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931.
The big easy: The direct coupling of Grignard reagents to isocyanates provides a facile and robust solution for the synthesis of sterically hindered and electron-deficient secondary amides. The products are obtained in high yields without the need for excess reagents or chromatographic purification. 相似文献
932.
933.
Robinson PS Khairallah GN da Silva G Lioe H O'Hair RA 《Angewandte Chemie (International ed. in English)》2012,51(16):3812-3817
Controversy resolved! A combination of gas-phase ion-molecule reactions and theoretical studies confirm bisligated mononuclear Au(I) complexes are unable to undergo oxidative addition of iodobenzene for Sonogashira coupling, but that the ligated gold clusters [Au(3)L(n)](+) (L=Ph(2)P(CH(2))(n)PPh(2); n=3-6) activate the C-I bond. DFT calculations on the transition states show that the linker size n tunes the cluster reactivity. 相似文献
934.
The multi-electron dissociative ionization (MEDI) of alkyl-halide clusters induced by 35 ps (at 266, 532 and 1064 nm) and 20 fs (at 400 and 800 nm) laser pulses is reported. In most cases, the MEDI of clusters is observed at substantially lower laser intensities than those reported for the monomer molecules, while the fragment ions are released with higher kinetic energies. From the comparative analysis of the experimental data, is concluded that the increase of molecular chain and/or the presence of a lighter halogen (I, Br, Cl) in the molecular skeleton results in the increase of the laser intensity thresholds for the appearance of the singly and multiply charged fragment ions. As far as the angular distributions of the ejected ions are concerned, they are found to be dependent on the laser pulse duration. For the observed experimental data, a physical mechanism is proposed, based on the combined action of the laser and the electric field created within the clusters after their single ionization. 相似文献
935.
Despite the wide use of carbon materials as supports for heterogeneous catalysis, generic labels are often used to describe the catalysts, i.e. Au/C, making comparisons between different Au/C catalysts difficult even for the same application. A variety of structures and chemically modified surfaces are in fact available, making gold nanoparticles supported on carbonaceous supports extremely versatile catalysts. 相似文献
936.
Fabiana Nador Yanina Moglie Andrés Ciolino Adriana Pierini Viviana Dorn Miguel Yus Francisco Alonso Gabriel Radivoy 《Tetrahedron letters》2012,53(25):3156-3160
A simple one-pot procedure for the direct reductive amination of aldehydes using lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB) or a polymer supported naphthalene as reducing system is described. The direct reductive amination of a variety of aldehydes with primary amines was achieved simply by adding a mixture of the corresponding carbonyl compound and the amine, over a solution of the lithium arenide in THF at room temperature. For most of the substrates tested the main reaction products were the secondary amines along with variable amounts of the corresponding alcohol and/or imine products. Theoretical DFT calculations have been applied in order to explain the differences in reactivity observed for aromatic substrates. 相似文献
937.
938.
Abril Carolina Castro Martha Audiffred Jose M. Mercero Jesus M. Ugalde Miguel A. Méndez-Rojas Gabriel Merino 《Chemical physics letters》2012
The structures and bonding of the CE42?clusters (E = Al, Ga, In, Tl) have been theoretically studied via B3LYP/def2-TZVP computations. Total energies were recalculated at the CCSD(T)/def2-TZVPP//B3LYP/def2-TZVP level in order to corroborate the energy differences. Our computations show that all the CE42?and CE4Li?clusters (E = Al, Ga, In,Tl) have a planar tetracoordinate carbon structure. Interestingly, while the most stable form of CAl4Li? and CGa4Li? is planar with coordination of Li+ to an edge of the CE42? fragment, for CIn4Li? and CTl4Li? the pyramidal structures with C4v symmetry are the lowest-energy structures. 相似文献
939.
García-Ramos JC Toledano-Magaña Y Talavera-Contreras LG Flores-Álamo M Ramírez-Delgado V Morales-León E Ortiz-Frade L Gutiérrez AG Vázquez-Aguirre A Mejía C Carrero JC Laclette JP Moreno-Esparza R Ruiz-Azuara L 《Dalton transactions (Cambridge, England : 2003)》2012,41(34):10164-10174
A new synthetic pathway was reported to obtain N6 donor ligand 2,9-bis-(2',5'-diazahexanyl)-1,10-phenanthroline (L1) and its coordination compounds of essential divalent metal ions Mn, Fe, Co, Ni, Cu and Zn. Complete characterization of all compounds was done with the conventional techniques. Crystal structures of [NiL1](PF(6))(2) and [ZnL1](PF(6))(2)·H(2)O were also reported. Electrochemical studies have shown an active participation of the aromatic moiety of the ligand in redox reactions. The in vitro tests of the cytotoxic activity against human tumour cell lines HeLa (cervix) and CHP-212 (neuroblastoma) showed that all coordination compounds that involve redox active metal ions exhibit noteworthy antiproliferative activity, superior in all cases to cisplatin. [CuL1](2+) showed the lower IC(50) value in the HeLa cell line with 1.84 μM, meanwhile, [CoL1](2+) showed the lower value in neuroblastoma CHP-212 with IC(50) = 45.28 μM. None of these compounds were active against the SK-N-SH neuroblastoma cell line. In Entamoeba histolytica cultures, remarkable nanomolar IC(50) values were found for [NiL1](2+) and [MnL1](2+) with 60 nM and 80 nM respectively, improving the antiproliferative activity more than 1000 times compared with the first choice drug for clinical treatments of human amoebiasis, metronidazole. On the other hand, a free ligand does not show antiproliferative activity either on human tumor cell lines or on Entamoeba histolytica trophozoites, highlighting the role played by metal ions to produce cytotoxicity in tumor cells and protozoa systems. 相似文献
940.