15,20-(4-sulphonatophenyl) porphyrin (TPPS₄) was synthesized via the acidification of a meso-tetraphenylporphyrin precursor. Interest in TPPS₄ results from its high-water dispersity, stability, and ability to generate singlet oxygen. Conjugation of ZnCuInS/ZnS QDs with TPPS₄ was performed by titrating porphyrin with different amounts of ZnCuInS/ZnS QDs while keeping all other experimental parameters constant. Comparative analysis of the conjugate to the bare QDs and porphyrin revealed enhanced spectral and photophysical properties. Comparative cytotoxicity assays were performed for TPPS₄ and ZnCuInS/ZnS–TPPS₄ conjugates in BHK21, Hela, A549, Hek 293 and B16-F10 Nex 2 cell lines using the MTT cell viability assay. The results showed negligible in vitro cytotoxicity indicating the conjugate is an excellent and biocompatible candidate for imaging and phototherapy applications. Full article

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12 pages, 2351 KiB

Open AccessArticle

Looking for a Safe Bridge: Synthesis of P3HT-Bridge-TBO Block-Copolymers and Their Performance in Perovskite Solar Cells

by Aleksandra N. Zhivchikova, Irina V. Klimovich, Maxim E. Sideltsev, Aly Elakshar, Artur T. Kapasharov, Alexander V. Akkuratov, Albert G. Nasibulin, Keith J. Stevenson and Marina M. Tepliakova

Organics 2023, 4(1), 97-108; https://doi.org/10.3390/org4010008 - 27 Feb 2023

Cited by 1 | Viewed by 1846

Abstract

Here, we present a synthesis of three novel conjugated block-copolymers (BCP) with general formula P3HT-bridge-TBO, where P3HT is a poly(3-hexyl)thiophene, TBO is a thiophene-benzothiadiazole block, and the bridge is composed of two fluorene units (FF) or two thiophenes (TT) or a mixture (TF). [...] Read more.

Here, we present a synthesis of three novel conjugated block-copolymers (BCP) with general formula P3HT-bridge-TBO, where P3HT is a poly(3-hexyl)thiophene, TBO is a thiophene-benzothiadiazole block, and the bridge is composed of two fluorene units (FF) or two thiophenes (TT) or a mixture (TF). It is demonstrated that the physicochemical properties of the materials with different bridges are similar. Furthermore, P3HT-bridge-TBO materials are investigated in PSCs with classical n-i-p configuration for the first time. PSCs with BCPs reach average efficiencies with a top of 14.4% for P3HT-FF-TBO. At the same time, devices demonstrate spectacular long-term operation stability after 1000 h under constant illumination with minor changes in efficiency, while PSCs with state-of-the-art hole-transport layer demonstrate unstable behavior. This groundbreaking work demonstrates the potential of BCP to ensure the stable operation of perovskite photovoltaics. Full article

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11 pages, 1656 KiB

Open AccessArticle

Thia-Michael Reaction under Heterogeneous Catalysis

by Giovanna Bosica, Roderick Abdilla and Alessio Petrellini

Organics 2023, 4(1), 86-96; https://doi.org/10.3390/org4010007 - 21 Feb 2023

Viewed by 1781

Abstract

Thia-Michael reactions between aliphatic and aromatic thiols and various Michael acceptors were performed under environmentally-friendly solvent-free conditions using Amberlyst^® A21 as a recyclable heterogeneous catalyst to efficiently obtain the corresponding adducts in high yields. Ethyl acrylate was the main acceptor used, although [...] Read more.

Thia-Michael reactions between aliphatic and aromatic thiols and various Michael acceptors were performed under environmentally-friendly solvent-free conditions using Amberlyst^® A21 as a recyclable heterogeneous catalyst to efficiently obtain the corresponding adducts in high yields. Ethyl acrylate was the main acceptor used, although others such as acrylamide, linear, and cyclic enones were also utilized successfully. Bifunctional Michael donor, 3-mercaptopropanoic acid, positively furnished the product, albeit in a lower yield and after leaving the reaction to take place for a longer time. The catalyst was easy and safe to handle and successfully recycled for five consecutive cycles. Full article

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16 pages, 1912 KiB

Open AccessArticle

Palladium Catalyzed Ring-Opening of Diazabicylic Olefins with 4-Halo-1,3-Dicarbonyl Compounds: Accessing 3(2H)-Furanone-Appended Cyclopentenes

by Vishnu K. Omanakuttan, Alisha Valsan, Henning Hopf and Jubi John

Organics 2023, 4(1), 70-85; https://doi.org/10.3390/org4010006 - 13 Feb 2023

Viewed by 1198

Abstract

We have realized a Pd-catalyzed ring-opening of diazabicyclic olefins with 4-halo-1,3-dicarbonyl compounds. This reaction resulted in the formation of 3(2H)-furanone-appended hydrazino cyclopentenes. The reaction proceeds via the formation of a π-allylpalladium intermediate which is attacked by the active methylene species, and [...] Read more.

