Copper-Catalyzed Azide–Alkyne Cycloaddition (CuAAC) by Functionalized NHC-Based Polynuclear Catalysts: Scope and Mechanistic Insights

A phthalimide-triazole derivative obtained by click chemistry exhibits trypanocidal activity, induces autophagy and ameliorates Trypanosoma cruzi infection

Chagas disease (CD), caused by Trypanosoma cruzi, remains a leading cause of cardiomyopathy and heart failure in Latin America. Since the 1970s, benznidazole (BNZ) and nifurtimox (NFX) have been the only chemotherapeutic agents used to treat CD. However, their toxicity and low effectiveness in the chronic phase of the disease, make the development of more efficient chemotherapeutics imperative. Here, we investigated the effects of 1,2,3-triazole hybrids, synthesized via click chemistry, containing either phthalimide (FT1, FT2, FT3, FT4) or naphthoquinone (NT1) moieties on T. cruzi and their cytotoxicity on mammalian cells. NT1 and FT1 were the most effective against intracellular parasite with an IC50 = 31.1 and 189.2 µM, respectively. FT1-FT4 showed low cytotoxicity to mammalian cells (CC50 > 754 µM), while NT1 exhibited moderate toxicity (CC50 ≥ 96.1 µM). FT1 demonstrated the highest selectivity towards trypomastigotes and amastigotes with selectivity indexes (SeI) of 6.9 and 6.7, respectively. Ultrastructural analysis of trypomastigotes treated with FT1 revealed mitochondrial alterations, lipid accumulation and Golgi complex disorganization. FT1 also decreased the mitochondrial membrane potential, increased mitochondrial reactive oxygen species (ROS) production, and induced late apoptosis in trypomastigotes. In infected cardiac cells, FT1 treatment led to degradation of amastigotes and Golgi disruption. An increase in autophagosomes in treated host cells and their interaction with intracellular parasites suggest that FT1-induced host cell autophagy may play a role in mitigating the infection and protecting cardiac cells from its deleterious effects.

Flavanone-enabled CuAAC Reaction: Noninnocent Reagents Driving a Mononuclear Mechanism Over the Dinuclear Paradigm

In this work, we report the use of the CuAAC (copper-catalyzed azide-alkyne cycloaddition) reaction to obtain different triazole derivatives bridged to the naringenin skeleton, leading to the combination of a triazole pharmacophoric group with a bioactive flavanone. The generation of Cu(I) active species was done using CuSO4 salts and sodium ascorbate, resulting in moderate to high yields when the DMSO-water binary system was used as solvents. Mechanistic studies were done using density functional theory calculations and high-resolution mass spectrometry (HRMS). We investigated the reduction process of Cu(II) to Cu(I), and the role of mononuclear and dinuclear copper species in the catalysis of the cycloaddition reaction. Our combined theoretical and experimental results indicate that the mechanism involving a single copper species is taking place, with the cycloaddition step being the rate-determining step. The calculations indicate that the mechanism involving two copper species has the deprotonation of the coordinated terminal alkyne as the rate-determining step.

Design and development of a copper-manganese oxide nanocatalyst for the sustainable synthesis of 1,4-disubstituted 1,2,3-triazoles

Designing heterogeneous nanocatalysts comprising abundantly available transition metals for various organic transformations has captured significant interest in recent years owing to their convenient separation, reusability and low metal contamination after the reaction. Herein, we report the design and synthesis of CuO@MnO2 nanocomposites using malachite, which is a renewable copper precursor with an E-factor of 1.64. The as-prepared CuO@MnO2 nanocomposites were well characterized through field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (pXRD), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller techniques (BET). The catalytic efficiency of CuO@MnO2 nanocomposites was explored for the synthesis of 1,4-disubstituted 1,2,3-triazoles from phenylacetylene, benzyl bromide and sodium azide under neat conditions. The sustainability of the present methodology was explored by evaluating green chemistry metrics such as the E-factor (0.84), reaction mass efficiency (54.45%), process mass intensity (1.84) and turnover number (901).

Stable Cu (I) Complexes for Intracellular Cu-Catalyzed Azide Alkyne Cycloaddition

The copper-catalyzed azide-alkyne cycloaddition (CuAAC) has heralded a new era of chemical biology and biomedicine. However, caveats of the CuAAC include formation of reactive oxygen species (ROS) and other copper-related toxicity. This limits utility in sensitive biological samples and matrices. Towards addressing these caveats, we synthesized and fully characterized two air and water stable trinuclear Cu(I) dimer complexes. The complexes were stable to oxidation in the presence of hydrogen peroxideand other chelators, which was reasoned to be due to the linear benzimidazole-Cu-benzimidazole geometry. Computational investigations of the catalytic cycle implicated two of the three coppers in the trimer complex as the active metal centers. The complexes were shown to catalyze the reaction at far below sub-toxic concentrations for intracellular click reactions to label triple negative breast cancer cells and compared to the current CuSO4-THPTA standard.

