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Search for "polarity" in Full Text gives 392 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Synthesis of new dihydroberberine and tetrahydroberberine analogues and evaluation of their antiproliferative activity on NCI-H1975 cells
Beilstein J. Org. Chem. 2020, 16, 1606–1616, doi:10.3762/bjoc.16.133
- -bromohydrazones 1a–n (Scheme 2). All the hydrazono-DHBERs 2a–n directly precipitate as pure products in the reaction medium with yields ranging from poor to good (30–83%). Probably the low affinity of the iminium and hydrazone groups of compounds 2a–n with a medium-low polarity solvent such as DCM causes their
Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers
Beilstein J. Org. Chem. 2020, 16, 1554–1563, doi:10.3762/bjoc.16.127
- allow them to act as polyfunctional monomers, permitting the crosslinking with bi- or multifunctional chemicals, such as dianhydrides, diisocyanates, diepoxides, and dicarboxylic acids, etc. The polarity and size of the polymer network can be easily tuned by varying the type of the crosslinker and
An overview on disulfide-catalyzed and -cocatalyzed photoreactions
Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118
- generated with a yield of 43–75% (Scheme 13). Reductive dehalogenation reactions In 2013, Curran and co-workers reported a light-induced dehalogenative reduction with polarity reversion catalyzed by diphenyl disulfide or boryl bissulfide (diMe–Imd–BH(SPh)2) as the catalyst and 1,3-dimethylimidazol-2
Recent synthesis of thietanes
Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116
- -donating substituents present in the allenes enhanced the overall reaction rate. There was little effect of the solvent polarity on the reaction rate. The formation of thietanes involved the excited triplet thiones and the π-bond of allenes [66]. In 1984, Bos and co-workers realized the photocycloaddition
Activated carbon as catalyst support: precursors, preparation, modification and characterization
Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104
- basic conditions, the pore size distribution and the chemical properties on the surface can be adjusted (polarity and hydrophobicity) according to the envisaged application. In addition, metal particles can be recovered simply by burning the carbon support [1][2]. Thus, porous carbon materials represent
Synthesis and properties of quinazoline-based versatile exciplex-forming compounds
Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101
- -transfer (CT) transitions [20]. The PLQY quantum yields of the dilute solutions did not exceed 2%. The dependence of the emission wavelengths of the derivatives on the solvent polarity was also tested. Figure 5 shows the emission spectra of the compounds dissolved in three solvents with increasing
- polarities, i.e., toluene (0.099), tetrahydrofuran (0.207) and dimethylformamide (0.4) (values in parentheses are the solvent polarities relative to water) [21]. The PL spectra of the solutions of compound 3 appeared to be solvent-polarity independent as only the structured emission band of the locally
- the 1LE transition at 375 nm. A 1CT state could be formed for compound 1 as evidenced by the PL spectrum of its solution in low-polarity toluene. A weak low energy 1CT band was also observed for the solution in THF with moderate polarity (see the zoomed spectrum of THF solution of compound 1, Figure
The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts
Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99
- , including the ring opening of epoxides by water and alcohols. A Diels–Alder reaction between cyclopentadiene and methyl vinyl ketone was also catalyzed by F-1 in heptane. Depending on the polarity of the solvent mixture, the CAHOF F-1 could function as a purely heterogeneous catalyst or partly dissociate
- efficiency of the reaction dropping as the size of the alcohol was increased and its polarity decreased (Table 2, runs 1–3). Water could also be used as the nucleophile (Table 2, runs 4 and 5) and led to the trans-cyclohexane diol 6 under the same experimental conditions used for the styrene oxide ring
- . Depending on the polarity of the solvent mixture, F-1 could function as a purely heterogeneous catalyst or as a reservoir, providing some soluble F-1 as the real catalyst. In all cases the catalyst could easily be recovered and recycled. The system has the potential for future elaboration, for example, by
Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties
Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93
- microscopic solvent polarity [43][44], ET(30), increased from toluene to dimethyl sulfoxide (see also Table 3). A 141 nm red-shift was observed for 7a (from 465 nm to 606 nm) and an 86 nm red-shift was observed for 7b (from 423 nm to 509 nm). In comparison for 7b, this red-shift was more pronounced for 7a
Suzuki–Miyaura cross coupling is not an informative reaction to demonstrate the performance of new solvents
Beilstein J. Org. Chem. 2020, 16, 1001–1005, doi:10.3762/bjoc.16.89
- , equilibria, solubility, and ultimately product yield. If there is an observable change in reaction performance correlating to one or more solvent properties (often polarity), then it is possible to identify and implement an optimum solvent. Suzuki–Miyaura cross coupling is the premier method of palladium