We have realized a Pd-catalyzed ring-opening of diazabicyclic olefins with 4-halo-1,3-dicarbonyl compounds. This reaction resulted in the formation of 3(2H)-furanone-appended hydrazino cyclopentenes. The reaction proceeds via the formation of a π-allylpalladium intermediate which is attacked by the active methylene species, and an intramolecular nucleophilic substitution in the 4-halo-1,3-dicarbonyl moiety furnishes the 3(2H)-furanone-substituted cyclopentene. We could extend this methodology to cyclopropane-appended spirotricyclic olefin for synthesizing 3(2H)-furanone-substituted spiro[2.4]hept-5-ene. Full article

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8 pages, 1364 KiB

Open AccessCommunication

Parallel Synthesis of Aurones Using a Homogeneous Scavenger

by Zachary E. Taylor and Scott T. Handy

Organics 2023, 4(1), 51-58; https://doi.org/10.3390/org4010004 - 28 Jan 2023

Cited by 1 | Viewed by 1468

Abstract

The ability to synthesize arrays of related compounds quickly and with good purity has become critical for a rapid exploration of their properties for biological or material applications. While a number of methods have been developed to enable this combinatorial synthesis, the existing [...] Read more.

The ability to synthesize arrays of related compounds quickly and with good purity has become critical for a rapid exploration of their properties for biological or material applications. While a number of methods have been developed to enable this combinatorial synthesis, the existing options were not readily appliable to the synthesis of aurones using the simple Knoevenagel condensation approach. In order to avoid the time, expense, and lowered yields associated with flash column chromatography, we developed a scavenging approach for their synthesis. This method uses an excess of aldehyde to ensure complete conversion to aurones, followed by selective removal of the remaining aldehyde using a simple, inexpensive scavenger – isoniazid – and subsequent extraction with dilute acid, to produce the desired compounds with good purity under operationally simple conditions. This approach is expected to be applicable to many other reactions involving aldehydes as one of the reactants. Full article

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2022

Jump to: 2023

8 pages, 1322 KiB

Open AccessArticle

Exploring the Limits of Reactivity of N-Methyl-1,2,4-triazoline-3,5-dione (MeTAD) with Disubstituted Bicycloalkadienes in the Homo-Diels–Alder Reaction

by Gary W. Breton and Kenneth L. Martin

Organics 2023, 4(1), 41-48; https://doi.org/10.3390/org4010002 - 31 Dec 2022

Viewed by 1374

Abstract

The [2+2+2] cycloaddition (homo-Diels–Alder reaction) of N-substituted 1,2,4-triazoline-3,5-diones (TADs) with bicycloalkadienes produces strained heterocyclic compounds. A reaction with the unsubstituted dienes occurs readily to produce only the expected homo-Diels–Alder adducts. However, previous work in the literature showed that the attachment of a [...] Read more.

The [2+2+2] cycloaddition (homo-Diels–Alder reaction) of N-substituted 1,2,4-triazoline-3,5-diones (TADs) with bicycloalkadienes produces strained heterocyclic compounds. A reaction with the unsubstituted dienes occurs readily to produce only the expected homo-Diels–Alder adducts. However, previous work in the literature showed that the attachment of a single electron-withdrawing group to the diene system results in the formation of not only the expected homo-Diels–Alder adducts, but also interesting “insertion” products. To probe the limits of reactivity of these diene systems, we investigated the reaction of N-methyl-1,2,4-triazoline-3,5-dione (MeTAD) with bicycloalkadienes substituted with two electron-withdrawing groups, i.e., two carbomethoxy or two cyano groups. We hoped to learn whether the reaction still proceeded, and if so, whether the homo-Diels–Alder adducts and/or other types of products were formed. We found that a reaction between MeTAD and the dienes takes place upon substitution with two carbomethoxy groups, albeit at a considerably slower rate than other reactions. The only products observed were the homo-Diels–Alder adducts. However, attachment of two CN groups completely inhibited reactivity. Full article

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40 pages, 16239 KiB

Open AccessReview

Phenyliodine(III)diacetate (PIDA): Applications in Organic Synthesis

by Ravi Varala, Vittal Seema and Narsimhaswamy Dubasi

Organics 2023, 4(1), 1-40; https://doi.org/10.3390/org4010001 - 23 Dec 2022

Cited by 3 | Viewed by 7682

Abstract

One of the hypervalent iodines most widely used as an oxidizing agent in organic chemistry is (diacetoxyiodo)benzene (PhI(OAc)₂), also known as (DAIB), phenyliodine(III) diacetate (PIDA). In this septennial mini-review, the authors have concisely and systematically presented representative applications of PIDA in [...] Read more.

