Copper-catalyzed Azide Alkyne Research Articles

Chromene-dihydropyrimidinone and xanthene-dihydropyrimidinone hybrids: design, synthesis, and antibacterial and antibiofilm activities

A series of chromene-dihydropyrimidinone and xanthene-dihydropyrimidinone hybrid compounds were easily synthesized through a multicomponent reaction followed by the copper-catalyzed alkyne–azide cycloaddition reaction.

CuAAC-methacrylate interpenetrating polymer network (IPN) properties modulated by visible-light photoinitiation.

Interpenetrating polymer networks (IPNs) are a class of materials with interwoven polymers that exhibit unique blended or enhanced properties useful to a variety of applications, ranging from restorative protective materials to conductive membranes and hydrophobic adhesives. The IPN formation kinetics can play a critical role in the development of the underlying morphology and in turn the properties of the material. Dual photoinitiation of copper-catalyzed azide-alkyne (CuAAC) and radical mediated methacrylate polymerization chemistries enable the manipulation of IPN microstructure and properties by controlling the kinetics of IPN formation via the intensity of the initiating light. Specifically, azide and alkyne-based polyethylene glycol monomers and tetraethylene glycol dimethacrylate (TEGDMA) were polymerized in a single pot to form IPNs and the properties were evaluated as a function of the photoinitiating light intensity. Morphological differences as a function of intensity were observed in the IPNs as determined by thermomechanical properties and phase-contrast imaging in tapping mode atomic force microscopy (AFM). At moderate intensities (20 mW/cm2) of visible light (470 nm), the TEGDMA polymerization gels first and therefore forms the underlying network scaffold. At low intensities (0.2 mW/cm2), the CuAAC polymerization can gel first. The ability to switch sequence of gelation and IPN trajectory (simultaneous vs. sequential), affords control over phase separation behavior. Thus, light not only allows for spatial and temporal control over the IPN formation but also provides control over their thermomechanical properties, representing a route for facile IPNs design, synthesis, and application.

Synthesis and Phytotoxic Evaluation of Isatin Derivatives Supported by 3D-QSAR Study.

Concerned about weed infestation, a major threat to food production and herbicide resistance that interferes in the mechanism of action of the main herbicides, we have synthesized eight isatin derivatives using the "Click Chemistry" approach through copper-catalyzed azide-alkyne cycloadditions (CuAAC). Sixteen isatin derivatives were evaluated for their phytotoxic activity against the seed culture of the model plants, Lactuca sativa and Allium cepa. Six of them showed phytotoxic activity similar to the positive control, trifluralin. Hypocotyl length measurement analysis in L. sativa revealed that triazole derivative 8 is more active than trifluralin. For A. cepa, root length measurement analyses revealed that 3, 10, 14, 16, and 17 were similar to the positive control trifluralin. Three-dimensional quantitative structure-activity relationship (3D-QSAR) comparative molecular field analysis (CoMFA) model construction using the acetolactate synthase (ALS) crystallographic structure displayed pki values of predicted inhibitory activity and contour maps revealing sterically bulky groups for 11, the CF3 group in ortho, and for 17, Br in ortho, favoring the inhibitory ALS activity.

“Copper catalyzed azide alkyne cycloaddition” based synthesis and applications of oligo-1, 2, 3-triazoles connected by suitable building blocks and “N-(CH)n-C” linked triazole oligomers

“Copper catalyzed azide alkyne cycloaddition” based synthesis and applications of oligo-1, 2, 3-triazoles connected by suitable building blocks and “N-(CH)n-C” linked triazole oligomers

Response to Comment on "Following Molecular Mobility during Chemical Reactions: No Evidence for Active Propulsion" and "Molecular Diffusivity of Click Reaction Components: The Diffusion Enhancement Question".

