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1.
Judit Sipos Benjamin Podnyi Istvn Hermecz Levente Pusztay Gbor Tth Lszl Szilgyi 《Journal of heterocyclic chemistry》1989,26(4):1061-1068
Ethyl 4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylates 1–4 , their piperidine ring homologues 5–6 and their 2-oxo isomers 7–9 were reacted with benzaldehyde. At low temperature, kinetically stable addition products were formed. Thermodynamically stable condensation products were obtained at higher temperature, which were also formed when the addition products were refluxed in benzene. The 9-benzyl derivatives were prepared by the hydrogenation of the condensation products over Pd/C. The stereochemical features of the new compounds were determined via 1H and 13C nmr chemical shift and coupling constant analysis and NOE measurements. 相似文献
2.
Donald S. Matteson Davis Maliakal Levente Fabry-Asztalos 《Journal of organometallic chemistry》2008,693(13):2258-2262
(Azidomethyl)boronic esters of 1,2-dicyclohexyl-1,2-ethanediol (“DICHED”) and pinanediol have been prepared from the corresponding (bromomethyl)boronic esters. Conversion to (2-azido-1-chloro- or bromoethyl)boronic esters by reaction with a (dihalomethyl)lithium followed. Attempted displacement of halide from DICHED (2-azido-1-haloethyl)boronates with alkoxides failed. Reaction of either pinanediol or DICHED (2-azido-1-chloromethyl)boronate with sodium acetate in acetic acid yielded the 1-acetoxy derivative as a ∼1:1 mixture of diastereomers, indicating probable involvement of an α-boryl carbocation intermediate. Hydrogenation of the pinanediol azido boronic ester over platinum in a solution of hydrogen chloride in dioxane was accompanied by deacetylation to form the impure (2-amino-1-hydroxyethyl)boronic ester hydrochloride. Attempted purification of this material resulted in deboronation to ethanolamine. Acetylation yielded pinanediol (2-acetamido-1-acetoxyethyl)boronate. 相似文献
3.
Martin Sahlberg Premysl Beran Thomas Kollin Nielsen Yngve Cerenius Krisztina Kads Marko P.J. Punkkinen Levente Vitos Olle Eriksson Torben R. Jensen Yvonne Andersson 《Journal of solid state chemistry》2009,182(11):3113-3117
A novel aluminium rich alloy for hydrogen storage has been discovered, ScAl0.8Mg0.2, which has very promising properties regarding hydrogen storage capacity, kinetics and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. The absorption of hydrogen was found to be very fast, even without adding any catalyst, and reversible. The discovered alloy crystallizes in a CsCl-type structure, but decomposes to ScH2 and Al(Mg) during hydrogen absorption. Detailed analysis of the hydrogen absorption in ScAl0.8Mg0.2 has been performed using in situ synchrotron radiation powder X-ray diffraction, neutron powder diffraction and quantum mechanical calculations. The results from theory and experiments are in good agreement with each other. 相似文献
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5.
JPC – Journal of Planar Chromatography – Modern TLC - Discoloration of industrially important woods causes substantial economic loss. Although color defects are not always associated... 相似文献
6.
Tolvaj L Persze L Albert L 《Journal of photochemistry and photobiology. B, Biology》2011,105(1):90-93
In this study, wood samples were exposed to light irradiations (direct sunlight, xenon lamp, mercury vapour lamp) and thermal treatments were carried out in dry- and in humid conditions at 90°C. One part of the samples was covered by an aluminium plate during light irradiation. The samples under the aluminium plate also suffered considerable chemical changes, monitored by infrared technique and colour measurement. The sunlight produced greater colour change under the aluminium plate than the artificial light sources. During light irradiation, the carbonyl band having two maximum at 1700 and 1,746 cm(-1) increased and the peak of the aromatic skeletal vibration arising from lignin (1,510 cm(-1)) decreased together with the guaiacyl vibrations at 1,275 cm(-1). There was absorption decrease at 1,174 cm(-1) because of the ether band splitting. Under the covered surface only the ether band at 1,174 cm(-1) decreased and one carbonyl band increased with a maximum at 1,715 cm(-1). Degradation of lignin was negligible for the covered surface. Colour change generated by thermal degradation was much greater in humid condition than in dry condition. 相似文献
7.
The formation of 1,4-thiazine and benzo-1,4-thiazine rings was performed at the 6,7-positions of the morphinan backbone in order to synthesize systems annulated with a new six-membered ring providing potential pharmacological activity and the opportunity of easy functionalization. An unexpected oxidation of cyclic sulfur was observed in both cases affording either sulfones or open-ringed bis-morphinan-type by-product. These phenomena are in conformity with the observations and mechanistic explanations made by several research groups in the past in connection with the photosensitized oxidation of cyclic sulfides. 相似文献
8.
Kárpáti Levente Hamar Gergely Vargha Viktória 《Journal of Thermal Analysis and Calorimetry》2019,136(2):737-747
Journal of Thermal Analysis and Calorimetry - Random amino-alcohol-based poly(ester amide)s were synthesized using adipic acid and differently substituted amino-alcohols, namely 2-amino-ethan-1-ol,... 相似文献
9.
Judit Éva Fleischer Radu Levente Novak John F. Hartmann Neda Beheshti Anna-Lena Kjøniksen Bo Nyström János Borbély 《Colloid and polymer science》2008,286(4):365-376
This work describes the formation of water-soluble hydrophilic nanoparticles from biosynthetic poly-γ-glutamic acid (PGA).
Nanoparticles were formed by cross-linking using 2,2′-(ethylenedioxy) diethylamine in the presence of water-soluble carbodiimide.
The structure was determined by nuclear magnetic resonance spectroscopy and the particle size by transmission electron microscopy
(TEM), size exclusion chromatography (SEC), and dynamic light-scattering (DLS) measurements. The results from TEM, SEC, and
DLS reveal that the particle size depends on the ratio of cross-linking. Particle size values measured by TEM were between
20 and 90 nm. Formation of cross-linked nanoparticles results in a dramatic viscosity drop compared to the viscosity of the
corresponding solution of the parent PGA. The viscosity and DLS experiments disclose an intriguing interplay between intrachain
and interchain cross-linking of the polymer chains, depending on the cross-linker density and polymer concentration. The SEC
measurements show that the retention time of the major portion of particles increase because of the higher cross-linking ratio.
At moderate cross-linker concentration, intramolecular cross-linking is the dominant process, whereas at higher cross-linker
densities, the interpolymer cross-linking plays an important role. As a result, large clusters are also formed. 相似文献
10.
Gbor Horvth Istvn Hermecz gnes Horvth Marianna Pongor-Cskvri Levente Pusztay rpd Istvn Kiss Lszl Czak Osman Hassan Abdirizak 《Journal of heterocyclic chemistry》1985,22(2):481-489
The characteristic features of ir and uv spectra of 43 4H-pyrido[1,2-a]pyrimidin-4-one derivatives with electron donor or acceptor groups in position 3, and positions 6, 7, 8, or 9, respectively, have been systematically studied. On the basis of the spectra some conclusions have been drawn for the molecular structure. The negative solvent effect of the lowest-energy π → π* transition is investigated by the PPP method. 相似文献