One of the hypervalent iodines most widely used as an oxidizing agent in organic chemistry is (diacetoxyiodo)benzene (PhI(OAc)₂), also known as (DAIB), phenyliodine(III) diacetate (PIDA). In this septennial mini-review, the authors have concisely and systematically presented representative applications of PIDA in organic synthesis involving C-H functionalization, hetero-hetero bond formations, heterocyclic ring construction, rearrangements or migrations and miscellaneous reactions along with their interesting mechanistic aspects starting from the summer of 2015 to the present. Full article

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13 pages, 2377 KiB

Open AccessArticle

Bis(3-methylthio-1-azulenyl)phenylmethyl Cations and Dications Connected by a 1,4-Phenylene Spacer: Synthesis and Their Electrochemical Properties

by Taku Shoji, Naoko Sakata, Ryuta Sekiguchi and Shunji Ito

Organics 2022, 3(4), 507-519; https://doi.org/10.3390/org3040034 - 16 Dec 2022

Viewed by 1317

Abstract

The preparation of bis(3-methylthio-1-azulenyl)phenylmethyl cations and 1,4-phenylenebis[bis(3,6-di-tert-butyl-1-azulenyl)methyl] dications was accomplished by the hydride abstraction of the corresponding hydride derivatives, which were synthesized by the acid-catalyzed condensation of 1-azulenyl methyl sulfide with benzaldehyde and terephthalaldehyde with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The intramolecular charge transfer among [...] Read more.

The preparation of bis(3-methylthio-1-azulenyl)phenylmethyl cations and 1,4-phenylenebis[bis(3,6-di-tert-butyl-1-azulenyl)methyl] dications was accomplished by the hydride abstraction of the corresponding hydride derivatives, which were synthesized by the acid-catalyzed condensation of 1-azulenyl methyl sulfide with benzaldehyde and terephthalaldehyde with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The intramolecular charge transfer among the azulene ring and the methylium moieties of these cations and dications was investigated by UV–Vis spectroscopy and electrochemical analyses. The pK_R⁺ values of the cations were examined for their thermodynamic stability spectrophotometrically. The voltammetry experiments of these cations revealed their reversible reduction waves on their cyclic voltammograms. Moreover, a notable spectral change of cations was observed by spectroelectrochemistry during electrochemical reduction conditions. Full article

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11 pages, 2242 KiB

Open AccessArticle

Phosphonated Polyethylenimine Maghemite Nanoparticles: A Convenient Support of Palladium for Cross-Coupling Reactions

by Clément Monteil, Etienne Jean, Nathalie Bar and Didier Villemin

Organics 2022, 3(4), 491-501; https://doi.org/10.3390/org3040032 - 21 Nov 2022

Cited by 1 | Viewed by 1362

Abstract

Phosphonated polyethylenimine grafted on iron oxide nanoparticles was used as a magnetic support for loading palladium. This cheap and accessible heterogeneous catalyst demonstrated good efficiency in Suzuki-Miyaura, Mizoroki-Heck, and Tsuji-Trost couplings. The nanocomposite is resistant to harsh conditions and can therefore be recycled [...] Read more.

Phosphonated polyethylenimine grafted on iron oxide nanoparticles was used as a magnetic support for loading palladium. This cheap and accessible heterogeneous catalyst demonstrated good efficiency in Suzuki-Miyaura, Mizoroki-Heck, and Tsuji-Trost couplings. The nanocomposite is resistant to harsh conditions and can therefore be recycled up to 10 cycles with high catalyst efficiency. Full article

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10 pages, 1899 KiB

Open AccessArticle

Synthesis of 3-Hydroxy-9H-fluorene-2-carboxylates via Michael Reaction, Robinson Annulation, and Aromatization

by Yu-Min Wang, Yi-Hung Liu and Shiuh-Tzung Liu

Organics 2022, 3(4), 481-490; https://doi.org/10.3390/org3040031 - 10 Nov 2022

Viewed by 1778

Abstract

A series of 3-hydroxy-fluorene-2-carboxylate compounds were prepared from Michael addition of acetoacetate to 2-benzylideneindan-l-one followed by Robinson annulation and aromatization. In this reaction, we were able to isolate two Robinson annulation products and characterize them. This sequential reaction could proceed without the isolation [...] Read more.

A series of 3-hydroxy-fluorene-2-carboxylate compounds were prepared from Michael addition of acetoacetate to 2-benzylideneindan-l-one followed by Robinson annulation and aromatization. In this reaction, we were able to isolate two Robinson annulation products and characterize them. This sequential reaction could proceed without the isolation of intermediates to give the desired products directly in reasonable yields. Full article

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16 pages, 6899 KiB

Open AccessReview

Synthetic Pathways to Pyrido[3,4-c]pyridazines and Their Polycyclic Derivatives

by Temitayo Omowumi Alegbejo Price, Flavio da Silva Emery and Wim Dehaen

Organics 2022, 3(4), 430-445; https://doi.org/10.3390/org3040028 - 18 Oct 2022

Viewed by 1850

Abstract

Pyrido[3,4-c]pyridazines are nitrogen-containing scaffolds that have been described as being promising in medicinal chemistry, but they are rather rare chemicals. In this review article, the literature on synthetic pathways towards pyrido[3,4-c]pyridazines is listed exhaustively, first with the bicyclic systems [...] Read more.