In their Comment (DOI: 10.1021/jacs.2c02965) on two related publications by our groups (J. Am. Chem. Soc. 2021, 143, 20884-20890; DOI: 10.1021/jacs.1c09455) and another (J. Am. Chem. Soc. 2022, 144, 1380-1388; DOI: 10.1021/jacs.1c11754), Huang and Granick discuss the diffusion NMR measurements of molecules during a copper-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reaction. Here we respond to these comments and maintain that no diffusion enhancement was observed for any species during the reaction. We show that the relaxation agent does not interfere with the CuAAC reaction kinetics nor the diffusion of the molecules involved. Similarly, the gradient pulse length and diffusion time do not affect the diffusion coefficients. Peak overlap was completely removed in our study with the use of hydrazine as the reducing agent. The steady-state assumption does not hold for these diffusion measurements that take several minutes, which is the reason monotonic gradient orders are not suitable. Finally, we discuss the other reactions where similar changes in diffusion have been claimed. Our conclusions are fully supported by the results represented in our original JACS Article and the corresponding Supporting Information.

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

Copper(I) [Cu2(μ-Br)2(tBuImCH2pyCH2L)]n (L = OMe, NEt2, NHtBu) compounds supported by flexible functionalized NHC-based polydentate ligands have been prepared in a one-pot procedure by reacting the corresponding imidazolium salt with an excess of copper powder and Ag2O. An X-ray diffraction analysis has revealed that [Cu2(μ-Br)2(tBuImCH2pyCH2NEt2)]n is a linear coordination polymer formed by bimetallic [Cu(μ-Br)]2 units linked by the lutidine-based NHC-py-NEt2 ligand, which acts as a heteroditopic ligand with a 1κC-2κ2N,N′ coordination mode. We propose that the polymeric compounds break down in the solution into more compact tetranuclear [Cu2(μ-Br)2(tBuImCH2pyCH2L)]2 compounds with a coordination mode identical to the functionalized NHC ligands. These compounds have been found to exhibit high catalytic activity in the Cu-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. In particular, [Cu2(μ-Br)2(tBuImCH2pyCH2NEt2)]2 efficiently catalyzes the click reaction of a range of azides and alkynes, under an inert atmosphere at room temperature in neat conditions at a very low catalyst loading, to quantitatively afford the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in a few minutes. The cycloaddition reaction of benzyl azide to phenylacetylene can be performed at 25–50 ppm catalyst loading by increasing the reaction time and/or temperature. Reactivity studies have shown that the activation of the polynuclear catalyst precursor involves the alkyne deprotonation by the NHC moiety of the polydentate ligand to afford a copper(I)-alkynyl species bearing a functionalized imidazolium ligand. DFT calculations support the participation of the dinuclear species [(CuBr)2(μ-tBuImCH2pyCH2NEt2)], resulting from the fragmentation of the tetranuclear compound, as the catalytically active species. The proposed reaction pathway proceeds through zwitterionic dinuclear intermediates and entails the active participation of both copper atoms, as well as the NHC moiety as an internal base, which activates the reacting alkyne via deprotonation.

CS@Cu2O and magnetic Fe3O4@SiO2-pAMBA-CS-Cu2O as heterogeneous catalysts for CuAAC click reaction

The recovery of agricultural and food wastes are one of the main areas of current research for optimal biowaste management to reduce greenhouse gas (GHG) emissions that are generated when it is not properly treated. Corn silk (CS) as biowaste from the agricultural sector is a rich source of natural compounds especially polysaccharides. We present here a chemical activation method to convert CS to values added heterogeneous catalyst for the synthesis of triazoles compounds via copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction. For this purpose, cuprous oxide coated CS ([email protected]2O) and multifunctional Fe3O4@SiO2–para-aminomethyl benzoic acid–CS–Cu2O composite (denoted as Fe3O4@SiO2‐pAMBA-CS‐Cu2O) were fabricated. Different analytical techniques have been used to describe the size, crystal structure, elemental composition and other physical properties of the fabricated catalysts. These heterogeneous catalysts showed excellent catalytic activities for the synthesis of 1,4-disubstituted-1,2,3-triazoles via click reaction in H2O at 70 °C under base and external-reductant-free conditions. The magnetic properties of the catalyst allowed easy separation after reaction by simply applying an external magnet. Other advantages of this work are the recyclability of the catalyst, the absence of reducing agent and base, besides utilisation of bio wastes for the production of heterogeneous catalyst.

