共查询到20条相似文献,搜索用时 15 毫秒
1.
D. V. Berdyshev V. P. Glazunov A. Ya. Yakubovskaya T. Yu. Kochergina V. F. Anufriev 《Journal of Applied Spectroscopy》2006,73(6):798-806
We have used B3LYP/6-31(d) density functional theory to calculate the frequencies and modes of the normal vibrations of 2-oxo-2,3-dihydro-and
2-methoxy-1,4-naphthoquinones. Based on these calculations within an additive model, we have assigned the carbonyl bands in
the IR spectra of 2,3-dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinones (diquinones 1–4). We have carried out a direct calculation of the vibrational spectra for diquinones 1–4 using PBE and B3LYP correlation functionals. We have shown that the calculation of the vibrational spectra of the diquinones
based on an additive model on the whole is quite consistent with the results of direct calculations and the experimental spectra.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 713–720, November–December, 2006. 相似文献
2.
The 1H- and 13C-NMR spectra of 6,7-dihalo-1,4-dihydro-4-oxo-1-(2,3,5-tri-0-benzoyl-pβ-D-ribofuranosyl)quinoline-3-carboxylic acids (3), (4), the ester (3a), 6-chloro-1-(2-deoxy-3,5-di-O-tolouyl-α- and β-D-erythropentofuranosyl)-7-fluoro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid (5), and its free a-nucleoside (5a) have been investigated. Resonance signals were assigned by homo- and heteronuclear two dimensional NMR methods (DQF-COSY, HMQC, and HMBC) for (3), (4), (5), and (5a). Ribosylation sites and anomeric configurations were identified from ROESY spectra. 相似文献
3.
Spectral-Luminescent Properties and Molecular Orbital Treatment of Some Mono- and Difluoroquinolones
Polishchuk AV Karaseva ET Emelina TB Cramariuc O Karasev VE 《Journal of fluorescence》2011,21(3):1293-1300
Electronic absorption and luminescent spectra of nonfluorinated nalidixic (nlqH) and pipemidic acid (pifqH), monofluoroquinolones
– norfloxacin (nfqH) and pefloxacin (pfqH) as well as of their difluorinated analogs 1-ethyl-6,8-difluoro-1,4-dihydro-7-(1-(4-methylpiperazinyl)
– 4-oxo-3-quinolinecarboxylic (mdfqH) acid and 1-ethyl-6,8-difluoro-1,4-dihydro-7-(1-piperazinyl) – 4-oxo-3-quinolinecarboxylic
acid (dfqH) - were investigated. Quantum yields, lifetimes of excited states and rate constants of radiative and nonradiative
transitions of the compounds were measured. The Mulliken charges of atoms from these compounds were calculated by quantum-chemical
complex GAMESS. Differences in the electronic structures of these compounds and their spectral-luminescent characteristics
were compared with the data of the phototoxicity degree of fluoroquinolones. Analysis of the Mulliken charges of the difluoroquinolones
points to the changes of the redistribution of the electron density along π-conjugated system, and on the oxygen atoms of
the carbonyl and carboxyl groups. The analysis of the molecular orbitals involved in the electronic transitions of the compounds
revealed that both defluorination and piperazine photolysis are photodecomposition mechanisms which may take place in the
excited states of these compounds. The relationship between the location order of the π-π* excited levels of the FQs and the
degree of their phototoxicity has been determined 相似文献
4.
I?aki Galve Raimon Puig de la Bellacasa David Sánchez-García Xavier Batllori Jordi Teixidó José I. Borrell 《Molecular diversity》2012,16(4):639-649
A practical protocol was developed for the synthesis of 2-arylamino substituted 4-amino-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones from ??,??-unsaturated esters, malononitrile, and an aryl substituted guanidine via the corresponding 3-aryl-3,4,5,6- tetrahydropyrido[2,3-d]pyrimidin-7(8H)-ones. Such compounds are formed upon treatment of 2-methoxy-6-oxo-1,4,5,6-tetrahydropyridine-3-carbonitriles with an aryl substituted guanidine in 1,4-dioxane and are converted to the desired 4-aminopyridopyrimidines with NaOMe/MeOH through a Dimroth rearrangement. The overall yields of this three-step protocol are, generally speaking, higher than the multicomponent reaction, previously developed by our group, between an ??,??-unsaturated ester, malononitrile, and an aryl substituted guanidine. 相似文献
5.