DNA-amphiphilic nanostructures: synthesis, characterization and applications

DNA's extraordinary potential reaches far beyond its role as a carrier of genetic information. It serves as a remarkably adaptable structural foundation for constructing intricate nanostructures with a diverse range of functionalities. This inherent programmability sets DNA apart from other biomolecules like peptides, proteins, and small molecules. By covalently attaching DNA to synthetic hydrophobic moieties, researchers create DNA amphiphiles capable of interacting with artificial lipid bilayers and cell membranes. These hybrid structures have rapidly gained prominence due to their promising potential in the medical field. This review provides a comprehensive overview of the latest advancements in the synthesis of DNA amphiphiles and their assembly into well-defined nanostructures. It explores the diverse applications of these nanostructures across various medical domains, including targeted drug delivery, innovative immunotherapies, and gene-silencing techniques. Moreover, the review delves into the current challenges and prospects of this rapidly evolving field, highlighting the potential of DNA hybrid materials to revolutionize medical treatments and diagnostics. By addressing the limitations and exploring new avenues of research, scientists aim to unlock the full potential of DNA nanotechnology for the benefit of human health.

Assessing the catalytic potential of novel halogen substituted carbene NHC (F, Cl, Br, I) catalysts in [3 + 2] cycloaddition reactions: A computational investigation

This study investigated the catalytic behavior of NHC-X ligands (X = F, Cl, Br, I) in cycloaddition reactions, focusing on both mononuclear and binuclear pathways. Using NCI (noncovalent interaction), RDG (reduced density gradient), ELF (electron localization function), and LOL (localized orbital locus) computational analyses, the electronic interactions and stability of the ligands were examined. The results showed that NHC-Cl exhibited the least steric hindrance and strongest transition state stabilization, making it the most efficient catalyst. NHC-F also demonstrated strong stabilization, particularly in the binuclear pathway. In contrast, NHC-Br showed moderate efficiency, whereas NHC-I was the least effective owing to higher Gibbs free energy values and greater steric hindrance, especially in polar solvents such as water and acetonitrile. This study emphasizes the crucial role of solvent effects and thermodynamic factors in influencing the catalytic efficiency. These findings provide a framework for optimizing NHC-based catalysts for chemical transformations.

Synthesis of chiral Cu(II) complexes from pro-chiral Schiff base ligand and investigation of their catalytic activity in the asymmetric synthesis of 1,2,3-triazoles

A pro-chiral Schiff base ligand (HL) was synthesized by the reaction of 2-amino-2-ethyl-1,3-propanediol and pyridine-2-carbaldehyde in methanol. The reaction of HL with CuCl2·2H2O and CuBr2 in methanol gave neutral mononuclear Cu(II) complexes with general formula of [Cu(HL)Cl2] (1) and [Cu(HL)Br2] (2), respectively. By slow evaporation of the methanolic solutions of 1 and 2, their enantiomers were isolated in crystalline format. The formation of pure chiral crystals in the racemic mixture was amply authenticated by single crystal X-ray analysis, which indicated that S-[Cu(HL)Cl2], R-[Cu(HL)Cl2], and S-[Cu(HL)Br2] are crystallized in chiral P212121 space group of orthorhombic system. Preferential crystallization was used to isolate the R and S enantiomers as single crystals and the isolated compounds were also studied by CD analysis. Structural studies indicated that the origin of the chirality in these compounds is related to the coordination mode of the employed pro-chiral ligand (HL) because one of its carbon atoms has been converted to a chiral center in the synthesized complexes. Subsequently, these complexes were used in click synthesis of a β-hydroxy-1,2,3-triazole and the results of catalytic studies indicated that 1 and 2 can act as enantioselective catalysts for the asymmetric synthesis of β-hydroxy-1,2,3-triazole product under mild condition. This study illustrates the significant capacity of the use of pro-chiral ligands in preparing chiral catalysts based on complexes which can also be considered as an effective approach to cheap chiral catalysts from achiral reagents.

Synthesis and Application of Task-Specific Bimetal-Organic Frameworks in the Synthesis of Biological Active Spiro-Oxindoles

The use of click chemistry as a smart and suitable method for the development of new heterogeneous catalysts is based on metal-organic frameworks as well as the production of organic compounds. The development of the click chemistry method can provide a new strategy to achieve superior properties of MOFs. Here, the two metals Co and Fe are used to create a bimetallic-organic framework. In the following, the click chemistry and postmodification method are well organized and an acidic heterogeneous porous catalyst is developed. This prepared catalyst was used as a highly efficient catalyst for the preparation of new spiro-oxindoles obtained through click chemistry with good to excellent yields (80-94%). This presented catalytic system can compete with the best reported catalytic systems. The findings showed that the presence of Co and Fe metals in the MOF, and the presence of the triazole ring on the catalyst, can increase the catalytic efficiencies. This study offers novel insights into the architecture of Metal-Organic Frameworks (MOFs), click chemistry, and biologically active compounds. Additionally, the research explores the antibacterial properties of the synthesized spiro-oxindoles and catalysts. The findings reveal significant antibacterial activities of the synthesized compounds against S. aureus, MRSA, and E. coli bacteria.

