Search results
Search for "polarity" in Full Text gives 406 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
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
Plasma membrane imaging with a fluorescent benzothiadiazole derivative
Beilstein J. Org. Chem. 2019, 15, 2644–2654, doi:10.3762/bjoc.15.257
- 2,1,3-benzothiadiazole (BTD) core and its derivatives that are successfully applied in bioimaging experiments. (Left) UV–vis, (center) fluorescence emission and (right) solvatochromic effect (Stokes shift in wavenumbers versus solvent polarity in ETN) of the synthesized BTD-4APTEG (10 μM for all
Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence
Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254
- emission maximum on changing to the polar solvent (Δλ = +7 nm). However, dye 19 features a solvatofluorochromic effect of Δλ = +41 nm under the same conditions. The dyes 16 and 18 show somewhat smaller bathochromic shifts on increasing the solvent polarity (Δλ = +20–22 nm). Regarding the fluorescence
Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red
Beilstein J. Org. Chem. 2019, 15, 2552–2562, doi:10.3762/bjoc.15.248
- permittivity of polymers and its spatial distribution play a crucial role in the behavior of thin films, such as those used, e.g., as sensor coatings. In an attempt to develop a conclusive approach to determine these quantities, the polarity of the model polymer poly(methyl methacrylate) (PMMA) in 600 nm thin
- films on a glass support was probed by the energy of the charge transfer transition in the oxazine dye Nile red (NR) at 25 °C. The absorption and fluorescence spectra of NR were observed to shift to the red with increasing solvent polarity, because of the intramolecular charge transfer character of the
- NR molecules in the ground state and slow sub-glass transition (Tg) relaxations in PMMA. Keywords: charge transfer; dipole moment; fluorescence; inhomogeneous broadening; oxazine dye; polarity probe; polymer permittivity; Introduction The chain and segment mobility as well as the permittivity of
Indium-mediated C-allylation of melibiose
Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238
- Zemplén-deprotection and ozonolysis compound 4-anti was obtained. Purification at this stage utilizing conventional column chromatography was not feasible due to the high polarity of the obtained compound mixture, which contained pyranoid as well as furanoid isomers in their α,β-forms. Thus, per-O
Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone
Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236
- isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime of the Z-form depends on solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time-resolved luminescence measurements evidence the presence of a main
- solvent polarity. On the contrary, the excited state lifetime of the Z-isomer depends on the solvent properties and is especially short in MeOH, suggesting that the excited state of the molecule could have a partial charge transfer nature. Finally, transient absorption spectroscopy was employed as an
Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes
Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235
- 504 nm in toluene, while a hypsochromic shift of 14 nm was observed in acetonitrile. This influence of solvent polarity was detected for all ligands [39]. The carbonyl group in the ethene bridge of 3 causes a significant bathochromic shift (68 nm in toluene) of the closed-ring isomer maximum in
Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors
Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214
- reversibly between two states comprising high amounts of (E)-11 and (Z)-11, respectively. The other part of the hypothesis was, that by this photoinduced isomerization a considerable drop of activity would occur due to the conformational change and the resulting changed geometry and polarity. However, this
- after irradiation, we would have predicted, that at least the significant difference in polarity of (E)-11 and (Z)-11 should lead to marked differences of sirtuin engagement in vitro. However, recent results from a carefully designed azologization study performed by Rustler et al. led to comparable
1,2,3-Triazolium macrocycles in supramolecular chemistry
Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211
- chemistry. Different hydrogen bond donors such as pyrrole N–H and benzene C–H along with the triazolium C5–H have been successfully incorporated within a single macrocyclic framework. The complex formation of anions with the hydrogen bond donors varied according to the polarity of the solvent. It was found
- that the binding constants for interaction with monoanions become smaller as the polarity of the solvent medium increases on moving from acetonitrile to methanol. Among all of the tested anions, macrocycle 10 has shown a high selectivity for pyrophosphate HP2O73−, and tetrahedral oxyanions HSO4−, H2PO4
- illustrated the way of utilizing different types of noncovalent interactions including hydrogen bonding, halogen and chalcogen bonding for the selective detection of anions by triazolium macrocycles. The selectivity and the ability of detection of anions are highly dependent on the solvent polarity. We have
Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica
Beilstein J. Org. Chem. 2019, 15, 1933–1944, doi:10.3762/bjoc.15.189
- domain between the helices 3, 5 and 7 [7][21]. Comparing the polarity of these compounds with compound 1 based on the formation of hydrogen bonds, the most polar compound capable of forming the highest number of hydrogen bonds is thapsigargin, the least polar is compound 1 (for details, see Supporting
Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation
Beilstein J. Org. Chem. 2019, 15, 1795–1804, doi:10.3762/bjoc.15.173
- different polarity can also affect the complexation between the hosts and the guests. As shown in Table 2, we found that performing the 1H NMR titrations of the host–guest complexation in CDCl3/acetone-d6 1:2 (v/v), the Ka values of the 1:1 host–guest complexes were about 103 M−1 except for H2 that showed
A golden opportunity: benzofuranone modifications of aurones and their influence on optical properties, toxicity, and potential as dyes
Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171
- at the 5-position resulted in a shift to longer wavelength by roughly 20 nm compared to a methoxy substituent at the 4-position and a strong dependence upon solvent polarity. While this shift was quite reasonably attributed to the inductive effect of the oxygen, no other substitution was studied
Other Beilstein-Institut Open Science Activities
