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Search for "polarity" in Full Text gives 383 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
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
- rotaxane 13 (Figure 11) [73]. The [2]rotaxane was obtained in 8% yield by a high-pressure clipping procedure in which the wheel 3 was formed around the pre-synthesized axle. In DMSO, the macrocycle is predominantly located on the central TTF moiety. However, in acetone, which has a lower polarity, the
A self-assembled photoresponsive gel consisting of chiral nanofibers
Beilstein J. Org. Chem. 2018, 14, 1994–2001, doi:10.3762/bjoc.14.174
- -xylene was not very strong but discernible. On the other hand, the CD signal in aromatic solvents, like benzene and toluene, was strong enough to confirm the formation of chiral structures. These results indicate that the chiral nanostructures can be only obtained in solvents with lower polarity
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
- accompanied by hypochromic effect in the EY absorption spectrum (Supporting Information File 1, Figure S1) is observed in addition to a change of the environment polarity due to the dye embedding into the hydrophobic domain of the premicellar aggregates [46]. The absorbance spectra of the ternary system
- of EY molecules into the hydrophobic domain of the aggregates and a corresponding decrease of the environment’s polarity (curve 4, Figure 5a). Thus, after decomplexation the EY molecules primarily concentrate inside the aggregate. A hypsochromic shift in the EY spectra pointing to the dye’s release
Strong binding and fluorescence sensing of bisphosphonates by guanidinium-modified calix[5]arene
Beilstein J. Org. Chem. 2018, 14, 1840–1845, doi:10.3762/bjoc.14.157
- , have been developed for detecting BPs in pharmaceuticals and biological materials [7][8]. Due to BPs′ high polarity, they are difficult to separate on reversed-phase columns. To make them more amenable to analysis, ion-pairing or complex-forming reagents were used to decrease the ionic character of the
Anomeric modification of carbohydrates using the Mitsunobu reaction
Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138
- phosphine reagents are triphenyl- (Ph3P) or tributylphosphine (n-Bu3P). In recent years, advances have been made using solid supported reagents, thus facilitating work-up conditions [17][18]. The polarity of the commonly aprotic solvents used in the Mitsunobu reaction, including toluene, tetrahydrofuran or
Recent advances in phosphorescent platinum complexes for organic light-emitting diodes
Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124
- properties. Indeed, bathochromic shifts in the emission energy were observed upon either grinding or incrementing solvent polarity. This emission was attributed to a radiative transition with triplet metal–metal-to-ligand charge transfer character (3MMLCT), which ultimately strongly depends on the platinum
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
- ] reported on the beneficial role of increased surface polarity of carbon nanofibers introduced by oxygen groups in the deoxygenation of stearic acid over Pd NPs deposited in addition on this support. They identified a favorable mode of adsorption of the stearic acid via the carboxylic group for high support
- polarity instead of a flat adsorption mode for low support polarity [40]. The upright adsorption mode facilitates the deoxygenation due to the close contact with the Pd NPs pointing to the importance of metal-support interactions [40]. A similar adsorption-induced effect may be present in glycerol
[3 + 2]-Cycloaddition reaction of sydnones with alkynes
Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113
- , for the cycloaddition of the structurally similar ethyl phenylpropiolate in various solvents only a small decrease of the bimolecular rate constant with increasing solvent polarity (in terms of relative permittivity) was observed excluding a transition state having a polarized character. Finally
- , substitution effects in the 3-(4-substituted phenyl) group of sydnones were studied and a relatively low Hammett reaction constant ρ ≈ +0.8 was estimated from four derivatives (MeO, Me, H and Cl). An even smaller dependence of the rate constants on the solvent polarity and substituent effect sensitivity (ρ
Oligonucleotide analogues with cationic backbone linkages
Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111
- biological mechanisms via sequence-specific molecular recognition makes them highly attractive candidates for drug development. However, their pharmacokinetic properties are problematic and represent a significant hurdle for their therapeutic application. First, the high polarity of ONs, mainly caused by
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
Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups
Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91
- unreacted BnTMS or BnBF3K. The results in Table 1 show that silyl groups seem to be superior to boron groups for the reaction to afford a good yield. The solvent choices were made based on low nucleophilicity and polarity being high enough to dissolve the hypervalent iodine starting material. Surprisingly
Mechanochemistry of nucleosides, nucleotides and related materials
Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81
- . LAG of a 1:1 mixture of 5FU/4-hydroxybenzoic acid using a variety of liquids yielded co-crystals exhibiting polymorphism which was dependent upon the polarity of the added liquid [84]. Co-crystals of structurally-related carboxylic acids with 5FU prepared using LAG in a MBM in the presence of water
Two novel blue phosphorescent host materials containing phenothiazine-5,5-dioxide structure derivatives
Beilstein J. Org. Chem. 2018, 14, 869–874, doi:10.3762/bjoc.14.73
- . Compared to the introduction of ethyl groups, the introduction of normal butyl groups to the phenothiazine-5,5-dioxide moieties appears to decrease the Td and Tg of CEPDO by 13 °C and 29 °C, respectively, relative to those of CBPDO. The reason may be the n-butyl chain is longer. It reduces the polarity and
Stepwise radical cation Diels–Alder reaction via multiple pathways
Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59
