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

• CACTUS, Campus Vida, 15782 Santiago de Compostela, Spain 10.3762/bjoc.19.145 Abstract The synthesis of zwitterionic dithiocarboxylate adducts was achieved by deprotonating various aldiminium or 1,2,3-triazolium salts with a strong base, followed by the nucleophilic addition of the in situ-generated

• prepared, while a few reports disclosed the formation of polynuclear clusters, in which the dithiocarboxylate unit underwent further chemical transformations [59][60][61]. To the best of our knowledge, 1,2,3-triazolium-5-dithiocarboxylate species are hitherto unknown in the literature, and only a single

• (−)-menthone was obtained in a separate step by deprotonating the corresponding aldiminium triflate with lithium diisopropylamide (LDA) at −78 °C [8]. Herein, we disclose the synthesis of three CAAC·CS2 and six MIC·CS2 inner salts from the corresponding aldiminium or 1,2,3-triazolium salts and carbon disulfide

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

• to be around 25 kcal mol−1 for model imidazol-2-ylidenes [7]. The ylidic structure confers NHC a nucleophilic character. Bertrand reported a new class of mesoionic carbenes 10 based on a 1,2,3-triazolium scaffold [8][9]. These NHCs, also known as remote or abnormal N-heterocyclic carbenes (aNHCs

• -worker [22] synthesized [(NHC)Cu(μ-I)2Cu(NHC)] complexes 16 (Scheme 8) from CuI and benzimidazolium salts and 18 (Scheme 9) from 1,2,3-triazolium salts. Both types of complexes turned out to be highly efficient catalysts for the [3 + 2] cycloaddition of azides with alkynes. The reactions were complete in

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

• -base tetracationic triazolium salt 156 in quantitative yield. Also, a free-base dyad 158c was obtained in 95% yield by the demetallation of zinc porphyrin 158a with trifluoroacetic acid in a CHCl3/MeOH mixture. These synthesized conjugates showed great affinity for major biological carriers like

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• through steric and electronic interactions involving peptoid amides and nearby side chains [17][18]. For example, N-substituted monomers bearing benzylic-type Nα-chiral groups including the phenylethyl [19][20][21], naphthylethyl [17][22][23][24], and triazolium groups [25][26][27], alkyl ammonium [28

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• performances as nucleophile precursors using a triazolium-amide chiral catalyst 34 [21] (Scheme 8a), as well as by Jacobsen in the desymmetrization of oxetanes 35 using TMSBr and squaramide 37 as catalyst [56] (Scheme 8b). For the latter, a more detailed mechanistic study was recently provided [57]. The

• ) vinylboronic acids. Enantioselective selenocyclization catalyzed by squaramide 28. Desymmetrization of meso-aziridines catalyzed by bifunctional thiourea catalyst 31. Anion-binding-catalyzed desymmetrization of a) meso-aziridines catalyzed by chiral triazolium catalyst 34 by Ooi et al., and b) oxetans

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• opening with allylamine. Purification gave 17 and 18, respectively, in a moderate yield as single diastereoisomers and with a good enantioselectivity. The mechanism of this NHC redox process is believed to proceed through the following mechanism (Scheme 3): After deprotonation of the triazolium salt

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• deprotonates the triazolium salt (Scheme 2). The reactivity of a series of cationic copper(I) complexes (1–6) was evaluated at 0.5 mol % loading using tosyl azide, phenylacetylene and diisopropylamine as benchmark substrates [31][32]. Various solvents were evaluated at room temperature under aerobic conditions

• through the formation of the corresponding triazolium salt B. The intermediate A can then react with the azide substrate to form a triazolyl–copper complex C. The latter can liberate the amidine product and regenerate either catalyst 6 (triazolium salt B is source of proton) or directly the acetylide

• complex A with concomitant loss of the triazolium salt Triaz.HBF4 (B, Scheme 9). To further confirm the formation of A, [Cu(Triaz)Cl] was reacted with phenylacetylene and sodium hydroxide (4 equiv), in toluene for 24 hours under an inert atmosphere. The independent synthesis of A was successfully achieved

Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• Xingyu Xu Shiqing Huang Zengyu Zhang Lei Cao Xiaoyu Yan Department of Chemistry, Renmin University of China, Beijing 100872, People’s Republic of China 10.3762/bjoc.16.10 Abstract The synthesis of 4,5-diiodo-1,3-dimesityl-1,2,3-triazolium salts with different anions have been developed. These

