Functionalization of 1,2,3-Triazole to Pyrimidine,Pyridine, Pyrazole,and Isoxazole Fluorophores with Antimicrobial Activity

Russian Journal of General Chemistry - The multi-component reaction of diacetyl triazole derivative with ethyl cyanoacetate and various aromatic aldehydes according to the conventional and solvent...     

Triazoles and fused triazoles,III: Facile and efficient synthesis of 2,5-disubstituted-s-triazolo[3,4-b]-1,3,4-thiadiazoles

Summary The development of a facile and efficient method for the synthesis of 2,5-diaryl-s-triazolo[3,4-b]-1,3,4-thiadiazoles4 a–e from the corresponding 3-aryl-4-amino-5-mercapto-s-triazole (2), is described. 3-Aryl-4-arylideneamino-5-mercapto-s-triazoles (3 a–e) were cyclized to compounds4 a–e by heating in nitrobenzene for a few minutes.Part II: See Ref. [11]     

Equilibrium geometry and electronic structure of benzylidene,arylethylidene, and heterocyclic arylidene malononitriles

The equilibrium geometry of some benzylidene, arylethylidene, and heterocyclic arylidene malononitriles has been calculated within the framework of the MNDO –MO formalism. Various structural factors are analyzed and discussed in terms of localized and delocalized MOS and π-interaction between methylene malononitrile (MMN) and aryl moieties. The possibility of charge transfer (CT ) from aryl to MMN moieties has been examined. The presence of a heterocyclic ring introduces a small perturbation into the MMN nuclear frame. p-Substituents have a pronounced effect on the magnitude and direction of the dipole moment. The variation of ionization potentials and bond order with the Hammet σ p are examined and a straight-line relationship is obtained. The correlation between physiological activity and quantum mechanical properties is analyzed in terms of heat of formation, ionization potential, dipole moment, and charge density on the aryl ring. © 1994 John Wiley & Sons, Inc.     

Effect of substituents on the polarographic behaviour of α-arylhydrazononitriles: Further evidence for the mechanism of polarographic reduction of α-arylhydrazononitriles

The polarographic behaviour of the α-arylhydrazonomesoxalonitrile derivatives (IIb-i) and of 2-arylhydrazono-3-keto-3-phenylpropionitriles (IIIb-f) was investigated. With the exception of the nitro-substituted derivatives IIh, i and IIIf all the investigated compounds showed polarographic waves similar to that of their respective parent compounds IIa and IIIa. The m-nitro derivatives IIh and IIIf were firstly reduced in a 4 e wave to the corresponding hydroxylamino derivatives which were subsequently reduced in the manner common to other α-arylhydrazononitriles. On the other hand, the p-nitro derivative IIi was first reduced to the hydroxylamino derivative which then lost water to yield the corresponding quinoneimine. Reduction of the latter product in a 2 e wave gave the p-amino derivative IIe, which then underwent 4 e reduction to p-phenylenediamine and aminomalonitrile. The E_1/2 values corresponding to reduction of the arylhydrazonic moiety of compounds IIa-i and IIIa-f at different pH values were correlated to Hammett's different sigma sets. Analysis of the results provided evidence for the suggested mechanism for reduction of these compounds.     

A novel approach for characterizing protein ligand complexes: molecular basis for specificity of small-molecule Bcl-2 inhibitors

The increasing diversity of small molecule libraries has been an important source for the development of new drugs and, more recently, for unraveling the mechanisms of cellular events-a process termed chemical genetics.(1) Unfortunately, the majority of currently available compounds are mechanism-based enzyme inhibitors, whereas most of cellular activity regulation proceeds on the level of protein-protein interactions. Hence, the development of small molecule inhibitors of protein-protein interactions is important. When screening compound libraries, low-micromolar inhibitors of protein interactions can be routinely found. The enhancement of affinities and rationalization of the binding mechanism require structural information about the protein-ligand complexes. Crystallization of low-affinity complexes is difficult, and their NMR analysis suffers from exchange broadening, which limits the number of obtainable intermolecular constraints. Here we present a novel method of ligand validation and optimization, which is based on the combination of structural and computational approaches. We successfully used this method to analyze the basis for structure-activity relationships of previously selected (2) small molecule inhibitors of the antiapoptotic protein Bcl-xL and identified new members of this inhibitor family.     