- two distinctive pathways, including “direct” and “indirect”, are possible to construct the Diels–Alder adduct. Keywords: Diels–Alder reaction; radical cation; rearrangement; single electron transfer; stepwise; Introduction Umpolung, also known as polarity inversion, is a powerful approach in
D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies
Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55
- solutions of toluene and n-hexane. The photoluminescence spectra of the n-hexane solutions show a peak at 517 nm with a shoulder at 545 nm, which can be considered as the radiative transition of 1LE states. Noticeably, the charge-transfer process is limited in n-hexane because of its lower polarity. Only
Synthesis and biological evaluation of RGD and isoDGR peptidomimetic-α-amanitin conjugates for tumor-targeting
Beilstein J. Org. Chem. 2018, 14, 407–415, doi:10.3762/bjoc.14.29
- is responsible for the transcription of DNA to mRNA [1][2]. Despite this strong inhibitory activity, α-amanitin exhibits only a micromolar cytotoxicity and low cellular uptake in most mammalian cells, due to its strong polarity and poor membrane permeability [2]. One notable exception are human
Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)
Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18
- architecture of the doped EML [29]. By selecting the host of appropriate polarity, the combination of D7 with the correct host could minimize the RISC barrier, optimize the RICS rate and thus maximize the TADF efficiency. While combining the blue TADF emitter D7 with a green and an orange TADF emitter, all
- concentration from 5 to 50 wt %. Such red shift is clearly caused by the interaction between CN-P1 molecules at high dopant concentrations. Parallel to this, CN-P1 molecules can also increase the polarity of the EML, thus introducing a solvatochromaticity-like shift comparable to that observed in solutions
- while varying the solvents polarity. The optimized device exhibited a maximum current efficiency of 47.7 cd·A−1, and a maximum power efficiency of 42.8 lm·W−1 without any light outcoupling structures, indicating that nearly 100% of excitons are harvested for light emission. Such high performance should
Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)
Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14
- to quinoline can be considered as an umpolung of the Skraup quinoline synthesis since it uses reversed polarity of reagents, where the C=C–NO2 fragment of the nitroarene is the electrophile reacting with an arylmethyl carbanion, the nucleophile (Scheme 2). Recently, we used the reactions of
Halogen-containing thiazole orange analogues – new fluorogenic DNA stains
Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283
- to procedure C1. In addition, our observation that lower amounts of the blue-colored byproduct were obtained in ethanol solution is probably related to the polarity and the basicity of the medium. We observed that filtration of the final dyes followed by washing the precipitate with ethanol dissolves
Position-dependent impact of hexafluoroleucine and trifluoroisoleucine on protease digestion
Beilstein J. Org. Chem. 2017, 13, 2869–2882, doi:10.3762/bjoc.13.279
- induced polarity and significant pKa-value changes of neighboring groups [9][10] can lead to fluorine-specific interactions between substrate and enzyme binding sites as well as to an exclusion of the cleavage-relevant peptide bonds from the active site. Furthermore, our investigations show that
The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands
Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276
- order to reduce its aggregation process. The inhibitory effect seems more pronounced by combining both the use of extended pentapeptides and the introduction of fluorine atoms. This positive effect of the trifluoromethylation can be due to the increased polarity of the hydroxy group in the CF3-Thr
Metal-mediated base pairs in parallel-stranded DNA
Beilstein J. Org. Chem. 2017, 13, 2671–2681, doi:10.3762/bjoc.13.265
- configuration at the C1’ position of the deoxyribonucleoside. When pairing an oligonucleotide comprising α-deoxyribonucleosides with an oligonucleotide consisting of canonical β-deoxyribonucleosides, a parallel-stranded duplex is formed [53]. Due to the reversal of the strand polarity and the concomitant
Preparation and isolation of isobenzofuran
Beilstein J. Org. Chem. 2017, 13, 2659–2662, doi:10.3762/bjoc.13.263
- reacted in situ, because it rapidly dimerizes or polymerizes in solvents of medium polarity such as chloroform (t1/2 = 2 h). We observed longer half-lives in low polarity solvents (t1/2 = 12 h in toluene-d8, 150 mM, 27 °C). We have been able to purify the compound by chromatography and to isolate it as a
Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones
Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259
- , unique heterocyclic ketimines, react with malonic acid under organic base catalysis to regioselectively provide either Michael- or Mannich-type decarboxylative addition products depending on solvent polarity. Malonic mono(thio)esters give exclusively Michael-type products. The two regioisomeric products
- supported by the known effect of solvent polarity on the decarboxylation rate of malonic acid derivatives which was claimed to be faster in polar media [40]. To study the substrate scope of the regioselective additions of malonic acid, we introduced substituted pyrimidones 2b–m in the reaction and performed
- . Presumably, in this case, the kinetically controlled Michael-type intermediate C is even far more prone to decarboxylation than the dicarboxylate intermediate A (Table 1) and hence, the reaction is sufficiently regioselective irrespective of the solvent polarity (Table 3, entries 1, and 6–9). Performing the
One-pot three-component route for the synthesis of S-trifluoromethyl dithiocarbamates using Togni’s reagent
Beilstein J. Org. Chem. 2017, 13, 2502–2508, doi:10.3762/bjoc.13.247
- fields of pharmaceuticals, agrochemicals, and materials sciences. The key properties such as metabolic and chemical stability, polarity, bioavailability, viscosity and lipophilicity can be altered in molecules containing the CF3 group in comparison with the nonfluorinated analogues. Numerous methods have
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