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71.
Daniel E. Vicentes Andrea L. Romero Ricuarte Rodríguez Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(5):446-453
An efficient synthesis of 1‐arylisochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐ones, involving the diazotization of 3‐amino‐4‐arylamino‐1H‐isochromen‐1‐ones in weakly acidic solution, has been developed and the spectroscopic characterization and crystal structures of four examples are reported. The molecules of 1‐phenylisochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, C15H9N3O2, (I), are linked into sheets by a combination of C—H…N and C—H…O hydrogen bonds, while the structures of 1‐(2‐methylphenyl)isochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, C16H11N3O2, (II), and 1‐(3‐chlorophenyl)isochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, C15H8ClN3O2, (III), each contain just one hydrogen bond which links the molecules into simple chains, which are further linked into sheets by π‐stacking interactions in (II) but not in (III). In the structure of 1‐(4‐chlorophenyl)isochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, (IV), isomeric with (III), a combination of C—H…O and C—H…π(arene) hydrogen bonds links the molecules into sheets. When compound (II) was exposed to a strong acid in methanol, quantitative conversion occurred to give the ring‐opened transesterification product methyl 2‐[4‐hydroxy‐1‐(2‐methylphenyl)‐1H‐1,2,3‐triazol‐5‐yl]benzoate, C17H15N3O3, (V), where the molecules are linked by paired O—H…O hydrogen bonds to form centrosymmetric dimers. 相似文献
72.
Noe Oña Antonio Romero Carmen Assiego Claudia Bello Pierre Vogel M. Soledad Pino-González 《Tetrahedron: Asymmetry》2010,21(17):2092-2099
An approach to the synthesis of polyhydroxyazepane derivatives from sugar-based epoxyamides or epoxyalcohols, in which the total regioselective epoxide opening by nitrogen nucleophiles is the key step, is described. Thus, novel polyhydroxyazepane carboxamides and aminomethyl polyhydroxyazepanes, with potential pharmacological interest, are synthesized from diacetone d-mannose. Configurational assignments of the obtained products were determined. 相似文献
73.
74.
Langlet A Latypov NV Wellmar U Bemm U Goede P Bergman J Romero I 《The Journal of organic chemistry》2002,67(22):7833-7838
Nitration of some 2-substituted pyrimidine-4,6-diones in sulfuric acid was studied, which afforded previously unknown 5,5-gem-dinitropyrimidine-4,6-diones in high yields. The gem-dinitro products were easily attacked by nucleophiles with concomitant formation of gem-dinitroacetyl derivatives, which in turn could be further hydrolyzed to salts of dinitromethane and triureas. 相似文献
75.
In the interaction of molecules with light endowed with orbital angular momentum, an exchange of orbital angular momentum in an electric dipole transition occurs only between the light and the center of mass motion; i.e., internal "electronic-type" motion does not participate in any exchange of orbital angular momentum in a dipole transition. A quadrupole transition is the lowest electric multipolar process in which an exchange of orbital angular momentum can occur between the light, the internal motion, and the center of mass motion. This rules out experiments seeking to observe exchange of orbital angular momentum between light beams and the internal motion in electric dipole transitions. 相似文献
76.
López-Urías F Muñoz-Sandoval E Reyes-Reyes M Romero AH Terrones M Morán-López JL 《Physical review letters》2005,94(21):216102
We report a novel magnetic phenomenon consisting of the formation of helical spin configurations during the magnetization of densely packed ferromagnetic nanowires encapsulated inside carbon nanotubes. We studied the hysteresis loops when the magnetic fields are applied parallel and perpendicular to the nanotubes axes. We also performed theoretical calculations on aligned nanowire arrays that clearly indicate the creation of helical spin vortices in the hysteresis loops. The latter are caused by the presence of strong dipolar interactions among neighboring wires. 相似文献
77.
We investigated the influences of different types of temporal correlations in the input signal on the functions and coding properties of neurons in the primary visual cortex (V1). We found that the temporal transfer functions of V1 neurons exhibit higher gain, and the spike responses exhibit higher coding efficiency and information transmission rates, for the 1/f (natural long-term correlation) signals than for 1/f(0) (no correlation) and 1/f(2) (stronger long-term correlation) signals. These results suggest that the intermediate long-term correlation ubiquitous to natural signals may play an important role in shaping and optimizing the machinery of neurons in their adaptation to the natural environment. 相似文献
78.
We report the development of a novel zeolite-incorporated optical fiber sensor and demonstrate its capability for in situ detection of chemical vapors. The sensor comprises a polycrystalline silicalite thin film grown upon the cleaved end face of a standard single-mode optical fiber. The sensor device operates by measuring the optical reflectivity of the zeolite crystals, which changes reversibly in response to the amount of chemical vapor adsorbed in its crystalline microporous structure. The sensor has been successfully demonstrated for measuring the concentration of isopropanol vapor in mixtures with nitrogen gas. 相似文献
79.
80.
L. Escobar-Alarcón E. Camps S. Romero O. Olea-Mejía S. Muhl A. Arrieta E. Haro-Poniatowski 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1133-1135
Amorphous carbon nitride (a-CN) thin films show luminescent properties that are of interest for many applications. Particularly interesting are their previously reported thermoluminescent characteristics. In order to optimize these properties, the plasma parameters (ion energy, plasma density and type of excited species) were studied in the present work as a function of the laser fluence and the working pressure. The plasma was produced using the fundamental line of a Nd:YAG laser with 28 ns pulse duration focused on a high purity graphite target. The laser fluences used in this work could be varied between 9 and 40 J/cm2. Measurements and deposition of a-CN films were carried out in a nitrogen atmosphere at pressures from 3×10-3 to 7.5×10-2 Torr. We observed an optimum value of pressure, close to 7.5×10-2 Torr, in which the nitrogen incorporation into the film achieved its maximum value close to 29 at.% and the thermoluminescent response of the material, after irradiation with UV becomes evident. PACS 81.15.Fg; 78.60.Kn; 81.05.Uw 相似文献