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Organics, Volume 3, Issue 3 (September 2022) – 13 articles

Cover Story (view full-size image): The excellent hydrogen transfer performance of proton-responsive azairidacycles prepared from cumylamine derivatives enables the hydrodefluorination of polyfluorobenzenes and polyfluoropyridines with HCOOK at ambient temperature. Under the optimized conditions, monodefluorination of pentafluoropyridine proceeded rapidly with up to a turnover number of 418 within 1 h. In addition, high regio- and chemoselectivities were demonstrated in the comparative studies using the cyano- and chloro-substituted substrates. The C–F bond cleavage took place favorably at the para position of substituents other than fluorine, which is in consonance with the nucleophilic aromatic substitution mechanism. View this paper
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44 pages, 13246 KiB  
Review
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 11 | Viewed by 5214
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
(This article belongs to the Collection Advanced Research Papers in Organics)
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16 pages, 3078 KiB  
Review
Total Syntheses of Chloropupukeananin and Its Related Natural Products
by Takahiro Suzuki
Organics 2022, 3(3), 304-319; https://doi.org/10.3390/org3030023 - 9 Sep 2022
Cited by 1 | Viewed by 2069
Abstract
Chloropupukeananin is a natural product that inhibits HIV-1 replication and has antitumor activity. Its structure consists of a chlorinated tricyclo[4.3.1.03,7]decane core skeleton with an array of highly oxidized multifunctional groups. In the biosynthesis of chloropupukeananin, (+)-iso-A82775C and (−)-maldoxin are employed as [...] Read more.
Chloropupukeananin is a natural product that inhibits HIV-1 replication and has antitumor activity. Its structure consists of a chlorinated tricyclo[4.3.1.03,7]decane core skeleton with an array of highly oxidized multifunctional groups. In the biosynthesis of chloropupukeananin, (+)-iso-A82775C and (−)-maldoxin are employed as biosynthetic precursors for the intermolecular Diels–Alder and carbonyl–ene reactions, followed by the migration of the p-orcellinate group. Chloropupukeanolides and chloropestolides are intermediates and isomers in biosynthesis; their unique chemical structures and biosynthetic pathways have attracted significant attention from synthetic chemists. In this review, I present the synthetic studies on chloropupukeananin and its related compounds that have been conducted thus far. Full article
(This article belongs to the Special Issue New Reactions and Strategies for Natural Product Synthesis)
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11 pages, 2347 KiB  
Article
Divergent Synthesis of Four Monomeric Ellagitannins toward the Total Synthesis of an Oligomeric Ellagitannin, Nobotanin K
by Hajime Hashimoto, Shinnosuke Wakamori, Kazutada Ikeuchi and Hidetoshi Yamada
Organics 2022, 3(3), 293-303; https://doi.org/10.3390/org3030022 - 6 Sep 2022
Cited by 2 | Viewed by 1842
Abstract
Oligomeric ellagitannins are challenging synthetic targets due to the need for an abundant supply of their composed monomeric ellagitannins and a synthetic methodology to connect them. This work focused on the divergent synthesis of the four monomeric ellagitannins from a common intermediate as [...] Read more.
Oligomeric ellagitannins are challenging synthetic targets due to the need for an abundant supply of their composed monomeric ellagitannins and a synthetic methodology to connect them. This work focused on the divergent synthesis of the four monomeric ellagitannins from a common intermediate as a step toward the total synthesis of nobotanin K, a class of compounds that includes oligomeric ellagitannins and were isolated in plants belonging to the Melastomataceae family. Implementing our method, the four natural products could be easily supplied, suggesting that through this novel route, the total synthesis of nobotanin K could be achieved smoothly. Full article
(This article belongs to the Special Issue New Reactions and Strategies for Natural Product Synthesis)
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12 pages, 3074 KiB  
Article
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 - 2 Sep 2022
Cited by 2 | Viewed by 1425
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 orthoendo 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
(This article belongs to the Collection Advanced Research Papers in Organics)
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6 pages, 601 KiB  
Communication
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 2231
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
(This article belongs to the Collection Advanced Research Papers in Organics)
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13 pages, 2153 KiB  
Article
Dihydrooxazine Byproduct of a McMurry–Melton Reaction en Route to a Synthetic Bacteriochlorin
by Vy-Phuong Tran, Nobuyuki Matsumoto, Phattananawee Nalaoh, Haoyu Jing, Chih-Yuan Chen and Jonathan S. Lindsey
Organics 2022, 3(3), 262-274; https://doi.org/10.3390/org3030019 - 8 Aug 2022
Cited by 5 | Viewed by 2046
Abstract
A synthetic route to gem-dimethyl-substituted bacteriochlorins—models of native bacteriochlorophylls—relies on the formation of a dihydrodipyrrin precursor via a series of established reactions: van Leusen pyrrole formation, Vilsmeier formylation, Henry reaction, borohydride reduction, Michael addition, and McMurry–Melton pyrroline formation. The latter is the least [...] Read more.