Development of Essential Oil Delivery Systems by 'Click Chemistry' Methods: Possible Ways to Manage Duchenne Muscular Dystrophy

Recently, rare diseases have received attention due to the need for improvement in diagnosed patients' and their families' lives. Duchenne muscular dystrophy (DMD) is a rare, severe, progressive, muscle-wasting disease. Today, the therapeutic standard for treating DMD is corticosteroids, which cause serious adverse side effects. Nutraceuticals, e.g., herbal extracts or essential oils (EOs), are possible active substances to develop new drug delivery systems to improve DMD patients' lives. New drug delivery systems lead to new drug effects, improved safety and accuracy, and new therapies for rare diseases. Herbal extracts and EOs combined with click chemistry can lead to the development of safer treatments for DMD. In this review, we focus on the need for novel drug delivery systems using EOs as the therapy for DMD and the potential use of click chemistry for drug delivery systems. New EO complex drug delivery systems may offer a new approach for improving muscle conditions and mental health issues associated with DMD. However, further research should identify the potential of these systems in the context of DMD. In this review, we discuss possibilities for applying EOs to DMD before implementing expensive research in a theoretical way.

Application of N-heterocyclic carbene-Cu(I) complexes as catalysts in organic synthesis: a review

N-Heterocyclic carbenes (NHCs) are a special type of carbenes in which the carbene carbon atom is part of the nitrogen heterocyclic ring. Due to the simplicity of their synthesis and the modularity of their stereoelectronic properties, NHCs have unquestionably emerged as one of the most fascinating and well-known species in chemical science. The remarkable stability of NHCs can be attributed to both kinetic as well as thermodynamic effects caused by its structural features. NHCs constitute a well-established class of new ligands in organometallic chemistry. Although initially NHCs were regarded as pure σ-donor ligands, later experimental and theoretical studies established the presence of a significant back donation from the d-orbital of the metal to the π* orbital of the NHC. Over the last two decades, NHC-metal complexes have been extensively used as efficient catalysts in different types of organic reactions. Of these, NHC-Cu(I) complexes found prominence for various reasons, such as ease of preparation, possibility of structural diversity, low cost, and versatile applications. This article overviews applications of NHC-Cu(I) complexes as catalysts in organic synthesis over the last 12 years, which include hydrosilylation reactions, conjugate addition, [3 + 2] cycloaddition, A3 reaction, boration and hydroboration, N-H and C(sp2)-H carboxylation, C(sp2)-H alkenylation and allylation, C(sp2)-H arylation, C(sp2)-H amidation, and C(sp2)-H thiolation. Preceding the section of applications, a brief description of the structure of NHCs, nature of NHC-metal bond, and methods of preparation of NHC-Cu complexes is provided.

Tetracopper(I) thiolate- and amido-(SNS) complexes and copper-catalyzed azide-alkyne cycloaddition in water

Two tetranuclear Cu(I) complexes bearing thiolate- and amido-SNS ligands were characterized by X-ray diffraction and mass spectrometry. Although the amido ligand undergoes irreversible N-protonation by the copper-bound alkyne, the thiolate complex demonstrates good activity in the copper-catalyzed azide-alkyne cycloaddition reaction with a variety of substrates. The base-free reactions are performed in water and afford excellent yields over 2 h at 70 °C. DFT calculations suggest a proton-shuttle role for the thiolate donor in formation of the initial dicopper σ,π-alkynyl intermediate.

Investigation of 1,4-Substituted 1,2,3-Triazole Derivatives as Antiarrhythmics: Synthesis, Structure, and Properties

Here, we investigated the reaction of 1,3-dipolar cycloaddition of 1,3-diazido-2-nitro-2- azapropane (DANP) to propargyl alcohol over a copper-based catalyst and identified the optimum reaction conditions that enable the synthesis of 2-nitro-1,3-bis(4,4'-dihydroxymethyl)-1,2,3-triazolyl-2-azapropane (1) in more than 84% yield. The reaction between DANP, 1,5-diazido-3-nitrazapentane, and phenylacetylene produced the respective 1,2,3-triazole derivatives in 83% and 71% yields, respectively. The structures of the resultant compounds were validated by infrared and NMR spectroscopies and elemental analysis. The structure of 1 was proved by single-crystal X-ray diffraction. This study demonstrated that 1 exhibits a dose-dependent antiarrhythmic activity towards calcium-chloride-induced arrhythmia and refers to Class III: moderately hazardous substances.