Pyrido[3,4-c]pyridazines are nitrogen-containing scaffolds that have been described as being promising in medicinal chemistry, but they are rather rare chemicals. In this review article, the literature on synthetic pathways towards pyrido[3,4-c]pyridazines is listed exhaustively, first with the bicyclic systems themselves that are obtained starting either from pyridines, pyridazines or other heterocycles. Then, the reports on the related tricyclic derivatives are discussed, again according to the source heterocycle, and finally we mention some examples on polycyclic systems. Full article

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15 pages, 6430 KiB

Open AccessArticle

Design, Synthesis, and Photo-Responsive Properties of a Collagen Model Peptide Bearing an Azobenzene

by Daisuke Sato, Hitomi Goto, Yui Ishizaki, Tetsuya Narimatsu and Tamaki Kato

Organics 2022, 3(4), 415-429; https://doi.org/10.3390/org3040027 - 11 Oct 2022

Viewed by 1423

Abstract

Collagen is a vital component of the extracellular matrix in animals. Collagen forms a characteristic triple helical structure and plays a key role in supporting connective tissues and cell adhesion. The ability to control the collagen triple helix structure is useful for medical [...] Read more.

Collagen is a vital component of the extracellular matrix in animals. Collagen forms a characteristic triple helical structure and plays a key role in supporting connective tissues and cell adhesion. The ability to control the collagen triple helix structure is useful for medical and conformational studies because the physicochemical properties of the collagen rely on its conformation. Although some photo-controllable collagen model peptides (CMPs) have been reported, satisfactory photo-control has not yet been achieved. To achieve this objective, detailed investigation of the isomerization behavior of the azobenzene moiety in CMPs is required. Herein, two CMPs were attached via an azobenzene linker to control collagen triple helix formation by light irradiation. Azo-(PPG)₁₀ with two (Pro-Pro-Gly)₁₀ CMPs linked via a photo-responsive azobenzene moiety was designed and synthesized. Conformational changes were evaluated by circular dichroism and the cis-to-trans isomerization rate calculated from the absorption of the azobenzene moiety indicated that the collagen triple helix structure was partially disrupted by isomerization of the internal azobenzene. Full article

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35 pages, 8646 KiB

Open AccessReview

Ten Years Milestones in Xanthine Oxidase Inhibitors Discovery: Febuxostat-Based Inhibitors Trends, Bifunctional Derivatives, and Automatized Screening Assays

by Miguel F. S. de Abreu, Camila A. Wegermann, Millena S. Ceroullo, Isabella G. M. Sant’Anna and Renato C. S. Lessa

Organics 2022, 3(4), 380-414; https://doi.org/10.3390/org3040026 - 10 Oct 2022

Cited by 2 | Viewed by 2303

Abstract

Xanthine oxidase (XO) is an enzyme involved in the oxidative process of hypoxanthine and xanthine to uric acid (UA). This process also produces reactive oxygen species (ROS) as byproducts. Both UA and ROS are dangerous for human health, and some health conditions trigger [...] Read more.

Xanthine oxidase (XO) is an enzyme involved in the oxidative process of hypoxanthine and xanthine to uric acid (UA). This process also produces reactive oxygen species (ROS) as byproducts. Both UA and ROS are dangerous for human health, and some health conditions trigger upregulation of XO activity, which results in many diseases (cancer, atherosclerosis, hepatitis, gout, and others) given the worsened scenario of ROS and UA overproduction. So, XO became an attractive target to produce and discover novel selective drugs based on febuxostat, the most recent XO inhibitor out of only two approved by FDA. Under this context, high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) have been successfully applied to rapidly and easily screen for bioactive compounds, isolated or in complex natural matrixes, that act as enzyme inhibitors through the use of an immobilized enzyme reactor (IMER). This article’s goal is to present advances comprising febuxostat-based XO inhibitors as a new trend, bifunctional moieties capable of inhibiting XO and modulating ROS activity, and in-flow techniques employing an IMER in HPLC and CE to screen for synthetic and natural compounds that act as XO inhibitors. Full article

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16 pages, 2020 KiB

Open AccessArticle

Theoretical Study on the Diels–Alder Reaction of Fullerenes: Analysis of Isomerism, Aromaticity, and Solvation

by Diogo J. L. Rodrigues, Luís M. N. B. F. Santos, André Melo and Carlos F. R. A. C. Lima

Organics 2022, 3(4), 364-379; https://doi.org/10.3390/org3040025 - 22 Sep 2022

Cited by 2 | Viewed by 1946

Abstract

Fullerenes are reactive as dienophiles in Diels–Alder reactions. Their distinctive molecular shape and properties result in interesting and sometimes elusive reaction patterns. Herein, to contribute to the understanding of fullerene reactivity, we evaluate the energies of reactions for Diels–Alder cycloadditions of C₆₀ [...] Read more.

