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Search for "cations" in Full Text gives 380 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies
Beilstein J. Org. Chem. 2018, 14, 1723–1733, doi:10.3762/bjoc.14.146
- that resorcinarenes are particularly suited hosts for both neutral and protonated N-heterocyclic compounds [19][20] and alkyl ammonium cations [21][22][23][24][25]. The resulting complexes have been extensively studied in both solid and solution state. The most common defined interactions involve
Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit
Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145
- initial trimesic tris-carboxylate anion (δ–, Figure 7a). Besides the electrostatic attraction between the tris-carboxylate anion and the P-1 piperazin-1-ium melamine G-1 cations, the occurrence of important H-bonding three interactions (>COδ(b)–···H(ax or eq)-NH+<) were identified, being supported by the
NH2+]3(–OOC)3C6H3 (Figure 1, linear connection, as a six-membered chelate, to the m-trivalent core), the H-bonding network in model 10 determined simpler angular connections of the P-1 piperazin-1-ium melamine G-1 cations around the trimesic tris-carboxylate anion core in a statistically favoured
A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene
Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134
- changes are rare. In this article, we present a thorough study on the host–guest chemistry of a conformationally adaptive macrocycle, namely per-O-ethoxyzorb[4]arene (ZB4). Similar to per-O-ethoxyoxatub[4]arene, ZB4 is capable of accommodating a wide range of organic cations. However, ZB4 does not show
- network. We have carefully looked into the properties of oxatub[n]arenes and found that the macrocycles have many unique properties. For example, oxatub[4]arene has a wide guest scope and can bind almost all of the common organic cations [32]. It also shows conformational responses to solvent change [33
- wide range of organic cations [32]. ZB4 is also a conformationally adaptive macrocycle. We wondered whether ZB4 has a wide guest binding scope. It was reported that quaternary ammonium-based organic cations (1+–3+) can be hosted by zorb[4]arenes [37][38]. Quaternary ammonium cations 4+ and 5+ and other
Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles
Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120
- , 44780 Bochum, Germany 10.3762/bjoc.14.120 Abstract The effects of the alkali cations Na+ and K+ were investigated in the alkaline electrochemical oxidation of glycerol over Pd nanoparticles (NPs) deposited on functionalized carbon nanotubes (CNTs). The electrocatalytic activity was assessed by cyclic
- reactions over Pt single crystal, polycrystalline Pt and Pt/C electrodes. They proposed two different adsorbate structures of hydrated alkali metal cations on the electrode, either via a hydrogen bonding between hydrating water and two OHad groups (1) or direct ion–dipole interactions between two OHad and
- the cation (2). The formation of the structures (1) or (2) was correlated to the hydration energies (ΔHM) of the cations. Highly charged species with a high ΔHM like Li+ were considered more likely to form structure (2), because the cation–OHads interaction is stronger than for cations with a low ΔHM
Recent applications of chiral calixarenes in asymmetric catalysis
Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117
- these catalysts confirmed the necessary role of the calixarene skeleton in phase-transfer catalysis by preorganizing and orienting the amide groups properly to favor the complexation of Na+ cations. The effect of the ester group in the substrate and other parameters on the reaction were also
- anion with the two hydroxy groups of the calixarene ligand to selectively direct the nucleophile towards one carbon atom of the π-allyl intermediate in the presence of potassium cations. In 2009 and 2010, Arnott et al. utilized a chiral isopropyloxazoline as an ortho-lithiation directing group in order
A three-armed cryptand with triazine and pyridine units: synthesis, structure and complexation with polycyclic aromatic compounds
Beilstein J. Org. Chem. 2018, 14, 1370–1377, doi:10.3762/bjoc.14.115
- titration; 1,3,5-triazine; Introduction Cryptands with C3-symmetric aromatic reference groups are exciting targets, on the one hand due to the challenges encountered in their synthesis and on the other due to their ability (macrobicyclic effect [1]) to form supramolecular assemblies with cations, anions or
Oligonucleotide analogues with cationic backbone linkages
Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111
- motifs, and nucleosyl amino acid (NAA)-derived modifications. The synthesis and properties of the corresponding oligonucleotide analogues are described. Keywords: backbone modifications; cations; DNA; oligonucleotides; zwitterions; Introduction Oligonucleotides have the unique ability to bind
One hundred years of benzotropone chemistry
Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98
- group were unable to determine the formation of homoazocinyl dianion intermediates due to the added benzene ring in 107 and 108 and concluded that the presence of imino ether does not enhance the homoaromaticity of 9C–10π dianions. Homoaromaticity, homotropylium cations, and homotropones have been
- of benzo[7]annulenylium cations 133a and 133b (Scheme 23) [49]. While the reaction of 11 with oxalyl bromide yielded bromobenzo[7]annulenenylium bromide 134a as a stable carbenium salt, the reaction of oxalyl chloride or phosgene with 11 afforded 7,7-dichloro-7H-benzo[7]annulene (135b) as a covalent