Design, Synthesis and In Vitro Anticancer Activity of Benzo[c]chromen-6- one-linked 1,2,3-Triazole

Background: The 1,2,3-triazole hybrids and conjugates containing natural or related compounds motif demonstrate diverse biological activities, including anticancer, antimicrobial, antitubercular, antiviral, antidiabetic, antimalarial, anti-leishmanial, and neuroprotective ones. Among a wide range of pharmacological applications, considerable attention is paid to the study of anticancer activity. In anticancer research, combining 1,2,3-triazole with other motifs, previously demonstrating antiproliferative activity into one hybrid molecule, is a common strategy for the creation of new bioactive molecules. The CuAAC (copper-catalyzed azide–alkyne cycloaddition) is a very convenient reaction for the rapid construction of drug-like 1,2,3-triazoles at room temperature in a short time. Methods: Based on the pharmacophore strategy, a virtual combinatorial library of benzo[c]chromen-6- one linked 1,2,3-triazole derivatives was designed and lead-likeness and molecular analysis were performed. Selected compounds were synthesized via CuAAC click reaction and the chemical structures of all new 1,2,3-triazole hybrids were proved by 1H, 13C NMR, MS and elemental analyses. Their anticancer activity in the human cancer cell lines was evaluated using the MTT assay. Results: A virtual in silico screening of novel benzo[c]chromen-6-one linked 1,2,3-triazole was carried out in order to discover potential antitumor agents. The synthesis of promising compounds was carried out via СuAAC reaction, and their antineoplastic action was studied on human tumor cells of HL-60, HCT116, HCT116 p53-/-, Skov3, U251, MDA231 lines. Their cytotoxic effect towards pseudo-normal human cells of HaCaT line was also evaluated. 2-((1H-1,2,3-triazol-4-yl)methoxy)-6H-benzo[c]chromen- 6-one (4c) with pyridin-3-yl substituent demonstrated the highest antiproliferative action in vitro (IC50 79.5 μM) towards human leukemia cells of HL-60 line, while all tested compounds at >100 μM concentration were tolerant for non-tumor human keratinocytes of HaCaT line. Conclusion: A novel benzo[c]chromen-6-one linked 1,2,3-triazoles exhibiting promising in vitro anticancer activity and low toxicity were designed. This study suggests new scaffolds for the development of anti-cancer drugs, which could be easily further optimized via the convenient synthetic procedure.

Click amidations, esterifications and one–pot reactions catalyzed by Cu salts and multimetal–organic frameworks (M–MOFs)

Amides and esters are prevalent chemicals in Nature, industry and academic laboratories. Thus, it is not surprising that a plethora of synthetic methods for these compounds has been developed along the years. However, these methods are not 100% atom economical and generally require harsh reagents or reaction conditions. Here we show a “spring–loaded”, 100% atom–efficient amidation and esterification protocol which consists in the ring opening of cyclopropenones with amines or alcohols. Some alkyl amines react spontaneously at room temperature in a variety of solvents and reaction conditions, including water at different pHs, while other alkyl amines, aromatic amines and alcohols react in the presence of catalytic amounts of simple Cu2+ salts or solids. A modular reactivity pattern (alkyl amines >> alkyl alcohols >> phenols >> aromatic amines) enables to design orthogonal and one–pot reactions on well–defined catalytic Multimetal–Organic Frameworks (M–MOFs, M= Cu, Ni, Pd), to easily functionalize the resulting cinnamides and cinnamic esters to more complex molecules. The strong resemblance of the amidation and esterification reaction conditions here reported with the copper–catalyzed azide–alkyne cycloaddition (CuAAC) allows to define this fast, clean and flexible protocol as a click reaction.

Covalent Attachment of Aggregation-Induced Emission Molecules to the Surface of Ultrasmall Gold Nanoparticles to Enhance Cell Penetration.

Three different alkyne-terminated aggregation-induced emission molecules based on a para-substituted di-thioether were attached to the surface of ultrasmall gold nanoparticles (2 nm) by copper-catalyzed azide–alkyne cycloaddition (click chemistry). They showed a strong fluorescence and were well water-dispersible, in contrast to the dissolved AIE molecules. The AIE-loaded nanoparticles were not cytotoxic and easily penetrated the membrane of HeLa cells, paving the way for an intracellular application of AIE molecules, e.g., for imaging.

