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12 pages, 2310 KiB

Open AccessArticle

[3+2] Cycloaddition to a Chiral 5-Methylene-1,3-dioxolan-4-one and Pyrolysis of the Spiro Adducts

by R. Alan Aitken, Lynn A. Power and Alexandra M. Z. Slawin

Molecules 2025, 30(6), 1246; https://doi.org/10.3390/molecules30061246 - 10 Mar 2025

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The [3+2] cycloaddition chemistry of (2S)-5-methylene-2-t-butyl-1,3-dioxolan-4-one, derived from lactic acid, has been examined, and spiro adducts have been obtained with benzonitrile oxide, acetonitrile oxide, diazomethane and diphenyldiazomethane. The structure and absolute stereochemistry of the benzonitrile oxide adduct has been confirmed by X-ray diffraction, and all the adducts have been fully characterised by ¹H and ¹³C NMR. Attempted cycloaddition with a nitrile sulfide, a nitrile imine and azides failed. Pyrolysis results in a range of novel gas-phase reactions, with the nitrile oxide adducts giving pivalaldehyde, CO₂, the nitrile and ketene, the diazomethane adduct losing only N₂ to give a cyclopropane-fused dioxolanone, and the diphenylcyclopropane derived from diphenyldiazomethane giving mainly benzophenone in a sequence involving the loss of pivalaldehyde and methyleneketene. Full article

(This article belongs to the Special Issue Advances in Synthesis and Biological Activity of Novel Derivatives Based on Five-Membered Heterocyclic Scaffolds and Their Intermediates—Second Edition)

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13 pages, 2237 KiB

Open AccessArticle

Research on Synthesis, Structure, and Catalytic Performance of Tetranuclear Copper(I) Clusters Supported by 2-Mercaptobenz-zole-Type Ligands

by Tingyu Zhu, Wangyuan Zhan, Weibin Fan and Xiaofeng Zhang

Molecules 2024, 29(17), 4228; https://doi.org/10.3390/molecules29174228 - 6 Sep 2024

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Abstract

Tetrahedral copper(I) clusters [Cu₄(MBIZ)₄(PPh₃)₂] (2), [Cu₄(MBOZ)₄(PPh₃)₄] (6) (MBIZ = 2-mercaptobenzimidazole, MBOZ = 2-mercaptobenzoxazole) were prepared by regulation of the copper-thiolate clusters [Cu₆(MBIZ)₆] (1) and [Cu₈(MBOZ)₈I]⁻ (5) with PPh₃. With the presence of iodide anion, the regulation provided the iodide-containing clusters [Cu^I₄(MBIZ)₃(PPh₃)₃I] (3) and [Cu^I₄(MBOZ)₃(PPh₃)₃I] (7). The cyclic voltammogram of 3 in MeCN (0.1 M ⁿBu₄NPF₆, 298 K) at a scan rate of 100 mV s⁻¹ shows two oxidation processes at E_p^a = +0.11 and +0.45 V with return waves observed at E_p^c = +0.25 V (vs. Fc⁺/Fc). Complex 3 has a higher capability to lose and gain electrons in the redox processes than complexes 2, 4, 4′, 6, and 7. Its thermal stability was confirmed by thermogravimetric analysis. The catalytic performance of 3 was demonstrated by the catalytic transformation of iodobenzenes to benzonitriles using AIBN as the cyanide source. The nitrile products show potential applications in the preparation of 1,3,5-triazine compounds for organic fluorescence materials. Full article

(This article belongs to the Section Inorganic Chemistry)

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18 pages, 3448 KiB

Open AccessArticle

Spectral Assignment in the [3 + 2] Cycloadditions of Methyl (2E)-3-(Acridin-4-yl)-prop-2-enoate and 4-[(E)-2-Phenylethenyl]acridin with Unstable Nitrile N-Oxides

by Lucia Ungvarská Maľučká and Mária Vilková

Molecules 2024, 29(12), 2756; https://doi.org/10.3390/molecules29122756 - 9 Jun 2024

Cited by 2 | Viewed by 1404

Abstract

The investigation of cycloaddition reactions involving acridine-based dipolarophiles revealed distinct regioselectivity patterns influenced mainly by the electronic factor. Specifically, the reactions of methyl-(2E)-3-(acridin-4-yl)-prop-2-enoate and 4-[(1E)-2-phenylethenyl]acridine with unstable benzonitrile N-oxides were studied. For methyl-(2E)-3-(acridin-4-yl)-prop-2-enoate, the formation of two regioisomers favoured the 5-(acridin-4-yl)-4,5-dihydro-1,2-oxazole-4-carboxylates, with remarkable exclusivity in the case of 4-methoxybenzonitrile oxide. Conversely, 4-[(1E)-2-phenylethenyl]acridine displayed reversed regioselectivity, favouring products 4-[3-(substituted phenyl)-5-phenyl-4,5-dihydro-1,2-oxazol-4-yl]acridine. Subsequent hydrolysis of isolated methyl 5-(acridin-4-yl)-3-phenyl-4,5-dihydro-1,2-oxazole-4-carboxylates resulted in the production of carboxylic acids, with nearly complete conversion. During NMR measurements of carboxylic acids in CDCl₃, decarboxylation was observed, indicating the formation of a new prochiral carbon centre C-4, further confirmed by a noticeable colour change. Overall, this investigation provides valuable insights into regioselectivity in cycloaddition reactions and subsequent transformations, suggesting potential applications across diverse scientific domains. Full article

