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371.
Oxidative homocoupling of arylboronic acids catalyzed by a 4‐aminoantipyrine–Pd(II)complex
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Claudia Araceli Contreras‐Celedón José Arturo Rincón‐Medina Darío Mendoza‐Rayo Luis Chacón‐García 《应用有机金属化学》2015,29(7):439-442
A one‐step synthesis of symmetric biaryls is reported under very mild conditions via the homocoupling reaction of substituted arylboronic acids using an air‐ and moisture‐stable 4‐aminoantipyrine–Pd(II) complex as catalyst. The reaction is conducted at a low catalyst loading of 0.1 mol% at room temperature in methanol in the presence of K2CO3 as the base and KMnO4 as the oxidant. The catalytic methodology is shown to be compatible with diverse functional groups and affords the desired biphenyls in good to excellent yields. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
372.
The IR and Raman spectra of Crystalline Tetrapropylammonium trichlorozincate (II) have been measured at room and liquid nitrogen temperatures. The spectra have been interpreted in terms of halogen bridged structures. The complete coincidence of the IR and Raman bands suggests a symmetry lower than D2h and rules out any centrosymmetric structure. 相似文献
373.
Apolonia Murillo Luis Manuel Chiquete Pedro Josephnathan Rosalinda Contreras 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):87-101
Abstract A series of new dibenzophosphoranes (1-6) bearing uncommon functions such as hydroxy-, alkoxy-, oxo-, amide- and dihydride- attached to the phosphorus atom have been prepared and characterized. The reactivities of the alkoxy derivative 1 and the amide 2 towards alcohols, amines, water and borane were studied mainly by 31P NMR. The structure of the diphenoxyamine-bis-phoshorane 4 was established by single crystal X-ray diffraction studies. 相似文献
374.
375.
Poly(?-caprolactone)-b-poly(ethylene glycol)-b-poly(?-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymer were synthesized by mean anionic activation of the hydroxyl end groups of poly(ethylene glycol) in presence of diphenylmethylsodium. Copolymers were characterized by SEC, FT-IR and 1H-NMR spectroscopy, TGA and DSC. Size exclusion chromatographic analysis of obtained copolymers indicated incorporation of CL monomer into PEG without formation of PCL homopolymer. Characterization by FT-IR and 1H NMR spectroscopy of the resulting polymeric products, with respect to their structure, end-groups and composition, showed that they are best described as ester-ether-ester triblock copolymers, whose compositions can be adjusted changing the feeding molar ratio of PEG to CL. The thermal stability of triblock copolymers was less that PEG precursor, but higher that PCL homopolymer. Analysis by mean DSC showed that all copolymers were semi-crystalline and their thermal behavior depending on their composition. 相似文献
376.
J. González O. Contreras Ch. Power E. Calderon M. Quintero D. Martínez-garcía 《高压研究》2013,33(2):119-135
II–VI and II1?x Mn x VI nanocrystals were prepared by the pressure cycle method using the Paris–Edinburgh cell. The recovered samples are nanocrystals in the cubic phase zinc-blend (ZB) structure and were characterized using transmission electron microscopy, electron diffraction, X-ray diffraction and Raman scattering. Transmission electron micrographs show that these nanocrystals are nearly spherical with diameters ranging from 20 to 50 nm depending on the sample under investigation. The Raman scattering measurements confirm the existence of II–VI nanocrystals in the cubic phase (ZB). The magnetic properties of Cd0.5Mn0.5Te nanoparticles were found to vary with the particle size and were different from those observed for the Cd0.5Mn0.5Te bulk initial samples. The χ vs. T data show temperature hysteresis due to spin-glass form, which occurs at T g=21 K, for both the bulk as well as for the recovered nanoparticle samples. The zero-field cooled and field-cooled χ vs. T curves for the nanoparticles showed a monotonous increase below T g. Below ~21 K, the M vs. B curve for the recovered nanoparticle samples exhibited magnetic hysteresis, and this is attributed to a weak ferromagnetic contribution. This contribution is also observed in the χ(T) curves and is due to a large surface/volume ratio of the nanoparticles, which enhances the magnetic interaction. 相似文献
377.
378.
Manuel D. Contreras Alfredo G. Hernández-Díaz 《Integral Equations and Operator Theory》2003,46(2):165-188
Let and be two analytic functions defined on such that. The operator given by is called a weighted composition
operator. In this paper we deal with the boundedness, compactness,
weak compactness, and complete continuity of weighted composition operators
from a Hardy space H
p
into another Hardy space H
q
.
We apply these results to study composition operators on Hardy spaces of a
half-plane.
Submitted: November 20, 2001. 相似文献
379.
We prove L2 orbital stability of Dirac solitons in the massive Thirring model. Our method uses local well posedness of the massive Thirring model in L2, conservation of the charge functional, and the auto–Bäcklund transformation. The latter transformation exists because the massive Thirring model is integrable via the inverse scattering transform method. 相似文献
380.
González Calderón José Amir Austria Gutiérrez Adrián Sanchez Gregorio Peña Juárez Mariana Gisela Contreras López David Pérez Elías Vallejo Montesinos Javier 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12365-12382
Journal of Thermal Analysis and Calorimetry - This work presents the surface functionalization of titanium dioxide nanoparticles with 1H-1-carboxylate of isopropyl-imidazole and... 相似文献