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Special Issue "Recent Advances in CuAAC Click Chemistry"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Synthesis".

Deadline for manuscript submissions: closed (30 September 2016)

Special Issue Editor

Guest Editor
Prof. Dr. James Crowley

University of Otago, Department of Chemistry, Dunedin, New Zealand
Website | E-Mail
Interests: CuAAC “click” chemistry; macrocycles; self-assembly; metallosupramolecular architectures; interlocked architectures; molecular machines; anti-cancer and anti-bacterial agents; catalysis

Special Issue Information

Dear Colleagues,

The past decade has seen rapid growth in the number of so-called “click” reactions, synthetic methods that exploit simple reaction conditions, are high yielding, regioselective and readily purified. These click methods have vastly improved our ability to rapidly produce functionalized molecules for applications in the biological and material sciences.

Of the “click” technologies available, the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) remains the go-to reaction due to the functional group tolerance of the process. Initially, the CuAAC reaction was mainly exploited to conjugate two components together in high yield through a 1,4-disubstituted 1,2,3-triazole unit. However, more recently it has been shown that the 1,2,3-triazole units generated via the CuAAC reaction can engage in hydrogen bonding and metal coordination further widening the interest in this “click” reaction.

This Special Issue of Molecules will seek to highlight the continuing growth in the use of CuAAC “click” chemistry in a range of areas including catalysis, coordination, medicinal and supramolecular chemistry, biology, material science and nanotechnology. I strongly encourage colleagues to submit their manuscript for this Special Issue, which will promote and celebrate the applications of this powerful synthetic technology.

Prof. Dr. James Crowley
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • click chemistry
  • CuAAC
  • chemical ligation
  • medicinal chemistry
  • supramolecular chemistry
  • coordination chemistry
  • catalysis
  • self-assembly
  • material science
  • nanotechnology

Published Papers (6 papers)