• triazolium salts show diverse aggregation via halogen bonding between C–I bonds and anions. Triazolium with halide anions exists as a tetramer with saddle conformation. Triazolium tetrafluoroborate exists as a trimer with Chinese lantern shape conformation. Triazolium trifluoroacetate and acetate exist as

• dimers, respectively, while the former shows boat conformation and the latter forms rectangle conformation. Triazolium salts form a linear polymer with polyiodide. Keywords: aggregation; 4,5-diiodo-1,2,3-triazolium salts; halogen bond; non-covalent interaction; Introduction The halogen bond (XB) is a

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• Mastaneh Safarnejad Shad Pulikkal Veettil Santhini Wim Dehaen Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium 10.3762/bjoc.15.211 Abstract In this short review, we describe different pathways for synthesizing 1,2,3-triazolium

• macrocycles and focus on their application in different areas of supramolecular chemistry. The synthesis is mostly relying on the well-known “click reaction” (CuAAC) leading to 1,4-disubstituted 1,2,3-triazoles that then can be quaternized. Applications of triazolium macrocycles thus prepared include

• -triazolium macrocycles; Review 1. Introduction Supramolecular chemistry – “The chemistry beyond the molecule” [1] – is an ever growing interdisciplinary area has emerged from the early host–guest chemistry to more elaborate bio-inspired supramolecular aggregates by exploiting various noncovalent

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• , followed by metalation of the triazolium salt 4 with silver oxide, which was immediately transmetalated with [RuCl2(p-cymene)]2. In our hands, purification using Albrecht’s trituration method was unsuccessful, however, neutral alumina column chromatography produced the desired model ruthenium metallocycle

• cycloaddition between monoazidocalix[4]arene 7 and phenylacetylene, affording monotriazolocalix[4]arene 11 in 87% yield (Scheme 4). Methylation of the triazole was also achieved using excess iodomethane in a rather protracted reaction, to yield the calix[4]arene triazolium iodide salt 12 in effectively

• even after using sub-stoichiometric quantities in the reaction. Attempted purification via alumina flash chromatography returned material that was assigned as the triazolium chloride salt (i.e., Cl– salt of triazolium 12; based on chemical shifts in the 1H and 13C NMR that were consistent with a

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• triazolochromene 14 and at the same time examine the stability under strong acidic conditions. Aldehyde appended triazolochromene 14 was synthesized in 85% yield, providing the proof for their relative stability under acidic conditions. Finally, triazolium salt 15 was prepared from 5a in 60% yield and renders a

• polar triazolium annulated chromene. Conclusion We developed a sequential one-pot three-component reaction to access a variety of novel triazolochromenes avoiding the purification of intermediate 3-nitro-2H-chromenes. The regiochemistry of the reaction was determined and proven, followed by a scope

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3⁺ + 2]-cycloaddition/rearrangement reactions

• Lin-bo Luan,
• Zi-jie Song,
• Zhi-ming Li and
• Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

• followed by a ring-expansion rearrangement. In the rearrangement reaction, the phenyl substituent in the initially formed spiro-triazolium adducts 16 underwent a [1,2]-migration from C(3) to the electron-deficient N(2). This led to the ring expansion from 6-membered piperidine to 7-membered diazepine

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• trichloroacetonitrile (Cl3CCN) [118]. This combination leads to the in situ formation of peroxy imidic acid 24, which then serves as the O-transfer reagent for the asymmetric α-hydroxylation of oxindoles 17 in the presence of the chiral triazolium-based ion pairing catalyst L1 (Scheme 11). Very recently, Toullec and co

• asymmetric α-amination reactions [145]. By using hydroxylamines 43 as simple N-containing reagents, the addition of these compounds to trichloroacetonitrile gives the reactive intermediates 44, which then serve as versatile electrophilic N-transfer reagents under asymmetric triazolium salt L catalysis

• (III)-based reductant. Asymmetric ammonium salt-catalysed α-photooxygenations. Asymmetric ammonium salt-catalysed α-hydroxylations using organic oxygen-transfer reagents. Asymmetric triazolium salt-catalysed α-hydroxylation with in situ generated peroxy imidic acid 24. Phase-transfer-catalysed