Anomeric 1,2,3-triazole-linked sialic acid derivatives show selective inhibition towards a bacterial neuraminidase over a trypanosome trans-sialidase.

Sialic acid is the natural substrate for sialidases and its chemical modification has been a useful approach to generate potent and selective inhibitors. Aiming at advancing the discovery of selective Trypanosoma cruzi trans-sialidase (TcTS) inhibitors, we have synthesised a small series of anomeric 1,2,3-triazole-linked sialic acid derivatives in good yields and high purity via copper-catalysed azide–alkyne cycloaddition (CuAAC, click chemistry) and evaluated their activity towards TcTS and neuraminidase. Surprisingly, the compounds showed practically no TcTS inhibition, whereas ca. 70% inhibition was observed for neuraminidase in relation to the analogues bearing hydrophobic substituents and ca. 5% for more polar substituents. These results suggest that polarity changes are less tolerated by neuraminidase due to the big difference in impact of hydrophobicity upon inhibition, thus indicating a simple approach to differentiate both enzymes. Moreover, such selectivity might be reasoned based on a possible steric hindrance caused by a bulky hydrophobic loop that sits over the TcTS active site and may prevent the hydrophobic inhibitors from binding. The present study is a step forward in exploiting subtle structural differences in sialidases that need to be addressed in order to achieve selective inhibition.

Rapid Access to Ironomycin Derivatives by Click Chemistry.

Salinomycin, a natural carboxylic polyether ionophore, shows a very interesting spectrum of biological activities, including selective toxicity toward cancer stem cells (CSCs). Recently, we have developed a C20-propargylamine derivative of salinomycin (ironomycin) that exhibits more potent activity in vivo and greater selectivity against breast CSCs compared to the parent natural product. Since ironomycin contains a terminal alkyne motif, it stands out as being an ideal candidate for further functionalization. Using copper-catalyzed azide–alkyne cycloaddition (CuAAC), we synthesized a series of 1,2,3-triazole analogs of ironomycin in good overall yields. The in vitro screening of these derivatives against a well-established model of breast CSCs (HMLER CD24low/CD44high) and its corresponding epithelial counterpart (HMLER CD24high/CD44low) revealed four new products characterized by higher potency and improved selectivity toward CSCs compared to the reference compound ironomycin. The present study highlights the therapeutic potential of a new class of semisynthetic salinomycin derivatives for targeting selectively the CSC niche and highlights ironomycin as a promising starting material for the development of new anticancer drug candidates.

Molecular Diffusivity of Click Reaction Components: The Diffusion Enhancement Question.

Micrometer-sized objects are widely known to exhibit chemically driven motility in systems away from equilibrium. Experimental observation of reaction-induced motility or enhancement in diffusivity at the much shorter length scale of small molecules is, however, still a matter of debate. Here, we investigate the molecular diffusivity of reactants, catalyst, and product of a model reaction, the copper-catalyzed azide–alkyne cycloaddition click reaction, and develop new NMR diffusion approaches that allow the probing of reaction-induced diffusion enhancement in nanosized molecular systems with higher accuracy than the state of the art. Following two different approaches that enable the accounting of time-dependent concentration changes during NMR experiments, we closely monitored the diffusion coefficient of reaction components during the reaction. The reaction components showed distinct changes in the diffusivity: while the two reactants underwent a time-dependent decrease in their diffusivity, the diffusion coefficient of the product gradually increased and the catalyst showed only slight diffusion enhancement within the range expected for reaction-induced sample heating. The decrease in diffusion coefficient of the alkyne, one of the two reactants of click reaction, was not reproduced during its copper coordination when the second reactant, azide, was absent. Our results do not support the catalysis-induced diffusion enhancement of the components of the click reaction and, instead, point to the role of a relatively large intermediate species within the reaction cycle with diffusivity lower than that of both the reactants and product molecule.

Copper(II)-Bis-Cyclen Intercalated Graphene Oxide as an Efficient Two-Dimensional Nanocomposite Material for Copper-Catalyzed Azide-Alkyne Cycloaddition Reaction.

