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581.
Indium promoted coupling reactions between propargyl aldehydes (3) and allyl halides under aqueous and organic conditions are reported. Coupling reactions under aqueous conditions occur via 1,2-addition with excellent yields to afford 4-hydroxy-1-ene-5-ynes (8). Coupling reactions under organic conditions also add in a 1,2-fashion, but the initial products can be induced to undergo oxy-Cope rearrangements giving 2,5-hexadienals (9). Oxy-Cope rearrangement of 8 followed by a secondary addition step under highly basic conditions leads to lactol formation (10) in good to excellent yields. This paper reveals the versatility and control of product formation which may be attained when working with propargyl aldehyde (3) and allyl halide systems under indium promoted coupling conditions. 相似文献
582.
Deshpande PP Ellsworth BA Buono FG Pullockaran A Singh J Kissick TP Huang MH Lobinger H Denzel T Mueller RH 《The Journal of organic chemistry》2007,72(25):9746-9749
An efficient and practical process to generate beta-C-arylglucoside derivatives was achieved. The process described involves Lewis acid mediated ionic reduction of a peracetylated 1-C-aryl methyl glucoside derived from the addition of an aryl-Li to selectively protected delta-D-gluconolactone. The reduction of the 2-acetoxy-1-C-oxacarbenium ion intermediates proceeds with a high degree of selectivity to give beta-C-arylglucosides without 2-acetoxy group participation. Furthermore, during the reduction process we also identified an unprecedented critical role of water. By changing from the usual benzyl ether protecting groups because of cost and chemical compatibility concerns, the new process is made additionally efficient and highly selective. 相似文献
583.
584.
This work describes the application of a three-dimensional gold nanoelectrode ensembles (GNEE) for monitoring l-dopa in standards and human urine samples using flow injection analysis (FIA) with amperometric detection. Analytical results reveal that the GNEE exhibited better electrocatalytic activity than a gold disk or glassy carbon electrode. Under optimal conditions of l-dopa analysis at GNEE, the calibration plot has a linear range of 5-300 ng/mL with a coefficient of variation (CV) of 3.1% in pH 7.0 phosphate buffer saline (PBS, pH 7.0). The detection limit was 3.0 ng/mL for FIA. The high precision and sensitivity of GNEE provides a feasible means of directly determining l-dopa in urine samples. 相似文献
585.
Annie Cuyt Brahim BenouahmaneHamsapriye Irem Yaman 《Applied Numerical Mathematics》2011,61(8):929-945
It is well known that Gaussian cubature rules are related to multivariate orthogonal polynomials. The cubature rules found in the literature use common zeroes of some linearly independent set of products of basically univariate polynomials. We show how a new family of multivariate orthogonal polynomials, so-called spherical orthogonal polynomials, leads to symbolic-numeric Gaussian cubature rules in a very natural way. They can be used for the integration of multivariate functions that in addition may depend on a vector of parameters and they are exact for multivariate parameterized polynomials. Purely numeric Gaussian cubature rules for the exact integration of multivariate polynomials can also be obtained.We illustrate their use for the symbolic-numeric solution of the partial differential equations satisfied by the Appell function F2, which arises frequently in various physical and chemical applications. The advantage of a symbolic-numeric formula over a purely numeric one is that one obtains a continuous extension, in terms of the parameters, of the numeric solution. The number of symbolic-numeric nodes in our Gaussian cubature rules is minimal, namely m for the exact integration of a polynomial of homogeneous degree 2m−1.In Section 1 we describe how the symbolic-numeric rules are constructed, in any dimension and for any order. In Sections 2, 3 and 4 we explicit them on different domains and for different weight functions. An illustration of the new formulas is given in Section 5 and we show in Section 6 how numeric cubature rules can be derived for the exact integration of multivariate polynomials. From Section 7 it is clear that there is a connection between our symbolic-numeric cubature rules and numeric cubature formulae with a minimal (or small) number of nodes. 相似文献
586.