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

• Jan Szabo,
• Julian Greiner and
• Gerhard Maas

Beilstein J. Org. Chem. 2017, 13, 579–588, doi:10.3762/bjoc.13.57

• either symmetrical N,N’,N’’-tris(N-acyl-N-benzylamido)guanidines 6 or mesoionic 4-amino-1,2,4-triazolium-3-hydrazinides 7. The latter were converted into 1,2,4-triazolium salts by protonation or methylation at the hydrazinide nitrogen atom. Neutral 1,2,4-triazoles 10 were obtained by catalytic

• hydrogenation of an N-benzyl derivative. Crystal structure analyses of a 4-benzylamino-1,2,4-triazolium-3-hydrazinide and of two derived 1,2,4-triazolium salts are presented. Keywords: guanidines; mesoionic compounds; triaminoguanidinium salts; 1,2,4-triazolium-3-aminides; Introduction Easily accessible by

• of the reaction product, called “nitron” [15][16], was much later recognized [17] and structurally confirmed [18] as the mesoionic 1,2,4-triazolium-3-aminide II (Scheme 1). “Nitron” became known as an analytical reagent for the quantitative determination of nitrate [16][19], perchlorate, and some

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• out hidden acid catalysis due to the formation of trace quantities of HBr through hydrolysis of the substrate. To further enhance the reactivity of the halogen bond donors, Huber and colleagues later designed 5-iodo-1,2,3-triazolium-based multidentate salts L18 [83][84]. Triazolium salts L18 were

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• aldehydes and α,β-unsaturated esters (Scheme 8) [25][26]. Catalyzed by triazolium NHC-catalyst 35, electron-poor and neutral aromatic aldehydes reacted with methyl 2-acetamidoacrylate to access α-amino esters 34a with excellent enantioselectivity [25]. As expected, less electrophilic 4-methoxybenzaldehyde

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• -derived NHCs have found widespread application as catalysts for benzoin reactions, whereas triazolium-derived NHCs have emerged as popular catalysts for enantioselective benzoin transformations. Review Homo-benzoin reactions The homo-benzoin condensation constitutes an overall catalytic dimerization of an

• ][7]. Some additional recent examples are discussed below. A selected list of chiral NHC catalysts that have been explored for mediating asymmetric benzoin reactions is presented in Scheme 5. The bis-triazolium catalyst 9 developed by You promoted asymmetric benzoin reactions in 95% ee [13]. Enders

• developed the pyroglutamic acid-derived triazolium salt 10 which mediated benzoin reactions in similar enantioselectivities [14]. The chiral triazolium catalyst 11 transfers chiral information to the benzoin products by engaging in hydrogen-bonding interactions [15]. Waser’s chiral bifunctional (thio)urea

Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities

• Carmen Mejuto,
• Beatriz Royo,
• Gregorio Guisado-Barrios and
• Eduardo Peris

Beilstein J. Org. Chem. 2015, 11, 2584–2590, doi:10.3762/bjoc.11.278

• was obtained by the in situ deprotonation of the tris-triazolium salt 1 with potassium bis(trimethyl)silyl amide (KHMDS) in the presence of [RhCl(COD)]2 in THF at −78 °C (Scheme 2). It was isolated in 84% yield after purification by column chromatography. For the preparation of the related iridium(I

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• nucleophilic attack by the alcohol to form ester 108. The mechanism of the aerobic oxidative coupling of benzaldehyde with methanol in the presence of the 4-ethyl-1-methyl-1H-1,2,4-triazolium iodide/DBU system was studied in detail [114]. It was shown that the reaction proceeds via another mechanism, involving

Modulating NHC catalysis with fluorine

• Yannick P. Rey and
• Ryan Gilmour

Beilstein J. Org. Chem. 2013, 9, 2812–2820, doi:10.3762/bjoc.9.316

• , Münster, Germany 10.3762/bjoc.9.316 Abstract Fluorination often confers a range of advantages in modulating the conformation and reactivity of small molecule organocatalysts. By strategically introducing fluorine substituents, as part of a β-fluoroamine motif, in a triazolium pre-catalyst, it was

• derivatives are presented and the conformations are discussed. Upon deprotonation, the fluorinated triazolium salts generate catalytically active N-heterocyclic carbenes, which can then participate in the enantioselective Steglich rearrangement of oxazolyl carbonates to C-carboxyazlactones (e.r. up to 87.0

