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991.
Rémy Morgentin Georges Pasquet Pascal Boutron Frédéric Jung Maryannick Lamorlette Mickaël Maudet Patrick Plé 《Tetrahedron》2008,64(12):2772-2782
This paper describes the different strategies devised and applied to overcome the selectivity issues in the syntheses of 6,7-disubstituted-1H-quinolin-4-one, 7-substituted-1H-1,6-naphthyridin-4-one and 6-substituted-1H-1,7-naphthyridin-4-one derivatives. They allowed us to improve the overall yields and the scaling-up feasibility. Several examples illustrate these strategies with their advantages and drawbacks. 相似文献
992.
Christian Lherbet David Soupaya Cécile Baudoin-Dehoux Chantal André Casimir Blonski Pascal Hoffmann 《Tetrahedron letters》2008,49(38):5449-5451
A new route to functionalized iso(thio)chromans is described. The compounds are accessible easily in a one pot-reaction by using different benzaldehydes and phenylethanethiol or phenylethanol in presence of bismuth triflate. 相似文献
993.
Applying semianalytical models of nonideal plasma, we evaluate the behavior of the metallic phase in metal-ammonia solutions (MAS). This behavior is mainly controlled by the degenerate electron gas, which remains stable down to 5 MPM due to high solvent polarizability and strong dielectric screening of solvated ions. Comparing the behavior of the metallic state with those of localized solvated electrons, we have estimated the miscibility gap Delta n for various alkali metals and found Delta n(Na)>Delta n(K). It is rather narrow in Rb-NH3 and does not occur in Cs-NH3 solutions, which is in full agreement with the experiments. The case of Li is discussed separately. The difference calculated in the excess free energies of the metallic and nonmetallic phases is in the order of kBT, yielding a thermally fluctuating mixed state at intermediate metal concentrations. It results in a continuous metal-nonmetal (MNM) transition above the consolute point Tc and a phase separation below Tc. We propose a criterion for the MNM transition which may be attributed to the line of the maximum of compressibility above Tc. This line crosses the spinodal one at the critical temperature. Finally, we assert that a new electronic phase similar to microemulsion should also arise between the spinodal and the binodal lines. 相似文献
994.
Belorizky E Fries PH Helm L Kowalewski J Kruk D Sharp RR Westlund PO 《The Journal of chemical physics》2008,128(5):052315
The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion [known as the paramagnetic relaxation enhancement (PRE)] arises primarily through the dipole-dipole (DD) interaction between the nuclear spins and the electron spins. In solution, the DD interaction is modulated mostly by reorientation of the nuclear spin-electron spin axis and by electron spin relaxation. Calculations of the PRE are in general complicated, mainly because the electron spin interacts so strongly with the other degrees of freedom that its relaxation cannot be described by second-order perturbation theory or the Redfield theory. Three approaches to resolve this problem exist in the literature: The so-called slow-motion theory, originating from Swedish groups [Benetis et al., Mol. Phys. 48, 329 (1983); Kowalewski et al., Adv. Inorg. Chem. 57, (2005); Larsson et al., J. Chem. Phys. 101, 1116 (1994); T. Nilsson et al., J. Magn. Reson. 154, 269 (2002)] and two different methods based on simulations of the dynamics of electron spin in time domain, developed in Grenoble [Fries and Belorizky, J. Chem. Phys. 126, 204503 (2007); Rast et al., ibid. 115, 7554 (2001)] and Ann Arbor [Abernathy and Sharp, J. Chem. Phys. 106, 9032 (1997); Schaefle and Sharp, ibid. 121, 5387 (2004); Schaefle and Sharp, J. Magn. Reson. 176, 160 (2005)], respectively. In this paper, we report a numerical comparison of the three methods for a large variety of parameter sets, meant to correspond to large and small complexes of gadolinium(III) and of nickel(II). It is found that the agreement between the Swedish and the Grenoble approaches is very good for practically all parameter sets, while the predictions of the Ann Arbor model are similar in a number of the calculations but deviate significantly in others, reflecting in part differences in the treatment of electron spin relaxation. The origins of the discrepancies are discussed briefly. 相似文献
995.
Zeghida W Debray J Chierici S Dumy P Demeunynck M 《The Journal of organic chemistry》2008,73(6):2473-2475
A novel and simple method of preparation of 2-alkylaminoquinazolin-4-ones with fused heteroaromatic rings from easily accessible (hetero)aromatic amines is described. The method is very efficient, and the 2-alkylaminoquinazolinone derivatives are obtained in three steps without chromatographic purification. The key step is the ring closure of the N-protected guanidine intermediates by intramolecular Friedel-Craft's type substitution. 相似文献
996.