We have used the PBE/3z, B3LYP/6-31G, B3LYP/6-31G(d), and B3LYP/6-311G(d) methods to study the conformational mobility of
2,3-dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinones (1–4). We have shown that more than 99% of these compounds exist as the major tautomeric form, while differences in the structure
of the Q2H (2,3-dihydro-2-oxo-1,4-naphthoquinones) and Q1,4 (1,4-naphthoquinon-2-yl) moieties lead to qualitative differences in the internal rotation potentials of the ethyl substituents
V(θEt−1) and V(θEt−2), and consequently each of compounds 1−4 exists as six different rotameric forms. For diquinone 3, we have calculated the dependences of the frequencies (ν) and intensities (A) of the normal vibrations on the torsional
angles θEt−1 and θEt−2, and also on the changes in the geometry of the ether bond. We have found that the values of ν and A for the bands in the
carbonyl region of the IR spectrum change little on going from one rotameric form to another, and also for the in-plane bends
of the ether bond, and change considerably for the out-of-plane bends of the ether bond. However, for T ≤ 300 K, there is
no qualitative change in the overall contour, and it can be interpreted based on a simple additive model.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 573–581, September–October, 2006. 相似文献
6.
Retro Diels-Alder mechanism is the main fragmentation pattern of the 7-chloro Pyrano oxazine (2),7-morpholino pyrano oxasine (3),5-morpholino carbonyl-4-oxo-3-substituted phenyl-2-thio-1-3-oxazine-6-ylacetomorpholide (4) and ethyl-6-ethoxy carbonyl methyl-4-oxo-3-(substituted phenyl)-2-thio-2H-1,3-oxazine-5-carboxylate (5). Further fragmentation routes were also discussed. 相似文献
7.
Studies of the luminescence of Eu(3+)/quinaldinic acid sodium [Eu(QA)(3)] and Eu(3+)/1,4-dihydro-4-oxo-quinoline-carboxylic acid sodium [Eu/(DOQCA)(3)], both in solid form and in aqueous solution, are presented in room temperature. The energy transfer to the emitting levels of the lanthanide ions are discussed on the basis of the emission spectra and lifetime data of (5)D(0) and (5)D(1) levels of Eu(3+). In the aquated Eu/(QA)(3) complex, the most intense spectral band belongs to the (5)D(0) --> (7)F(1) transition (592 nm) and not to (5)D(0) --> (7)F(2) (616 nm), which otherwise occurs usually. In the cases of the Eu/(DOQCA)(3) complex the hypersensitive transition (5)D(0) --> (7)F(2) is the most intense as so far was reported for various Eu(3+) chelates. 相似文献
8.
Junzo Hirano Kenji Hamase Hiroyuki Miyata Kiyoshi Zaitsu 《Journal of fluorescence》2010,20(2):615-624
A novel fluorescence enhancement-type derivatizing reagent for amino compounds, 6,7-difluoro-1,4-dihydro-1-methyl-4-oxo-3-quinolinecarboxylic
acid (FMQC), was developed. FMQC reacts with aliphatic primary amino compounds to afford strong fluorescent derivatives having
high photo-and thermo-stabilities. The FMQC derivatives of amino compounds showed 12–159 times higher fluorescence quantum
efficiencies than those of FMQC in aqueous and polar organic media. Additionally, the absorption and fluorescence emission
wavelength of the derivatives are red-shifted from those of FMQC. These differences in the fluorescence properties between
FMQC and the fluorescent derivative enabled the simple and highly sensitive determination of amino compounds without removing
any excess unreacted FMQC by using a simple spectrofluorometer as well as HPLC. 相似文献
9.