Fullerenes are reactive as dienophiles in Diels–Alder reactions. Their distinctive molecular shape and properties result in interesting and sometimes elusive reaction patterns. Herein, to contribute to the understanding of fullerene reactivity, we evaluate the energies of reactions for Diels–Alder cycloadditions of C₆₀, C₇₀, and IC₆₀MA with anthracene (Ant), by means of DFT computational analysis in vacuum and solution. The methods used showed little differentiation between the reactivity of the different fullerenes. The C₇₀-Ant adducts where addition takes place near the edge of the fullerene were found to be the most stable regioisomers. For the IC₆₀MA-Ant adducts, the calculated energies of reaction increase in the order: equatorial > trans-3 > trans-2 ≈ trans-4 ≈ trans-1 > cis-3 > cis-2. The change in the functional suggests the existence of stabilizing dispersive interactions between the surface of the fullerene and the addends. HOMA (harmonic oscillator model of aromaticity) analysis indicated an increase in aromaticity in the fullerene hexagons adjacent to the bonded addend. This increase is bigger in the rings of bisadduct isomers that are simultaneously adjacent to both addends, which helps explain the extra stability of the equatorial isomers. Solvation by m-xylene decreases the exothermicity of the reactions studied but has little distinguishing effect on the possible isomers. Thermal corrections reduce the exothermicity of the reactions by ~10 kJ∙mol⁻¹. Full article

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44 pages, 13246 KiB

Open AccessReview

Recent Developments in Stereoselective Reactions of Sulfonium Ylides

by Mukulesh Mondal, Sophie Connolly, Shi Chen, Shubhanjan Mitra and Nessan J. Kerrigan

Organics 2022, 3(3), 320-363; https://doi.org/10.3390/org3030024 - 15 Sep 2022

Cited by 8 | Viewed by 4279

Abstract

This review describes advances in the literature since the mid-1990s in the area of reactions of sulfonium ylide chemistry, with particular attention paid to stereoselective examples. Although the chemistry of sulfonium ylides was first popularized and applied in a substantial way in the [...] Read more.

This review describes advances in the literature since the mid-1990s in the area of reactions of sulfonium ylide chemistry, with particular attention paid to stereoselective examples. Although the chemistry of sulfonium ylides was first popularized and applied in a substantial way in the 1960s, there has been sustained interest in the chemistry of sulfonium ylides since then. Many new ways of exploiting sulfonium ylides in productive stereoselective methodologies have emerged, often taking advantage of advances in organocatalysis and transition metal catalysis, to access stereodefined structurally complex motifs. The development of many different chiral sulfides over the last 20–30 years has also played a role in accelerating their study in a variety of reaction settings. In general, formal cycloaddition reactions ([2 + 1] and [4 + 1]) of sulfonium ylides follow a similar mechanistic pathway: initial addition of the nucleophilic ylide carbanion to an electrophile to form a zwitterionic betaine intermediate, followed by cyclization of the zwitterionic intermediate to afford the desired three-membered cyclic product (e.g., epoxide, cyclopropane, or aziridine), five-membered monocyclic (e.g., oxazolidinone), or fused bicyclic product (e.g., benzofuran, indoline). Full article

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12 pages, 3074 KiB

Open AccessArticle

Unveiling the Origin of the Selectivity and the Molecular Mechanism in the [3+2] Cycloaddition Reaction of N-aryl-C-carbamoylnitrone with N-arylitaconimide

by Abdelmalek Khorief Nacereddine and Fouad Chafaa

Organics 2022, 3(3), 281-292; https://doi.org/10.3390/org3030021 - 02 Sep 2022

Cited by 2 | Viewed by 1209

Abstract

The [3+2] cycloaddition reaction of N-aryl-C-carbamoylnitrone (nitrone 1) with N-arylitaconimide (ethylene 2) was computationally studied using the B3LYP/6-31G(d) level of theory. An analysis of the different energetic profiles and the transition states’ optimized structures clearly indicated that this 32CA occurred through [...] Read more.