Blanca M. Muñoz Mario Rodríguez Margarita Romero Pascal G. Lacroix Gabriel Ramos-Ortíz 《Journal of organometallic chemistry》2008,693(7):1321-1334
The condensation in one step of a series of salicylaldehydes and 2-amino-5-nitrophenol with 1-naphthylboronic acid, 2-naphthylboronic acid, and o-tolylboronic acid to give the corresponding boronates 1a-3a, 1b-3b and 1c-3d, is reported. The X-ray crystal structures of 1a, 2b and 3b allowed determining the α- and β-angle between the stilbene skeleton and the aryl or naphthylboronic fragments; these values are indicative of different conformations for the aryl moieties around the (B-C) boron-carbon bond which could potentially modulate the electronic properties on the boron stilbene compounds. All compounds were characterized by 1H, 11B and 13C NMR spectroscopy, UV, IR and mass spectrometry. Second- and third-order non-linear optical characterizations were also performed by EFISH and THG Maker Fringe techniques, respectively. Compounds 3a-3d containing an -N(Et)2 donor group gave the best NLO response in second- and third-order. 相似文献
997.
Murielle Rivenet Pascal Roussel Francis Abraham 《Journal of solid state chemistry》2008,181(10):2586-2590
Single crystals of Bi(C2O4)OH were obtained by the slow diffusion of Bi3+ cations through silica gel impregnated with oxalic acid. The structure was solved in the Pnma space group with a=6.0853(2) Å, b=11.4479(3) Å, c=5.9722(2) Å, leading to R=0.0188 and wR=0.0190 from 513 unique reflections. The bismuth coordination polyhedron is a BiO6E pentagonal bipyramid with the lone pair E sitting at an axial vertex. The opposite axial vertex is occupied by a hydroxyl oxygen atom, which is also an equatorial corner of a neighboring BiO6E bipyramid. The sharing of the hydroxyl oxygen atoms build zig-zag chains running down the [100] direction. These chains are aligned in a sheet parallel to the (010) plane and are further connected through oxalate ions to form a three-dimensional arrangement. On heating, Bi(C2O4)OH decomposes to the meta-stable quadratic β-Bi2O3 phase. 相似文献
998.
Ou M Lu G Shen H Descamps A Marquette CA Blum LJ Roux S Tillement O Cheng B Perriat P 《Photochemistry and photobiology》2008,84(5):1244-1248
Abstract Au and Ag biochips were fabricated to investigate the influence of pH upon the chemiluminescence (CL) of luminol at vicinity of surface-adsorbed peroxidase. A nanoscaled-corrugation of the metal induces an enhancement of the luminol CL which is maximal in the pH range favoring peroxidase catalysis and greater for gold than for silver. This is the proof that, in the CL process, the reactions involving peroxidase are surface-enhanced near corrugated surfaces. 相似文献
999.
The concept of DNA biosensors is sustained by the need for rapid and highly sensitive analytical tools for genetic detection. Their implementation is based on three key steps: (i) immobilization of single-stranded oligonucleotide probes onto a substrate; (ii) hybridization and (iii) reading. These steps involve complementary knowledge in various disciplinary fields such as surface physics and chemistry, molecular electrochemistry, micro-technologies, optics, electronics and biochemistry. We present here, in a non-exhaustive way, the recent advances in the two steps of immobilization and detection that rely upon increasing integration of the number of reading points or/and of the reading strategy. 相似文献
1000.
Montiel-Palma V Piechaczyk O Picot A Auffrant A Vendier L Le Floch P Sabo-Etienne S 《Inorganic chemistry》2008,47(19):8601-8603
The phosphinosilane compound PPh 2CH 2OSiMe 2H is potentially a bifunctional P approximately Si-H ligand. By treatment with the Ru (II) precursor RuH 2(H 2) 2(PCy 3) 2, the complex Ru(PPh 2CH 2OSiMe 2H) 3 ( 2), resulting from the coordination of three ligands and the displacement of two PCy 3 and two dihydrogen ligands, was formed. The different bonding modes for each of the three bifunctional P approximately Si-H ligands are discussed on the basis of multinuclear NMR, X-ray diffraction, and density functional theory studies. One ligand acts as a monodentate phosphine ligand with a pendant Si-H group, whereas the two others act as bidentate ligands with different Si-H bond activations. Indeed, an intermediate structure between two arrested forms 2a and 2b can be proposed: a dihydrido(disilyl)ruthenium(IV) species (form 2a) resulting from two Si-H oxidative additions or a hydrido(silyl)ruthenium(II) species (form 2b) presenting an agostic Si-H bond and only one oxidative addition. 相似文献