We report stable and heterogeneous graphene oxide (GO)–intercalated copper as an efficient catalyst for the organic transformations in green solvents. The GO-intercalated copper(II) complex of bis(1,4,7,10-tetraazacyclododecane) [Cu(II)-bis-cyclen] was prepared by a facile synthetic approach with a high dilution technique. The as-prepared GO-Cu(II)-bis-cyclen nanocomposite was used as a click catalyst for the 1,3 dipolar Huisgen cycloaddition reaction of terminal alkyne and azide substrates. On directing a great deal of attention toward the feasibility of the rapid electron transfer rate of the catalyst in proliferating the yield of 1,2,3-triazole products, the click catalyst GO-Cu(II)-bis-cyclen nanocomposite was designed and synthesized via non-covalent functionalization. The presence of a higher coordination site in an efficient 2D nanocomposite promotes the stabilization of Cu(I) L-acetylide intermediate during the catalytic cycle initiated by the addition of reductants. From the XRD analysis, the enhancement in the d-interlayer spacing of 1.04 nm was observed due to the intercalation of the Cu(II)-bis-cyclen complex in between the GO basal planes. It was also characterized by XPS, FT-IR, RAMAN, UV, SEM, AFM, and TGA techniques. The recyclability of the heterogeneous catalyst [GO-Cu(II)-cyclen] with the solvent effect has also been studied. This class of GO-Cu(II)-bis-cyclen nanocomposite paves the way for bioconjugation of macromolecules through the click chemistry approach.

Large-scale synthesis of Notum inhibitor 1-(2,4-dichloro-3-(trifluoromethyl)-phenyl)-1H-1,2,3-triazole (ARUK3001185) employing a modified Sakai reaction as the key step.

1-Phenyl-1H-1,2,3-triazole 1 (ARUK3001185) was prepared on large scale from aniline 4 by application of both (1) a copper catalyzed azide–alkyne cycloaddition (CuAAC) with (trimethylsilyl)acetylene, and (2) a Clark modification of the Sakai reaction. The one-pot Sakai–Clark method with (MeO)2CHCH Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> NNHTos (2b) proved to be superior as it was operationally simple, metal-free, and avoided the use of aryl azide 7. The Sakai–Clark method has been reliably performed on large scale to produce >100 g of 1 in good efficiency and high purity.

Uniform wrapping of copper(I) oxide nanocubes by self-controlled copper-catalyzed azide-alkyne cycloaddition toward selective carbon dioxide electrocatalysis.

Copper(I) oxide nanocubes were wrapped with an extremely uniform organic layer grown by self-controlled, Cu-mediated catalysis. This layer aided in retaining the initial cubic structure of the copper nanocubes during their use as a CO2 reduction electrocatalyst, resulting in high CO2 reduction selectivity by strong suppression of hydrogen evolution because of exclusion of water from the surface.

Silencing of proinflammatory NF-κB and inhibition of herpes simplex virus (HSV) replication by ultrasmall gold nanoparticles (2 nm) conjugated with small-interfering RNA.

Azide-terminated ultrasmall gold nanoparticles (2 nm gold core) were covalently functionalized with alkyne-terminated small-interfering siRNA duplexes by copper-catalyzed azide-alkyne cycloaddition (CuAAC; click chemistry). The nanoparticle core was visualized by transmission electron microscopy. The number of attached siRNA molecules per nanoparticle was determined by a combination of atomic absorption spectroscopy (AAS; for gold) and UV-Vis spectroscopy (for siRNA). Each nanoparticle carried between 6 and 10 siRNA duplex molecules which corresponds to a weight ratio of siRNA to gold of about 2.2 : 1. Different kinds of siRNA were conjugated to the nanoparticles, depending on the gene to be silenced. In general, the nanoparticles were readily taken up by cells and highly efficient in gene silencing, in contrast to free siRNA. This was demonstrated in HeLa-eGFP cells (silencing of eGFP) and in LPS-stimulated macrophages (silencing of NF-κB). Furthermore, we demonstrated that nanoparticles carrying antiviral siRNA potently inhibited the replication of Herpes simplex virus 2 (HSV-2) in vitro. This highlights the strong potential of siRNA-functionalized ultrasmall gold nanoparticles in a broad spectrum of applications, including gene silencing and treatment of viral infections, combined with a minimal dose of gold.

