Cycloaddition Research Articles

Synthesis of 1,10-phenanthroline-2,9-bistriazoles: Evaluation as G-quadruplex binders and anti-tumor activity.

Novel 1,10-phenanthroline-2,9-bistriazoles derivatives have been synthesized by copper-catalyzed azide/alkyne cycloaddition reactions and assessed for their ability to bind and stabilize G-quadruplex (G4) structures. Ten novel compounds were evaluated using Förster resonance energy transfer (FRET) melting, circular dichroism (CD), and fluorescence spectroscopy on several G4 sequences. Biophysical characterization led to the identification of compounds 4a, 4b, and 5b as good G4 ligands of KRAS G4 sequences. The cell viability of all derivatives was also assessed, revealing weak effects. However, compound 2a exhibited cytotoxicity activity on A549 and H1299 cancer cells and low cytotoxicity towards non-malignant cells MRC-5 not connected with its G4-binding ability. Flow cytometry showed that 2a induced a cell viability decrease in S and G2/M phases for A549 and H1299; thus, more studies should be performed to explore the proteins involved in cell cycle regulation.

Pyrazoline and Analogs: Substrate-based Synthetic Strategies.

Among the many reports published on strategies applicable to synthesizing pyrazolines and its analogs, The 1,3-dipolar cycloaddition offers a remarkably wide range of utility. Many 1,3-dipolar cycloaddition reactions used for the synthesis of pyrazolines provide better selectivity, eco-friendly, and less expensive chemical processes. In the presented study, we have reviewed various recently adopted strategies for the synthesis of pyrazoline, which followed the 1,3-dipolar cycloaddition reactions mechanism and classified them based on starting materials such as nitrile imines, diazo compounds, different zwitter ions, chalcones, and isoprene units. The manuscript also focused on the synthesis of pyrazolines starting from Seyferth-Gilbert reagents (SGR) and Psilostachyin (PSH) reagents. We hope this work will help those engaged or have plans to research pyrazoline or its analogs, as synthetic protocols based on starting material are rarely available for pyrazolines. Thus, this article holds a valuable complement to the development of newer pyrazoline and its derivatives.

The Use of the Carbonyl Group (C-3) of Isatin for the Construction of Pyrazoline Moiety and the Study of its Antioxidant Activity

A series of novel pyrazoline derivatives 5-13 were synthesized in three steps from isatin, with yields ranging from 40 to 72% over the multistep procedure. The first step included the condensation of isatin with p-aminoacetophenone to afford the corresponding Schiff base 1 in a 75% yield. In the second step, the enolate form of Schiff base 1 was reacted with different aromatic aldehydes (benzaldehyde, p-nitrobenzaldehyde, and p-chlorobenzaldehyde) to give the title chalcone derivatives 2-4 in 60-72 yields. In the third step, pyrazoline derivatives 5-13 were synthesized via cycloaddition reactions between compounds 2-4 and hydrazine hydrate, phenyl hydrazine, or p-nitrophenyl hydrazine. The cycloaddition produced the target pyrazoline compounds in 40-72% isolated yields. All prepared compounds were characterized by FT-IR and 1H NMR spectroscopy. Some of the prepared compounds were tested for antioxidant properties.

Enantioselective Cascade Reactions of Aminocatalytic Dienamines and Trienamines Initiated by a Cycloaddition Reaction.

Cycloadditions are widely accepted as a group of reactions that rapidly generate molecular complexity. Being highly atom economic and often predictable, these reactions can generate up to four stereogenic centers and two C-C (or C-X) bonds in one reaction step. During the last two decades, asymmetric aminocatalysis has shown to be a successful strategy for controlling stereoselectivity and enabling reactivity of cycloaddition reactions. By increasing the conjugation of the carbonyl species employed, dienamines and trienamines can be catalytically formed. Not only can these facilitate the cycloaddition, often accompanied by high levels of stereocontrol, but they also leave a residual enamine or carbonyl (by hydrolysis) in the cycloadduct. This residual functionality can engage in further intramolecular reactions generating complex cyclic systems in a one-pot cascade manner. In this regard, asymmetric aminocatalysis can add another layer of complexity to the already complex nature of cycloadditions. In this review, we will present the general concept of such reactivity patterns of dienamines and trienamines, and hereafter showcase examples in the literature. We aspire that the chemical community can use these concepts to design new enantioselective aminocatalytic cascade reactions to access enantioenriched, complex compounds, and perhaps use these in complex molecule synthesis.

