Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• ]arene. Pillararenes have electron-rich cavities that facilitate the combination with various electron-deficient guest molecules, such as alkylammonium, pyridinium, and imidazolium cations. Compared to other macrocycles, pillararenes exhibit a high degree of symmetry and rigidity, which gives them a

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• [36][37][38], conjugated polymers [39][40][41][42], quantum dots [43][44] and sensors based on organic receptors such as imidazolium, ammonium, guanidinium [45][46][47][48][49][50][51][52], etc. have also been developed. Imidazolium based synthetic receptors typically utilize a combination of

• electrostatic and (C–H)···O− hydrogen bonds involving the acidic proton at the 2-position of the imidazolium moiety to bind to ATP and other phosphate analytes [46]. A number of cyclophanes and tweezers [53][54][55][56] have been reported possessing the following common structural features: a) the presence of

• multiple imidazolium groups to overcome the high hydration enthalpy of phosphates and b) the imidazolium groups are connected to aromatic moieties such as anthracene, pyrene, etc. The variation in the luminescence of the aromatic moieties signals the binding event and furthermore, they provide additional

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• binding of these anions to the immobilized receptor units strengthened their interaction with a simultaneously present bis(imidazolium) ion, which in turn caused nanoparticle crosslinking [16][17]. Our group recently showed that a mixed monolayer-protected AuNP containing solubilizing triethylene glycol

Synergy between supported ionic liquid-like phases and immobilized palladium N-heterocyclic carbene–phosphine complexes for the Negishi reaction under flow conditions

• Edgar Peris,
• Raúl Porcar,
• María Macia,
• Jesús Alcázar,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2020, 16, 1924–1935, doi:10.3762/bjoc.16.159

• corresponding Pd–NHC complexes 4a and 4b (Scheme 1) were obtained by treatment of the supported imidazolium species with Pd(OAc)2 in the presence of a base. The amount of immobilized NHC ligand was determined by elemental analysis, while the palladium loaded on the polymer was determined by ICP analyses (see

• inactive species and keeping their activity for further catalytic cycles. Three different SILLPs were evaluated displaying different imidazolium substitution patterns and a loading of IL-like fragments of 13–24% by weight. Figure 4 summarizes the results obtained for this study. The presence of SILLPs

• affected both activity and Pd leaching. Regarding the activity, the presence of methyl imidazolium groups in SILLP 9a slightly reduced the catalytic activity, while the presence of butyl- and methyldecylimidazolium units (SILLPs 9b and 9c, respectively) led to more active systems. This can be clearly

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

• products (e.g., 316) yielded nonracemic secondary (e.g., 317) and tertiary alcohols (e.g., 319). The presence of Cu(OTf)2, an imidazolium salt, and NaOMe leads to a chiral NHC–Cu complex, which, in the presence of B2pin2, generates the corresponding B–Cu species followed by its addition to allylic

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

• Cu(I)-catalyzed cyclization between CRGO–N3 (93) and 1-propargyl-3-methylimidazolium bromide (94) was used to attach the imidazolium moiety to the surface of the CRGO. Finally, a graphene-containing copper complex of N-heterocyclic carbene, (NHC)-Cu (96), was produced via proton exchange of the

• imidazolium scaffold with a Cu(I) (Scheme 21). The reaction between benzyl azide and alkynes proceeded in deuterated THF at 40 °C within 72 h using 2.0 mol % of the catalyst to obtain the desired products with good to high yields (Scheme 21). The nanocatalyst 96 could be readily recycled for use in more than

Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands

• Shohei Mimura,
• Sho Mizushima,
• Yohei Shimizu and
• Masaya Sawamura

Beilstein J. Org. Chem. 2020, 16, 537–543, doi:10.3762/bjoc.16.50

• protons of the acidic imidazolium C–H and phenol O–H groups of the L4·HBF4 adduct in the presence of CuCl to generate a phenoxy copper(I) species A. As a result, all LiOt-Bu (20 mol %) is consumed in this step. Thus, the system is neutral. Transmetalation between A and (EtO)2MeSiH produces the copper

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• sterically crowded biaryl ligands as they showed outstanding performances [8]. Phosphines with imidazole and imidazoline functional groups present some interesting features. The imidazolium functionality mimics active sites in biological molecules [83][84]. The ionic nature adds another dimension to the

• advantage of this fact by synthesizing a class of N-tethered phosphine imidazole ligands (Scheme 16, route A). The lithiation of the presynthesized chloromethylimidazolium iodide 82 and subsequent trapping with borane-protected di-tert-butylphosphine gave the imidazolium borane adduct 83a. The subsequent

• chlorodiphenylphosphine, afforded 1-methyl-4,5-bis(diphenylphosphino)imidazole (85). Finally, N-methylation gave the imidazolium salt derivative 86 in good yield (65%). Preparation of N-heterocyclic phosphines via metal-catalyzed P–C/N bond formation There is limited availability of certain N-containing precursors and