The [3+2] cycloaddition reaction of N-aryl-C-carbamoylnitrone (nitrone 1) with N-arylitaconimide (ethylene 2) was computationally studied using the B3LYP/6-31G(d) level of theory. An analysis of the different energetic profiles and the transition states’ optimized structures clearly indicated that this 32CA occurred through a non-polar, asynchronous, one-step mechanism, favoring the formation of the ortho–endo cycloadduct, as observed experimentally. The analysis of the reactivity indices derived from the conceptual DFT explains well the low polarity of this 32CA reaction. Parr functions and a dual reactivity descriptors analysis correctly explained the regioselectivity ortho of this 32CA reaction. Solvent effects did not modify the obtained selectivity but it increased the activation energies and decreased the exothermic character of this 32CA reaction. A thermodynamic parameters analysis indicated that this 32CA wascharacterized by an ortho regioselectivity and endostereoselectivity and exothermic and exergonic characters. Full article

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6 pages, 601 KiB

Open AccessCommunication

An Unexpected Reaction between Diaryliodonium Salts and DMSO

by Konrad Kepski and Wesley James Moran

Organics 2022, 3(3), 275-280; https://doi.org/10.3390/org3030020 - 31 Aug 2022

Cited by 2 | Viewed by 1863

Abstract

Diaryliodonium salts are useful arylating reagents that have been exploited widely. In this Communication, we demonstrate that heating diphenyliodonium triflate in the solvent DMSO leads to an unexpected arylation reaction. It is postulated that arylation of DMSO at oxygen, followed by a thia-Sommelet–Hauser [...] Read more.

Diaryliodonium salts are useful arylating reagents that have been exploited widely. In this Communication, we demonstrate that heating diphenyliodonium triflate in the solvent DMSO leads to an unexpected arylation reaction. It is postulated that arylation of DMSO at oxygen, followed by a thia-Sommelet–Hauser rearrangement, leads to the formation of 2-thiomethylphenols. More substituted diaryliodonium salts and cyclic diaryliodonium salts are shown to be more stable and less likely to react with DMSO. In conclusion, when using iodonium salts dissolved in DMSO, beware of side-reactions. Full article

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Scheme 1

30 pages, 7604 KiB

Open AccessReview

Palladium-Catalyzed Cross-Coupling Reactions of Borylated Alkenes for the Stereoselective Synthesis of Tetrasubstituted Double Bond

by Tomáš Tobrman and Sergej Mrkobrada

Organics 2022, 3(3), 210-239; https://doi.org/10.3390/org3030017 - 20 Jul 2022

Cited by 5 | Viewed by 2277

Abstract

The stereoselective formation of tetrasubstituted alkenes remains one of the key goals of modern organic synthesis. In addition to other methods, the stereoselective synthesis of tetrasubstituted alkenes can be achieved by means of cross-coupling reactions of electrophilic and nucleophilic alkene templates. The use [...] Read more.

The stereoselective formation of tetrasubstituted alkenes remains one of the key goals of modern organic synthesis. In addition to other methods, the stereoselective synthesis of tetrasubstituted alkenes can be achieved by means of cross-coupling reactions of electrophilic and nucleophilic alkene templates. The use of electrophilic templates for the stereoselective synthesis of tetrasubstituted alkenes has previously been described. Therefore, the present review summarizes the procedures available for the stereoselective preparation of tetrasubstituted alkenes using stable and isolable nucleophilic templates. Full article

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14 pages, 5486 KiB

Open AccessArticle

Synthesis and Theoretical Studies of Aromatic Azaborines

by Pipsa Hirva, Petri Turhanen and Juri M. Timonen

Organics 2022, 3(3), 196-209; https://doi.org/10.3390/org3030016 - 11 Jul 2022

Viewed by 1735

Abstract

Organoboron compounds are well known for their use as synthetic building blocks in several significant reactions, e.g., palladium-catalyzed Suzuki-Miyaura cross-coupling. As an element, boron is fascinating; as part of a molecule it structurally resembles a three-valent atom, but if there is a lone [...] Read more.

Organoboron compounds are well known for their use as synthetic building blocks in several significant reactions, e.g., palladium-catalyzed Suzuki-Miyaura cross-coupling. As an element, boron is fascinating; as part of a molecule it structurally resembles a three-valent atom, but if there is a lone pair of electrons nearby, the boron atom’s empty p-orbital may capture the lone pair and form a covalent bond. This is the main aspect that is challenging chemistry during the synthesis of boron containing molecules and may lead into unexpected reactions and products. To study this, we synthesized and studied novel aromatic azaborines for better understanding of their structures and reactions. Here, we report a one-pot method for the synthesis of substituted aromatic azaborines and computational studies of their structure to explain their observed chemical properties. Full article

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11 pages, 5177 KiB

Open AccessArticle

Regioselective Transfer Hydrogenative Defluorination of Polyfluoroarenes Catalyzed by Bifunctional Azairidacycle

by Asuka Matsunami, Shigeki Kuwata and Yoshihito Kayaki

Organics 2022, 3(3), 150-160; https://doi.org/10.3390/org3030012 - 22 Jun 2022

Cited by 1 | Viewed by 2274

Abstract

The catalytic hydrodefluorination (HDF) with a bifunctional azairidacycle using HCOOK was examined for cyano- and chloro-substituted fluoroarenes, including penta- and tetrafluorobenzonitriles, tetrafluoroterephthalonitrile, tetrafluorophthalonitrile, 3-chloro-2,4,5,6-tetrafluoropyridine, and 4-cyano-2,3,5,6-tetrafluoropyridine. The reaction was performed in the presence of a controlled amount of HCOOK with a substrate/catalyst ratio [...] Read more.

