A new facile method for the synthesis of 3-imidazolylpropionic acid N-oxides

Chemistry of Heterocyclic Compounds - A facile and efficient method for the preparation of 3-imidazolylpropionic acid N-oxides has been developed. It involves condensation of 2-unsubstituted...     

Convenient synthesis of O-functionalized mandelic acids via Lewis acid mediated transformation of 1,3-dioxolan-4-ones

An efficient method for the synthesis of O-substituted mandelic acids containing alkenyl, alkynyl, methoxycarbonyl, or phenacyl fragments via the Lewis acid-catalyzed reaction of 1,3-dioxolan-4-ones with different C-nucleophiles is proposed.     

Reactions of levulinic acid and pseudolevulinic esters with various C-nucleophiles

The reactions of levulinic acid and its pseudo esters, which are readily available from carbohydrate-containing raw materials, with various C-nucleophiles are described. Different reaction pathways were demonstrated depending on the nature of the leaving groups and nucleophiles. For 5-methyl-5-methoxydihydrofuran-2(3H)-one, the reaction was found to proceed by a route giving hept-6-enoic acid derivatives. In contrast, the reaction of 2-methyl-5-oxotetrahydrofuran-2-yl acetate proceeds via intramolecular cyclization to form γ-valerolactone derivatives.     

Chemical and electrochemical synthesis,structure, photoluminescent properties,and biological activity of 4-methyl-N-[2-[(Z)-2-(2-pyridyl)alkyliminomethyl]phenyl]benzenesulfamide zinc(II) complexes

A series of Zn(II) complexes of the tridentate azomethine ligands, condensation products of 2-(N-tosylamino)benzaldehyde and 2-aminoalkylpyridines, were synthesized by chemical and electrochemical methods. All compounds were characterized on the basis of C, H, N elemental analysis, Fourier-transform infrared, ¹H nuclear magnetic resonance, UV–Vis, and photoluminescence studies. The local atomic structures of complexes were determined from analysis of extended X-ray absorption fine structure and X-ray absorption near-edge structure of Zn K-edges. The molecular structure of chloro-{4-methyl-N-[2-[(Z)-2-pyridyl)ethyliminomethyl]phenyl]benzenesulfamide}zinc(II) was determined by X-ray single-crystal diffraction. The fluorescence spectra show that these complexes in dimethyl sulfoxide solutions at room temperature emit bright blue luminescence at 435–461 nm with fluorescence quantum yields in the range of 0.20–0.31. The assignment and the nature of the bands in experimental UV–Vis spectra of complexes were analyzed using time-dependent density functional theory calculations B3LYP/6-31G(d). The azomethines and complexes of zinc have been screened for their antibacterial, protistocidal, and fungistatic activities against Penicillium italicum, Colpoda steinii, Escherichia coli 078, and Staphylococcus aureus P-209, and the results are compared with the activity of furazolidone, chloroquine, and Fundazol.     

Control of the nonlinear dynamics of a truck and trailer combination

Nonlinear Dynamics - The directional instability problem of a truck and trailer combination in a forward motion has been investigated by developing a dynamic model of the planar rigid-body dynamics...     

Non-symmetric viscoelasticity of anisotropic polymer liquids

The liquid crystalline (LC) polymers are considered as anisotropic viscoelastic liquids with nonsymmetric stresses. A simple constitutive equation for nematic polymers describing the coupled relaxation of symmetric and antisymmetric parts of the stress tensor is formulated. For illustration of non-symmetric anisotropic viscoelasticity, the simplest viscometric flows of polymeric nematics in the magnetic field are considered. The frequency and shear rate dependencies of extended set of Miesowicz viscosities are predicted. Received: 23 March 1999/Accepted: 13 December 1999     

To what extent can a conjugation between two pairs of peri‐nitro and peri‐amino groups be realized through the naphthalene core?

Through‐conjugation for a wide range of 1,8‐diamino‐4,5‐dinitronaphthalenes (N‐acylated, N‐alkylated, N,N′‐bridged, N‐heterocyclic, and N‐deprotonated compounds) was for the first time quantified in solution by means of ultraviolet–visible and proton nuclear magnetic resonance spectroscopy and compared with that of the simpler naphthalene and benzene push‐pull systems. Surprisingly, an extent of conjugation in 1,8‐diamino‐4‐nitro‐ and 1,8‐diamino‐4,5‐dinitronaphthalenes measured in dimethyl sulfoxide is commensurable. On the whole, the repulsive peri‐interactions between the amino groups in systems with N‐alkylated and N‐deprotonated amino groups are more favorable for an effective D‐π‐A charge transfer than in N,N′‐bridged compounds (perimidines, 2,3‐dihydroperimidines and perimidin‐2‐ones). The best electron donors from peri‐positions are pyrrolidin‐1‐yl and methylamido groups. The conclusions obtained from solution studies were deepened by solid‐ state X‐ray experiments for a number of push–pull naphthalenes, including 6,7‐dinitroperimidine N‐anion and two representatives of 4,5‐diaminonaphthalene‐1,8‐dicarbaldehydes. In particular, they helped to trace changes in the bond order redistribution and twisting of the naphthalene core. The latter reaches a record value of 27° for 4,5‐dinitro‐1,8‐di(pyrrolidin‐1‐yl)naphthalene. Copyright © 2013 John Wiley & Sons, Ltd.     

General quasi-nonspreading linear three-dimensional wave packets

We introduce a general approach for generation of sets of three-dimensional quasi-nonspreading wave packets propagating in linear media, also referred to as linear light bullets. The spectrum of rigorously nonspreading wave packets in media with anomalous group velocity dispersion is localized on the surface of a sphere, thus drastically restricting the possible wave packet shapes. However, broadening slightly the spectrum affords the generation of a large variety of quasi-nonspreading distributions featuring complex topologies and shapes in space and time that are of interest in different areas, such as biophysics or nanosurgery. Here we discuss the method and show several illustrative examples of its potential.