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31.
Volodymyr Semeniuchenko Yana Garazd Myroslav Garazd Tetyana Shokol Ulrich Groth Volodymyr Khilya 《Monatshefte für Chemie / Chemical Monthly》2009,25(3):1503-1512
Abstract
A highly efficient procedure for glucosylation of flavonoids by acetobromoglucose is described. Glucosylation is carried out in a two-phase system CHCl3/H2O over 96 h using tetrabutylammonium bromide as phase-transfer catalyst. A purification procedure can be performed without column chromatography, and the yields of the glucosylated flavonoids are mostly quantitative. Acetylated glucosides were deprotected with sodium methanolate to afford the desired glucosides of flavonoids. 相似文献32.
[reaction: see text] Calix[4]arenes bearing one, two, or four 1,8-naphthyl imide groups at the wide rim and bis-calix[4]arenes connected via perylene-bisimide dye spacers have been synthesized. The low-temperature NMR spectrum of the tetranaphthylimide suggests, in agreement with a crystal structure, a C2-symmetrical pinched cone conformation stabilized via face-to-face pi-pi interactions between opposite naphthylimide groups. UV-vis and fluorescence studies have been carried out for the perylene bis-calix[4]arene dyes. 相似文献
33.
Pop A Vysotsky MO Saadioui M Böhmer V 《Chemical communications (Cambridge, England)》2003,(10):1124-1125
The possibilities to form dimeric capsules with supramolecular chirality from tetraurea calix[4]arenes composed of two different phenolic urea units are discussed in general and demonstrated experimentally for various selected examples. 相似文献
34.
Bohdan Zapeka Andriy Say Oxana Vlokh Myroslav Kostyrko Iryna Martynyuk-Lototska 《Phase Transitions》2015,88(2):192-200
We have studied special points that appear on the (x, T)-phase diagram of mixed K2xRb2(1?x)Cd2(SO4)3 crystals. This phase diagram has been constructed issuing from the changes in domain structure occurring in the course of phase transitions. We have found that two triple points on the (x, T)-phase diagram of the above solid solutions are very close to each other in the phase space and can change their places or transform into a quadruple point. These special points are associated with disappearance of ferroelectric phases with the symmetries P1 and P21 taking place when Rb2+ are substituted with K2+ ions. 相似文献
35.
[reaction: see text] Calix[4]arenes 4, substituted at the wide rim by four N-tolyl-urethane groups, were synthesized, as well as derivatives 10a,b bearing two or three tolyl-urea groups beside of one or two urethane group(s). In contrast to tetra-tolyl urea 11, the urethane derivatives do not form hydrogen-bonded, dimeric capsules in CDCl3 or benzene-d6, but the dimerization can be induced for the triurea 10b by tetraethylammonium cations as guests. The quantitative formation of heterodimers is observed for all urethanes 4 and 10a,bin benzene-d6 in mixtures with a "tetra-loop" tetraurea 14, while "bisloop" tetraureas 13 require di- or triurea derivatives 10a,b for a clean heterodimerization. 相似文献
36.
Cao Y Wang L Bolte M Vysotsky MO Böhmer V 《Chemical communications (Cambridge, England)》2005,(25):3132-3134
Macrocycles with up to 100 atoms have been synthesised using two calix[4]arenes as templates: first, (3,5-dialkenyloxy)phenyl groups are attached to the wide rim of a calix[4]arene via urea links, then the alkenyl groups are connected via a metathesis reaction using a tetratosylurea calix[4]arene for their correct prearrangement and finally the urea functions are cleaved to detach the newly formed macrocycles. 相似文献
37.