A synthetic route to gem-dimethyl-substituted bacteriochlorins—models of native bacteriochlorophylls—relies on the formation of a dihydrodipyrrin precursor via a series of established reactions: van Leusen pyrrole formation, Vilsmeier formylation, Henry reaction, borohydride reduction, Michael addition, and McMurry–Melton pyrroline formation. The latter is the least known of the series. Here, the McMurry–Melton reaction of a 2-(6-oxo-2-nitrohexyl)pyrrole in the presence of TiCl3 and an ammonium acetate buffer formed the expected Δ1-pyrroline, as well as an unexpected polar, cyclic byproduct (a 5,6-dihydro-4H-1,2-oxazin-6-ol), each attached to the 2-methylpyrrole unit. Both species were characterized by single-crystal X-ray diffraction. The McMurry–Melton reaction is a type of intercepted Nef reaction (the transformation of a nitroalkyl motif into a carbonyl group), where both the Δ1-pyrroline and the dihydrooxazine derive from the reaction of the nitrogen derived from the nitro group upon complete or partial reductive deoxygenation, respectively, with the γ-keto group. The report also considers competing Nef and McMurry–Melton reactions, the nature of available TiCl3 reagents, and the use of ammonium acetate for buffering the TiCl3/HCl reagent. Full article
(This article belongs to the Special Issue Chemistry of Heterocycles)
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22 pages, 9369 KiB  
Review
Specific Bifunctionalization on the Surface of Phosphorus Dendrimers Syntheses and Properties
by Massimo Petriccone, Régis Laurent, Cédric-Olivier Turrin, Rosa Maria Sebastián and Anne-Marie Caminade
Organics 2022, 3(3), 240-261; https://doi.org/10.3390/org3030018 - 3 Aug 2022
Cited by 4 | Viewed by 2281
Abstract
Dendrimers are highly branched macromolecules possessing, in most cases, identical terminal functions. However, it is sometimes desirable to have two types of surface functions in order to fulfil specific properties. The stochastic functionalization is frequently used for such purposes, but the presence of [...] Read more.
Dendrimers are highly branched macromolecules possessing, in most cases, identical terminal functions. However, it is sometimes desirable to have two types of surface functions in order to fulfil specific properties. The stochastic functionalization is frequently used for such purposes, but the presence of an uncontrolled number of each type of terminal function, albeit acceptable for research purposes, has no practical use. Thus, it is highly desirable to find strategies suitable for the precise grafting of two different functional groups on the surface of dendrimers. The easiest way, and the most widely used, consists in using a bifunctional monomer to be grafted to all of the surface functions of the dendrimers. Two other strategies are known but are rarely used: the modification of an existing function, to generate two functions, and the sequential grafting of one function then of a second function. The three methods are illustrated in this review with polyphosphorhydrazone (PPH) dendrimers, together with their properties as catalysts, for materials, and as biological tools. Full article
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30 pages, 7604 KiB  
Review
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 8 | Viewed by 2789
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
(This article belongs to the Collection Advanced Research Papers in Organics)
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14 pages, 5486 KiB  
Article
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 2125
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
(This article belongs to the Collection Advanced Research Papers in Organics)
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9 pages, 1695 KiB  
Article
Enantioselective Total Synthesis of Multifidene, a Sex Pheromone of Brown Algae
by Taiki Umezawa, Misaki Hara, Nana Kinoshita-Terauchi and Fuyuhiko Matsuda
Organics 2022, 3(3), 187-195; https://doi.org/10.3390/org3030015 - 8 Jul 2022
Cited by 2 | Viewed by 2009
Abstract
The total synthesis of multifidene, a sex pheromone found in brown algae, is described. The synthesis features the highly enantioselective and diastereoselective addition reaction of an aldehyde to a nitroolefin in the presence of a Hayashi–Jørgensen catalyst and a Nef reaction initiated by [...] Read more.