1,5-Benzodiazepines as a platform for the design of carbonic anhydrase inhibitors.

A series of novel N-triazolo-benzene sulfonamides-1,5-benzodiazepines 9a-d and 10d were designed and prepared through the copper-catalyzed azide alkyne cycloaddition click chemistry procedure, reacting the N1 -propargyl-1,5-benzodiazepine 2 and the N1 ,N5 -dipropargyl analog 6 with various benzene sulfonamide azides 8a-d. The synthesized compounds were found to show nanomolar affinity toward relevant isoforms of human carbonic anhydrase such as hCA I, II, IV, VII, IX, and XII. The divalent derivative 10d showed a particularly high inhibitory activity against all hCA isoforms when compared with acetazolamide, and showed potent multivalent effects, better than reported previously for divalent CA inhibitors.

Optimized Production of Fc Fusion Proteins by Sortase Enzymatic Ligation.

Fc fusions are a growing class of drugs comprising an antibody Fc domain covalently linked to a protein or peptide and can pose manufacturing challenges. In this study we evaluated three synthetic approaches to generate Fc fusions, using Fc-insulin as a model drug candidate. Engineered human IgG1 was digested with HRV3C to produce an Fc fragment with a C-terminal sortase tag (Fc-LPETGGH6). The synthesis of Fc-insulin2 from Fc-LPETGGH6 was evaluated with direct sortase-mediated ligation (SML) and two chemoenzymatic strategies. Direct SML was performed with triglycine-insulin, and chemoenzymatic strategies used to SML fuse either triglycine-azide or triglycine-DBCO prior to linking insulin with copper-catalyzed or strain-promoted azidealkyne cycloaddition. Reaction conditions were optimized by evaluating reagent concentrations, relative equivalents, temperature, and time. Direct SML provided the most effective reaction yields, converting 60-70% of Fc-LPETGGH6 to Fc-insulin2, whereas our optimized chemoenzymatic synthesis converted 30-40% of Fc-LPETGGH6 to Fc-insulin2. Here we show that SML is a practical and efficient method to synthesize Fc fusions and provide an optimized pathway for fusion drug synthesis.

Chitin Deacetylase as a Biocatalyst for the Selective N-Acylation of Chitosan Oligo- and Polymers

Chitosans, derived from the abundant natural resource chitin, are among the most versatile and promising functional biopolymers due to their unique physicochemical properties and biological activities. These can be further improved or modified by various functionalizations, targeting both the hydroxy and amino groups. However, the chemical routes used for functionalization typically use harsh chemicals, increasing the ecological footprint of the products, tend to yield low degrees of substitution, and often lack chemoselectivity. We here report on an alternative, biocatalytic route of chitosan N-acylation using a recombinant chitin deacetylase (CDA). These enzymes are known for their ability to chemo- and regioselectively N-acetylate glucosamine oligomers, and they were recently shown to also exhibit this reverse activity toward polyglucosamine, yielding partially acetylated chitosan polymers with a nonrandom pattern of acetylation. As chitin deacetylases can possess a certain cosubstrate promiscuity, we explored the ability of a CDA from the fungus Colletotrichum lindemuthianum (ClCDA) to N-acylate glucosamine tetramers and polyglucosamines using a range of small carboxylic acids as cosubstrates. The resulting tetramers were analyzed using ultra-high-performance hydrophilic liquid chromatography-tandem mass spectrometry (UHPLC-HILIC-MS), and the kinetic parameters of the acylation reactions thus determined gave deeper insight into the limitation of the cosubstrate scope of ClCDA. Using polyglucosamines as substrates, we obtained N-propiolated chitosan polymers with high fractions of substitution of 0.7. Copper-catalyzed azide–alkyne cycloaddition (CuAAC) then yielded a fluorescence-labeled polymer, providing proof-of-principle for click functionalization of chitosans using this chemoenzymatic approach. Given the known regioselectivity of chitin deacetylases, which is retained during reverse N-acetylation, this process might give access to a broad variety of functionalized chitosans with nonrandom substitution patterns.