(This article belongs to the Special Issue New Insights into Nuclear Magnetic Resonance (NMR) Spectroscopy)

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11 pages, 5229 KiB

Open AccessEditor’s ChoiceCommunication

2-Pyridylselenenyl versus 2-Pyridyltellurenyl Halides: Symmetrical Chalcogen Bonding in the Solid State and Reactivity towards Nitriles

by Ivan V. Buslov, Alexander S. Novikov, Victor N. Khrustalev, Mariya V. Grudova, Alexey S. Kubasov, Zhanna V. Matsulevich, Alexander V. Borisov, Julia M. Lukiyanova, Maria M. Grishina, Anatoly A. Kirichuk, Tatiyana V. Serebryanskaya, Andreii S. Kritchenkov and Alexander G. Tskhovrebov

Symmetry 2021, 13(12), 2350; https://doi.org/10.3390/sym13122350 - 7 Dec 2021

Cited by 19 | Viewed by 4591

Abstract

The synthesis of 2-pyridyltellurenyl bromide via Br₂ oxidative cleavage of the Te–Te bond of dipyridylditelluride is reported. Single-crystal X-ray diffraction analysis of 2-pyridyltellurenyl bromide demonstrated that the Te atom of 2-pyridyltellurenyl bromide was involved in four different noncovalent contacts: Te⋯Te interactions, two Te⋯Br ChB, and one Te⋯N ChB contact forming 3D supramolecular symmetrical framework. In contrast to 2-pyridylselenenyl halides, the Te congener does not react with nitriles furnishing cyclization products. 2-Pyridylselenenyl chloride was demonstrated to easily form the corresponding adduct with benzonitrile. The cyclization product was studied by the single-crystal X-ray diffraction analysis, which revealed that in contrast to earlier studied cationic 1,2,4-selenadiazoles, here we observed that the adduct with benzonitrile formed supramolecular dimers via Se⋯Se interactions in the solid state, which were never observed before for 1,2,4-selenadiazoles. Full article

(This article belongs to the Section Chemistry: Symmetry/Asymmetry)

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16 pages, 1625 KiB

Open AccessArticle

Direct Metal-Free Transformation of Alkynes to Nitriles: Computational Evidence for the Precise Reaction Mechanism

by Lucija Hok and Robert Vianello

Int. J. Mol. Sci. 2021, 22(6), 3193; https://doi.org/10.3390/ijms22063193 - 21 Mar 2021

Cited by 8 | Viewed by 4718

Abstract

Density functional theory calculations elucidated the precise reaction mechanism for the conversion of diphenylacetylenes into benzonitriles involving the cleavage of the triple C≡C bond, with N-iodosuccinimide (NIS) as an oxidant and trimethylsilyl azide (TMSN₃) as a nitrogen donor. The reaction requires six steps with the activation barrier ΔG^‡ = 33.5 kcal mol⁻¹ and a highly exergonic reaction free-energy ΔG_R = −191.9 kcal mol⁻¹ in MeCN. Reaction profiles agree with several experimental observations, offering evidence for the formation of molecular I₂, interpreting the necessity to increase the temperature to finalize the reaction, and revealing thermodynamic aspects allowing higher yields for alkynes with para-electron-donating groups. In addition, the proposed mechanism indicates usefulness of this concept for both internal and terminal alkynes, eliminates the option to replace NIS by its Cl- or Br-analogues, and strongly promotes NaN₃ as an alternative to TMSN₃. Lastly, our results advise increasing the solvent polarity as another route to advance this metal-free strategy towards more efficient processes. Full article

(This article belongs to the Special Issue From Molecules to Colloids: Recent Advances in Their Chemical Physics)

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12 pages, 5289 KiB

Open AccessArticle

Application of β-Phosphorylated Nitroethenes in [3+2] Cycloaddition Reactions Involving Benzonitrile N-Oxide in the Light of a DFT Computational Study

by Karolina Zawadzińska and Karolina Kula

Organics 2021, 2(1), 26-37; https://doi.org/10.3390/org2010003 - 16 Feb 2021

Cited by 29 | Viewed by 8187

Abstract

The regiochemistry of [3+2] cycloaddition (32CA) processes between benzonitrile N-oxide 1 and β-phosphorylated analogues of nitroethenes 2a–c has been studied using the Density Functional Theory (DFT) at the M062X/6-31+G(d) theory level. The obtained results of reactivity indices show that benzonitrile N-oxide 1 can be classified both as a moderate electrophile and moderate nucleophile, while β-phosphorylated analogues of nitroethenes 2a–c can be classified as strong electrophiles and marginal nucleophiles. Moreover, the analysis of CDFT shows that for [3+2] cycloadditions with the participation of β-phosphorylatednitroethene 2a and β-phosphorylated α-cyanonitroethene 2b, the more favored reaction path forms 4-nitro-substituted Δ²-isoxazolines 3a–b, while for a reaction with β-phosphorylated β-cyanonitroethene 2c, the more favored path forms 5-nitro-substituted Δ²-isoxazoline 4c. This is due to the presence of a cyano group in the alkene. The CDFT study correlates well with the analysis of the kinetic description of the considered reaction channels. Moreover, DFT calculations have proven the clearly polar nature of all analyzed [3+2] cycloaddition reactions according to the polar one-step mechanism. Full article

(This article belongs to the Special Issue Cycloaddition Reaction in Organic Synthesis)

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