HPLC monitored synthesis of R2NCH2 substituted benzene derivatives used as (C,N)-ligands for organometallic compounds

2-(Diethylaminomethyl)phenyl bromide and 1,3-bis(dimethylaminomethyl)-benzene, useful ligands for the synthesis of hypervalent organometallic compounds, were prepared and characterized by NMR (¹H, ¹³C, 2D experiments) spectroscopy. Their synthesis was monitored by the HPLC method. The compounds were eluted on a Nucleosil 120 Si column (5 μm, 25×0.4 cm) with n-hexane at room temperature using a 1.0 ml/min flow-rate. The maximum values of absorbance for the studied compounds, excepting the diethylamine, were located in a narrow range around 212 nm, the wavelength used for their UV detection. The diethylamine was detected at 190 nm. The calibration curves are straight lines with correlation factors r>0.995. The HPLC data are in good agreement with those provided by NMR spectroscopy.     

Chemie von α-Aminonitrilen. 13. Mitteilung. Über die Bildung von 2-Oxoethyl-phosphaten (“Glycoladehyd-phosphaten”) aus rac-Oxirancarbonitril und anorganischem Phosphat und über (formale) Konstitutionelle Zusammenhänge zwischen 2-Oxoethyl-phosphaten und Oligo (hexo- und pentopyranosyl)nucleotid-Rückgraten

Chemistry of α-Aminonitriles. Formation of 2-Oxoethyl Phosphates (“Glycolaldehyde Phosphates”) from rac-Oxiranecarbonitrile and on (Formal) Constitutional Relationships between 2-Oxoethyl Phosphates and Oligo(hexo- and pentopyranosyl)nucleotide Backbones Oxiranecarbonitrile in basic acqueous solution at room temperature reacts regioselectively with inorganic phosphate to give the cyanohydrin of 2-oxoethyl phosphate (“glycolaldehyde phosphate”), a source of (the hydrate of) the free aldehyde, preferably in the presence of formaldehyde. In aqueous phosphate solution buffered to nearly neutral pH, oxiranecarbonitrile produces the phosphodiester of glycoladehyde as its bis-cyanohydrin in good yield. In contrast to mono- and dialkylation, trialkylation of phosphate with oxiranecarbonitrile is difficult, and the triester derivative is highly sensitive to hydrolysis. Glycolaldehyde phosphate per se is of prebiotic interest, since it had been shown [5] to aldomerize in basic aqueous solution regioselectively to rac-hexose 2, 4, 6-triphosphates and – in the presence of formaldehyde - mainly to rac-pentose 2, 4-diphosphates with, under appropriate conditions, rac-pentose 2, 4-diphosphates as the major reaction product. However, the question as to whether oxiranecarbonitrile itself has the potential of having been a prebiological natural constituent remains unanswered. Backbone structures of hexopyranosyl-oligonucleotides with phosphodiester linkages specifically between the positions 6′ → 4′, 6′ → 2′, or 4′ → 2′ of the sugar residues can formally be derived via the (hypothetical) aldomerization pathway, a combinatorial intermolecular aldomerization of glycoladehyde phosphate and bis(glycolaldehyde)-phosphodiester in a 1: 1 ratio. The constitutional relationships revealed by this synthetic analysis has played a decisive role as a selection criterion in the pursuit of our experimental studies toward a chemical etiology of the natural nucleic acids' structure. The Discussion in this paper delineates how the analysis contributed to the conception of the structure of p-RNA. The English Footnotes to Schemes 1–11 provide an extension of this summary.     

