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1.
Ramin Ghorbani-Vaghei Seyedeh Mina Malaekehpour 《Central European Journal of Chemistry》2010,8(5):1086-1089
N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl
naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.
相似文献
2.
Sergej Naumov Marija Bonifačić Richard S. Glass Klaus-Dieter Asmus 《Research on Chemical Intermediates》2009,35(4):479-496
A complementary quantum mechanical and experimental study has been undertaken on the reactivity, formation and properties
of Se∴N and S∴N σ2/σ* three-electron-bonded radical species, generated upon one-electron oxidation of selenomethionine, methionine and structurally
related compounds. The quantum chemical calculations were based on density functional theory (DFT) hybrid B3LYP and BHandHLYP
methods with basis sets ranging from 6-31G(d) to 6-311+G(d,p). Solvent effects, which play an important role concerning structure
and energy of ground and excited states, were taken into account as dielectric continuum as well as explicit water molecules.
They fully confirm new and previously obtained experimental results concerning the Vis/near-UV absorptions and thermodynamic
stability. Special emphasis was put on a comparison between selenium and sulfur. The calculations clearly confirm the higher
thermodynamic stability of the Se∴N radical species relative to the S∴N ones, and also corroborate the observed much higher
kinetic stability of the former. Concerning optical absorptions, the calculations predict the Se∴N transients to exhibit a
blue-shift by about 20 nm relative to the S-based analogues, confirming the few experimental data available so far. The theoretical
study includes a comparison of various calculation levels and the influence of the solvent environment, by comparison with
vacuum. New experimental data within the scope of this study have been obtained on intramolecularly-formed S∴N radical cation moieties, structurally stabilized by a rigid norbornane backbone. The methionine-related
species, with an endo-2-amino, exo-2-carboxyl, and endo-6 methylthio substitution, for example, exhibits almost identical
optical and kinetic stability properties as the corresponding species from free methionine. Its optical absorption depends
on the protonation state of the carboxyl group, with λmax at 410 nm for the carboxylate (zwitterionic) form and at 390 nm for the overall cationic form with the protonated carboxyl
group. The fast exponential decays with t
1/2 of 490 ns and 2 μs pertain to the decarboxylation of the respective species. A much longer-lived S∴N species with t
1/2 > 500 μs and second order decay kinetics (λmax 465 nm) was obtained from an endo-2-cyclohexylamino norbornane analogue which does not carry a carboxyl group. The methionine-based
S∴N species is not stable anymore in vacuum and in low polarity solvents. This is explained by a decrease in stabilization
energy of the 3-e-bond and a faster electron transfer from the carboxylate into the cationic 3-e-center. In conclusion, selenium
enhances the thermodynamic and kinetic stability of its radical transients, relative to the sulfur analogues. 相似文献
3.
Sánchez-Fernández EM Rísquez-Cuadro R Ortiz Mellet C García Fernández JM Nieto PM Angulo J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(27):8527-8539
The synthesis of mimics of the α(1→6)- and α(1→4)-linked disaccharides isomaltose and maltose featuring a bicyclic sp(2)-iminosugar nonreducing moiety O-, S-, or N-linked to a glucopyranoside residue is reported. The strong generalized anomeric effect operating in sp(2)-iminosugars determines the α-stereochemical outcome of the glycosylation reactions, independent of the presence or not of participating protecting groups and of the nature of the heteroatom. It also imparts chemical stability to the resulting aminoacetal, aminothioacetal, or gem-diamine functionalities. All the three isomaltose mimics behave as potent and very selective inhibitors of isomaltase and maltase, two α-glucosidases that bind the parent disaccharides either as substrate or inhibitor. In contrast, large differences in the inhibitory properties were observed among the maltose mimics, with the O-linked derivative being a more potent inhibitor than the N-linked analogue; the S-linked pseudodisaccharide did not inhibit either of the two target enzymes. A comparative conformational analysis based on NMR and molecular modelling revealed remarkable differences in the flexibility about the glycosidic linkage as a function of the nature of the linking atom in this series. Thus, the N-pseudodisaccharide is more rigid than the O-linked derivative, which exhibits conformational properties very similar to those of the natural maltose. The analogous pseudothiomaltoside is much more flexible than the N- or O-linked derivatives, and can access a broader area of the conformational space, which probably implies a strong entropic penalty upon binding to the enzymes. Together, the present results illustrate the importance of taking conformational aspects into consideration in the design of functional oligosaccharide mimetics. 相似文献
4.