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Research

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Open AccessArticle Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes
Molecules 2017, 22(1), 89; doi:10.3390/molecules22010089
Received: 21 November 2016 / Revised: 22 December 2016 / Accepted: 25 December 2016 / Published: 9 January 2017
Cited by 2 | PDF Full-text (2018 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane
[...] Read more.
Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane synthesis with a diyne in which, following the formation of the first mechanical bond, the steric bulk of the macrocycle tempers the reactivity of the second alkyne unit. We have now extended this approach to the use of 1,3,5-triethynylbenzene in order to successively prepare [2]-, [3]- and [4]rotaxanes without the need for protecting group chemistry. Whilst the first two iterations proceeded in good yield, the steric shielding that affords this selectivity also significantly reduces the efficacy of the active template (AT)-CuAAC reaction of the third alkyne towards the preparation of [4]rotaxanes, resulting in severely diminished yields. Full article
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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Open AccessArticle Structural Determinants of Alkyne Reactivity in Copper-Catalyzed Azide-Alkyne Cycloadditions
Molecules 2016, 21(12), 1697; doi:10.3390/molecules21121697
Received: 2 November 2016 / Revised: 3 December 2016 / Accepted: 5 December 2016 / Published: 9 December 2016
Cited by 3 | PDF Full-text (5544 KB) | HTML Full-text | XML Full-text
Abstract
This work represents our initial effort in identifying azide/alkyne pairs for optimal reactivity in copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. In previous works, we have identified chelating azides, in particular 2-picolyl azide, as “privileged” azide substrates with high CuAAC reactivity. In the current work,
[...] Read more.
This work represents our initial effort in identifying azide/alkyne pairs for optimal reactivity in copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. In previous works, we have identified chelating azides, in particular 2-picolyl azide, as “privileged” azide substrates with high CuAAC reactivity. In the current work, two types of alkynes are shown to undergo rapid CuAAC reactions under both copper(II)- (via an induction period) and copper(I)-catalyzed conditions. The first type of the alkynes bears relatively acidic ethynyl C-H bonds, while the second type contains an N-(triazolylmethyl)propargylic moiety that produces a self-accelerating effect. The rankings of reactivity under both copper(II)- and copper(I)-catalyzed conditions are provided. The observations on how other reaction parameters such as accelerating ligand, reducing agent, or identity of azide alter the relative reactivity of alkynes are described and, to the best of our ability, explained. Full article
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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Open AccessArticle Palladium(ii)-Acetylacetonato Complexes with Mesoionic Carbenes: Synthesis, Structures and Their Application in the Suzuki-Miyaura Cross Coupling Reaction
Molecules 2016, 21(11), 1561; doi:10.3390/molecules21111561
Received: 20 September 2016 / Revised: 2 November 2016 / Accepted: 12 November 2016 / Published: 17 November 2016
Cited by 1 | PDF Full-text (1432 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of novel palladium(ii) acetylacetonato complexes bearing mesoionic carbenes (MICs) have been synthesized and characterized. The synthesis of the complexes of type (MIC)Pd(acac)I (MIC = 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (1), 1,4-(2,4,6-methyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (2), 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (3); acac = acetylacetonato)
[...] Read more.
A series of novel palladium(ii) acetylacetonato complexes bearing mesoionic carbenes (MICs) have been synthesized and characterized. The synthesis of the complexes of type (MIC)Pd(acac)I (MIC = 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (1), 1,4-(2,4,6-methyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (2), 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (3); acac = acetylacetonato) via direct metalation starting from the corresponding triazolium iodides and palladium(ii) acetylacetonate is described herein. All complexes were characterized by 1H- and 13C-NMR spectroscopy and high resolution mass spectrometry. Additionally, two of the complexes were characterized by single crystal X-ray crystallography confirming a square-planar coordination geometry of the palladium(ii) center. A delocalized bonding situation was observed within the triazolylidene rings as well as for the acac ligand respectively. Complex 2 was found to be an efficient pre-catalyst for the Suzuki-Miyaura cross coupling reaction between aryl-bromides or -chlorides with phenylboronic acid. Full article
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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Open AccessArticle Oxidatively Locked [Co2L3]6+ Cylinders Derived from Bis(bidentate) 2-Pyridyl-1,2,3-triazole “Click” Ligands: Synthesis, Stability, and Antimicrobial Studies
Molecules 2016, 21(11), 1548; doi:10.3390/molecules21111548
Received: 30 September 2016 / Revised: 4 November 2016 / Accepted: 10 November 2016 / Published: 16 November 2016
Cited by 1 | PDF Full-text (1689 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A small family of [Co2(Lpytrz)3]6+ cylinders was synthesised from bis(bidentate) 2-pyridyl-1,2,3-triazole “click” ligands (Lpytrz) through an “assembly-followed-by-oxidation” method. The cylinders were characterised using 1H, 13C, and DOSY NMR, IR, and
[...] Read more.
A small family of [Co2(Lpytrz)3]6+ cylinders was synthesised from bis(bidentate) 2-pyridyl-1,2,3-triazole “click” ligands (Lpytrz) through an “assembly-followed-by-oxidation” method. The cylinders were characterised using 1H, 13C, and DOSY NMR, IR, and UV-Vis spectroscopies, along with electrospray ionisation mass spectrometry (ESMS). Stability studies were conducted in dimethyl sulfoxide (DMSO) and D2O. In contrast to similar, previously studied, [Fe2(Lpytrz)3]4+ helicates the more kinetically inert [Co2(Lpytrz)3]6+ systems proved stable (over a period of days) when exposed to DMSO and were even more stable in D2O. The triply stranded [Co2(Lpytrz)3]6+ systems and the corresponding “free” ligands were tested for antimicrobial activity in vitro against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) microorganisms. Agar-based disk diffusion and Mueller–Hinton broth micro-dilution assays showed that the [Co2(Lpytrz)3]6+ cylinders were not active against either strain of bacteria. It is presumed that a high charge of the [Co2(Lpytrz)3]6+ cylinders is preventing them from crossing the bacterial cell membranes, rendering the compounds biologically inactive. Full article
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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Open AccessArticle Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes
Molecules 2016, 21(10), 1382; doi:10.3390/molecules21101382
Received: 29 September 2016 / Revised: 11 October 2016 / Accepted: 12 October 2016 / Published: 18 October 2016
PDF Full-text (2560 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The complex [Os(btzpy)2][PF6]2 (1, btzpy = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine) has been prepared and characterised. Complex 1 exhibits phosphorescence (λem = 595 nm, τ = 937 ns, φem = 9.3% in degassed acetonitrile) in contrast to its
[...] Read more.
The complex [Os(btzpy)2][PF6]2 (1, btzpy = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine) has been prepared and characterised. Complex 1 exhibits phosphorescence (λem = 595 nm, τ = 937 ns, φem = 9.3% in degassed acetonitrile) in contrast to its known ruthenium(II) analogue, which is non-emissive at room temperature. The complex undergoes significant oxygen-dependent quenching of emission with a 43-fold reduction in luminescence intensity between degassed and aerated acetonitrile solutions, indicating its potential to act as a singlet oxygen sensitiser. Complex 1 underwent counterion metathesis to yield [Os(btzpy)2]Cl2 (1Cl), which shows near identical optical absorption and emission spectra to those of 1. Direct measurement of the yield of singlet oxygen sensitised by 1Cl was carried out (φ (1O2) = 57%) for air equilibrated acetonitrile solutions. On the basis of these photophysical properties, preliminary cellular uptake and luminescence microscopy imaging studies were conducted. Complex 1Cl readily entered the cancer cell lines HeLa and U2OS with mitochondrial staining seen and intense emission allowing for imaging at concentrations as low as 1 μM. Long-term toxicity results indicate low toxicity in HeLa cells with LD50 >100 μM. Osmium(II) complexes based on 1 therefore present an excellent platform for the development of novel theranostic agents for anticancer activity. Full article
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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Review

Jump to: Research

Open AccessReview Development and Applications of the Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) as a Bioorthogonal Reaction
Molecules 2016, 21(10), 1393; doi:10.3390/molecules21101393
Received: 29 September 2016 / Revised: 14 October 2016 / Accepted: 15 October 2016 / Published: 24 October 2016
Cited by 5 | PDF Full-text (3330 KB) | HTML Full-text | XML Full-text
Abstract
The emergence of bioorthogonal reactions has greatly broadened the scope of biomolecule labeling and detecting. Of all the bioorthogonal reactions that have been developed, the copper-catalyzed azide-alkyne cycloaddition (CuAAC) is the most widely applied one, mainly because of its relatively fast kinetics and
[...] Read more.
The emergence of bioorthogonal reactions has greatly broadened the scope of biomolecule labeling and detecting. Of all the bioorthogonal reactions that have been developed, the copper-catalyzed azide-alkyne cycloaddition (CuAAC) is the most widely applied one, mainly because of its relatively fast kinetics and high efficiency. However, the introduction of copper species to in vivo systems raises the issue of potential toxicity. In order to reduce the copper-induced toxicity and further improve the reaction kinetics and efficiency, different strategies have been adopted, including the development of diverse copper chelating ligands to assist the catalytic cycle and the development of chelating azides as reagents. Up to now, the optimization of CuAAC has facilitated its applications in labeling and identifying either specific biomolecule species or on the omics level. Herein, we mainly discuss the efforts in the development of CuAAC to better fit the bioorthogonal reaction criteria and its bioorthogonal applications both in vivo and in vitro. Full article
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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