Enhanced thermodynamic and kinetic stability of calix[4]arene dimers locked in the cone conformation
Vysotsky MO Mogck O Rudzevich Y Shivanyuk A Böhmer V Brody MS Cho YL Rudkevich DM Rebek J 《The Journal of organic chemistry》2004,69(18):6115-6120
Wide rim tetraurea derivatives (2a,b) have been prepared from a calix[4]arene rigidified in the cone conformation by two diethyleneglycol ether bridges between adjacent oxygens. In comparison to the analogous tetraurea derivatives (3a,b) of a tetrapentoxy calix[4]arene, 2a,b show an increased thermodynamic stability in mixtures of CDCl(3) and DMSO-d(6). Their kinetic stability as expressed by the rate of guest exchange (benzene or cyclohexane against the solvent benzene-d(6)) is also strongly increased by factors of 30-38. Noticeable differences for the inclusion of selected guests are found. 相似文献
38.
Molokanova O Bogdan A Vysotsky MO Bolte M Ikai T Okamoto Y Böhmer V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(21):6157-6170
The exclusive formation of hydrogen-bonded dimers between tetraaryl and tetratosylurea calix[4]arenes has been used to prepare a series of ten "bisloop" tetraurea calix[4]arenes 3, in which adjacent phenylurea groups are covalently linked through alpha,omega-dioxyalkane chains. This dimerization with tetratosylurea 2 as template preorganizes the alkenyl residues of tetra(m-alkenyloxyphenyl) ureas 1 and enables their selective connection in high yield (up to 95 %) by olefin metathesis followed by hydrogenation. The "bisloop" calixarenes 3 also exclusively form heterodimers with 1. Thus, in a separated metathesis/hydrogenation sequence, a series of 14 cyclic bis[2]catenanes 4, in which two calix[4]arenes are connected through their wide rims by two pairs of interlocked rings (total size 29 to 41 atoms), were prepared in yields of up to 97 %. Optical resolution of these chiral bis[2]catenanes was studied by HPLC on chiral stationary phases. The single-crystal X-ray structure of one example (4(P,10)) confirmed the interlocking rings and revealed that the hydrogen-bonded dimeric capsule of the calix[4]arene can be "completely" opened. 相似文献
39.
Olexandr Halaiev Myroslav Garazd Andrzej Gzella Roman Lesyk 《Tetrahedron letters》2017,58(13):1324-1325
Unexpected regioselectivity for the Skraup-Doebner-Von Miller reaction was observed during the synthesis of quinolines from 4-aminoindoles and acetone in the presence of hydrochloric acid as a catalyst. The products were unambiguously assigned as 1-alkyl-3,5,5-trimethyl-5,6-dihydro-1H-azepino[4,3,2-cd]indoles instead of 2,2,4-trimethyl-2,7-dihydro-1H-pyrrolo[2,3-h]quinolones based on NMR spectroscopy and X-ray crystallographic analysis. 相似文献
40.
Myroslav Sprynskyy Roman Golembiewski Bogus?aw Buszewski 《Journal of Physics and Chemistry of Solids》2010,71(9):1269-1277
The porous structure of the raw and the modified clinoptilolite has been investigated by nitrogen adsorption method, polarized light, scanning electron and atomic force microscopy as well as by thermogravimetric analysis. The relative moisture, specific gravity, bulk density and inter-particle porosity have been tested using thermostatic, pycnometric and hydrostatic weighing methods. The geometric method has been used to calculate the external surface area of the clinoptilolite crystallites in the clinoptilolite rock and to evaluate the volume of the clinoptilolite framework channels. Generally two types of porosities such as primary porosity and secondary one are observed. The primary porosity may be defined as microporosity presented by nanotube system of the clinoptilolite 3-dimensional aluminosilicate framework. The secondary porosity is formed by meso- and macropores, where the first ones are presented by slot pores determined mainly by cleavability of the zeolite crystallites. Total volume of the zeolite channels equals 0.332 cm3/g which has been obtained using a geometric method. Micropores volumes of the raw and the acid-treated samples are 0.0031 and 0.0342 cm3/g by nitrogen adsorption, respectively. According to thermogravimetric analysis the structural water lost at 150-750 °C placed the pore volume 0.087 cm3/g with the surface area 360 m2/g. 相似文献