I. V. Fedorova M. G. Kiselev L. P. Safonova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(12):2103-2109
The molecular dynamics simulation method was for the first time used to study the structural and energy parameters of H3PO4, H2PO4−, and (DMFA)H+ (protonated dimethylformamide) in liquid N,N-dimethylformamide. The predominant orientation of the nearest neighbors of H3PO4, H2PO4−, DMFA, and (DMFA)H+ was determined from ranked distribution functions. The most probable structure of H-bonded complexes was obtained. It was
shown that H3PO4 formed H-bonds with two DMFA molecules, and and (DMFA)H+ formed H-bonds with one molecule. The dependence of Coulomb interaction energies on the distance between H3PO4, H2PO4−, (DMFA)H+, and DMFA had the form of damped oscillations, as is characteristic of intermolecular interactions in pure DMFA. The molecular
dynamics simulation of the H2PO4−-(DMFA)H+-DMFA ternary system showed a high probability of the formation of contact ion pairs. 相似文献
5.
Synthetic methods were developed for nitrates of the natural bioactive lipids anandamide and prostamides E2 and F2α
in addition to their analogs that contained nitrates of ethanolamine and 3-amino-1,2-propanediol as the NO-generating fragment. 相似文献
6.
V. V. Frolov A. G. Mazhuga E. K. Beloglazkina N. V. Zyk M. P. Egorov 《Russian Chemical Bulletin》2010,59(3):544-549
A method for the synthesis of new tetradentate organic ligand of the N2S2 type, viz., N,N’-bis-(2-mercaptophenyl)propane-1,3-diamine has been developed, starting from 2-( tert-butyl-thio)aniline and malonyl dichloride. Coordination compound of this ligand with NiII according to the X-ray diffraction data has a square-planar geometry of the metal ion coordination sphere. 相似文献
7.
《Polyhedron》1988,7(1):43-47
Complexes of transition metal ions with the oxygen-nitrogen containing ligand 1,3-bis(2-pyridyl)-1,3-propanedione (bpypH) have been synthesized. These present stoichiometries which do not conform with the usual tendency manifested by β-diketones, since molecular formulas with the composition M(bpyp)X are found. A nitrogen methylated ligand N,N′-dimethyl-1,3-bis(2-pyridyl)-1,3-propanedione methyl sulphate [dimebpypH] (MeSO4)2 has also been synthesized and its complexes with transition metal ions studied. The stoichiometries now, resemble those of typical β-diketones, namely [dimepyp]2MX4 with four anions because of the dicationic nature of the original ligand. This, together with IR evidence suggests a dual type of coordination by bpip via the β-diketone and the pyridyl moieties. 相似文献
8.
The structures of a closo-hedral cluster (HAlNH)12 and endohedral complexes 4/2X@(HAlNH)12 (X = N, P, As, C−, Si−) are studied by density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency (ν1), energetic parameters, magnetic shielding constants (σ), and nucleus independent chemical shifts (NICSs) are discussed.
It is found that all guest species are minima at the cage center. Inclusion energies (ΔE
inc) of all species are negative except those of 4N and 4/2P. In all species, the endohedral quartet states (4X) are energetically less favorable than their doublet states (2X). The calculations predict that caged X states only donate <0.50 e to the cage and preserve their unencapsulated ground
states. 相似文献
9.
V. R. Akhmetova E. B. Rakhimova A. B. Minnebaev R. V. Kunakova N. F. Galimzyanova 《Russian Journal of Organic Chemistry》2012,48(2):202-208
Cyclothiomethylation was performed of heterochain (O, S-S, NH) α,ω-diamines with formaldehyde and H2S in aqueous medium at 20–60°C to obtain new α,ω-bis(1,3,5-dithiazinanes). The cyclocondensation of N-(3-aminopropyl)butane-1,4-diamine
(spermidine), formaldehyde, and H2S proceeds efficiently in the medium of BuOH-H2O at 0°C and leads to the formation of previously unknown O,S-containing macroheterocycle, 1,7-dioxa-3,5,9,11-tetrathiacyclododecane.
A fungicidal activity was found in 5,5′-(3,6-dioxaoctane-1,8-diyl)bis-1,3,5-dithiazinane with respect to microscopic fungi
affecting agriculture. 相似文献
10.
Silmar A. do Monte Elizete Ventura Tamires F. da Costa Sidney R. de Santana 《Structural chemistry》2011,22(3):497-507
Abstract
Ab initio and DFT calculations have been performed to characterize some ground state structures of the title molecules. Relative energies, rotational barriers, NBO charges, and dipole moments (μ) have been calculated and analyzed. It has been confirmed that only highly correlated methods (e.g., CCSD) are able to yield the non-planar structure as a minimum, for the H2NNO molecule. On the other hand, all computational levels here employed are able to yield a planar C2NNO frame for the (CH3)2NNO as a minimum. Important correlations between atomic charges and bond distances are discussed. Replacement of H by methyl group increases the rotational barrier and μ values by at least 3 kcal/mol and 0.4 D, respectively. The largest μ values are obtained for the structures in which the nitrogen lone pair is parallel to the NO group π system, and are consistent with a larger contribution of a dipolar resonance structure. 相似文献11.
