Alkyne Cycloaddition Reaction Research Articles

Synthesis of novel 3-[(1-glycosyl-1H-1,2,3-triazol-4-yl)- methylamino]ket-2-en-1-ones

Nine 3-[(1-β-D-ribofuranosyl- and 3-[(1-β-D-glucopyranosyl-1H-1,2,3-triazol-4-yl)methylamino]ket-2-en-1-ones have been synthesized by copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction between propargylamine derivatives and 1-azido-2,3,5-tri-O-benzoylβ-D-ribofuranose or 2,3,4,6-tetra-O-acetyl-1-azido-β-D-glucopyranose, followed by deprotection of the resulting tri-O-benzoyl- or tetraO-acetyl-1-β-D-glycosyltriazoles in good yields. The precursor propargylamine derivatives were synthesized by Sonogashira reaction of substituted acetylenes and benzoyl chloride followed by Michael-type addition of propargylamine to the resulting substituted alkynes in good yields. The precursor azido sugars, 1-azido-2,3,5-tri-O-benzoyl-β-D-ribofuranose and 2,3,4,6-tetra-O-acetyl-1-azido-β-D-glucopyranose, were synthesized by azidation of 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose and β-D-glucopyranose pentacetate, respectively, with azidotrimethylsilane in the presence of tin(IV) chloride. All products were unambiguously characterized on the basis of the spectral data analysis.

Ferrocenylchalcone–uracil conjugates: synthesis and cytotoxic evaluation

Huisgen’s azide–alkyne cycloaddition reaction was employed to synthesize a series of 1H-1,2,3-triazole-tethered uracil–ferrocenyl chalcone conjugates with the aim of evaluating their in vitro anti-proliferative efficacy on human leukemia (CCRF-CEM) and human breast adenocarcinoma (MDA-MB-468) cell lines. Cytotoxic evaluation studies identified a number of synthesized conjugates that inhibited the proliferation of leukemia cancer cells by ~70% after 72 h. The selected synthesized conjugates were found to be significantly less cytotoxic against normal kidney cell line (LLC-PK1) when compared with CCRF-CEM cancer cells.

Grafting polycaprolactone diol onto cellulose nanocrystals via click chemistry: Enhancing thermal stability and hydrophobic property

Hydrophobic and thermally-stable cellulose nanocrystals (CNCs) were synthesized by polycarpolactone diol (PCL diol) grafting via click chemistry strategy. The synthesis was designed as a three-step procedure containing azide-modification of CNCs, alkyne-modification of PCL diol and sequent copper(I)-catalyzed azide–alkyne cycloaddition reaction. The structure of azide-modified CNCs and alkyne-modified PCL diol, the structure, hydrophobic ability and thermal stability of click products CNC-PCL were characterized. FTIR, XPS and H1 NMR results indicated a successful grafting of the N3 groups onto the CNCs, synthesis of PCL diol-CCH, and formation of the CNC-PCL material. CNC-PCL had enhanced dispersion in the non-polar solvent chloroform owing to the well-maintained microscale size and PCL-induced hydrophobic surface. The thermal stability of CNC-PCL was largely increased due to the grafting of thermally-stable PCL. This work demonstrates that click chemistry is an attractive modification strategy to graft CNCs with polyester chains for further potential application in polymer composites.

Copper(II)-dipicolinate-mediated clickable azide–alkyne cycloaddition in water as solvent

Copper(II)-dipicolinate complex [CuII(dipic)(H2O)2] (1) (H2L = dipicolinic acid (H2dipic)) was synthesized via oxidation of copper(I) iodide and pyridine-2,6-dicarboxylic acid in water and acetonitrile in the presence of glycine. Complex 1 was characterized by FT-IR and elemental analysis and its structure confirmed by single crystal X-ray analysis. This complex is an efficient precatalyst that mediates azide–alkyne cycloaddition reactions in water at room temperature either in the absence or presence of a reducing agent. Compound 1-mediated azide–alkyne cycloaddition affords alkyl/aryl substituted 1,2,3-triazole heterocycles in a regioselective manner and excellent yields under very mild reaction conditions matching the criteria of greener protocols.

Construction of polymeric Cu(I) N-heterocyclic carbene complex utilizing terpyridine-Fe(II) as linkers: formation of an efficient and recyclable catalyst

A metal-coordination-driven self-assembly using the predesigned building block has been developed. Herein, the catalytic active NHC–Cu(I) units were introduced into the terpyridine metal coordination polymers. The self-assembled architecture, as a heterogeneous catalyst, was successfully used to catalyze the A3-coupling reaction of aldehyde, alkyne, and amine and Huisgen 1,3-dipolar cycloaddition reaction of azide and alkyne in high yields.

Liposomes formed from photo-cleavable phospholipids: in situ formation and photo-induced enhancement in permeability.

Photocleavable liposomes were formed in situ through the coupling of an o-nitrobenzyl-containing azide tail precursor and an alkyne-functionalized lysolipid by the copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. Inclusion of the photolabile o-nitrobenzyl-structure enables control over the permeability and morphology of the liposomes. Photolysis of the o-nitrobenzyl group changes the molecular structure of the photolabile phospholipids, inducing phase transitions and permeability increases in the bilayer membrane, ultimately disrupting the liposome entity.

