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Search for "cations" in Full Text gives 393 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions
Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268
- , D2SO4), (arysulfonyl)allenes (ArSO2–CR1=C=CR2R3) and (arylsulfinyl)allenes (ArSO–CR1=C=CR2R3) undergo cyclization into the corresponding stable 1,2-oxathiolium ions, which were studied by means of NMR and DFT calculations. Quenching of solutions of these cations with low nucleophilic media, aqueous HCl
- of species A, B. The comparison of 13C NMR spectra of oxathiolylium A, B and oxaphospholium P1, P2 ions shows that for the former species the signal of carbon C5 is about 10–15 ppm downfield shifted relatively the same signal in the cations P1, P2 (Table 1). This reveals that carbon C5 bears a rather
- large positive charge in cations A, B. For dication Bh, different signals were detected for quaternary carbons C5 and C5', and vinyl carbons C4 and C4', etc., that, probably, indicates formation of two diastereomers (one meso-form and one pair of enantiomers) due to the stereogenic sulfur centers. In
Oxidative and reductive cyclization in stiff dithienylethenes
Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259
- radical cations [34][35] and simple dithienylethenes [36][37][38]. As such, we postulate an equilibrium between both E- and Z-radical cations with the latter rapidly reacting to the closed isomer. To gain a deeper mechanistic understanding of the oxidative cyclization, the evolution of the UV–vis
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
Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253
- cations. The 1H NMR spectrum displayed all protons of two -NMe2 groups as a singlet in the region of 3–3.2 ppm. On the other hand, the carbon chemical shift of C=N appeared around 134.7 ppm and 119.9 ppm attributed to two types of the chemical environment of the C=N carbon [46]. The three-component
Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers
Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241
- deprivation, pH, anaerobiosis, as well as biocides, polyamines, cations and carbon sources could also act as external triggers leading to adaptive resistance. The common effect of these stimuli seems to be an alteration in expression patterns ultimately impacting, e.g., efflux pump or enzymatic activity, as
Carbonylonium ions: the onium ions of the carbonyl group
Beilstein J. Org. Chem. 2018, 14, 2568–2571, doi:10.3762/bjoc.14.233
- Daniel Blanco-Ania Floris P. J. T. Rutjes Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands 10.3762/bjoc.14.233 Abstract The nomenclature of cations R1C(=O+R3)R2 (R1, R2, R3 = H or organyl) has been examined and shown to be in a state
Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide
Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210
- cycloaddition of azides with activated dipolarophiles such as strained cyclic alkynes, enamines, enolates, electron-deficient olefins, ylides, iminium cations and alkyne anions, etc., have been identified as reliable approaches to access 1,2,3-triazole scaffolds with multiple substitution patterns [39][40][41
Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands
Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195
- . This is the reverse Hofmeister effect, and in complex biomacromolecules we surmise that both effects are in operation, and that in very general terms it is the balance between these that dictates the properties of a particular macromolecule under specific conditions. Cations can also induce Hofmeister
- effects, but these are usually much weaker, and we believe there are two reasons for this. First, simple metal cations are generally more strongly solvated than comparable anions that can induce Hofmeister effects. Second, the anions that predominate in biomacromolecules are carboxylates, phosphates and
- titration with various halide salts. The fifteen salts studied were a matrix of the alkali metal cations Li+, Na+, K+, and Cs+ in combination with the halides F− through I−, the one omission being poorly soluble lithium fluoride (maximum solubility = 0.134 g mL−1). Unsurprisingly, given the pKa values of
Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules
Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190
- connected by a C=C double bond. The first oxidation converts one ring into an aromatic 6π-electron system, which is further stabilized by a mixed-valence resonance structure. The second oxidation yields two aromatic 1,3-dithiolium cations (2 × 6π electrons) which are connected by a C–C single bond. The
- complexes in solution can be easily traced by the emergence and fading of these characteristic charge-transfer bands. Another outstanding feature of TTFs is that their radical cations can reversibly form cofacial dimers (Figure 3) [34][35][36]. The two monomers 1 and 1●+ spontaneously self-assemble into a
- dimer interaction can be an emergent low-energy absorption band, usually in the NIR region. Both monomers show usually no absorption in this region. The radical-cation dimer (1●+)2 instead forms from two 1●+ radical cations and exhibits a very unusual binding situation. Whereas both monomers are
Revisiting ring-degenerate rearrangements of 1-substituted-4-imino-1,2,3-triazoles
Beilstein J. Org. Chem. 2018, 14, 2098–2105, doi:10.3762/bjoc.14.184
- cations, and have impacted fields that include bioimaging [26][27] and chemosensing [28][29]. Surprisingly, the reported examples partnering 1,2,3-triazole and imine N-donor groups are limited [30][31][32], despite the ubiquity of such Schiff base subunits in coordination chemistry. 4-Iminotriazole
Synthesis and supramolecular self-assembly of glutamic acid-based squaramides
Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180
- asymmetric catalysis and molecular recognition [5][6]. Besides, squaramides present a dual ability to recognize anions and cations through hydrogen bonding interactions, acting as ion sensors and transmembrane anion transporters [7]. This property has been crucial for the development of new drugs [8][9
Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates
Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173
- nucleotides must possess selectivity towards these anions. From this point of view, nucleotide receptors based on polyammonium cations are of great demand because the electrostatic interactions of such polyammonium systems and negatively charged phosphates are strong. Hydrogen bonding [8] and π-stacking
- MOPAC 2016 program [61] with discard of repeated duplicates. Then unique conformers were combined with calix[4]arene core, and corresponding cations and complexes with ATP/ADP were optimized by DFT calculations. For DFT calculations Priroda 16 program [62] with build-in PBE functional on L2 basis level
Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril
Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171
- cyclohexylmethylammonium (cyH) cations by displacement titrations (see below) in our mixture of 30% (v/v) ACN/H2O, which gave Ka(Bnz) = 1.4 × 105 M−1 and Ka(cyH) = 1.5 × 107 M−1. This indicated that the binding affinity is lowered 100 to 1000-fold by reducing the hydrophobic effect in presence of 30% acetonitrile as also
Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions
Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161
- composition, however, was unanimously proven by the data. Derivative 2b crystallizes with one molecule of CHCl3 as lattice solvent in the highly symmetric orthorhombic space group I2/a with 8 molecules in the unit cell. Both cations are essentially planar and π-stacked in an anti-head-to-tail (ht) arrangement
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
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