The catalytic hydrodefluorination (HDF) with a bifunctional azairidacycle using HCOOK was examined for cyano- and chloro-substituted fluoroarenes, including penta- and tetrafluorobenzonitriles, tetrafluoroterephthalonitrile, tetrafluorophthalonitrile, 3-chloro-2,4,5,6-tetrafluoropyridine, and 4-cyano-2,3,5,6-tetrafluoropyridine. The reaction was performed in the presence of a controlled amount of HCOOK with a substrate/catalyst ratio (S/C) of 100 in a 1:1 mixture of 1,2-dimethoxyethane (DME) and H₂O at an ambient temperature of 30 °C to obtain partially fluorinated compounds with satisfactory regioselectivities. The C–F bond cleavage proceeded favorably at the para position of substituents other than fluorine, which is in consonance with the nucleophilic aromatic substitution mechanism. In the HDF of tetrafluoroterephthalonitrile and 4-cyano-2,3,5,6-tetrafluoropyridine, which do not contain a fluorine atom at the para position of the cyano group, the double defluorination occurred solely at the 2- and 5-positions, as confirmed by X-ray crystallography. The HDF of 3-chloro-2,4,5,6-tetrafluoropyridine gave preference to the C–F bond cleavage over the C–Cl bond cleavage, unlike the dehalogenation pathway via electron-transfer radical anion fragmentation. In addition, new azairidacycles with an electron-donating methoxy substituent on the C–N chelating ligand were synthesized and served as a catalyst precursor (0.2 mol%) for the transfer hydrogenative defluorination of pentafluoropyridine, leading to 2,3,5,6-tetrafluoropyridine with up to a turnover number (TON) of 418. Full article

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13 pages, 5460 KiB

Open AccessArticle

Synthesis of Amino-Acid-Based Nitroalkenes

by Velisaria-Eleni Gerogianni, Giorgos S. Koutoulogenis, Dimitrios Triantafyllos Gerokonstantis and George Kokotos

Organics 2022, 3(2), 137-149; https://doi.org/10.3390/org3020011 - 14 Jun 2022

Viewed by 1668

Abstract

Fatty-acid-based nitroalkenes have recently received great attention because of their bioactivities. On the contrary, peptide- or amino-acid-based nitroalkenes have been scarcely explored so far, although they may exhibit interesting biological properties, for example, as enzyme inhibitors. In this work, we study protocols for [...] Read more.

Fatty-acid-based nitroalkenes have recently received great attention because of their bioactivities. On the contrary, peptide- or amino-acid-based nitroalkenes have been scarcely explored so far, although they may exhibit interesting biological properties, for example, as enzyme inhibitors. In this work, we study protocols for the efficient synthesis of nitroalkenes based on natural amino acids. A variety of N-protected amino alcohols and Weinreb amides, derived from α-amino acids, were converted to the corresponding N-protected amino aldehydes, and, through a Henry reaction with nitroalkanes, produced the corresponding nitro alcohols. The subsequent elimination reaction led to the (E)-isomer of amino-acid-based nitroalkenes in moderate to high yields. Full article

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11 pages, 10938 KiB

Open AccessArticle

Acid Catalyzed N-Alkylation of Pyrazoles with Trichloroacetimidates

by Rowan I. L. Meador, Nilamber A. Mate and John D. Chisholm

Organics 2022, 3(2), 111-121; https://doi.org/10.3390/org3020009 - 24 May 2022

Viewed by 2790

Abstract

N-Alkyl pyrazoles are important heterocycles in organic and medicinal chemistry, demonstrating a wide range of biological activity. A new method for the N-alkylation of pyrazoles has been developed using trichloroacetimidate electrophiles and a Brønsted acid catalyst. These reactions provide ready access [...] Read more.