High‐Pressure‐Mediated Fragment Library Synthesis of 1,2‐Disubsituted Cyclobutane Derivatives

AbstractCyclobutanes have attracted significant interest in medicinal chemistry because of their unique structure and potential advantages in pharmacological properties. Nevertheless, 1,2‐disubstituted cyclobutanes remain underrepresented, both in the general chemical space and in fragment‐based drug discovery libraries. In this study, a two‐diversification‐point library of cyclobutanesulfonamides was synthesized through a hyperbaric [2+2] cycloaddition reaction between ethenesulfonyl fluoride and tert‐butyl vinyl ether as the key step. The sulfonyl fluoride was subsequently transformed into various sulfonamides, whereas the tert‐butyl ether was converted into carbamates and triazoles to synthesize a fragment library. Overall, this synthesis contributes to addressing the underrepresentation of 1,2‐disubstituted cyclobutane fragments, making a valuable addition to the field of fragment‐based drug discovery.

Azobenzene-Attached (NHC)Gold(I) and (NHC)Copper(I) Complexes as Photoswitchable Catalysts.

Photoswitchable (pre)catalysts, N,N'-bis-azobenzene-based (NHC)gold(I) and N,N'-bis-azobenzene-derived (NHC)copper(I) complexes are reported. Trans to cis isomerization of the attached photoswitchable moieties in the Au(I) complex enables four-fold decrement in the rate of oxazoline formation reaction. Whereas the progress of the copper(I) catalyzed, azide-alkyne cycloaddition reaction gets reduced by at least threefold. Alternate exposure to UV and blue light could easily toggle the rate of reactions remotely. The catalytic activity of thermodynamically stable trans-trans isomers is found to be similar to the common N-aryl substituted NHC-Au/Cu(I) complexes. NHC-Au(I) and -Cu(I) compounds bearing (trans)azobenzene moieties were characterized by X-ray diffraction. Photoswitching, recyclability studies, and the metastable isomer's thermal half-life in both complexes were studied via UV-visible spectroscopy. Whereas the extent of photoswitching and concomitant formation of geometrical isomers were investigated by using 1H-NMR spectroscopic study. Calculated percentage buried volumes of the three geometrical isomers show the trend trans-trans<trans-cis<cis-cis.

Lewis Acid Catalyzed Cycloaddition Reaction of Bicyclo[1.1.0]butanes

In recent years, the formal cycloaddition reactions involving bicyclo[1.1.0]butanes (BCBs) have furnished an array of innovative methodologies and strategies for the efficient synthesis of bicyclo [2.1.1] hexanes (BCHs). Most methods can be broadly classified into two main modes: the radical pathway and the two-electron pathway. This Synpacts article will summarize the recent advancements in Lewis acid-catalyzed formal cycloaddition reactions involving BCBs with alkenes, dipolar molecules, and alkynes, spanning the period from 2022 to 2024. Additionally, we introduce the formal cycloaddition reaction of BCBs with ynamides, catalyzed by Sc(OTf)3, which has been recently developed by our group. This approach offers a novel and efficient method for the synthesis of polysubstituted 2-amino-bicyclo[2.1.1]hexenes.

Catalytic Application of Cs‐Substituted Phosphotungstic Acid (CsxH3‐xPW12O40)‐Mesoporous Zirconium Phosphate (m‐ZrP) Nanocomposite Towards Synthesis of Structurally Diverse Tetrazole Moieties

AbstractThe rational design of a high surface area heterogeneous nanocomposite catalyst with well‐defined surface acidic sites and structural porosity is a promising approach with potential application in expeditious synthesis of biologically active molecules/scaffolds. In this work, mesoporous zirconium phosphate (m‐ZrP) was synthesized through a hydrothermal process and used as a porous matrix for dispersion of cesium‐exchanged phosphotungstic acid (CsxH3‐xPW12O40) nanoparticles to prepare CsxH3‐xPW12O40‐mZrP nanocomposite systems. Various characterization techniques, including XRD, UV–vis‐DRS, FTIR, FESEM, HRTEM, TGA‐DTA, BET, and TPD, were used to understand the structural, morphological, and surface properties of the composites. XRD analysis revealed the presence of m‐ZrP and cubic CsxH3‐xPW12O40 crystalline phases in the nanocomposite materials. A microscopic study indicated the existence of rod‐shaped morphology that was formed by the coalescence of a large number of spherical nanoparticles with diameters between 150 and 200 nm. The dispersion of CsxH3‐xPW12O40 over the m‐ZrP surface results in significant enhancement of medium and strong acidic sites, with the maximum number of acidic sites observed for the Cs0.5‐PTA‐mZrP composite (0.406 mmol g−1). The catalytic activity of the CsxH3‐xPW12O40‐mZrP nanocomposites was evaluated for rapid synthesis of tetrazole derivatives through [3 + 2] cycloaddition reactions of substituted nitrile and NaN3 under mild conditions. The detailed optimization study revealed that the use of Cs0.5‐PTA‐mZrP catalyst in DMF media afforded 90% yield of the tetrazole at 120 °C. Reaction kinetics study suggested that the optimal Cs0.5‐PTA‐mZrP catalyst exhibited the highest reaction rate of 2.06 × 10−3 mmol h−1m−2 towards tetrazole formation. Structurally diverse tetrazole derivatives in high yield and purity were synthesized under mild conditions using CsxH3‐xPW12O40‐mZrP nanocomposite as catalyst.

