Russian Journal of Organic Chemistry - The reaction of 1,5-bis[1-(prop-2-yn-1-yl)uracil-3-yl]pentane with 2',3',5'-tri-O-acetyl-β-d-ribofuranosylazide followed by removing of... 相似文献
Russian Journal of Organic Chemistry - A simple and efficient protocol has been described for the synthesis of [1,2,4]triazolo[4,3-a]pyridines and 3,5-disubstituted-1,2,4-oxadiazoles by... 相似文献
Journal of Thermal Analysis and Calorimetry - A model is proposed to fit differential scanning calorimetry (DSC) isothermal crystallization curves obtained from the molten state at different... 相似文献
Journal of Thermal Analysis and Calorimetry - In the present study, the thermal efficiency, convective heat transfer and friction factor analysis are investigated for a flat plate solar collector... 相似文献
The results of geometric analysis of 588 crystal structures of square-planar nickel complexes containing short intermolecular Ni…X contacts (X is a non-metal atom) are reported. The frequency of occurrence of Ni…X interactions of a particular type was evaluated depending on the nature of the X atom and geometric characteristics. The promolecular functions RDG and sign(λ2)?ρ(r) were used to analyze the character of Ni…X interactions in attractive/repulsive terms. The relative strength of these interactions was determined as the function of the nature of the X atom and the direction of charge transfer. 相似文献
The results of theoretical search for model transition states of the electrophilic substitution reaction in 2H-tetrazole (1) without the preliminary formation of N-protonated azolium salts are presented for two routes that were previously suggested by the authors and thermodynamically investigated: A, the attack of molecule 1 by the nucleophile (HO–(aq)) to form the anion to which the electrophile H3O+(aq)) is added and B, the attack of molecule 1 by the same electrophile followed by the addition of the same nucleophile to the specifically solvated protonated species formed in the preceding reaction step. The calculations were performed using the DFT/B3LYP/6-31G(d) method and the scanning procedure of the potential energy surface (PES). Both steps of route A turned out to be nearly barrierless, while in route B only its first step is barrierless and the second one is conjugated with passing an activation barrier of ~45 kcal mol–1 between non-interacting or weakly interacting reactants and electrophilic substitution products. Unlike the specifically solvated protonated species of 1H-tetrazole in an aqueous solution, a similar species of 2H-tetrazole does not form a prereaction complex with the attacking nucleophile (HO–(aq)) and the five-membered ring is destroyed in fact in the nitrogen-containing reaction product formed after passing the activation barrier. The optimized structure of the transition state differs strongly from the nitrogen-containing structure of the reaction product with the destroyed ring, which was found by scanning of the PES. 相似文献
The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with an excess of europium metal in 1,2-dimethoxyethane (dme) produces a divalent europium complex with the dpp-bian dianion, [(dpp-bian)Eu(dme)2] (1). The reactions of 1 with phenyl-acetylene and camphor proceed via protonation of the diimine ligand to form the monomeric amido-amino complexes of divalent europium — [H(dpp-bian)Eu(C≡CPh)(dme)2] (2) and [H(dpp-bian)Eu(camphor)(dme)2] (3), respectively. Compounds 2 and 3 were characterized by IR spectroscopy and elemental analysis. Their molecular structures were determined by X-ray diffraction. Compounds 2 and 3 were shown to be monomeric seven-coordinate europium(ii) complexes with terminal phenylethynyl and enol ligands, respectively. According to the IR spectroscopic data, the terminal ligands in complexes 2 and 3 undergo tautomerization involving backward proton transfer from the amido-amino ligand to the substrate. The magnetic moment of compound 2 (8.03 μB) remains constant in the temperature range of 4—300 К and confirms the presence of divalent europium. 相似文献
O-Sialylation of a substituted indolin-3-one under phase-transfer catalysis conditions, which does not occur when N-acetylsialyl chloride is used, proceeds with N,N-diacetylsialyl chloride as the glycosyl donor. A study using dynamic light scattering of solutions of both sialyl chlorides under conditions close to the conditions used for glycosylation showed a difference in the correlation radii of light scattering particles in such solutions. This suggests that the introduction of an additional N-acetyl group into the sialyl chloride significantly alters the structure of the supramers of glycosyl donor, which apparently have an increased accessibility of individual molecules for the attack by a nucleophile, which increases its reactivity.