Copper catalysis: a constantly evolving field

• Elena Fernández and
• Jaesook Yun

Beilstein J. Org. Chem. 2025, 21, 1477–1479, doi:10.3762/bjoc.21.109

• , Burley, Watson, and co-workers present a new synthesis of germyl triazoles from germyl alkynes through a copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction [6]. The resulting Ge-substituted triazoles could be further diversified. For example, through chemoselective transition-metal-catalyzed

Germanyl triazoles as a platform for CuAAC diversification and chemoselective orthogonal cross-coupling

• John M. Halford-McGuff,
• Thomas M. Richardson,
• Aidan P. McKay,
• Frederik Peschke,
• Glenn A. Burley and
• Allan J. B. Watson

Beilstein J. Org. Chem. 2024, 20, 3198–3204, doi:10.3762/bjoc.20.265

• extensive scope across a range of benign solvent conditions [7][8][9][10]. In addition, the CuAAC reaction uses inexpensive Cu catalysts [11], is insensitive towards oxygen and water [12][13], and consistently delivers high yields and (where relevant) enantioselectivities [8][9][10][14][15][16][17][18][19

• converted to a mechanistically-required Cu(I) species in situ through the addition of a reductant (e.g., sodium ascorbate, NaAsc) [31][32], or via Glaser–Hay alkyne homocoupling [33][34]. The mild and accessible nature of the CuAAC reaction has allowed the use of azide or alkyne components that bear

• dialkynyl germane to access 1,2-bis(triazolyl)tetraphenyldigermanes [70]. Here, we report the development of germanyl alkynes as CuAAC components, with exploration of their scope and downstream diversification. Results and Discussion We undertook an exploratory survey of CuAAC reaction conditions using

Improved deconvolution of natural products’ protein targets using diagnostic ions from chemical proteomics linkers

• Andreas Wiest and
• Pavel Kielkowski

Beilstein J. Org. Chem. 2024, 20, 2323–2341, doi:10.3762/bjoc.20.199

• alkyne probe from the CuAAC reaction mixture or by increasing the concentration of the reducing agent such as tris(2-carboxyethyl)phosphine (TCEP). The reversed chemical proteomics approach in which the azide probe and alkyne tag are used suffers from similar unspecific reactivity of the terminal alkyne

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

Synthesis of substituted triazole–pyrazole hybrids using triazenylpyrazole precursors

• Simone Gräßle,
• Laura Holzhauer,
• Nicolai Wippert,
• Olaf Fuhr,
• Martin Nieger,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2024, 20, 1396–1404, doi:10.3762/bjoc.20.121

• experiments in solution, a one-pot cleavage from the resin combined with the CuAAC reaction to the triazole–pyrazole hybrid was conducted exemplarily and gave the target product 21gd in 30% yield. The solid-phase reaction route allows for roughly equally high overall yields compared to the solution synthesis

• to the respective triazole product in a CuAAC reaction; this step could also successfully be conducted in a sequential one-pot approach from the triazenylpyrazole precursor. The developed protocol was adapted for solid-phase synthesis to demonstrate the applicability of triazenylpyrazoles as

The Ugi4CR as effective tool to access promising anticancer isatin-based α-acetamide carboxamide oxindole hybrids

• Carolina S. Marques,
• Aday González-Bakker and
• José M. Padrón

Beilstein J. Org. Chem. 2024, 20, 1213–1220, doi:10.3762/bjoc.20.104

• –alkyne cycloaddition (CuAAC) reaction, or commonly entitled “click” reaction, is a widely and straightforward tool to access the 1,2,3-triazole ring [26][27]. Due to the presence of an alkyne group on the Ugi-adduct 5bb (Scheme 2) we decided to use the CuAAC reaction to introduce a 1,2,3-triazole unit

• into the scaffold. Benzyl azide (6), obtained using a previously reported procedure [27], was used in the CuAAC reaction. The α-acetamide carboxamide 1,2,3-triazole oxindole hybrid 7 was easily obtained in 61% yield using Cu(OAc)2 as catalyst, ascorbic acid, DMF as solvent, and microwave reaction

• obtained using an Ugi four-component reaction (Ugi4CR). (B) The synthetic strategy reported in this work. Library of α-acetamide carboxamide oxindole hybrids 5 accessed via the Ugi4CR. Microwave-assisted CuAAC reaction to access α-acetamide carboxamide 1,2,3-triazole oxindole hybrid 7. Library of α

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• ). The active catalytic species for the CuAAC reaction were generated by reducing copper(II) sulfate with sodium ascorbate according to literature procedures [66][67]. 2-Azido-1,3,5-trimethylbenzene (mesityl azide) was easily synthesized in a distinct, preliminary step through the Sandmeyer reaction of

