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

• [75]. However, the major drawback with using these catalysts in A3 reactions was the loss of the catalyst at the end of the reaction. Furthermore, on using Au(I), Ag(I), and Cu(I) in ionic liquids, as well as supported Au(III), Ag(I), CuI, and CuCl to catalyze A3 coupling reactions under heterogeneous

• employed for the preparation of numerous NHC–Cu complexes, requires the use of strong bases and rigorous inert conditions. However, an alternative method called transmetallation method has also been employed for the preparation of NHC–Cu(I) complexes by using NHC transfer reagents. For this purpose, NHC–Ag

• (I) complexes are frequently used to prepare NHC complexes of late transition metals [37]. As mentioned earlier, Diez-González et al. prepared some NHC–Cu(I) complexes, such as 69 through transmetallation by reacting [(SIPr)AgCl] 68 with the corresponding copper salt at rt (Scheme 23). However

Enantioselective total synthesis of putative dihydrorosefuran, a monoterpene with an unique 2,5-dihydrofuran structure

• Irene Torres-García,
• Josefa L. López-Martínez,
• Rocío López-Domene,
• Manuel Muñoz-Dorado,
• Ignacio Rodríguez-García and
• Miriam Álvarez-Corral

Beilstein J. Org. Chem. 2022, 18, 1264–1269, doi:10.3762/bjoc.18.132

• dihydrorosefuran, a compound allegedly identified in Artemisia pallens and Tagetes mendocina, has been developed. The key steps in the five-step 36% overall yield synthesis are a CpTiIIICl2 mediated Barbier-type allenylation of a linear aldehyde and the formation of a 2,5-dihydrofuran scaffold through a Ag(I

• . Keywords: Ag(I) cyclization; allenylation; CpTiCl2; 2,5-dihydrofurans; monoterpenes; Introduction Artemisia pallens is an aromatic plant from southern India whose essential oil, known as Davana oil, has shown increasing interest mainly for its use in some beverages, cakes, pastries, etc., as well as in

• decided to perform its total synthesis. Results and Discussion Our synthetic strategy is based on two metal-mediated steps (Scheme 1). In this way, we thought that the 2,5-dihydrofuran structural motif that is found in the target molecule 1 could be prepared through a Ag(I)-induced intramolecular addition

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• compatible with the nucleophilic capture process. In the proposed mechanism, the α-hydrogen of the alkyl nitrile is deprotonated to form an organosilver species which undergoes SET oxidation with Ag(I) to afford the alkyl radical. Next, the α-cyanocarbon radical can add across the styrene derivative

• generating a benzylic radical which can be oxidized by Ag(I) to afford the corresponding benzylic cation. Nucleophilic trapping with an amine will produce the final product. In the same year, Song and co-workers reported a dehydrogenative 1,2-difunctionalization of conjugated alkenes 107 with silanes 92 and

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• Pd(II) [8][9][10], Ru(II) [11][12][13], Rh(III) [14][15][16], Mn(II) [17][18][19], Au(II/I) [20][21][22], Ag(I) [23][24][25] etc. in both cascade and sequential reactions have been published. Electrophilic Hg(II) salts are important reagents in organic synthesis and there is published literature

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• excellent yields and enantioselectivities in most of the cases (with up to 99% yield and 99% ee; entries 6–24, Table 2). Several substrates did not even require the addition of Ag(I) salts to achieve high yields (entries 7, 10, 12, 17, 22, and 23, Table 2) [34][35]. An interesting finding was that β-(2

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• observed. These findings imply that the transformation may involve a radical process rather than an ionic process. On the basis of previous reports [23][24][25][26], we propose a radical mechanism involving the silver promoter, as illustrated in Scheme 5. In this mechanism, Ag(I) was oxidized by

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• mispairs with a reduced ATP affinity. A fluorescence spectroscopy assay and a binding assay with immobilized ATP were used to evaluate the aptamer derivatives. Upon the addition of one Ag(I) ion per mispair, stabilizing Im–Ag(I)–Im base pairs were formed. As a result, the affinity of the aptamer derivative

• precedence for an aptamer whose affinity is restored upon metal-mediated base-pair formation. One example exists of a Ag(I)-binding aptamer, but that aptamer does not rely on the formation of a Ag(I)-mediated base pair [23][24]. The aptamer selected for this study is the ATP-binding aptamer (ATP, adenosine

• versatility. The metal-mediated base pair chosen for this study is based on the artificial imidazole 2’-deoxyribonucleoside (Im). This nucleoside is well known to form highly stabilizing Ag(I)-mediated Im–Ag(I)–Im base pairs (Figure 1) [30][31][32][33] and has already been proposed for a use in various