The total synthesis of multifidene, a sex pheromone found in brown algae, is described. The synthesis features the highly enantioselective and diastereoselective addition reaction of an aldehyde to a nitroolefin in the presence of a Hayashi–Jørgensen catalyst and a Nef reaction initiated by visible light irradiation. These key reactions enabled the 11-step synthesis from commercially available compounds. The synthetic pheromones are examined with gametes. Full article
(This article belongs to the Special Issue New Reactions and Strategies for Natural Product Synthesis)
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14 pages, 1524 KiB  
Article
Mo2C as Pre-Catalyst for the C-H Allylic Oxygenation of Alkenes and Terpenoids in the Presence of H2O2
by Michael G. Kallitsakis, Dimitra K. Gioftsidou, Marina A. Tzani, Panagiotis A. Angaridis, Michael A. Terzidis and Ioannis N. Lykakis
Organics 2022, 3(3), 173-186; https://doi.org/10.3390/org3030014 - 4 Jul 2022
Viewed by 2528
Abstract
In this study, commercially available molybdenum carbide (Mo2C) was used, in the presence of H2O2, as an efficient pre-catalyst for the selective C-H allylic oxygenation of several unsaturated molecules into the corresponding allylic alcohols. Under these basic [...] Read more.
In this study, commercially available molybdenum carbide (Mo2C) was used, in the presence of H2O2, as an efficient pre-catalyst for the selective C-H allylic oxygenation of several unsaturated molecules into the corresponding allylic alcohols. Under these basic conditions, an air-stable, molybdenum-based polyoxometalate cluster (Mo-POM) was formed in situ, leading to the generation of singlet oxygen (1O2), which is responsible for the oxygenation reactions. X-ray diffraction, SEM/EDX and HRMS analyses support the formation mainly of the Mo6O192− cluster. Following the proposed procedure, a series of cycloalkenes, styrenes, terpenoids and methyl oleate were successfully transformed into hydroperoxides. After subsequent reduction, the corresponding allylic alcohols were produced with good yields and in lab-scale quantities. A mechanistic study excluded a hydrogen atom transfer pathway and supported the twix-selective oxygenation of cycloalkenes on the more sterically hindered side via the 1O2 generation. Full article
(This article belongs to the Special Issue Redox Transformations in Advanced Organic Synthesis)
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12 pages, 686 KiB  
Article
Regioselective N- versus P-Deprotonation of Aminophosphane Tungsten(0) Complexes
by Tatjana Terschüren, Philip Junker, Alexander Schmer, Arturo Espinosa Ferao and Rainer Streubel
Organics 2022, 3(3), 161-172; https://doi.org/10.3390/org3030013 - 22 Jun 2022
Viewed by 1962
Abstract
1,2-Bifunctional ligands are rare, in general, which holds especially for those with a P-N linkage. Herein, we report on the synthesis of P-tert-butyl substituted aminophosphane W(CO)5 complexes 3a-f (a: R = R’ = H; b: R = H, R = Me; [...] Read more.
1,2-Bifunctional ligands are rare, in general, which holds especially for those with a P-N linkage. Herein, we report on the synthesis of P-tert-butyl substituted aminophosphane W(CO)5 complexes 3a-f (a: R = R’ = H; b: R = H, R = Me; c: R = H, R’ = ally; d: R = H, R’ = i-Pr; e: R = H, R’ = t-Bu; f: R = R’ = Me) obtained via formal N-H insertion reactions of Li/Cl phosphinidenoid complex 2 into NH bonds of ammonia and different amines. The 1,2-bifunctionality of 3b was addressed in targeted regioselective deprotonation reactions leading to amidophosphane complexes M-4b or M/N(H)Me phosphinidenoid complexes M-5b, respectively (M = Li, K). Remarkable was the observation that reactions of M-4b and M-5b with MeI as the electrophile resulted in the formation of the same product 7b. The constitution of all the compounds has been established by means of NMR and IR spectroscopy and mass spectrometry. Two possible reaction pathways were studied in detail using high-level DFT calculations. Full article
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11 pages, 5177 KiB  
Article
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 2 | Viewed by 2689
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
(This article belongs to the Collection Advanced Research Papers in Organics)
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