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• molecule which catalyzes the macrocyclization reaction around the axle (Figure 1b). Results and Discussion In order to access the target [2]rotaxanes we made use of the CuAAC reaction, performed in the presence of a copper(I) N-heterocyclic carbene, a very stable and efficient class of catalysts used in

• . Our results proved that the CuAAC reaction catalyzed by copper(I) N-heterocyclic carbenes can be successfully used in the synthesis of [2]rotaxanes. This, combined with the fast and simple assembly of [CuCl(SIMes)] [45][46] could lead to the development of a Cu(I) NHC click chemistry in the field of

• . Synthesis of the key intermediates 6 and 8 and of the reference macrocycle M1. Synthesis of [2]rotaxanes R1 and R2. Supporting Information Supporting Information File 18: Copies of NMR and HRMS spectra. Acknowledgements We thank Dr. Arnaud Gautier for providing us the catalyst used in CuAAC reaction and

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• equal quantities (Scheme 5, reaction 1). Again, the addition of TBTA as ligand strongly improved the performance of the CuAAC reaction: the symmetric divalent compound 14 with two 1,2-oxazinyl end groups was isolated in very satisfying 87% yield (Scheme 5, reaction 2). When 1,4-bis(bromomethyl)benzene

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• -dipolar cycloaddition reaction between an azide and a terminal alkyne, also popular as "click reaction" or CuAAC reaction. Moreover, the 1,2,3-triazole ring also serves as a spacer and an electron transfer bridge between the porphyrin and the attached chromophores. In order to provide a critical overview

• catalyst at room temperature. In addition, the free-base porphyrin-carborane conjugate 76b was successfully obtained after the treatment of 76a with trifluoroacetic acid in СН2Сl2. The research group of Ravikanth [42] prepared the triazole-bridged porphyrin-BODIPY conjugates 78 and 80 via CuAAC reaction in

• porphyrin-carboline conjugate 85 [43] and porphyrin-psoralen conjugates 87 [44] as shown in Scheme 17. Firstly, zinc(II) porphyrin-carboline conjugate 84 and porphyrin-psoralen conjugate 86b were synthesized in good yields by the CuAAC reaction between porphyrin 81b and azide 82 or 83. Interestingly, the

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• desymmetrization of the molecule caused by a partial and reversible self-inclusion of the triazole moiety into the CD cavity, as was previously studied in detail for the CD dimers prepared by CuAAC reaction [15]. Although such self-inclusion was not prominent for dimers based on the short propargyl ether linker

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• , Germany 10.3762/bjoc.18.111 Abstract The conversion of tetrazolo[1,5-a]quinoxalines to 1,2,3-triazoloquinoxalines and triazoloimidazoquinoxalines under typical conditions of a CuAAC reaction has been investigated. Derivatives of the novel compound class of triazoloimidazoquinoxalines (TIQ) and rhenium(I

Synthesis of a new water-soluble hexacarboxylated tribenzotriquinacene derivative and its competitive host–guest interaction for drug delivery

• Man-Ping Li,
• Nan Yang and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2022, 18, 539–548, doi:10.3762/bjoc.18.56

• synthesized starting from the known TBTQ-based hexakis(propargyl ether) 1 [29] (Scheme 1a). Through the CuAAC reaction with ethyl azidoacetate under Cu(I) catalysis, the TBTQ-based hexakis(ethyl acetate) compound 2 was obtained in 73% yield. Subsequent hydrolysis with sodium hydroxide followed by

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

• Peterson de Andrade,
• Sanaz Ahmadipour and
• Robert A. Field

Beilstein J. Org. Chem. 2022, 18, 208–216, doi:10.3762/bjoc.18.24

• 13C NMR experiment, where the α-anomer is a doublet and the β-anomer is a singlet [28]. The key intermediate 1 was further used in CuAAC reaction [29][30][31][32] with eleven (hetero)aromatic and non-aromatic terminal alkynes readily available in our lab [23]. Although CuAAC is reputedly tolerant of a

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• , Turkey King Abdulaziz University, Faculty of Science, Chemistry Department, 21589 Jeddah, Saudi Arabia 10.3762/bjoc.17.164 Abstract The development of long-wavelength photoinduced copper-catalyzed azide–alkyne click (CuAAC) reaction routes is attractive for organic and polymer chemistry. In this study

• , we present a novel synthetic methodology for the photoinduced CuAAC reaction utilizing exfoliated two-dimensional (2D) few-layer black phosphorus nanosheets (BPNs) as photocatalysts under white LED and near-IR (NIR) light irradiation. Upon irradiation, BPNs generated excited electrons and holes on