An efficient synthesis of acetylide/trimetal/acetylide molecular wires

Efficient syntheses are reported for incorporating trimetal units of the type M(3)(dpa)(4)(2+) (M = Cr, Co, Ni, and dpa = 2,2'-dipyridylamide) into polyalkynyl assemblies to give the prototypical bis-phenylacetylide complexes M(3)(dpa)(4)(CCPh)(2). Reactions of M(3)(dpa)(4)Cl(2) with LiCCPh have led only to mixtures of products which cocrystallize forming materials of the composition M(3)(dpa)(4)(CCPh)(x)()Cl(2)(-)(x)(). Here we report that acetonitrile complexes [M(3)(dpa)(4)(NCCH(3))(2)](PF(6))(2) react cleanly with LiCCPh in MeCN to afford the desired target molecules in 40-60% yield and in excellent purity. Isolation of the mixed ligand complex [Co(3)(dpa)(4)(NCCH(3))(CCPh)]PF(6) has been accomplished, which suggests that these reactions are stepwise and that it will be possible to synthesize mixed acetylide complexes (i.e., M(3)(dpa)(4)(CCR)(CCR')) via this method.     

On the diameter of planar curves and Fourier coefficients

Summary LetF denote a complex valued function on , which is absolutely continuous and periodic with a period 2. Its complex Fourier coefficientsc _n satisfy the inequality 2|c _n |d,n0, whered denotes the diameter of the closed planar curve defined byF. In this paper those functionsF are considered, which give equality for a specificn.

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Zusammenfassung Es seiF eine komplexwertige Funktion auf , die absolut stetig und periodisch ist mit einer Periode 2. Sie definiert eine geschlossene ebene Kurve. Zwischen ihrem Durchmesserd und den komplexen Fourierkoeffizientenc _n besteht die Ungleichung 2|c _n |d fürn0. Es werden jene FunktionenF betrachtet, für die in dieser Ungleichung, für ein gegebenesn, Gleichheit besteht.

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Dedicated to my colleague for many years, Professor Eduard Stiefel

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This research was supported in part by the National Research Council of Canada A-7339     

Regiospecific synthesis of cepanolide,a cancer chemoprotective micronutrient found in green onions

The naturally occurring γ-hydroxy-β-sulfanylbutenolide cepanolide and a range of new analogues were synthesized in concise, regiospecific manner through the combined use of 2-silyloxyfuran oxyfunctionalization and tandem thio-Michael addition/elimination.     

Local self-similarity and the Hausdorff dimension

Let X be a locally self-similar stochastic process of index 0<H<1 whose sample paths are a.s. C^H?ε for all ε>0. Then the Hausdorff dimension of the graph of X is a.s. 2?H. To cite this article: A. Benassi et al., C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Fully adaptive multiresolution finite volume schemes for conservation laws

The use of multiresolution decompositions in the context of finite volume schemes for conservation laws was first proposed by A. Harten for the purpose of accelerating the evaluation of numerical fluxes through an adaptive computation. In this approach the solution is still represented at each time step on the finest grid, resulting in an inherent limitation of the potential gain in memory space and computational time. The present paper is concerned with the development and the numerical analysis of fully adaptive multiresolution schemes, in which the solution is represented and computed in a dynamically evolved adaptive grid. A crucial problem is then the accurate computation of the flux without the full knowledge of fine grid cell averages. Several solutions to this problem are proposed, analyzed, and compared in terms of accuracy and complexity.

     

Electron–phonon effect on the ground-state binding energy of hydrogenic impurity in quantum-well wire in presence of an electric field

The hydrogenic impurity binding energy in rectangular quantum well wire including both barriers of finite height and an applied electric field are studied. The polaron effects on the ground-state binding energy in electric field are investigated by means of Landau-Pekar variation technique. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied electric field and the position of the impurity. Our calculations are compared with previous results in quantum wires of comparable dimensions.     

The polaron effect on the binding energy of a shallow donor impurity in quantum-well wires in an electric field

Using a variational technique, the effect of electron-longitudinal optical (LO) phonon interaction on the ground and the first few excited states of a hydrogenic impurity in a semiconductor quantum wire of rectangular cross section under an external electric field is studied theoretically for the impurity atom doped at various positions. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied uniform electric field and the position of the impurity. It is found that the presence of optical phonons changes significantly the values of the impurity binding energies of the system. Taking into account the electron–LO phonon interaction the 1s→2p_y and 1s→2p_z transition energies are calculated as a function of applied electric field for different impurity positions.