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61.
62.
Four tetra-azapentalenes, pyrazolo[1,5-b], pyrazolo[3,2-c], imidazo[1,2-b] and imidazo[2,1-c]s-triazole, have been studied. The synthesis of the third compound and of a salt of the last are described for the first time. Physical properties calculated for the more stable tautomer by CNDO/2 and CNDO/S (reactivity, proton chemical shift, dipole moment and electronic absorption) are in good agreement with experimental values.The protonation sites of imidazo[1,2-b] and imidazo[2,1-c]s-triazole as shown by UV and NMR are compared with theoretical results. 相似文献
63.
A capillary electrophoresis (CE) method was successfully developed to quantify the impurity profile of a new substance of pharmacological interest: LAS 35917. CE method was developed in order to separate the chloromethylated, monomethylated and hydroxylated impurities (molecules with very similar chemical structures) having the three coelution in the reversed-phase LC method initially established. Taking into account the structure of the impurities of LAS 35917, separation by conventional liquid chromatography (LC) methods would be longer and tedious than separation by CE, which is an appropriate and versatile technique giving easier and quicker methods. Among the three potential impurities mentioned of LAS 35917, two are due to the synthesis route of this drug, and the third arises from degradation. These drug-related impurities were separated using a capillary of 56 cm of effective length and 50 microm I.D., a 60 mM tetraborate buffer, at pH 9.2, and a positive voltage of 20 kV. The optimised CE method was preliminary validated with regard to specificity, linearity, limits of detection and quantitation, repeatability and solution stability. The method allows the detection and quantitation of impurities above 0.04 and 0.08% level, respectively. All three related substances were separated, detected and quantified from their parent drug in the analysis of real samples of LAS 35917, stressed or not stressed, with this simple and fast CE method. 相似文献
64.
Sanz D Pérez-Torralba M Alarcón SH Claramunt RM Foces-Foces C Elguero J 《The Journal of organic chemistry》2002,67(5):1462-1471
To study systems able to sustain intramolecular proton-transfer, we have prepared a series of six aminofulvene aldimines including several labeled with (15)N and (2)H. These compounds show coupling constants through the hydrogen bond, (1h)J((15)N- (1)H) and (2h)J((15)N-(15)N). The position of the tautomeric equilibria, i.e., on what nitrogen atom is the proton, was determined in the solid state and in solution. The crystal structure of N[[5-[(phenylamino)methylene]-1,3-cyclopentadien-1-yl]methylene]pyrrole-1-amine (3) has been determined by X-ray analysis. In solution, both N-H and C-H tautomers were observed and their structures assigned by NMR spectroscopy. Particularly useful is the value of the (1)J((15)N-(1)H) coupling constant. 相似文献
65.
L.A. Oro M. Esteban R.M. Claramunt J. Elguero C. Foces-Foces F.H. Cano 《Journal of organometallic chemistry》1984,276(1):79-97
The synthesis and properties of neutral and cationic complexes of general formulae [{RhCl(diolefin)}2(CH2(pz)2)], [Rh(CO)2 (CH2(pz)2)][RhCl2(CO)2], (Rh(diolefin)(CH2(pz)2)]ClO2, [{Rh(diolefin)(PPh3)}2(CH2(pz)2)](ClO4)2, [Rh(CO)2(CH2(pz)2)]ClO4 and [Rh(CO)(CH2(pz)2)(PPh3)]ClO4 are described. The NMR spectra of [Rh(COD)(CH2(pz)2)]ClO4 complexes are discussed. X-ray structural analysis of [Rh(COD)(CH2(Pz)2)]ClO4 · C2H4Cl2 is presented; the final R factor is 0.061 for 2436 observed data, recorded with Cu-Kα, not corrected for absorption and with the sample inside a capillary. The Rh atom presents a distorted square planar coordination in a mononuclear arrangement. The COD ring has a twisted boat conformation, and the two halves of the CH2(Pz)2 moiety, which are quite similar to one another, form an angle of 47.2(4)°. 相似文献
66.
Both isomers of N-(2′,4′-dinitrophenyl)benzotriazole, the 1(3)- and the 2-substituted, have been characterized and their reciprocal isomerism was studied. Cross-experiments in the presence of 5(6)-nitro-1H-benzotriazole proved that the isomerization of 2-(2′,4′-dinitrophenyl)-2H-benzotriazole into the 1-isomer occurs by an intermolecular mechanism. The reported reaction of 5(6)-nitro-1H-benzotriazole with 1-chloro-2,4-dinitrobenzene has been reexamined discovering that there is an error in the proportions of N-substituted isomers. A possible explanation for the observed isomerizations was proposed. Identification of all compounds by multinuclear magnetic resonance, including solid-state studies, has been achieved. 相似文献
67.
Nieto Carla I. Cabildo Pilar Claramunt Rosa M. Cornago Pilar Sanz Dionisia Torralba M. Carmen Torres M. Rosario Ferraro Marta B. Alkorta Ibon Marín-Luna Marta Elguero José 《Structural chemistry》2016,27(2):705-730
Structural Chemistry - Structural data are reported on sixteen ketoenols of β-diketones: solution NMR, solid-state NMR (CPMAS and MAS) and X-ray crystallography (four compounds, where three... 相似文献
68.
A theoretical (B3LYP/6-31G∗∗) study of 30 pyrazoles, most of them existing in two tautomeric forms, has been carried out. 3(5)-(2-Benzylphenyl)-5(3)-methyl-1H-pyrazole (11) and 3(5)-(2-benzylbenzylphenyl)-5(3)-phenyl-1H-pyrazole (20) were synthesized from 2-benzoylacetophenone, and their annular tautomeric equilibrium determined. The substituent effects were statistically analyzed and discussed with the help of Hammett substituent constants. In the case of the 5-(2-benzylphenyl) groups, the strength of the N-H?π hydrogen bond depends on the electronic effect of the substituent at position 3. 相似文献
69.
In this paper, we present a threshold proportional reinsurance strategy and we analyze the effect on some solvency measures: ruin probability and time of ruin. This dynamic reinsurance strategy assumes a retention level that is not constant and depends on the level of the surplus. In a model with inter-occurrence times being generalized Erlang(n)-distributed, we obtain the integro-differential equation for the Gerber?CShiu function. Then, we present the solution for inter-occurrence times exponentially distributed and claim amount phase-type(N). Some examples for exponential and phase-type(2) claim amount are presented. Finally, we show some comparisons between threshold reinsurance and proportional reinsurance. 相似文献
70.
A Spectroscopic Study of Colchicine in the Solid State and in Solution by Multinuclear Magnetic Resonance and Vibrational Circular Dichroism
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Albert Virgili Ma Mar Quesada‐Moreno Juan Ramón Avilés‐Moreno Juan Jesús López‐González M. Ángeles García Rosa M. Claramunt M. Rosario Torres M. Luisa Jimeno Felipe Reviriego Ibon Alkorta José Elguero 《Helvetica chimica acta》2014,97(4):471-490
Although almost 200‐years‐old, several unknown aspects remain to be explored of colchicine, the unique available drug for acute flares of gout. In this article, we report density‐functional theory (DFT) studies of geometry, energy, and NMR; 1H‐, 13C‐, and 15N‐NMR chemical shifts and some spin‐spin coupling constants, including the complete analysis of the saturated part (ring B); the assignment of both enantiomers by NMR using a chiral solvating agent; solid‐state NMR experiments of the different forms of natural and racemic colchicine, and IR and vibrational circular dichroism (VCD) studies of these same forms. 相似文献