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

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• and copper salts in the presence of NaOt-Bu in THF [15]. All attempts to prepare the corresponding iodide-containing compounds resulted in the formation of [(NHC)2Cu]+ species [15]. The copper complexes bearing ICy and It-Bu ligands were found to be sensitive to the excess of base and hence could not

• ). The complexes were obtained in high yields (>95%). The copper complexes were air and moisture-stable as solids but decomposed in chlorinated solvents after several days. It may be mentioned that Cu(I) halide and pseudohalide complexes with NHCs Me2L, Et2L and AdL were prepared from direct reaction of

• stable monomeric copper complexes. The X-ray structure shows a nearly linear C–Cu–CHF2 bond angle of 178°. Riant, Leyssens and co-workers obtained NHC–Cu(I)–bifluoride complexes 92 by reacting (IPr)CuCl successively with KOt-Bu and NEt3·3HF under inert atmosphere (Scheme 32) [45]. In place of KOt-Bu and

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• copper complexes of benzo[f]chromeno[2,3-h]quinoxalinoporphyrins 3–7 were converted to the corresponding free-base porphyrinoids 9–13 through a standard demetallation process using conc. H2SO4 in CHCl3 under cooling conditions (Scheme 1). On complexation with zinc by using Zn(OAc)2 in CHCl3/MeOH, free

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• )ium salt, a copper precursor and a suitably strong base (e.g., NaH, NaOt-Bu, KHMDS or n-BuLi) [20][21][22][23][24][25][26] are challenging for copper complexes 2 as they tend to give low yields (Scheme 1a) [5][6][13][16][17][18][19]. One elegant protocol employing K2CO3 as weak base in combination

Synthesis of meso-pyrrole-substituted corroles by condensation of 1,9-diformyldipyrromethanes with pyrrole

• Baris Temelli and
• Pinar Kapci

Beilstein J. Org. Chem. 2022, 18, 1403–1409, doi:10.3762/bjoc.18.145

• Baris Temelli Pinar Kapci Hacettepe University, Department of Chemistry, Beytepe Campus, 06800, Ankara, Turkey 10.3762/bjoc.18.145 Abstract A copper triflate-mediated approach to access copper complexes of pyrrole-substituted corroles from the reaction of 1,9-diformyldipyrromethanes and an excess

• with corroles, here we describe the first synthesis of copper complexes of trans-A2B-corroles possessing pyrrol-2-yl substituents at positions 5 and 15 by the condensation reaction of 1,9-diformylated dipyrromethanes with pyrrole in the presence of copper triflate. Results and Discussion At the

• resulted in 5,15-diphenylporphyrin (3) and 5-phenylporphyrin (4) in 4% and 1% yields, respectively. No pyrrole-substituted porphyrin product was detected. The structures of compounds 3 [33] and 4 [34] are in agreement with the literature data. Conclusion In summary, we report the first example of copper

The asymmetric Henry reaction as synthetic tool for the preparation of the drugs linezolid and rivaroxaban

• Martin Vrbický,
• Karel Macek,
• Jaroslav Pochobradský,
• Jan Svoboda,
• Miloš Sedlák and
• Pavel Drabina

Beilstein J. Org. Chem. 2022, 18, 438–445, doi:10.3762/bjoc.18.46

• highly efficient catalysts based on copper complexes of different types of chiral ligands, 2-(pyridin-2-yl)imidazolidine-4-ones (I–III), bis-oxazolines (IV–VII), or diamine (VIII) were chosen for the study (Figure 2). Furthermore, the modification of the structure of the prochiral aldehyde intermediates

• catalysts based on copper(II) complexes with chiral nitrogen ligands were chosen. Generally, chiral copper complexes possess many advantages valuable for the pharmaceutical industry. They exhibit low toxicity (compared to other metal-based complexes) and many of them exist in forms suitable for recycling

• -one derivative. Here, we extended the series of catalysts to include copper complexes with another six 2-(pyridin-2-yl)imidazolidin-4-ones Ia,b–IIIa,b [20][21][22], four bisoxazolines IV–VII [23][24], and as chiral diamine, the alkaloid (+)-sparteine VIII [25] (Figure 2). All Henry reactions were

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• renewable energy and green chemistry for many years. Ruthenium and iridium, which can be used as photoredox catalysts, are expensive and scarce in nature. Thus, the further development of catalysts based on these transition metals is discouraged. Alternative photocatalysts based on copper complexes are

• ruthenium-based catalysts and copper-based catalysts are discussed, and the strong reduction ability of copper complexes is explained. Subsequently, mechanisms of the photoredox catalysis by CuI and CuII are summarized, and the copper-catalyzed reactions, including alkene functionalization, alkyne

• functionalization, organic halides functionalization, and alkyl C–H functionalization, are highlighted. Review 1. Special features of photoredox-catalyzed processes by copper complexes To understand photoredox-catalyzed processes, a discussion of the general mechanism of [Ru(bpy)3]2+ is needed [25][26][27]. When