The adsorption reactions and binding configurations of cyclohexene, 1,3-cyclohexadiene and 1,4-cyclohexadiene on Si(1 1 1)-7 × 7 were studied using high-resolution electron energy loss spectroscopy (HREELS), ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and DFT calculation. The covalent attachments of these unsaturated hydrocarbons to Si(1 1 1)-7 × 7 through the formation of Si–C linkages are clearly demonstrated by the observation of the Si–C stretching mode at 450–500 cm−1 in their HREELS spectra. For chemisorbed cyclohexene, the involvement of πC=C in binding is further supported by the absence of C=C stretching modes and the disappearance of the πC=C photoemission. The chemisorption of both 1,3-cyclohexadiene and 1,4-cyclohexadiene leads to the formation of cyclohexene-like intermediates through di-σ bonding. The existence of one πC=C bond in their chemisorbed states is confirmed by the observation of the C=C and (sp2)C---H stretching modes and the UPS and XPS results. DFT calculations show that [4 + 2]-like cycloaddition is thermodynamically preferred for 1,3-cyclohexadiene on Si(1 1 1)-7 × 7, but a [2 + 2]-like reaction mechanism is proposed for the covalent attachment of cyclohexene and 1,4-cyclohexadiene. 相似文献
10.
The coordination ability of 2-oxo-2H-chromene-3-phosphonic acid with Pt(II) both in solution and in solid state is elucidated by means of conventional and linear-polarized IR spectroscopy of oriented colloid suspensions in nematic liquid crystal, 1H-, 13C-, and 31P-NMR, UV-Vis spectroscopy, positive and negative mass spectrometry (ESI and FAB), and TGV and DSC methods. A comparison with the spectroscopic data of ammonium salt of 2-oxo-2H-chromene-3-phosphonic acid is carried out as well. 相似文献
11.
We report the synthesis and characterization two coumarin-based fluorescence probes, N′-{[7-(diethylamino)-2-oxo-2H-chromen-3-yl]carbonyl}pyridine-3-carbohydrazide (3) and N′-benzoyl-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (4), proposed as a novel fluorescent chemosensor. The two probes designed showed an instant turn-off fluorescence response to Cu2+ over other metal ions in ethanol-water mixture based on intramolecular charge transfer (ICT). It was found that pyridine-analogue coumarin is highly selective and sensitive sensor for Cu2+. The 3 sensor coordinates Cu2+ in 1:1 stoichiometry with a binding constant, Ka = 5.22 M?1 and the detection limit was calculated 1.97 × 10?9 M. 相似文献
12.
In the synthesis of combinatorial chemical libraries on solid phase, there is a need to cleave the compounds from the solid
support before the library can be tested for biological activity. It is advantageous to use linkers which will release the
libraries by mild photolytic cleavage. We have developed six new linkers of the photosensitive α-methyl 2-nitrobenzyl type
containing amino, hydroxy, bromo and methylamino groups, and also 4-nitrophenoxycarbonyl activated OH and NH2 groups.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Niloofar Tavakoli-Hoseini Majid M. HeraviFatemeh F. Bamoharram Abolghasem DavoodniaMitra Ghassemzadeh 《Journal of Molecular Liquids》2011,163(3):122-127
Under solvent-free conditions and in the presence of 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [MIM(CH2)4SO3H][HSO4], a Brønsted acidic ionic liquid, the reaction of aromatic aldehydes with 4-hydroxycoumarin has been investigated. A wide range of aromatic aldehydes easily undergoes condensation with 4-hydroxycoumarin to afford biscoumarins with good purity in excellent yields. However, reaction of 2-hydroxybenzaldehyde with 4-hydroxycoumarin gave, not the corresponding biscoumarin, but a tetracyclic compound, 7-(2-hydroxy-4-oxo-4H-chromen-3-yl)-6H,7H-chromeno[4,3-b]chromen-6-one, in high yield. 相似文献
14.