Synthesis of Functionalized 3‐Azabicyclo[3.2.0]Heptanes via Visible‐Light Energy‐Transfer Catalysis

AbstractFunctionalized cyclobutanes are three‐dimensional scaffolds widely found in natural products and bioactive molecules. Herein, we report a visible‐light‐induced intermolecular [2+2] cycloaddition reaction of a diverse array of alkenes with N‐substituted maleimides to access functionalized azabicyclo[3.2.0]heptanes. The reaction showed broad substrate scope with good chemo‐, regio‐ and diastereoselectivity under mild conditions. The robustness of this photo‐mediated [2+2] cycloaddition was demonstrated by carrying out a reaction on a 100 g scale (58 % yield). The prepared functionalized azabicyclo[3.2.0]heptanes are synthetic scaffolds for drug discovery.

Semi-Preparation and X-ray Single-Crystal Structures of Sophocarpine-Based Isoxazoline Derivatives and Their Pesticidal Effects and Toxicology Study.

Recently, research and development of novel pesticides from natural plant products have received much attention. To accelerate the application of sophocarpine as the agrochemical candidate, a series of novel sophocarpine-based isoxazoline derivatives were prepared by the 1,3-dipolar [2 + 3] cycloaddition reaction of sophocarpine with different chloroximes. Their structures were well characterized by high-resolution mass spectra, infrared spectra, and proton/carbon-13 nuclear magnetic resonance spectra. Eight steric configurations of compounds 5a, 5e', 5f, 5g, 5h, 5i, 5r, and 5u' were further determined by X-ray single-crystallography. Against Aphis citricola Van der Goot, compounds 5n (LD50: 0.032 μg/nymph) and 5o (LD50: 0.024 μg/nymph) exhibited greater than 3.7- and 4.9-fold potent aphicidal activity compared to sophocarpine (LD50: 0.118 μg/nymph). Against Tetranychus cinnabarinus Boisduval, derivative 5g displayed the most promising acaricidal activity with the LC50 value of 0.247 mg/mL, which was 14.2-fold that of sophocarpine. Compounds 5d and 5g also exhibited good control efficacy against T. cinnabarinus. Scanning electron microscopy images indicated that compound 5g can destroy the mite cuticle layer. These results will provide the foundation for the structural modification and use of sophocarpine derivatives as agrochemicals in the future.

Unexpected Course of Reaction Between (1E,3E)-1,4-Dinitro-1,3-butadiene and N-Methyl Azomethine Ylide—A Comprehensive Experimental and Quantum-Chemical Study

In recent times, interest in the chemistry of conjugated nitrodienes is still significantly increasing. In particular, the application of these compounds as building blocks to obtain heterocycles is a popular object of research. Therefore, in continuation of our research devoted to the topic of conjugated nitrodienes, experimental and quantum-chemical studies of a cycloaddition reaction between (1E,3E)-1,4-dinitro-1,3-butadiene and N-methyl azomethine ylide have been investigated. The computational results present that the tested reaction is realized through a pdr-type polar mechanism. In turn, the experimental study shows that in a course of this cycloaddition, only one reaction product in the form of 1-methyl-3-(trans-2-nitrovinyl)-Δ3-pyrroline is created. The constitution of this compound has been confirmed via spectroscopic methods. Finally, ADME analysis indicated that the synthesized Δ3-pyrroline exhibits biological potential, and it is a good drug candidate according to Lipinski, Veber and Egan rules. Nevertheless, PASS simulation showed that the compound exhibits weak antimicrobial, inhibitory and antagonist properties. Preliminary in silico research shows that although the obtained Δ3-pyrroline is not a good candidate for a drug, the presence of a nitrovinyl moiety in its structure indicates that the compound is an initial basis for further modifications.