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• amines with cyanoguanidine in refluxing water in the presence of CuCl2. The pink copper complexes were then treated with hydrogen sulfide to release the desired compounds. As a representative example, N1-butylbiguanide (buformin) was obtained as a hydrochloride salt, with a 47% yield (Scheme 2). Other

• results in the biguanides as copper complexes, which in many cases remained dissolved in the hot reaction mixture and could be visually determined. The isolation of the compounds was accomplished after decomplexation in an alkaline medium. The rate of the reaction depended greatly on the nature of the

• the addition of aliphatic or aromatic amines to an activated cyanoguanidine derivative in a suitable solvent. The temperature requirements are lower compared to the fusion approach, and the work-up procedures are facilitated by the absence of copper complexes. Interestingly, microwave activation was

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• reagents for perfluoroalkylation reactions [66], Hartwig developed in 2011 the (Phen)CuCF3 and (Phen)CuCF2CF2CF3 complexes from inexpensive reagents. Indeed, when mixing (CuOt-Bu)4, 1,10-phenanthroline and the corresponding TMSRF, the perfluoroalkyl copper complexes were isolated for the first time (Scheme

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• applications in various synthetic fields by utilizing the ability of copper to sustain mono- and bielectronic elementary steps. Further to the development of well-defined copper complexes with classical ligands such as phosphines and N-heterocyclic carbenes, a new and fast-expanding area of research is

• electron transfer. This review aims to present the latest results in the area of copper-based cooperative catalysis with redox-active ligands. Keywords: bioinspired catalysis; biomimetic copper complexes; cooperative catalysis; redox-active ligands; redox catalysis; Introduction Interaction of earth

• copper intermediates in oxidation reactions in biological systems is very well documented [9]. It is therefore not surprising that this would be an area of choice for the development of bioinspired and/or redox-active copper complexes. Inspired by the pioneering works by Stack [10], Wieghardt and

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• interest involving optically active organoboron derivatives and their intermediacy as precursors to other functional groups, such as nonracemic alcohols. Achiral substrates in the presence of well-defined chiral copper complexes deliver chiral products, while nonracemic substrates can also react with

Copper-catalyzed O-alkenylation of phosphonates

• Nuria Vázquez-Galiñanes,
• Mariña Andón-Rodríguez,
• Patricia Gómez-Roibás and
• Martín Fañanás-Mastral

Beilstein J. Org. Chem. 2020, 16, 611–615, doi:10.3762/bjoc.16.56

• , although low conversion and yield were observed (Table 1, entry 1). A screening of copper complexes at a higher temperature (50 °C) revealed that CuTC (TC = thiophene-2-carboxylate) is the most efficient catalyst for this transformation (Table 1, entries 2–6). Finally, by using 2 equiv of 2a full

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

• is to consider the recently published developments (2014–2019) in the synthesis and catalytic applications of copper supported by silica nanocomposites, carbon nanocomposites, and magnetic nanocomposites for expanding the “click” chemistry. Keywords: “click” reaction; copper complexes; reusable

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• in photocatalysis using copper complexes. Their applications in various reactions, such as ATRA, reduction, oxidation, proton-coupled electron transfer, and energy transfer reactions are discussed. Keywords: ATRA reactions; copper catalysis; energy transfer; oxidation; PCET reactions; photocatalysis

• chlorotrifluoromethylated product (Scheme 3). In 2019, Bissember and co-workers reported the synthesis of new homoleptic copper complexes by modifying the structure of the phenanthroline ligand at the 1- and 10-positions with various aromatic substituents [19]. These complexes were fully characterized and evaluated in a

• resulting peroxyl radical reacts with the Cu complex, forming a new [Cu(II)] species that collapses to deliver the product and regenerates the active [Cu(II)] catalyst. 2 Heteroleptic Cu(I) complexes Heteroleptic copper complexes appeared as an interesting and promising alternative to the homoleptic

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• that the physicochemical properties remained widely unchanged. However, further studies must be undertaken in order to gain knowledge on the bioactivity of this SeCF3-containing analog. In situ synthesis of trifluoromethylselenolated compounds using copper complexes One-pot procedures that rely on the

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• copper complexes have an interesting antiproliferative capacity towards a range of human cancer cell lines, inducing early apoptosis, followed by secondary necrosis [64]. The fluorescent analog having pyridine imine and PEG terminal functions shown in Scheme 7 has been synthesized with the aim of

• intracellular space in a high proportion [59]. Besides the copper complexes, the gold complexes of these dendrimers display higher antiproliferative activities, in particular against both KB and HL-60 tumor cell lines (oral epidermoid carcinoma and human leukaemia, respectively), showing IC50s (the quantity of

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• a prevalent catalyst in a huge number of organic transformations. Similar to palladium complexes, copper complexes generally exist in four oxidation states, Cu(0), Cu(I), Cu(II), and Cu(III) and various fluorination reactions could be developed by different catalytic mechanisms. Fluorination of