• charge at nitrogen generates the requisite X–Cα–Cβ–Fδ− system (X = N+), thus providing a facile approach to controlling rotation around this bond (ΦXCCF ≈ 60°). In this study, the influence of fluorination on catalyst behaviour is extended to the study of triazolium salts such as 2, which can be

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• including cinchona alkaloid derivatives, chiral phosphoric acids, chiral amino alcohols, chiral thioureas, chiral guanidines, and chiral 1,2,3-triazolium chlorides. In this review, the research work of enantioselective desymmetrization of meso-aziridines is organized into sections according to the employed

• generation of carbamodithioic acids from amine and carbon disulfide is also investigated to provide ring-opened products 76 to 80 in high yields and good enantioselectivities (Scheme 11). Chiral 1,2,3-triazolium chlorides Most recently, Ooi [52] and colleagues have described a desymmetrization of meso-N-p

• -tert-butylphenylsulfonylaziridines with trimethylsilyl halides by using novel chiral 1,2,3-triazolium chlorides (OC-49 to OC-55) as catalysts (Figure 11). The treatment of meso-aziridine with 1 equiv of chiral 1,2,3-triazolium chloride OC-49·Cl or Me3SiCl in toluene at −40 °C for 12 h did not result in

Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki–Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies

• Jeelani Basha Shaik,
• Venkatachalam Ramkumar,
• Babu Varghese and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2013, 9, 698–704, doi:10.3762/bjoc.9.79

• -dimesityl-3-methyl-1,2,3-triazolium iodide with freshly prepared silver oxide followed by transmetalation with Pd(Cl)2(CH3CN)2 yielded 1 as a pale yellow solid in 87% (Scheme 1). The acetate complex 2 was prepared by the transmetalation of the silver carbene complex with Pd(OAc)2. Addition of Pd(OAc)2 to in

• electronics applications. Experimental 1,4-Dimesityl-3-methyl-1,2,3-triazolium iodide was prepared from the corresponding triazole, which in turn was prepared by the click reaction of mesitylacetylene and mesitylazide according to the literature [27]. Complex 1 was synthesized in a similar manner as reported

• previously [27]. Synthesis of complex 1 [27] 1,4-Dimesityl-3-methyl-1,2,3-triazolium iodide (250 mg, 0.56 mmol) was treated with freshly prepared silver oxide (78 mg, 0.34 mmol, 0.6 equiv) in CH2Cl2 (12 mL). The solution was stirred at room temperature in the dark for 8 h. The silver carbene complex thus

Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids

• Paweł Borowiecki,
• Małgorzata Milner-Krawczyk and
• Jan Plenkiewicz

Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56

• (+)-8a–c and (+)-8e–f, which are exceedingly viscous liquids (gums), all of the chiral hydroxy-functionalized imidazolium and one of the triazolium salts are liquid at room temperature. Final products were characterized by 1H, 13C NMR and FTIR spectroscopy as well as high-resolution electrospray

• 5). Moreover, the chemical nature of the cationic head group influenced the overall toxicity of the CILs, which is in good agreement with several previous studies [60]. The imidazolium CILs exhibited visibly stronger antibacterial and antifungal activity than triazolium CILs (Tables 4–6). However

• compounds exhibited biological activity that was significantly dependent on the alkyl chain length, with considerably high toxicity of the substituents with 10–16 carbon atoms. The imidazolium salts revealed stronger antibacterial activity than their triazolium analogues. Model for the configurational

N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• -coupling of 1a was obtained. Encouraged by this result, we then attempted the other precatalysts 3b–e depicted in Figure 2. Imidazolium salt 3b and simple triazolium salt 3c gave no coupled product 5a (Table 1, entries 2 and 3). Further screening revealed that bicyclic triazolium salt 3d could catalyze the

• the cross-aza-benzoin reaction is shown in Scheme 3. Carbene I is generated by deprotonation of triazolium salt 3e in the presence of K2CO3. The carbene I reacts with aldehyde 1 to afford Breslow intermediate II, which could lead to benzoin (6), or tetrahedral intermediate III when treated with α

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• -unsaturated aldehydes can thus be explained by the low acidity of imidazolium ions [59]. Unlike triazolium and tetrazolium ions, imidazolium ions are unable to transfer a proton to the enamine unit in 16 (corresponding to 5 in the general Figure 2), which is necessary to close the catalytic cycle shown in