Click Synthesis of Shape-Persistent Azodendrimers and their Orthogonal Self-Assembly to Nanofibres

The copper(i)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction has been efficiently utilized to synthesize a series of dendrons with amino functionalities. The aminodendrons successfully underwent azodimerization to furnish a series of pyridyl- and phenyl-based azodendrimers with peripheral alkyl or ether side chain substituents. The molecular structures of the azodendrimers were fully assigned using different spectroscopic techniques, such as 1H NMR and 13C NMR, and the molecular weights were determined using MALDI-TOF mass spectrometry. The molecular self-assembly of the azodendrimers was investigated by scanning electron microscopy and transmission electron microscopy, which revealed the formation of highly ordered and uniform self-assembled nanofibres.

Diversified polyoxovanadate derivatives obtained by copper(i)-catalysed azide-alkyne cycloaddition reaction: their synthesis and structural characterization.

In this work, we confirmed that the copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction is an effective method for the organic-functionalization of polyoxometalates (POMs). Herein, for the first time, four novel 1,2,3-triazole functionalized polyoxovanadate (POV) organic-inorganic hybrids, (Bu4N)2[V6O13{(OCH2)3C5H6N3O}2]·1.5CH3CN 2, (Bu4N)2[V6O13{(OCH2)3C7H8N3O2}2]·2CH3CN 3, (Bu4N)2[V6O13{(OCH2)3C11H10N3}2] 4 and (Bu4N)2[V6O13{(OCH2)3C10H7N3Cl}2] 5 were prepared through the CuAAC reaction using the azide functionalized hexavanadate, (Bu4N)2[V6O13{(OCH2)3CCH2N3}2]·2.5CH3CN 1, as the precursor, where CuI was used as the catalyst and N,N-diisopropylethylamine (DIPEA) as a stabilizer for CuI. All the four compounds were structurally and compositionally characterized by single-crystal X-ray diffraction, elemental analyses, powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), 1H NMR, ESI-MS, UV-Vis and thermogravimetric analysis (TGA).

Three-way competition in a topochemical reaction: permutative azide–alkyne cycloaddition reactions leading to a vast library of products in the crystal

Crystals of 5-azido-3-O-propargyl-1,2-O-isopropylidene-α-d-ribofuranose undergo topochemical azide–alkyne cycloaddition reaction in three different pathways leading to a library of products.

Reactive cycloalkane plasticizers covalently linked to energetic polyurethane bindersviafacile control of anin situCu-free azide–alkyne 1,3-dipolar cycloaddition reaction

The kinetic performance of a spacer-controlled Huisgen azide–alkyne cycloaddition reaction for alkyne-bearing reactive cycloalkane plasticizers is explored in combination with the computational protocol.

Correction: Diversified polyoxovanadate derivatives obtained by copper(i)-catalysed azide-alkyne cycloaddition reaction: their synthesis and structural characterization.

Correction for 'Diversified polyoxovanadate derivatives obtained by copper(i)-catalysed azide-alkyne cycloaddition reaction: their synthesis and structural characterization' by Hongli Jia et al., Dalton Trans., 2018, 47, 577-584.

Synthesis of a heterogeneous Cu(OAc)2-anchored SBA-15 catalyst and its application in the CuAAC reaction

A dinuclear Cu(OAc)2-anchored SBA-15 silica was synthesized, confirmed and showed excellent catalytic activity for the azide–alkyne cycloaddition reaction in water.

Azide-alkyne cycloaddition reactions in water via recyclable heterogeneous Cu catalysts: reverse phase silica gel and thermoresponsive hydrogels.

Functionalized reverse phase silica gel and thermoresponsive hydrogels were synthesized as heterogeneous catalysts supports. Cu(i) and Cu(ii) catalysts immobilized onto two types of supports were prepared and characterized. The copper catalyzed azide–alkyne cycloaddition was performed in water via a one-pot reaction and yielded good results. These catalysts are air stable and reusable over multiple uses.

Imaging of a clickable anticancer iridium catalyst

Iridium-based anticancer reagents are receiving increasing attention for their high cytotoxicity. Herein, by activating CH bonds in the well-known antioxidant α-phenyl-N-tert-butylnitrone (PBN), we synthesized and characterized a series of new iridium complexes. Complex 1-AMP exhibited the best antiproliferation activity towards human ovarian cancer A2780 cells. The azide group in complex 1-AMP underwent the Cu(I)-catalysed azide−alkyne cycloaddition (CuAAC) reaction and the resulting fluorescent imaging in cells suggested it mainly accumulated in mitochondria. In comparison, to eliminate cytotoxicity of Cu(I) catalyst, we conducted a reaction between complex 1-AMP and a commercialized dye via strain-promoted alkyne–azide cycloaddition (SPAAC) reaction in live cells, confirming its targeting mainly in the mitochondria. Iridium-based anticancer complexes containing a nitrone ligand and azide group may offer a useful tool to probe the mechanism of metallodrugs.