An efficient solid-phase synthesis of 2-substituted 4-aminopyrido[2,3-d]pyrimidines 15 is reported. The procedure started by solid supporting a p-hydroxybenzaldehyde 8 to the Wang resin by using the Mitsunobu protocol. The resulting aldehyde 17 was treated with a substituted acid methyl malonate 10 to afford the corresponding alpha, beta-unsaturated ester 18, which was converted to the Michael adduct 21 by reaction with malononitrile. Cyclization of 21 with an amidine system 13 yielded the solid supported pyridopyrimidine 22, which afforded the corresponding 2-substituted 4-aminopyrido[2,3-d]pyrimidine 15 upon treatment with TFA:DCM. Compounds 15 present three diversity centers R1, R2 and R3. Having validated the chemistry on solid support, a 32-membered combinatorial library was obtained using this protocol. 相似文献
15.
16.
Mohammad A. Khalilzadeh Zinatossadat Hossaini Faramarz Rostami Charati Sara Hallajian Mehdi Rajabi 《Molecular diversity》2011,15(2):445-450
An efficient synthesis of 2-hydroxy-3-[2-oxo-2-phenylethylidene]-2-phenyl-2, 3-dihydro-4 H-furo[3, 2-c]chromene-4(2H)-one is described. This involves the reaction between dibenzoylacetylene and 4-hydroxycoumarine in the presence of NaH (10 mol
%) in nearly quantitative yield. Treatment of this heterocyclic system with trimethyl chlorosilane in CHCl3 leads quantitatively to 4-oxo-3-[2-oxo-2-phenylethylidene]-2-phenyl-3H, 4H-furo[3,2-c]chromene-1-ium chloride. Direct addition of nucleophiles, such as alcohols, amines or trialkyl phosphites to this
salt in water as the solvent produces functionalized 2-phenyl-4H-furo[3,2-c] chromen derivatives in excellent yields. 相似文献
17.
Sergey Dobrin 《Surface science》2004,561(1):11-24
A comparative study is reported of the thermal reaction of 1,2- and 1,4-dibromobenzene (1,2- and 1,4-diBrPh) on Si(1 1 1)-7 × 7, investigated by STM. Some results are given for the intermediate case of 1,3-diBrPh. The STM images gave evidence of a different pattern of reaction to yield pairs of Br-Si for 1,2-, 1,3- and 1,4-diBrPh. The ratio of pairs of Br-Si to single bromination events was 1:2 for 1,2-diBrPh and 1:3 for 1,4-diBrPh. In many cases organic residue from the bromination reaction, R-Si, was evident in the STM image. The products R-Si and Br-Si were found to be bound to adjacent Si, for both 1,2- and 1,4-diBrPh. The mean Br?Br pair separation at the surface depended on the parent molecule, being 7.6 Å for 1,2-diBrPh, 10.3 Å for 1,3-diBrPh, and 11.3 Å for 1,4-diBrPh. These separations are, in each case, about 4 Å greater than the separation of the Br-atoms in the intact parent molecule, which increases systematically down the series. There was a marked decrease in the percentage of R-Si accompanying the Br-Si in going down the series, decreasing from 70% for 1,2- to 20% for 1,4-diBrPh; this was interpreted as being due to a decrease in the percentage of `benzene-mediated' reaction dynamics, in which the benzene ring was bound to the surface. At moderately increased surface temperature (45 °C) the reaction of 1,2- and also 1,4-diBrPh no longer resulted in R-Si formation, suggesting that the dynamics had altered from benzene-mediated to `bromine-mediated'. 相似文献
18.
4-Fluoro-3-nitrobenzoic acid attached to a solid support was shown to react under mild conditions with a wide range of functionalized
phenols to yield, after cleavage, the corresponding biaryl ethers in excellent purity. In a similar fashion, biaryl thioethers
could be obtained. Further elaboration of immobilized biaryl ethers demonstrates the potential for combinatorial library generation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
20.
A combinatorial approach towards identifying inhibitors of VALA-4 was investigated. A library of piperazine-peptoid-bisarylureas was assembled in solid phase and screening in the novel v-well assay enabled the identificationof active compounds 相似文献