• its conduction (CB) and valence band (VB), respectively. The excited electrons thus formed were then transferred to the CuII ions to produce active CuI catalysts. The ability of BPNs to initiate the CuAAC reaction was investigated by studying the reaction between various low molar mass alkyne and

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• the nucleophilic opening of O-2,2′-anhydrouridine [44]. The azido nucleoside 12 was reacted with N6-benzoyl-N9-propargyladenine (13a) and N1-propargylthymine (13b) via a CuAAC reaction where the triazole-containing linker connected the additional thymine or adenine to the 2′-position of 2

• -ethynylpyrene (40) under copper-catalyzed alkyne–azide cycloaddition (CuAAC) reaction conditions to yield the double-headed nucleoside 41 (Scheme 10) [23]. The double-headed nucleoside 41 was phosphitylated and then incorporated into oligonucleotides and was found to form highly stable DNA duplexes and three

• nucleosides were further reacted with propargylated nucleobases through a copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction followed by treatment with methanolic ammonia to give the C-3′-substituted double-headed ribofuranonucleosides 46a–c and 50a–e (Scheme 11) [36]. The double-headed nucleosides

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• (CuAAC) reaction provides the target product IV (Scheme 1, pathway A) [59][60][61]. Pathway B is designed on the basis of our group investigations on the synthesis of 2,6-bistriazolylpurine derivatives and their application in reactions with N-, S- and P-nucleophiles making use of regioselective SNAr

• reactions at C(6) (V→VI→IV, Scheme 1) [11][14][62][63][77][78]. The main advantage of pathway B is a straightforward access to 2,6-diazidopurines V and 2,6-bistriazolylpurines VI due to excellent nucleophilic properties of the azide ion and well-established CuAAC reaction. Pathway B also avoids performing

• -bistriazolylpurine derivatives 2a–c were obtained in the synthetic procedures developed by us before [11][14][67]. The CuAAC reaction was performed between diazide derivatives 1a and 1b and phenylacetylene or methyl propiolate (Scheme 2). SNAr reactions between bistriazolylpurine derivatives and O-nucleophiles were

Easy access to a carbohydrate-based template for stimuli-responsive surfactants

• Thomas Holmstrøm,
• Daniel Raydan and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2020, 16, 2788–2794, doi:10.3762/bjoc.16.229

• ]. Furthermore, starting from the azide 8, it was possible to achieve ester functionalities by a CuAAC reaction [23][24] in the presence of the two different alkynes 14 and 15, giving rise to the diester derivative 12 and the tetraester derivative 13 (Scheme 2). Subsequently, the esters could be hydrolyzed by

• group has earlier been used as metal chelator [25]. At this stage, it was possible to separate both anomers of the diazide 18 using flash column chromatography. The pure α-anomer was then subjected to a CuAAC reaction using 1-heptyne and, in only two steps, the new surfactant 19 could be prepared from

• functionalization. The azido groups also can undergo a CuAAC reaction with alkynes substituted with ester functionalities, which can subsequently be hydrolyzed to either the di- or tetra acids. Using the CuAAC reaction, it was also possible to install aliphatic chains. Introducing picoline residues on the 3,6

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• 31% yield. The subsequent CuAAC reaction with 1-azido-2,3,4,6-tetraacetylglucose, which was prepared according to the reported method [39], in the presence of Cu(I) as the catalyst afforded the acetyl-protected, sugar-functionalized derivative TBTQ-(OAcG)6 in 50% yield. As expected, compound TBTQ

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• -tethered BODIPY derivatives serve as a substrate in the copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction, which is known as “click” reaction, allowing for a biological tissue labelling [35][36]. In addition, ethynyl-substituted BODIPYs yield unique π-conjugated BODIPY-based macrocycles by

• substitution-site-dependent spectral features, for instance, the extent of the bathochromic shifts of the absorption and fluorescence, variable Stokes shift and the emission quantum yields. The TIPS-protected ethynyl groups of these BODIPY dyes can be applied as substrates for the “click” CuAAC reaction toward

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

• Sara Tejera,
• Giada Caniglia,
• Rosa L. Dorta,
• Andrea Favero,
• Javier González-Platas and
• Jesús T. Vázquez

Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

• "click" chemistry [16][17][18] of azides and alkynes catalyzed by Cu(I) salts, the CuAAC reaction. Self-assembling properties were not observed for any of the prepared monotriazoles, namely the 4-substituted 1-glucopyranosyltriazoles 1a–g and 2a–g (Scheme 1) [15]. However, most ditriazoles 7a–g and 8a–g

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• heterocycles have also been used as linkers and for labeling biomolecules in chemical biology [43]. Moreover, this synthetic approach provides high yields, selectivity, mild reaction conditions and simple purification methods. It was demonstrated that the CuAAC reaction of porphyrins 3a and 3b with N