- catalysed carbon–carbon bond formation, making it an obvious case study to validate the performance of novel solvents [1][2][3][4][5][6][7]. The polarity of the solvent is known to determine the structure and activity of catalytic intermediates, the rate determining step, and stereochemistry (where
- Supporting Information Supporting Information File 292: Synthetic procedures and calculation of reaction conversions and solvent polarity data. Funding This research was funded by the Bio-Based Industries Joint Undertaking (JU) under the European Union's Horizon 2020 research and innovation programme
Aryl-substituted acridanes as hosts for TADF-based OLEDs
Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88
- were decreased by ca. 0.23 eV with respect to that of the other studied compounds due to the π-electronic coupling between the acridan and vinylphenyl moieties. The absorption spectra were not affected by the polarity of the solvent. Relatively structured PL spectra were obtained for solutions and
- to polarity and aggregation effects. Despite these observations, emission of compounds 3–6 can mainly be assigned to π–π* transitions of local excited states. However, a slight contribution of charge transfer (CT) can be also recognized in the emission of the studied compounds 3–6 (Figure 3a). The
Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates
Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82
- position of the absorption maximum and the quantum yields or the rate constants of the forward and reverse reaction also depend largely on the solvent polarity as well as on the position and the nature of the substituents either at the indoline or the chromene unit. Surprisingly, there are only a few
Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties
Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81
- fluorescence was only moderately quenched with increasing solvent polarity, and the quantum yields of 64 and 66% were recorded in acetonitrile for cNMI2H and cNMI3H, respectively. To explore the chiral properties of the helically distorted boomerangs, the separation of enantiomers was attempted for all of them
Aldehydes as powerful initiators for photochemical transformations
Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76
- state quencher, as well as by the lowered rate of the reaction in the presence of the triplet energy quencher 2,5-dimethylhexa-2,4-diene or pyridazines, additives with lower triplet state energies than 4-anisaldehyde (52). The fact that the solvent polarity did not affect the sensitivity of the process
Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid
Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73
- modifications at the C3-OH group of 18β-glycyrrhetinic acid are identified to be relatively common and effective. The modification of the C3-OH group, altering the molecular polarity of 18β-glycyrrhetinic acid, may be an advantage in achieving better cytotoxicity or antiproliferative activity [8][9][10]. For
Towards triptycene functionalization and triptycene-linked porphyrin arrays
Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70
- isolated as a purple solid in 60% yield. Subsequently, an in situ deprotection of the TIPS group was carried out with a solution of the triptycene-linked porphyrin 14. The polarity of the in situ deprotected product and TIPS protected starting material were very similar so TLC analysis was unable to
Recent advances in Cu-catalyzed C(sp3)–Si and C(sp3)–B bond formation
Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67
- , Ohmiya and co-workers envisioned inverting the polarity of an aldehyde 81 via conversion into the corresponding α-alkoxyalkyl Cu(I) anion 78. Utilizing 78, which undergoes transmetallation to an initially formed Pd(II) intermediate (from oxidative addition) led to cross couplings affording benzhydryl
Synthesis of organic liquid crystals containing selectively fluorinated cyclopropanes
Beilstein J. Org. Chem. 2020, 16, 674–680, doi:10.3762/bjoc.16.65
- vertical alignment (VA) LCD technology, liquid crystals with negative dielectric anisotropy are required [3]. Fluorine, as the most electronegative atom, forms stable bonds to carbon and can thus induce polarity. It is also attractive as a design feature due to the low polarizability of the C–F bond
- dielectric anisotropic liquid crystals and the more rigid 1,1,6,7-tetrafluoroindane 4 led to an enhanced polarity and improved negative dielectric anisotropy character [8]. Other liquid crystals of this class are the recently reported fluorinated cyclohexane 5 and 1,1,2,2-tetrafluorocyclohexane 6 [9][10
- should induce a large value for dielectric anisotropy. Compounds 8 and 9 were found to exhibit the expected negative Δε values, however, the overall polarity is low (8 = −0.5, 9 = −0.2). This is presumably due to the ability of the C–C bond attached to cyclopropane to rotate, and thus the compound will
Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid
Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38
- formed and no desired acid. Therefore, we investigated the effect of polarity on the selectivity of the reaction by mixing acetonitrile with benzene (Table 3). Based on the result with pure acetonitrile as a solvent (Scheme 2 and Scheme 3), we expected a lower yield with higher concentrations of
- unlikely to compete with ring closure to F for entropic reasons. All attempts to trap intermediate C using methanol or acetic acid as co-solvent (see Table 2) were unsuccessful and resulted in lower yields, especially in the case of methanol, likely due to the increased polarity of the reaction mixture
Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes
Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17
- in organic chemistry [3]. The C–F bond is highly polarized and this polarity inhibits the lone pair donation from fluorine, making this element a weak coordinator. These properties are the basis for the unique properties of perfluoroalkylated compounds such as high viscosity, high density, high
- chemical stability, low surface tension, low dielectric constants and low refractive index [4]. The usefulness of these properties makes fluorine an element of choice for the enhancement of promising properties, remained inaccessible otherwise. However, the combination of small size and high polarity of
- relative to the other heteroatoms, suggesting that Oxd 1 is more polar than Oxd 2. Such a difference in polarity was corroborated by the direction of the dipole moment of RC (Table 5). Therefore, it is not surprising to find the molecular electron-deficient center so far from the axis of the molecule in
Potent hemithioindigo-based antimitotics photocontrol the microtubule cytoskeleton in cellulo
Beilstein J. Org. Chem. 2020, 16, 125–134, doi:10.3762/bjoc.16.14
- unit of indanocine (which is attached in ortho-position to the key south ring methoxy group) by a hydroxy function, giving HITub-1 (Figure 2). When HITub-1 later proved less bioactive than we had wished, we explored steric and polarity changes to this south ring hydroxy group by methylation (HITub-2
- (in ortho-position to the key south ring methoxy group) has been replaced by a synthetically more accessible hydroxy group (delivered via demethylation of a trimethoxy precursor through BBr3). The hydroxy and amino groups have similar size and polarity, and can both act as H-bond donors or acceptors
- absolute sense and the overall photoswitchability of potency comparing E- and Z-isomers. We began by methylating the south ring hydroxy group (HITub-2) to see how changes in size and polarity affect the bioactivity; surprisingly, the potency loss was not dramatic (indicating that this position is not a key
Light-controllable dithienylethene-modified cyclic peptides: photoswitching the in vivo toxicity in zebrafish embryos
Beilstein J. Org. Chem. 2020, 16, 39–49, doi:10.3762/bjoc.16.6
- derivatives of 2 [30]. The library contained 29 compounds grouped into several series: with natural amino acid mutations affecting the amphipathicity (series i), with point mutations that modulate polarity and conformational stability of the β-structural elements (series ii), with backbone N-alkylation and
- between the empirical low-pH hydrophobicity of the peptides (as assessed from the retention times in reversed-phase HPLC) and toxicity against zebrafish embryos. Independent on the photoisomeric state and the type of toxicity assay, decreasing polarity of the peptides is accompanied by an increase in
Facile regiodivergent synthesis of spiro pyrrole-substituted pseudothiohydantoins and thiohydantoins via reaction of [e]-fused 1H-pyrrole-2,3-diones with thiourea
Beilstein J. Org. Chem. 2019, 15, 2864–2871, doi:10.3762/bjoc.15.280
- temperature of the reaction, but also on the polarity of the solvent. We found that optimal conditions for dominant formation of pseudothiohydantoin 3a were applied by stirring the reaction mixture at room temperature in ethyl or butyl acetate (Table 1, entries 2 and 6). For the development of a convenient
An improved, scalable synthesis of Notum inhibitor LP-922056 using 1-chloro-1,2-benziodoxol-3-one as a superior electrophilic chlorinating agent
Beilstein J. Org. Chem. 2019, 15, 2790–2797, doi:10.3762/bjoc.15.271
- signalling pathway has been shown to regulate crucial aspects of cell fate determination, organogenesis, cell migration and polarity [1]. Importantly, compromised Wnt signalling has been implicated in the perturbation of synaptic integrity and function in Alzheimer’s disease (AD) [2]. Palmitoleoylation of
A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions
Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264
- chirally modified electrodes Electrochemical oxidation reactions have long served as substantial synthetic tool because of their ability to increase the functionality of organic molecules via reversing the polarity of electron-rich functional groups and thereby generating highly reactive intermediates
Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences
Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262
- %. Furthermore, the N,N-dimethylaminophenyl-derivative 6c shows a pronounced emission solvatochromism (Figure 11, Table 9). While the polarity effect on the absorption maximum is only minor within a range of the longest wavelength maximum between 469 and 490 nm, the emission maximum is shifted bathochromically
- with increasing solvent polarity in a range from green fluorescence (529 nm) in toluene to red fluorescence in DMSO (638 nm) (Figure 12). The observed positive emission solvatochromism is a consequence of a significant change in the dipole moment from the electronic ground to the vibrationally relaxed
- quantum yield of 99% in solution and 11% in the solid state was achieved. Interestingly, the isomeric p-N,N-dimethylaminophenyl substitution in 6-position represents a system with aggregation-induced emission enhancement. These design principles of luminescent 1H-pyridines and α-pyrones as polarity
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