Ionic Liquid‐Functionalized Porous Materials for Catalyzing CO2 Cycloaddition Reaction

AbstractIonic liquids (ILs) are incorporated into traditional porous materials to create ILs‐functionalized porous materials, which exhibit excellent absorption capacity and good catalytic activity for CO2. As a result, they are extensively utilized in the chemical conversion of CO2. This paper specifically focuses on the utilization of ILs‐functionalized organic porous materials, ILs‐functionalized inorganic porous materials, and ILs‐functionalized organic‐inorganic hybrid porous materials in the conversion of CO2. The synergistic effects of combining ILs with porous materials in CO2 conversion are thoroughly discussed. Furthermore, an in‐depth analysis is provided regarding the potential prospects and future applications of utilizing ILs‐functionalized porous materials within the broader realm of catalytic CO2 conversion technologies.

Sterically Hindered Derivatives of Pentacene and Octafluoropentacene.

6,13-Diethynylpentacene derivatives with sterically bulky substituents (Tr*, tris(3,5-di-tert-butylphenyl)methyl groups) appended to the ethynyl moieties at the 6- and 13-positions have been synthesized, as well as derivatives with electron-withdrawing fluorine groups on the 1,2,3,4,8,9,10,11-positions. These molecules are designed to investigate relationships between steric and electronic effects on the stability of pentacene toward endoperoxide formation via reaction with photosensitized oxygen in solution under ambient light (i. e., 'laboratory' conditions). It is evident from the study that stabilization through changes to the electronic characteristics of pentacene are more effective than the incorporation of sterically bulky groups at the acetylenic termini. Selected pentacene derivatives have been made into binary, amorphous films with the fullerene derivative PCBM to investigate the stability imparted by substituents against cycloaddition reactions. Overall, the introduction of steric protection through the incorporation of Tr* groups is not an efficient strategy for enhancing the persistence of pentacenes. Stabilization through fluorination proves successful for extending the lifetime of the pentacene derivatives by an order of magnitude in solution. Notably, the persistence of pentacene derivatives in solution can also be enhanced through the use of ethereal solvents stabilized with butylated hydroxy toluene (BHT) and/or an increased number of trialkylsilyl groups as substituents.

A MOF@MOF S-scheme Heterojunction with Lewis Acid-Base Sites Synergistically Boosts Cocatalyst-Free CO2 Cycloaddition.

The photocatalytic cycloaddition reaction between CO2 and epoxide is one of the most promising green routes for CO2 utilization, for which high performance photocatalysts are intensely desired. Herein, we have constructed an S-scheme heterojunction of MIL-125@ZIF-67 modified by amino groups, which achieves a cyclic carbonate yield of as high as 99 % without employing any co-catalyst, outperforming the previously reported photocatalysts. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in-situ electron paramagnetic resonance (EPR) spectroscopy reveal the important role of photogenerated electron migration from Lewis acid (Co) sites to the O atom of epoxide in triggering its ring-opening (the rate-determining step of CO2 cycloaddition reaction) under the assistance of photogenerated hole. Synergistically and concurrently, the Lewis base (amino groups) sites activate CO2 to CO2*, facilitating the following CO2 cycloaddition. Such a synergistic effect provides a most favorable approach to design efficient heterogeneous photocatalysts with dual/multiple-active sites for CO2 cycloaddition reaction.

Quinazoline-Derived Azomethine Imines as Substrates To Access Polycyclic Compounds.

Quinazolines are essential structural constituents of many pharmaceuticals and bioactive natural products. Quinazoline-derived azomethine imines (QAIs) have emerged recently as valuable building blocks for the synthesis of various quinazoline derivatives. This Synopsis presents recent advances in (formal) cycloaddition reactions of QAIs for the synthesis of quinazoline-fused 5- to 8-membered heterocycles as well as three-dimensional compounds.

Recent Advances on the Construction of Functionalized Indolizine and Imidazo[1,2-a]pyridine Derivatives.