Let Mn be an n-dimensional complete connected and oriented hypersurface in a hyperbolic space Hn+1(c) with non-zero constant mean curvature H and two distinct principal curvatures. In this paper, we show that (1) if the multiplicities of the two distinct principal curvatures are greater than 1,then Mn is isometric to the Riemannian product Sk(r)×Hn-k(-1/(r2 + ρ2)), where r > 0 and 1 < k < n - 1;(2)if H2 > -c and one of the two distinct principal curvatures is simple, then Mn is isometric to the Riemannian product Sn-1(r) × H1(-1/(r2 +ρ2)) or S1(r) × Hn-1(-1/(r2 +ρ2)),r > 0, if one of the following conditions is satisfied (i) S≤(n-1)t22+c2t-22 on Mn or (ii)S≥ (n-1)t21+c2t-21 on Mn or(iii)(n-1)t22+c2t-22≤ S≤(n-1)t21+c2t-21 on Mn, where t1 and t2 are the positive real roots of (1.5). 相似文献
587.
Yu DG Zhu LM Bligh SW Branford-White C White KN 《Chemical communications (Cambridge, England)》2011,47(4):1216-1218
We show that coaxial electrospinning using organic solvent as the sheath fluid is a viable way to produce tailor-made nanofibers composed of polyvinylpyrrolidine, tristearic and naproxen. Self-assembled hybrid nanoparticles are generated from the composite nanofibers under aqueous conditions and particle size has a linear relationship with fiber diameter. 相似文献
588.
Trioctylphosphine oxide capped cadmium selenide quantum dots, synthesized in organic media were rendered water soluble by
silica overcoating. Silanisation was done by a simple reverse microemulsion method using aminopropyl silane as the silica
precursor. Further, the strong photoluminescence of the silica-coated CdSe quantum dots has been utilized to visualize rabbit
adipose tissue-derived mesenchymal stem cells (RADMSCs) and Daltons lymphoma ascites (DLA) cancerous cells in vitro. Subsequently
the in vivo fluorescence behaviours of QDs in the tissues were also demonstrated by intravenous administration of the QDs
in Swiss albino mice. The fluorescence microscopic images in the stem cells, cancer cells and semi-thin sections of mice organs
proved the strong luminescence property of silica-coated quantum dots under biological systems. These results establish silica-coated
CdSe QDs as extremely useful tools for molecular imaging and cell tracking to study the cell division and metastasis of cancer
and other diseases. 相似文献
589.
Thirty N-substituted Hantzsch 1,4-dihydropyridines were prepared under mild and neutral conditions from N-substituted enaminocarbonyl derivatives and aldehydes activated under the form of N-(1-chloroalkyl)pyridinium chlorides by means of thionyl chloride and pyridine. The scope of the method is discussed. 相似文献
590.
Gayet F Marty JD Brûlet A Lauth-de Viguerie N 《Langmuir : the ACS journal of surfaces and colloids》2011,27(16):9706-9710
The formation of vesicles from 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) in several room-temperature ionic liquids, namely, 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF(4)), 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf(2)), and N-benzylpyridinium bis(trifluoromethylsulfonyl)imide (BnPyNTf(2)), as well as in a water/BmimBF(4) mixture, was investigated. In pure ionic liquids, observations by staining transmission electron microscopy demonstrated clearly the formation of spherical structures with diameters of 200-400 nm. The morphological characteristics of these vesicles in ionic liquids, in particular, the membrane thicknesses, were first investigated by small-angle neutron scattering measurements. The mean bilayer thickness was found to be ~63 ± 1 ? in a deuterated ionic liquid (BnPyNTf(2)-d). This value was similar to that observed in water. The effect of ILs on the modification of the phase physical properties of multilamellar vesicles (MLVs) was then investigated by differential scanning calorimetry. In pure IL as in water, DPPC exhibited an endothermic pretransition followed by the main transition. These transition temperatures and the associated enthalpies in ILs were higher than those in water because of a reduction of the electrostatic repulsion between zwitterionic head groups. To better understand the effect of ionic liquid on the formation of multilamellar vesicles, mixtures of BmimBF(4) and water, which are miscible in all proportions, were analyzed (BmimBF(4)/water ratio from 0% to 100%). SANS and DSC experiments demonstrated that the bilayer structure and stability were strongly modified by the IL content. Moreover, matching SANS experiments showed that BmimBF(4) molecules prefer to be located inside the DPPC membrane rather than in water. 相似文献