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors

• Delphine Pichon,
• Jennifer Morvan,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24

• -catalyzed conjugate addition of alkyl boranes to α,β-unsaturated 2-acyl-1-methylbenzimidazoles 33 [36]. Based on a previous study dealing with the CuCl/IMes-catalyzed addition of various alkylated 9BBN derivatives [37], the authors screened a set of various chiral NHC precursors. The imidazolium compound

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• systems could operate copper-free [25][27][29] and/or auxiliary base-free conditions [30]. Recently, some “designer" ionic liquids were also developed for this purpose [29][30][31][32][33] from which an imidazolium-based piperidine-appended one could act as task specific compound operating either as a

• of valerate-based ionic liquids, the conventional imidazolium-type media and tetrabutylphosphonium 4-ethoxyvalerate ([TBP][4EtOV]) were compared in the coupling of iodobenzene (1a) and phenylacetylene (2a) as a model reaction (Scheme 1) under typically used “Sonogashira conditions” [7][35]. Because

• detected in imidazolium-type ILs. However, complete conversion of 1a was observed in [TBP][4EtOV], without Et3N, proving that the solvent can act as a base in itself (Table 1, #2) as it was demonstrated for Cu-catalyzed C–N coupling reactions [34]. When, we attempted to couple 1a and 2a in the absence of

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• , phenolates), acyl anions (generated by umpolung of aldehydes with imidazolium salts) and by palladium-catalyzed cross-coupling reactions (Suzuki, Stille) [10]. A related Stille cross coupling of a benzo[c][2,7]naphthyridine bearing a triflate group at C-5 gave an intermediate for the total synthesis of

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

• and imidazolium which can recognize different anions, have been reported in the literature. As a matter of fact, porphyrin macrocycles are used for sensing of anionic compounds by a measurable physical response due to their intrinsic optical and redox properties [38]. Beer and co-workers have

• examined with chloride, acetate, cyanide and dihydrogenphosphate anions by 1H NMR titrations in CD3CN, DMSO-d6 or CDCl3 using the corresponding salts. The titrations of triazolium macrocycle 11 with acetate showed that the bis(imidazolium) receptor 11 underwent a de-shielding of its C(5)–H heteroaromatic

• its bis(imidazolium) analogue. Given that, the highest affinity of this heterophane system was toward acetate (Ka = 5.0 × 103 M−1) in CD3CN. Although the iodide ion is biologically important because of its indispensable role in thyroid gland function, among all of the reported receptors in the

Installation of -SO₂F groups onto primary amides

• Jing Liu,
• Shi-Meng Wang,
• Njud S. Alharbi and
• Hua-Li Qin

Beilstein J. Org. Chem. 2019, 15, 1907–1912, doi:10.3762/bjoc.15.186

• reactions of phenols (or alcohols) with SO2F2 [29] or the fluorosulfuryl imidazolium salt were developed for mild and effective formation of the corresponding fluorosulfates to act as biological probes in chemical proteomics studies (Scheme 1, (1)) [1][30]. On the other hand, the reactions of aliphatic or

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• -containing ruthenium catalysts required preliminary synthesis of the imidazolium ligand and o-vinylbenzylamines (Figure 2). Whereas numerous methods for the preparation of the carbene precursor are known, no satisfactory suitable approach for the synthesis of ortho-substituted styrenes was found. Several

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• imidazole N-oxides with 1-bromopentane or 1-bromododecane open access to diversely substituted, non-symmetric 1,3-dialkoxyimidazolium salts. Adamantyloxyamine reacts with glyoxal and formaldehyde in the presence of hydrobromic acid yielding symmetric 1,3-di(adamantyloxy)-1H-imidazolium bromide in good yield

• . Deprotonation of the latter with triethylamine in the presence of elemental sulfur allows the in situ generation of the corresponding imidazol-2-ylidene, which traps elemental sulfur yielding a 1,3-dihydro-2H-imidazole-2-thione as the final product. Keywords: alkoxyamines; imidazole N-oxides; imidazolium salts

• approach to these products comprises the alkylation (in most cases methylation) of 1-hydroxyimidazole N-oxides. However, the products of the monomethylation could not be obtained, but symmetric N,N-disubstituted imidazolium salts resulting from double O-alkylation were isolated [18]. On the other hand

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• ][37]. In an attempt, Gogoi et al. have reported new nanostructured sulfonated catalysts (3-methyl-1-sulfo-1H-imidazolium metal chlorides) containing both Lewis and Brønsted acidic sites 3–5 using the reaction of 3-methyl-1-sulfo-1H-imidazolium chloride (2) with FeCl3, ZnCl2 or CuCl in an inert