- compound that ionizes in liquid SO2 to the cation 134b. Treatment of cations with nucleophiles that are preferably added to the benzylic position (C-5 or C-9) yielded chloro- and bromo-5H-benzo[7]annulenes 136–143. According to Hückel molecular orbital (HMO) calculations, this observed regiochemistry is
An overview of recent advances in duplex DNA recognition by small molecules
Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93
- particular, we cover the advances made in DNA minor groove recognition using new analogues and derivatives of classical minor groove binders such as distamycin, netropsin, polyamides, bisbenzimidazoles and organic cations. We have also included new intercalating agents as well as major groove binding ligands
Polysubstituted ferrocenes as tunable redox mediators
Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86
- of 1.1 V and 1.4 V, respectively, probably due to a fast diffusion of 3 and 4 to the anode in the beam path (Figure 4, Figures S11–S14, Supporting Information File 1). In addition, precipitation of some poorly soluble [4][X] also occurs. During oxidation to the respective ferrocenium cations, the C=O
- Information File 1). The energy of the absorptions of the ferrocenium cations 1+–4+ decreases with the electron-withdrawing nature of the Cp ligands in the series 1+–4+, similar to the vis absorption maxima of the neutral ferrocenes 1–4. For the prominent band I of the cations 1+–4+, a linear and stronger
- potential in solution by spectroscopic techniques. Conclusion Ferrocenyl esters 1–4 with one to four ester substituents are reversibly oxidized to the respective ferrocenium cations 1+–4+, spanning a broad electrochemical potential range from 260 mV for 1 to 900 mV for 4 vs the ferrocene/ferrocenium redox
Phosphodiester models for cleavage of nucleic acids
Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68
- hydrogen bonding to the carbonyl groups of uracil base and the other cyclen serves as an electrophilic catalyst by interacting with the phosphodiester linkage. The tetra- and penta-cations of 2,6-bis(1,4,7,10-tetraazacyclododecan-1-ylmethyl)pyridine (11b) have given similar results. The possible role of
Stepwise radical cation Diels–Alder reaction via multiple pathways
Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59
- produces a radical cation species, which offers electrophilic reactivity for subsequent transformations. Enol ether radical cations are among the simplest members of this class and thus have been widely used in synthetic organic chemistry [13][14][15]. The Diels–Alder reaction is a classic reaction, and
Investigating radical cation chain processes in the electrocatalytic Diels–Alder reaction
Beilstein J. Org. Chem. 2018, 14, 642–647, doi:10.3762/bjoc.14.51
- cations (1·+, 3·+) at the cathode. Therefore, we tested higher concentrations of the substrates to facilitate the bulk SET processes. Gratifyingly, we were able to achieve increased current efficiencies when 100 mM and 300 mM concentrations of trans-anethole (1) were used (Table 1, entries 2 and 3
Synthesis of a sucrose-based macrocycle with unsymmetrical monosaccharides "arms"
Beilstein J. Org. Chem. 2018, 14, 634–641, doi:10.3762/bjoc.14.50
- ; Introduction Chiral macrocyclic compounds play an important role in supramolecular and biological systems [1][2]. Many of them serve as convenient receptors for cations [3], anions [4], ion pairs [5], neutral molecules [6] etc. Binaphthols [7][8][9], amino acids [10], chiral diamines [11][12], carbohydrates
Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis
Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269
- were not included in the above-mentioned review article. Increasing interest in phosphonium salts is also due to their use in drug design. It was demonstrated in the last decade that lipophilic cations having a triphenylphosphonium residue in the structure can be used as effective carriers of
- possible only in the presence of a strong base, such as, for example, DBU [34][35][36]. In the case of a real tautomeric equilibrium between aminovinylphosphonium and α-iminoalkylphosphonium cations, the isotopic exchange should occur easily (Scheme 20). Borodkin et al. have recently reported a new method
- -aminovinylphosphonium salts and tautomeric equilibrium between aminovinylphosphonium and α-iminoalkylphosphonium cations. Synthesis of 2-aminovinylphosphonium salts by reaction of (formylmethyl)triphenylphosphonium chloride with amines. Generation of ylides by reaction of vinyltriphenylphosphonium bromide with
Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study
Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268
- known from the literature as NMR shift reagent able to perform chiral recognition [24][25][26][27]. Guests 1–12 were selected for their diverse structural features. We considered both neutral and ionic species, in particular aliphatic and aromatic cations of different size and hydrophobic character
- and 2 and aliphatic cations 3 and 4 do not appreciably interact with the host. Lack of binding with the anions can be easily attributed to the occurrence of unfavourable Coulomb repulsion. On the other hand, the fact that even cations 3 and 4 do not show appreciable affinity for the host clearly
- the behaviour of diverse calix[4]resorcinarenes, including a proline derivative very similar to CAP. In particular, it was observed that the relevant octo-anion shows remarkable affinity towards aliphatic ammonium cations (as well as the tetra-anion of the title ligand bearing no proline groups
Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review
Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239
- metals to be used in these systems is of great importance. Several metal species are known to display important biological activities that are applied for the treatment or diagnosis of several diseases. So, BioMOFs should contain either endogenous metal cations essential for life or exogenous metals that
- water at approximately 80 °C and melt/decompose above 200–250 °C [124]. This type of BioMOFs enclosing lanthanides and cations with potential luminescence properties can be explored for theranostic applications. Figure 1 shows some examples of the networks obtained. Braga et al. synthesized new BioMOFs
Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole
Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232
- -free click reactions. Electron spin resonance (ESR) spectroscopy ESR is an ideal technique for validating the oxidation and spin state of copper cations. Elemental copper and copper(I) are ESR silent, whereas the copper(II) shows strong and characteristic lines revealing local properties of this ion
- and acetic acid added) showed that there are no copper(II) cations present in the final mixture (Figure 4). The ESR spectrum reveals only the presence of free radicals, characterized by sharp signal with g-value g ≈ 2.01. Milling the azide and alkyne with copper(I) catalytic system (CuI/DIPEA/acetic
Phosphonic acid: preparation and applications
Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219
- agents [95]. The high affinity of phosphonic acid to calcium ions is another feature of the coordination properties of phosphonic acids that triggered biomedical applications. This coordination property for calcium cations was further enhanced by placing two phosphonic acid moieties and one hydroxy group
Complexation of molecular clips containing fragments of diphenylglycoluril and benzocrown ethers with paraquat and its derivatives
Beilstein J. Org. Chem. 2017, 13, 2056–2067, doi:10.3762/bjoc.13.203
- in the crystals. Meanwhile the hydrogen bond between one hydroxy group of cation 82+ and an oxygen atom of the polyether chain of clip 3 has been observed. The inclusion complexes of clips 2 and 3 with cations 82+ and 92+ have 1:1 composition in the crystal phase (Figure 8 and Figure 9). Similar to
p-tert-Butylthiacalix[4]arenes functionalized by N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests
Beilstein J. Org. Chem. 2017, 13, 1940–1949, doi:10.3762/bjoc.13.188
- anions are larger in size than cations and therefore have a smaller charge in relation to their radius. It means that the electrostatic interactions for anions binding are weaker than for cations. Anions have various shape and geometry, and the design of receptors that are complementary to a specific
Mechanochemical synthesis of thioureas, ureas and guanidines
Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178
- research, Friščić et al. introduced the so called "ion and liquid-assisted grinding" or ILAG by recognizing the effect of cations such as Na+, K+ or NH4+ or anions like Cl−, NO3− and SO42− on the formation of polymorphs during LAG synthesis of metal-organic frameworks [21]. Recently, Jones et al. employed
Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles
Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170
- turned out that scandium clearly outperforms other rare earth cations hereby, which makes it thus difficult to say if this is really a classical phase-transfer-catalysed reaction or rather a Lewis acid catalysed transformation controlled by a chiral counter anion (it is well known that chiral counter
Block copolymers from ionic liquids for the preparation of thin carbonaceous shells
Beilstein J. Org. Chem. 2017, 13, 1693–1701, doi:10.3762/bjoc.13.163
- organic asymmetric cations, like imidazolium, pyridinium or alkylammonium and inorganic anions, such as halides, mineral acid anions, or polyatomic inorganic anions (PF6−, BF4−) [3]. Because of the steric hindrance, they are not able to build a strong lattice like inorganic salts. Therefore, not much
- incorporation of conductive carbon was shown to be a successful strategy [27]. While nanostructuring of inorganic particles increases the electrode/electrolyte contact area and allows an easier diffusion of the cations, the incorporation of electronic transport pathways allows an improved charging of the
Synthesis and metal binding properties of N-alkylcarboxyspiropyrans
Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154
- . In this study, we describe an efficient synthesis of spiropyrans with 2–12 carbon atom alkylcarboxylate substituents, and a systematic analysis of their interactions with metal cations using 1H NMR and UV-visible spectroscopy. All N-alkylcarboxyspiropyrans in this study displayed a strong preference
- for binding divalent metal cations and a modest increase in M2+ binding affinity correlated with increased alkycarboxylate tether length. Keywords: carboxylate ligand; merocyanine; metal binding; photochromism; spiropyran; Introduction Spiropyrans are a class of spiro-fused indolochromene (e.g
- been extensively exploited [2]. Spiropyrans bearing an N-alkylcarboxylate tether are photo-reversible colourimetric/fluorimetric receptors for metal cations [3][4][5] and amino acids [6], and serve as convenient building blocks in the synthesis of dynamic materials [7] (Figure 1). In this latter role
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