I. V. Taydakov B. E. Zaitsev S. S. Krasnosel’sky I. N. Polyakova V. S. Sergienko 《Russian Journal of Inorganic Chemistry》2011,56(3):345-349
[Na(H2O)4][EuL4] · 0.775CH2Cl2 (I) has been synthesized by the reaction of Eu(NO3)3 · 6H2O with 1,3-bis(1,3-dimethyl-1H-pyrasol-4-yl)-1,3-propanedione (HL) in the presence of NaOH. Its crystal structure has been solved by X-ray diffraction analysis. Crystals are tetragonal; a = 16.2401(5) Å, c = 11.9113(4) Å, V= 3141.50(17) Å3, ρcalcd = 1.427 g/cm3, μ(MoK α) = 1.140 mm?1, space group P4/n, Z = 2. The structural units forming a crystal of compound I are [EuL4]? complex anions, [Na(H2O)4]+ cations, and CH2Cl2 molecules. The coordination polyhedron of the Eu atom is an Archimedean antiprism formed by the O atoms of four bidentate chelate ligands L?. 相似文献
12.
G. V. Girichev N. I. Giricheva N. V. Tverdova A. O. Simakov N. P. Kuz’mina O. V. Kotova 《Journal of Structural Chemistry》2010,51(2):223-230
Gas electron diffraction at a temperature T of 641(5) K is used to study the structure of an N,N′-ethylenebis(salicylaldiminato) zinc(II) molecule, ZnO2N2C16H14, further Zn(salen). The structure of a gaseous Zn(salen) complex has C 2 symmetry and is characterized by a substantial turn of two chelating fragments of the ligand with respect to each other, and also by a big difference in the length of coordination bonds: r h1(Zn-O)=1.902(7) Å r h1(Zn-N)= 2.027(7) Å. Results of the DFT/B3LYP calculation with 6-31G* and CEP,TZV basis sets of the molecule structure well agree with the experimental data. The electronic structure of Ni(salen), Cu(salen), Zn(salen), and Zn(acacen) molecules is considered. 相似文献
13.
G. V. Kornienko G. A. Kolyagin V. L. Kornienko V. A. Parfenov 《Russian Journal of Electrochemistry》2016,52(10):983-987
New graphitized carbon materials: technical carbon N220, С140, and СН85 (Omsktekhuglerod) were studied as catalysts of electrosynthesis of alkaline solutions of hydrogen peroxide from oxygen in gasdiffusion electrodes (GDEs). The kinetic parameters of oxygen reduction in alkaline solution and the capacity of gas-diffusion electrodes based on technical carbon N220, С140, and СН85 were determined. Data on the kinetics of hydrogen peroxide accumulation were obtained at different current densities. The fraction of current γ spent on the reduction of oxygen to hydrogen peroxide was determined. The rate constants of hydrogen peroxide decomposition under the given conditions were calculated. 相似文献
14.
Esko Taskinen 《Structural chemistry》2002,13(1):61-71
Selected group frequencies of the IR spectra of a number of 2-substituted 4-methylene-1,3-dioxolanes (a) and their endocyclic isomers, 2-substituted 4-methyl-1,3-dioxoles (b), have been studied to establish their usefulness as a measure of the strength of p– conjugation in the O—C=C moieties of the title compounds. In the exo compounds (a), the C=C stretching frequencies C=C and the in-phase, out-of-plane bending (wagging) frequencies CH2
w of the =CH2 group were found to be linearly related, besides to each other, also to the electron-donating character of the substituents and the 13C NMR chemical shift of the C atom of the exocyclic CH2 group. This suggests that the two IR group frequencies of the exo isomers are linearly related to the strength of p– conjugation in the O—C=C moiety. The C=C stretching absorption of the exo compounds in the 1600–1700 cm–1 region appeared as a doublet, shown to arise from Fermi resonance of the C=C fundamental with the CH2
w overtone. The C=C frequencies of the endo compounds support some previous findings of an unexpected strength of p– conjugation in the 2-alkoxy derivatives. Finally, DFT calculations at the B3LYP/6-31G* level of theory are shown to give accurate predictions of the effect of 2-substituents on the group frequencies. 相似文献
15.