• atmosphere for 2 h. The 3-methyl-1-sulfo-1H-imidazolium metal chlorides [Msim][FeCl4] (3), [Msim][ZnCl3] (4), and [Msim][CuCl2] (5) were examined for the selective synthesis of bis(indolyl)methane derivatives 8 and the results showed that more acidic [Msim][FeCl4] catalyst 3 produces excellent yields of

• product solution in chloroform [39]. 1,3-Disulfo-1H-imidazolium carboxylate ILs [Dsim][carboxylate] 17–19 were synthesized using environmentally benign reactions between 1,3-disulfo-1H-imidazolium chloride [Dsim][Cl] (10) and three different carboxylic acids (CH3COOH, CCl3COOH, CF3COOH). The more acidic

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• the p-tert-butylthiacalix[4]arene platform with 1,3-alternate conformation having polyammonium binding sites. They were shown to effectively interact with calf thymus DNA causing a 4-fold compaction of the latter [25]. Related macrocycles containing two cationic imidazolium fragments demonstrated a

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• rate. High buffer concentration has to be used and this makes elimination of salt and co-solute effects difficult. Since histidine residues are known to play a central role in the catalytic center of RNase A [58], one of the most extensively studied protein nucleases, catalysis by imidazole/imidazolium

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• temperature. While monodentate phosphines such as PPh3 and PCy3 were entirely ineffective (Table 1, entries 1 and 2), common bulky NHC precursors such as 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride (IMes·HCl) and 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride (IPr·HCl) promoted the coupling

Enhanced quantum yields by sterically demanding aryl-substituted β-diketonate ancillary ligands

• Rebecca Pittkowski and
• Thomas Strassner

Beilstein J. Org. Chem. 2018, 14, 664–671, doi:10.3762/bjoc.14.54

• β-diketonates on the emission properties of C^C* cyclometalated complexes, employing the unsubstituted methyl-phenyl-imidazolium ligand. The quantum yield was significantly enhanced by changing the auxiliary ligand from acetylacetonate, where the corresponding platinum(II) complex shows only a very

• synthesized from 3-methyl-1-phenylimidazolium iodide (1) according to a modified literature procedure (Scheme 1) [41][42]. The starting imidazolium salt 1 was prepared from phenylimidazole by addition of methyl iodide as previously described [43]. Complexes 2 and 3 were obtained as yellow solids in isolated

• calculations. Experimental Both complexes were characterized by 1H, 13C, and 195Pt NMR spectroscopy, ESIMS, and elemental analysis. Formation of the carbene complexes was verified by the disappearance of the characteristic NCHN proton signal of the imidazolium salt in the 1H NMR experiment. The syntheses of

Enzyme-free genetic copying of DNA and RNA sequences

• Marilyne Sosson and
• Clemens Richert

Beilstein J. Org. Chem. 2018, 14, 603–617, doi:10.3762/bjoc.14.47

• direction (P3'→N5'), using 3'-phosphates of 3'-amino-2',3'-dideoxynucleosides [47]. Activation chemistry Imidazolium bisphosphates During our work on the effect of leaving groups on the yield of primer extension reactions, we noticed a burst phase in the kinetics of methylimidazolides that was only observed

• with monomers that were not carefully purified. The high reactivity was traced to a species with a chemical shift of −10.8 ppm in the 31P NMR spectrum that was identified as the imidazolium bisphosphate (Figure 12 and Figure 13) [34]. We calculated a second order rate constant for the reaction of the

• imidazolium bisphosphate with the primer of 2.9 × 104 M−1 h−1, which is approx. 600-fold larger than that of the pure methylimidazolide. The kinetics and analytical data were presented in the Supporting Information of ref. [34]. Shortly afterwards, Szostak and co-workers published a series of papers on the

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• derivatives, obtained by anchoring suitable polyammonium or imidazolium pendant groups onto the main macrocycle scaffold [23][24][25][26][27][28]. The latter example is interesting, because of the well-known ability of these macrocycles to form inclusion complexes with diverse organic guest molecules [29][30

Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268

• outlines an important role assumed by π–π interactions. In fact, the small aromatic imidazolium cation 5 is appreciably included into CAP−2, although with a relatively small binding constant (K = 250 ± 20 M−1; ΔΘ = −14.6 ± 0.4 deg dm−1 M−1). It is interesting to notice that significant affinity towards CAP

• mono-cations 6, 9 and 12 (the dication 11 cannot be compared, because it forms only the 2:1 complexes with CAP−2 and CAP−3). However, the relevant trends for K1 values are slightly different. Similarly to guest 7, the imidazolium cation 12 shows a bell-shaped trend with its maximum for CAP−2 (the p

• forms a stable 2:1 complex only with CAP−3, whereas the imidazolium derivative 12 forms a 2:1 complex with CAP−2. The whole of these results suggests that the stability of a possible 2:1 complex requires once again a compromise between several factors, and that the optimum conditions largely vary