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• establish high-yielding and selective oxidative coupling reactions, has afforded new and greener synthetic protocols for biaryls [5][6][7]. Several oxidants, such as the salts of Ag(I&II) [8], Ti(III&IV) [9], Mn(III) [10], Ce(IV) [11], Sn(IV) [12] and Fe(III) [13], as well as the hypervalent iodine reagents

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• , together with a metal hydride or a low-valent metal complex. Hence, in order to reoxidize the metal catalyst, excess of an external oxidant, such as Cu(II) or Ag(I) salts, was frequently used. On the other hand, photoredox catalysis has been mainly employed for electron-transfer reactions and, remarkably

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• highlighted the two possible arrangements of the ligands that led to different diastereoisomeric macrocycles (Figure 1a,b). In Figure 1a, each silver cation was coordinated to two sulfur atoms with the same configuration (named head-to-head coordination mode for ligands) meanwhile in Figure 1b, each Ag(I

• nitrate complex was thus soluble in chlorinated solvents. In the presence of the bulky triphenylphosphine silver triflate salt, a monocoordination occurred between Ag(I) and each sulfur atom of ligand 1 leading to a discrete complex (syn-1)·(Ph3PAgOTf)2, as revealed by 1H NMR and X-ray (Figure 3). The

• /cycloisomerization was previously described in high yields (>95%) using 5 mol % catalyst loadings starting from 2-(alkynyl)quinoline-3-carbaldehyde [60][61] with AgOTf catalyst and starting from 2-alkynylbenzaldehyde derivatives [62] in the presence of a macrocyclic pyridine-tetraaza complex of Ag(I) as a catalyst

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• -modifications, encompassing the use of catalysts based on complexes of Fe(III), Co(III), Ni(II), Cu(II), Ru(II), Rh(III), Ir(III), Pd(II), Ag(I) and Au(I) [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Limitations of the latter strategy, such as the poor reactivity and

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

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• (terpyridines; Figure 1c) ligands [49]. The model systems depicted in Figure 1 are constructed using metals like Pd(II) or Pt(II) ions for square planar geometry, Cu(I) or Ag(I) ions for tetrahedral geometry and Co(II)/Cu(II)/Fe(II)/Zn(II)/Hg(II) for octahedral organization [50]. In Figure 2, Busch’s first

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

• Vaida Milišiūnaitė,
• Rūta Paulavičiūtė,
• Eglė Arbačiauskienė,
• Vytas Martynaitis,
• Wolfgang Holzer and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2019, 15, 679–684, doi:10.3762/bjoc.15.62

• construction of the 2H-furo[2,3-c]pyrazole ring system by a Sonogashira-type alkynylation of 4-iodopyrazol-3-ol and subsequent intramolecular 5-endo-dig cyclization of the obtained hydroxyalkynyl substrate mediated by a Ag(I) catalyst. Results and Discussion The synthetic strategy designed to construct the 2H

Tandem copper and photoredox catalysis in photocatalytic alkene difunctionalization reactions

• Nicholas L. Reed,
• Madeline I. Herman,
• Vladimir P. Miltchev and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2019, 15, 351–356, doi:10.3762/bjoc.15.30

• describe a method for alkene oxyamination and diamination that utilizes simple carbamate and urea groups as nucleophilic heteroatom donors. This method uses a tandem copper–photoredox catalyst system that is operationally convenient. The identity of the terminal oxidant is critical in these studies. Ag(I

• oxidant in a stoichiometric fashion. Thus, it seems clear that the role of the Ag(I) additive in this reaction is to re-oxidize Cu(I) to Cu(II), and that the Cu(II) salt in this transformation is indeed a cocatalyst for the oxidative difunctionalization of styrenes. Efforts to render this transformation

• secondary terminal oxidant, and that Ag(I) salts appear to be uniquely effective in this capacity. This work thus provides a platform for the development of enantioselective photocatalytic alkene difunctionalization reactions that can use a chiral Cu(II) complex as a substoichiometric catalyst rather than

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• functionalization reaction. However, AgNO3 was superior than FeSO4 according to the reaction yields and time. Interestingly, aromatic cyclopropanols delivered higher yields than aliphatic ones. The mechanism for the Ag(I)-catalyzed oxidative ring-opening and functionalization of cyclopropanols with quinones is

• outlined in Scheme 21. Firstly, the sulfate radical anion 97 is generated from persulfate 96 under the action of Ag(I). Next, the radical 97 reacts with cyclopropanol 91 to give the cyclopropoxy radical 98, which undergoes a ring-opening process to produce β-keto radical 99. The radical 100 is formed

• through the addition of radical 99 to the quinones 94. Finally, the intermediate 100 occurres reoxidation with Ag(II) to provide the final product 95 along with regenerated Ag(I). In 2015, Duan et al. developed a Ag(I)-catalyzed oxidative ring-opening of cyclopropanols 91 with heteroarenes 101 or 103 for