Indolizines and imidazo[1,2-a]pyridines are commonly found in natural products, synthetic drugs, and bioactive molecules. These two types of derivatives possess good antibacterial, antiparasitic, anticancer activities, and so on. The functionalization of indolizines and imidazo[1,2-a]pyridines has always been a hot topic in organic chemistry research and has made significant progress. In recent years, our group has been dedicated to developing diverse synthetic methods for the preparation of such important compounds. 1) We have developed diverse C-H functionalization reactions for efficient modification of the parent indolizines and imidazo[1,2-a]pyridines. 2) A variety of cycloaddition reactions were established for the construction of indolizine and imidazo[1,2-a]pyridine derivatives from simple raw materials. 3) We have developed intriguing deconstruction-functionalization reactions of indolizines, enabling the reorganization of heterocyclic frameworks. This paper outlines our group's latest advancements in constructing structurally diverse indolizine and imidazo[1,2-a]pyridine derivatives. We hope that this work will offer valuable insights and inspiration for the ongoing research in the field of N-heterocyclic compounds.

Exploring the Antitumor Potential of New Indazole-indolizines Designed by Molecular Hybridization

Background: Cancer represents the major health problem faced by the population of the world, remaining one of the main causes of death. Hence, the development of new targeted antitumor drugs with high efficacy and lower toxicity is still needed. Objective: As a continuation of our work to discover new molecules with cytotoxic properties, two heterocyclic scaffolds, namely indolizine, and indazole, were combined in the same molecule, aiming to improve the bioactivity. This article focused on the synthesis, characterization, and biological evaluation of a series of new indazole-indolizine hybrid compounds. Methods: The biological potential of the synthesized compound was investigated in vitro against the human farnesyltransferase enzyme and NCI 60 tumor cell lines panel. While the farnesyltransferase inhibitory activity was modest, a very good antiproliferative action was observed for compound 4a, which, at a concentration of 10 μM, inhibited the growth of 20 types of cancer cells by more than 50% and showed cytotoxic action against the ovarian cancer cell line OVCAR-4. Results: A series of novel indazole-indolizine hybrids were synthesized via a [3+2] cycloaddition reaction, fully characterized and biologically evaluated for antitumor potential. Conclusion: Compound 4a could be a promising starting point in the development of new antitumoral agents. Further biological investigations will be performed to identify the biological target of the compounds. Moreover, different synthetic strategies to introduce new substituents on the indolizine core will be addressed.

Non-Ionic Peterson-Type Olefination Reactivity and its Use in a Silicon-Promoted Carbonyl-Carbonyl Cross Coupling Reaction.

The [2+2] cycloaddition reaction between the Si=C double bond of adamantylsilene and the carbonyl group of aliphatic, aromatic or acetylenic ketones and aldehydes is demonstrated. The product of this reaction that is central to a non-ionic version of the Peterson olefination is an unusual four-membered 1,2-silaoxetane heterocycle that was characterized spectroscopically and crystallographically. In the presence of SiO2, the silaoxetane undergoes retro-cycloaddition with the formation of alkene products. As the [2+2] cycloaddition proceeds without the necessity of any base, enolizable ketones can be converted into olefins. In addition, it is shown that the adamantylsilene can be produced in situ by a sila-Peterson reaction, providing valuable input for the development of a new one-pot silicon-based reductive carbonyl-carbonyl cross coupling methodology.

1,2‐Diaza‐1,3‐Dienes as a Multifaceted Synthons for the Synthesis of Heterocycles: A Fifteen‐Years Update

AbstractThe discovery of structurally unique scaffolds entities with increased complexity and balanced physicochemical properties has the potential to allow synthetic chemists to exploit areas of chemical space that were previously inaccessible. Among the different strategies employed for generating N‐heterocycles, cyclization and cycloaddition reactions represent a valuable synthetic tool. The purpose of this minireview is to summarize the recent advances (2009‐present) from our laboratory on the generation of intriguing five‐, six‐ and seven‐membered mono‐ or poly‐heterocyclic architectures (linear, fused and spiro) employing 1,2‐diaza‐1,3‐dienes (DDs) as key synthons.

Construction of Dihydropyrano[2,3‐c]pyrazolone via Photo‐induced Wolff Rearrangement/Chiral Isothiourea Catalyzed [4+2] Cyclization Reaction

AbstractA photoinduced Wolff rearrangement/chiral isothiourea catalyzed [4+2] cycloaddition reaction of pyrazolone derivatives and α‐diazoketones was developed, affording the corresponding dihydropyrano[2,3‐c]pyrazolone derivatives in moderate to good yields (50–94 %) with satisfactory to excellent diastereoselectivities (&gt;20 : 1 dr, in almost all cases) and enantioselectivities of 31–99 %. This protocol features readily available substrates, mild reaction conditions, and effective construction of vicinal tertiary and quaternary carbon stereocenters.