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• -cost metals such as copper complexes or iron complexes which will be described in detail in the paragraph below. 2.1.2 The second generation of metal-based PCs: copper and iron complexes: Due to their earth-abundant property, iron and copper have received increasing attention and development of Fe and

• applications (see Part 3). The development of efficient photoluminescent copper complexes is possible by choosing appropriate ligands. The fine tunings of both redox potentials and visible light absorption properties are also possible [59]. Copper complexes can show really interesting properties for photoredox

• ]. This year, the first use of TADF complexes as photoredox catalysts in polymerization was reported [75]. CuC 4 whose properties are presented in Table 6 is one of them. The synthesis of this complex has been reported in ref [58]. Other TADF copper complexes which can be used in photoredox cycles are

Cationic cobalt-catalyzed [1,3]-rearrangement of N-alkoxycarbonyloxyanilines

• Itaru Nakamura,
• Mao Owada,
• Takeru Jo and
• Masahiro Terada

Beilstein J. Org. Chem. 2018, 14, 1972–1979, doi:10.3762/bjoc.14.172

• -catalysed cascade reaction involving rearrangement via N–O bond cleavage [14]. While divalent copper acetate and copper chloride did not show any catalytic activities (Table 1, entries 1 and 2), more Lewis acidic copper complexes, such as [Cu(MeCN)4](PF6)2 and [Cu(OTf)]2·toluene, afforded the corresponding

Copper-catalyzed asymmetric methylation of fluoroalkylated pyruvates with dimethylzinc

• Kohsuke Aikawa,
• Kohei Yabuuchi,
• Kota Torii and
• Koichi Mikami

Beilstein J. Org. Chem. 2018, 14, 576–582, doi:10.3762/bjoc.14.44

• methylation to give the desired alcohol 4a in 87% yield and 24% ee. Conclusion In summary, we have succeeded in the catalytic enantioselective methylation of fluoroalkylated pyruvates in the presence of chiral diphosphine–copper complexes, providing the corresponding tertiary alcohols with an RF group such as

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• detected. The luminescence of the reaction mixture gradually changed during milling and the final spectrum after 213 minutes milling exhibited a single luminescent maximum centered at around 1500 cm−1 (Figure 2a) possibly due the formation of different copper complexes as milling progressed. Milling by

Comparative profiling of well-defined copper reagents and precursors for the trifluoromethylation of aryl iodides

• Peter T. Kaplan,
• Jessica A. Lloyd,
• Mason T. Chin and
• David A. Vicic

Beilstein J. Org. Chem. 2017, 13, 2297–2303, doi:10.3762/bjoc.13.225

• TMSCF3 (A2) afforded the highest yields at extended reaction times. It is interesting to note here, for the trifluoromethylation of 4-iodobiphenyl with SIMes copper complexes under the reported literature conditions, that the better performer was not the isolated and well-defined LCu–CF3 complex, but

• )] generated in situ at the 22 hour mark. However, the yield versus time plot revealed that the phen-based reagent was clearly better at early reaction times. The plots revealed other interesting information. For the electron-rich aryl iodides, the reactivity difference for the SIMes copper complexes was

2-Methyl-2,4-pentanediol (MPD) boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization

• Julia Kinzel,
• Daniel F. Sauer,
• Marco Bocola,
• Marcus Arlt,
• Tayebeh Mirzaei Garakani,
• Andreas Thiel,
• Klaus Beckerle,
• Tino Polen,
• Jun Okuda and
• Ulrich Schwaneberg

Beilstein J. Org. Chem. 2017, 13, 1498–1506, doi:10.3762/bjoc.13.148

• reported for the Grubbs–Hoveyda type [29][47] or copper complexes [10] (Scheme 1). FhuA ΔCVFtev was dissolved in a solution containing 1.25% SDS. The state of FhuA ΔCVFtev is partially unfolded. The catalyst 1 easily accesses the thiol group (Cys545, numbering based on FhuA WT with PDB ID 1BY3 [24

α-Acetoxyarone synthesis via iodine-catalyzed and tert-butyl hydroperoxide-mediateded self-intermolecular oxidative coupling of aryl ketones

• Liquan Tan,
• Cui Chen and
• Weibing Liu

Beilstein J. Org. Chem. 2017, 13, 1079–1084, doi:10.3762/bjoc.13.107

• was limited to α-substituted aryl ketones, and acetophenones were unsuitable for this conversion. In addition, this method requires harsh catalytic conditions, using scarce iron and copper complexes. The development of novel metal-free methods for the preparation of α-acetoxyaryl ketones is therefore

Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

• Anne L. Schöffler,
• Ata Makarem,
• Frank Rominger and
• Bernd F. Straub

Beilstein J. Org. Chem. 2016, 12, 1566–1572, doi:10.3762/bjoc.12.151

• of the mandatory role of dinuclear copper complexes as catalyst intermediates has vastly improved (Scheme 1) [33][34][35][36][37]. In 2013, the Fokin group provided evidence for the dicopper pathway of CuAAC reactions by a series of kinetic and isotopic labeling studies [34]. In 2015, the Bertrand