Topochemical azide–alkyne cycloaddition reactions in crystals and organogels

Topochemical azide–alkyne cycloaddition reactions in crystals and organogels

Synthesis and Evaluation of Radiolabeled Phosphoramide Mustard with Selectivity for Hypoxic Cancer Cells.

Tumor hypoxia has been widely explored over the years as a diagnostic and therapeutic marker. Herein, we synthesized an alkyne functionalized version of evofosfamide, a hypoxia-selective prodrug. The purpose of this effort was to investigate if this novel 2-nitroimidazole phosphoramide nitrogen mustard (2-NIPAM) retained hypoxia selectivity and could be utilized in radiopharmaceutical development to significantly increase retention of conjugated agents in hypoxic cells. 2-NIPAM demonstrated good hypoxia selectivity with a 62- and 225-fold increase in cytotoxicity toward PC-3 and DU145 human prostate cancer cell lines, respectively, under hypoxic conditions. Radiolabeling of 2-NIPAM with 125I was accomplished through a Cu(I)-mediated azide-alkyne cycloaddition reaction. The 125I-conjugate demonstrated 13.6 and 17.8% lower efflux rates for DU145 and PC-3 cells, correspondingly, under hypoxic conditions, suggesting that the increased retention is likely due to the known intracellular trapping mechanism. In conclusion, these studies demonstrate the potential of 2-NIPAM in serving as a trapping agent for radiopharmaceutical development.

Synthesis of Purine‐based Triazoles by Copper (I)‐catalyzed Huisgen Azide–Alkyne Cycloaddition Reaction

An efficient protocol for the synthesis of substituted 1,2,3‐triazol‐9H‐purines via copper (I)‐catalyzed click chemistry of 2,6‐dichloropurine with aromatic azide has been reported. A wide range of 1,4‐disubstituted triazoles (N‐9 substituted purines) was accessible in good‐to‐excellent yields with remarkable functional group tolerance. The base‐catalyst ratio was tuned to achieve optimum reaction condition (>95% conversion and purity in most cases). Furthermore, the structure of 4i has been unambiguously assigned by X‐ray crystallographic study to yield structural information on the 1,3‐dipoles entering the reaction.

Highly K+ -Selective Fluorescent Probes for Lifetime Sensing of K+ in Living Cells.

The new K+ -selective fluorescent probes 1 and 2 were obtained by CuI -catalyzed 1,3-dipolar azide alkyne cycloaddition (CuAAC) reactions of an alkyne-substituted [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD) ester fluorophore with azido-functionalized N-phenylaza-18-crown-6 ether and N-(o-isopropoxy) phenylaza-18-crown-6 ether, respectively. Probes 1 and 2 allow the detection of K+ in the presence of Na+ in water by fluorescence enhancement (2.2 for 1 at 2000 mm K+ and 2.5 for 2 at 160 mm K+ ). Fluorescence lifetime measurements in the absence and presence of K+ revealed bi-exponential decay kinetics with similar lifetimes, however with different proportions changing the averaged fluorescence decay times (τf(av) ). For 1 a decrease of τf(av) from 12.4 to 9.3 ns and for 2 an increase from 17.8 to 21.8 ns was observed. Variation of the substituent in ortho position of the aniline unit of the N-phenylaza-18-crown-6 host permits the modulation of the Kd value for a certain K+ concentration. For example, substitution of H in 1 by the isopropoxy group (2) decreased the Kd value from >300 mm to 10 mm. 2 was chosen for studying the efflux of K+ from human red blood cells (RBC). Upon addition of the Ca2+ ionophor ionomycin to a RBC suspension in a buffer containing Ca2+ , the fluorescence of 2 slightly rose within 10 min, however, after 120 min a significant increase was observed.

Direct [3+2]-cycloaddition of electron-deficient alkynes with CF3CHN2: Regioselective one-pot synthesis of 3-trifluoromethylpyrazoles

A direct and facile cycloaddition reaction of electron-deficient terminal alkynes with 2,2,2-trifluorodiazoethane under mild conditions to afford a series of 5-substituted 3-trifluoromethylpyrazoles in high yields is described. The potential application of this cycloaddition reaction was demonstrated via the efficient synthesis of a key intermediate of the antiviral drug AS-136A and a fluorinated analog of Tebufenpyrad.

Synthesis of Sulfur Perfluorophenyl Compounds Using a Pentafluorobenzenesulfonyl Hypervalent Iodonium Ylide.

A novel pentafluorobenzenesulfonyl hypervalent iodonium ylide 3 was designed and synthesized as a useful tool for the preparation of sulfur pentafluorophenyl compounds containing a C6F5S or C6F5SO2 unit. Electrophilic pentafluorophenylthiolation of enamines, formal [3+2] cycloaddition reaction of nitriles and alkynes, and intramolecular SNAr cyclization were achieved using iodonium ylide 3. The fluoro-click reaction was also demonstrated using one of the products via an intermolecular SNAr reaction with heterocentered nucleophiles.