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41.
Analysis of the influence of the substitution on indolylmagnesium salts in the reaction with benzoyl chlo ride, acrylonitrile and methyl iodide, giving the C- and N-derivatives, have been carried out. The yield in the C- and N-product depends upon the electronic character and position of the substituent (methyl or phenyl) on the indole ring and of the ethereal solvent as well as the concentration and molar ratio of the reagents. The 2- or 3-phenyl substituted indolylmagnesium salts with acrylonitrile always gave the 1-(2-cyanoethyl)indole derivative. 相似文献
42.
Avenoza A Busto JH Jiménez-Osés G Peregrina JM 《The Journal of organic chemistry》2005,70(14):5721-5724
[reaction: see text] This report describes two straightforward synthetic methodologies to obtain alpha-CF3-isoserine, a new alpha,alpha-disubstituted beta-amino acid, from alpha-(trifluoromethyl)acrylic acid. The routes involve the synthesis of five-membered cyclic sulfates (using sulfuryl chloride) or sulfamidates (using the Burgess reagent) from the corresponding chiral diols, which are obtained by a catalytic asymmetric dihydroxylation (AD) reaction. 相似文献
43.
The synthesis of dendrons with the end-capped 5-(N,N-dimethylamino)naphthyl-1-ethynyl unit connected to conjugated naphthylethynyl or p-phenylethynyl chains, as the branches of the 1,3,5-substituted benzene core, have been undertaken by heterocoupling reaction between 1,3,5-triiodobenzene and the convenient end-capped 5-(N,N-dimethylamino)naphthylacetylene or 5-(N,N-dimethylamino)naphthylethynylphenylacetylene in the presence of the palladium-copper catalyst system, in excellent yields. The influence of the alternating naphthylethynyl-phenylethynyl chains on the fluorescence emission radiation, in the dendron structures, has been analyzed. 相似文献
44.
45.
Jorge Labella Dr. Gonzalo Durán-Sampedro Swathi Krishna Prof. M. Victoria Martínez-Díaz Prof. Dirk M. Guldi Prof. Tomás Torres 《Angewandte Chemie (International ed. in English)》2023,62(5):e202214543
Large π-conjugated systems are key in the area of molecular materials. Herein, we prepare via AuI-catalyzed cyclization a series of fully π-conjugated anthracene-fused oligo-BODIPYs. Their structural and optoelectronic properties were studied by several techniques, ranging from X-ray, UV/Vis, and cyclic voltammetry to transient absorption spectroscopy. As a complement, their electronic structures were explored by means of Density Functional Theory (DFT) calculations. Depending on the size and shape of the π-conjugated skeleton, unique features—such as face-to-face supramolecular organization, NIR absorption and fluorescence as well as strong electron accepting character—were noted. All in all, the aforementioned features render them valuable for technological applications. 相似文献
46.
Dr. Yanira Méndez Dr. Aldrin V. Vasco Galway Ivey Ana Laura Dias Dr. Peter Gierth Bárbara B. Sousa Dr. Claudio D. Navo Angel Torres-Mozas Dr. Tiago Rodrigues Dr. Gonzalo Jiménez-Osés Prof. Gonçalo J. L. Bernardes 《Angewandte Chemie (International ed. in English)》2023,62(44):e202311186
Multicomponent reactions are of utmost importance at generating a unique, wide, and complex chemical space. Herein we describe a novel multicomponent approach based on the combination of the isonitrile-tetrazine (4+1) cycloaddition and the Ugi four-component reaction to generate pyrazole amide derivatives. The scope of the reaction as well as mechanistic insights governing the 4H-pyrazol-4-imine tautomerization are provided. This multicomponent process provides access to a new chemical space of pyrazole amide derivatives and offers a tool for peptide modification and stapling. 相似文献
47.
A lattice spin-fermion model for diluted magnetic semiconductors (DMS) is investigated numerically, improving on previously used mean-field approximations. Curie temperatures are obtained varying the Mn spin x and hole n densities, and the impurity-hole exchange J in units of the hop-ping t. Optimal values are found in the subtle intermediate regime between itinerant and localized carriers. At intermediate and large J/t, a "clustered" state is observed above the Curie temperature and ferromagnetism is suppressed. Formal analogies between DMS and manganites are discussed. 相似文献
48.
Cordero BM Pérez Pavón JL García Pinto C Fernández Laespada ME Carabias Martínez R Rodriguez Gonzalo E 《Journal of chromatography. A》2000,902(1):195-204
An overview of the analytical applications of membrane-based systems for sample enrichment in chromatography and capillary electrophoresis is presented. A brief introduction to the different types of membranes and the main forces related to the transport through them is also given. 相似文献
49.
We describe a device where the nonlocal spin-spin interaction between quantum dots (QDs) can be turned on and off with a small magnetic field. The setup consists of two QDs at the edge of two two-dimensional electron gases (2DEGs). The QDs' spins are coupled through a RKKY-like interaction mediated by the electrons in the 2DEGs. A magnetic field B(z) perpendicular to the plane of the 2DEG is used as a tuning parameter. When the cyclotron radius is commensurate with the interdot distance, the spin-spin interaction is amplified by a few orders of magnitude. The sign of the interaction is controlled by finely tuning B(z). Our setup allows for several dots to be coupled in a linear arrangement and it is not restricted to nearest-neighbor interaction. 相似文献
50.
Olmo GJ 《Physical review letters》2005,95(26):261102
In this work we show that the gravity Lagrangian at relatively low curvatures in both metric and Palatini formalisms is a bounded function that can only depart from the linearity within the limits defined by well-known functions. We obtain those functions by analyzing a set of inequalities that any theory must satisfy in order to be compatible with laboratory and solar system observational constraints. This result implies that the recently suggested f(R)gravity theories with nonlinear terms that dominate at low curvatures are incompatible with observations and, therefore, cannot represent a valid mechanism to justify the cosmic speedup. 相似文献