N-Alkyl pyrazoles are important heterocycles in organic and medicinal chemistry, demonstrating a wide range of biological activity. A new method for the N-alkylation of pyrazoles has been developed using trichloroacetimidate electrophiles and a Brønsted acid catalyst. These reactions provide ready access to N-alkyl pyrazoles which are present in a variety of medicinally relevant lead structures. Benzylic, phenethyl and benzhydryl trichloroacetimidates provide good yields of the N-alkyl pyrazole products. Unsymmetrical pyrazoles provide a mixture of the two possible regioisomers, with the major product being controlled by sterics. This methodology provides an alternative to other alkylation methods that require strong base or high temperature. Full article

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7 pages, 2400 KiB

Open AccessArticle

A Theoretical Study on the Photochemical Isomerization of 2,6-Dimethylpyrazine

by Maurizio D’Auria

Organics 2022, 3(2), 95-101; https://doi.org/10.3390/org3020007 - 12 May 2022

Cited by 1 | Viewed by 1511

Abstract

DFT calculations on the photoisomerization of 2,6-dimethylpyrazine allowed us to confirm the role of benzvalene isomers in the isomerization of hexatomic heterocyclic compounds. 2,6-Dimethylpyrazine in the excited singlet states can be converted into the corresponding Dewar isomers. If the S₂ state is [...] Read more.

DFT calculations on the photoisomerization of 2,6-dimethylpyrazine allowed us to confirm the role of benzvalene isomers in the isomerization of hexatomic heterocyclic compounds. 2,6-Dimethylpyrazine in the excited singlet states can be converted into the corresponding Dewar isomers. If the S₂ state is populated, two Dewar isomers can be obtained, while the S₁ state allows the formation of only one of the possible Dewar isomers. Both Dewar isomers can be converted into the benzvalene isomer, that is, the precursor of 4,5-dimethylpyrimidine, the reaction product. In fact, the benzvalene isomer can be obtained from the Dewar isomers in processes that occur without an activation energy, and it is the more stable benzvalene isomers that can be obtained from the Dewar isomers. CASSCF study indicates the presence of a conical intersection allowing the direct formation of the benzvalene isomer. Full article

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8 pages, 1920 KiB

Open AccessArticle

Stabilized Arylzinc Iodides in Negishi Acylative Cross-Coupling: A Modular Synthesis of Chalcones

by Michele Pierigé, Anna Iuliano, Gaetano Angelici and Gianluca Casotti

Organics 2022, 3(2), 87-94; https://doi.org/10.3390/org3020006 - 23 Apr 2022

Cited by 2 | Viewed by 2336

Abstract

Stabilized arylzinc iodides, synthesized by direct insertion of zinc into the corresponding halides, were used as nucleophiles into an acylative Negishi coupling reaction to synthesize chalcones. The reaction conditions were optimized to afford optimal results on a model reaction and then applied to [...] Read more.

Stabilized arylzinc iodides, synthesized by direct insertion of zinc into the corresponding halides, were used as nucleophiles into an acylative Negishi coupling reaction to synthesize chalcones. The reaction conditions were optimized to afford optimal results on a model reaction and then applied to synthesize nine compounds. Esters, chlorides, electron-rich, electron-poor and sterically hindered substrates are well tolerated and even heteroaryl derivatives can be synthesized. Full article

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Graphical abstract

16 pages, 3556 KiB

Open AccessArticle

De Novo Synthesis of Bacteriochlorins Bearing Four Trideuteriomethyl Groups

by Haoyu Jing, Qun Tang, David F. Bocian and Jonathan S. Lindsey

Organics 2022, 3(1), 22-37; https://doi.org/10.3390/org3010002 - 07 Feb 2022

Cited by 3 | Viewed by 2293

Abstract

Site-specific introduction of isotopes in tetrapyrrole macrocycles provides the foundation for probing physicochemical features germane to photosynthetic energy-transduction processes, but has chiefly been done with porphyrins rather than the more biologically relevant hydroporphyrin analogues of native photosynthetic pigments. A prior study incorporated pairwise [...] Read more.

Site-specific introduction of isotopes in tetrapyrrole macrocycles provides the foundation for probing physicochemical features germane to photosynthetic energy-transduction processes, but has chiefly been done with porphyrins rather than the more biologically relevant hydroporphyrin analogues of native photosynthetic pigments. A prior study incorporated pairwise ¹³C or ¹⁵N atoms in the skeleton of a bacteriochlorin containing a gem-dimethyl group in each pyrroline ring. Here, a complementary effort is reported that installs deuterium atoms in substituents at the perimeter of a bacteriochlorin. Thus, perdeuteriated 3-methyl-2,4-pentanedione was converted in an 8-step synthesis via the intermediacy of tert-butyl 5-formyl-3,4-bis(trideuteriomethyl)pyrrole-2-carboxylate to the 2,3,12,13-tetrakis(trideuteriomethyl)-8,8,18,18-tetramethylbacteriochlorin (BC-2). The fidelity of isotope substitution was maintained throughout the synthesis. Resonance Raman spectroscopy of the copper chelate (CuBC-2) revealed that addition of the four β-pyrrolic substituents alone is not sufficient to account for the vibronic complexity observed for the copper chelate of bacteriochlorophyll a (CuBChl a). The increased vibronic activity exhibited by the natural pigments and CuBChl a must arise from the increased structural complexity of the macrocycle. Full article

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