An efficient and facile access to highly functionalized pyrrole derivatives

• Meng Gao,
• Wenting Zhao,
• Hongyi Zhao,
• Ziyun Lin,
• Dongfeng Zhang and
• Haihong Huang

Beilstein J. Org. Chem. 2018, 14, 884–890, doi:10.3762/bjoc.14.75

• Chinese Academy of Medical Sciences, 1 Xian Nong Tan Street, Beijing 100050, China 10.3762/bjoc.14.75 Abstract A straightforward and one-pot synthesis of pyrrolo[3,4-c]pyrrole-1,3-diones via Ag(I)-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with N-alkyl maleimide, followed by readily

• -1,3-diones [8][9][10] via 1,3-dipolar cycloaddition without any chiral catalysts/ligands and a facile access to highly substituted pyrroles with amide groups or ester groups. Herein, we propose a straightforward and one-pot synthesis of pyrrolo[3,4-c]pyrrole-1,3-diones via Ag(I)-catalyzed 1,3-dipolar

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• catalytic amount of AgNO3 as reported by Tan and co-workers (Scheme 26) [47]. In the absence of AgNO3 the reaction did not work. Notably, N-alkyl and N-aryl protected substrates worked well, whereas N-acyl and N–H derivatives failed to deliver the desired products. Mechanistically, Ag(I) was initially

• methacrylamides, so far described, provided oxindoles via a 5-exo trig cyclization. Starting from cinnamamides 53, Mai, Xiao and co-workers reported a 6-endo trig cyclisation leading to 3,4-disubstituted dihydroquinolin-2(1H)-ones 54 (Scheme 30) [52]. Ag(I) was oxidised by the persulfate anion (S2O82–) to

Metal-mediated base pairs in parallel-stranded DNA

• Jens Müller

Beilstein J. Org. Chem. 2017, 13, 2671–2681, doi:10.3762/bjoc.13.265

• glycosidic bonds, parallel-stranded duplexes have been investigated. In many cases, such as the well-established cytosine–Ag(I)–cytosine base pair, metal complex formation is more stabilizing in parallel-stranded DNA than in antiparallel-stranded DNA. This review presents an overview of all metal-mediated

• -mediated base pairs One of the first metal-mediated base pairs investigated both in parallel- and antiparallel-stranded DNA duplexes is the C–Ag(I)–C pair. The geometry of this base pair within regular B-DNA is depicted in Scheme 4a. It has been unambiguously proven by experimental structure determinations

• was found to be slightly asymmetric with an N–Ag(I)–N angle of 161.7°. This asymmetry contrasts that of the symmetric hemiprotonated CH+:C base pair known from i-motif structures and is the result of the larger size of the Ag(I) ion compared with a proton. Hence, only one rather than two hydrogen

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• mol % of either a Cu(I), Ag(I), or Pd(II) catalyst in the presence of MeOH (or other simple alcohols, not shown) at room temperature. In all cases the yield was either very high or quantitative, the conditions were mild, and the reaction stereoselective for the 1,2-cis methyl glycoside (Table 8). The

Direct arylation catalysis with chloro[8-(dimesitylboryl)quinoline-κN]copper(I)

• Sem Raj Tamang and
• James D. Hoefelmeyer

Beilstein J. Org. Chem. 2016, 12, 2757–2762, doi:10.3762/bjoc.12.272

• use of ambiphilic molecules as ligands for transition metals has given rise to an important new class of catalysts [49]. In previous work from our laboratory, we prepared the intramolecular frustrated Lewis pair 8-quinolyldimesitylborane (1) and its complexes with Cu(I), Ag(I), and Pd(II) [50

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• product (Scheme 14; unoptimized yields). Notably, all three stoichiometric reactions now proceeded in the absence of other additives, such as BQ or Ag(I) salts, which are required for the catalytic versions to proceed efficiently. Although Lloyd-Jones and Booker-Milburn also reported the reaction of a

• indicating that no catalyst turnover was occurring in the absence of a Ag(I) salt. Surprisingly, when 15 equivalents of AgOAc were added along with an excess of both coupling partners, but without the addition of HBF4 beyond the three equivalents required for initial palladacycle formation, no coupling

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• 4 with ferricenium hexafluorophosphate led to a stable biferrocenium polymer while oxidation with Au(III) or Ag(I) allowed the formation of networks with nanosnake morphology, consisting of mixed-valent Fe(II)–Fe(III) polymers that encapsulate metal (Au or Ag) nanoparticles (NPs). These polymers

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• /H2O, catalyzed by CuSO4/sodium ascorbate, providing the first triazole-bearing intermediate (Scheme 11). They then performed the Ag(I)-catalyzed deprotection of the TMS-protected alkyne moiety, followed by another CuAAC reaction of the unmasked terminal alkyne with the second azide, giving the desired