E. A. Dikusar V. I. Potkin N. G. Kozlov A. P. Yuvchenko 《Russian Journal of General Chemistry》2009,79(2):258-263
Starting with the vanillin series aldehydes, by reaction with 1,3-phenylenediamine in absolute methanol E,E-N,N′-bis-[3-alkoxy-4-(hydroxy-, alkoxy-, acyloxy)phenylme-thylene]-1,3-phenyl-enediamines (Shiff bases) are synthesized from reduction with Na[BH(OAc)3] in benzene were prepared respective N,N′-bis-[3-alkoxy-4-(hydroxy-, alkoxy-, acyloxy)phenylmethyl]-1,3-phenyl-enediamines. 相似文献
16.
Esko Taskinen 《Structural chemistry》2002,13(1):53-60
The 17O NMR spectra of a number of unsaturated 5-membered cyclic acetals, 2-substituted 4-methylene-1,3-dioxolanes and their endocyclic isomers, 4-methyl-1,3-dioxoles, have been recorded. The 17O NMR chemical shifts, in comparison with those of similarly 2-substituted 1,3-dioxolanes, were used to explore the variation of the strength of p– conjugation in the unsaturated acetals as a function of the nature of substitution at C2. The 17O NMR shift data reveal that alkoxy substituents have a significantly more favorable effect on the strength of p– conjugation in 4-methyl-1,3-dioxoles than in 4-methylene-1,3-dioxolanes. This fact appears to be responsible for the previously observed unexpectedly large effect of alkoxy substitution on the relative thermodynamic stabilities of these two classes of isomeric compounds. Additional information of the unexpected charge distribution in 4-methyl-1,3-dioxoles is provided by their 1H and 13C NMR spectra. 相似文献
17.
Aryl-substitutedpyrazolederivativeshavealreadyattractedwideattentioninrecentdecadesbecausetheywerereportedtoshowabroadspectrum0fbi0logicalactivities.Forinstance,severalsubstitutedpyrazolyIpyrazoIesdemonstratedhighpreemergentherbicidalactivityagainstawidevarietyofbroadleafweedspecies"'.Pyraz0lyl-pyrimidinesexhibiteds0mefungicidalactivity'.Fripronil(5-amino-3-cyan0-l-(2',6,-dichloro-4'-trifluoromethylphenyisanewpyrazoleinsecticidethatprovidesexcellentc0ntrolofmanysoilandf0liarinsects0nawidevari… 相似文献
18.
XIAO Li-wei ZHANG Min SUN Wen-hua . Faculty of Chemistry Material Science Langfang Teachers College Langfang P. R. China . Key Laboratory of Engineering Plastics Beijing National Laboratory for Molecular Sciences 《高等学校化学研究》2011,(2):228-231
An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups are bearable from reactants to products. 相似文献
19.
A σ-hole is defined as an electron-deficient region on the extension of a covalently bonded group IV–VII atoms. If the electronic density in the σ-hole is sufficiently low, then this region will have a positive electrostatic potential, which allows attractive noncovalent interactions with negative sites. SO2X2 and SeO2X2 (X = F, Cl and Br) have three Lewis acid sites of σ-hole located in the outermost of chalcogen atom and X end, participating in the chalcogen and halogen bonds with NH3 and H2O, respectively. MP2/aug-cc-pVTZ and M06-2X/aug-cc-pVTZ calculations reveal that for a given halogen atom, SeO2X2 forms stronger chalcogen bond interactions than SO2X2 counterpart. Almost a perfect linear relationship is evident between the interaction energies and the magnitudes of the product of most positive and negative electrostatic potentials. The interaction energies calculated by M06-2X and MP2 methods are almost consistent with each other. 相似文献
20.
Two cobalt containing products CpCoMn2(CO)6(μ3-S)2, 2 and Cp2FeCoMn(CO)3(μ3-S)2, 3 were obtained from the reaction of [CpFeMn(CO)5(μ-S2)]2, 1 with CpCo(CO)2 at room temperature. The two rhodium containing products: Cp*RhMn2(CO)6(μ3-S)2, 4 (11% yield) and CpFeCp*RhMn(CO)3(μ3-S)2, 5 (9% yield), were obtained from the reaction of 1 with Cp*Rh(CO)2. Compounds 3 and 5 were characterized structurally by single crystal X-ray diffraction methods. Compounds 3 and 5 both contain triangular clusters of three different types of metal atoms and have triply bridging sulfido ligands on each side of the cluster. A mechanism for their formation from 1 is proposed.†Dedicated to F. A. Cotton on the occasion of his 75th birthday. 相似文献