Paramagnetic charge-transfer guest–host coordination polymers. Thiophene compounds encapsulated within the channels of the three-dimensional coordination polymers [(R3Sn)3Fe(CN)6] n,R = Me,n-Bu or Ph

Various thiophene compounds have been shown to be encapsulated and partly oxidized within the channels of the three-dimensional (3D) host coordination polymers [(R₃Sn)₃Fe(CN)₆] _n (R = Me, n-Bu or Ph) to give guest–host encapsulated systems. The structure and physical properties of these systems were studied by X-ray powder diffraction, i.r., u.v.–vis., e.p.r. spectra and magnetic measurements. Thiophene compounds do not polymerize within the channels of the host, but rather give paramagnetic charge-transfer guest–host systems.     

Studies on enaminonitriles: A new synthesis of 1,3‐substituted pyrazole‐4‐carbonitrile

3‐Diethylaminoacrylonitrile ( 1 ) reacts with hydrazonyl halides ( 2a‐d ) to yield 1,3‐disubstituted pyrazole‐4‐carbonitriles 5a‐d. The acetyl 1‐p‐chlorophenylpyrazole‐4‐carbonitrile ( 5a ) condensed with hydrazine hydrate to yield the bishydrazone 10 and with dimethylformamide dimethylacetal to yield 1‐aryl‐3‐(3‐dimethylamino)acryloyl pyrazole‐4‐carbonitrile ( 11 ). This enamine reacts with hydrazine hydrate to yield the pyrazolylpyrazole ( 12 ) and with naphthoquinone to yield the 3‐naphthofuranoyl pyrazole 13. The pyra‐zolyl pyridine derivative 14 was obtained upon treatment of 11 with acetylacetone in the presence of ammonium acetate. Compound 11 was coupled with p‐chlorobenzene diazonium chloride to yield the hydrazone 16 that was coupled further with p‐chlorobenzenediazonium chloride to yield the formazane 18.     

Damage Assessment of Reinforced Concrete Structures Using Fractal Analysis of Residual Crack Patterns

Currently, assessing the performance and safety of reinforced concrete structures relies on routine-based visual inspection (VI). Cracks width measurements are commonly used as a convenient indicator of damage; however other factors, such as distribution and pattern of the cracks should be considered equally important in measuring the extent of damage present in the structure. As a result, condition assessed by VI is subjective in nature and depends on the experience, knowledge, expertise, and judgment of the inspector carrying out the assessment. A new approach based on the fractal analysis of residual crack patterns is proposed in this paper to assess the structural integrity of reinforced concrete elements. A new damage index is presented to quantitatively perform a damage classification. The methodology is validated through experimental studies on two large-scale reinforced concrete shear walls subjected to a displacement controlled reversed cyclic loading. Damage grades are also identified based on width of cracks and proposed damage index (DI). The results demonstrate a more accurate estimation of damage grades using DI. Furthermore, it is demonstrated that the DI can estimate the relative stiffness loss of the specimens with acceptable accuracy.     

New Polymer Syntheses Part 60: A Facile Synthetic Route to Polyamides Based on Thieno[2,3-b]thiophene and Their Corrosion Inhibition Behavior

Polyamides containing thieno[2,3-b]thiophene moiety were prepared via a simple polycondensation reaction of the diaminothieno[2,3-b]thiophene monomer 1 a with different kinds of diacid chlorides(including oxalyl, adipoyl, sebacoyl, isophthaloyl,terephthaloyl, 4,4′-azodibenzoyl, 3,3′-azodibenzoyl, p-phenylene diacryloyl) in the presence of Li Cl and NMP as a solvent through lowtemperature solution polycondensation. The chemical structures of model compound and synthesized polyamides were confirmed by FTIR, nuclear magnetic resonance spectroscopy(including ~1H-NMR and ~(13)C-NMR) and elemental analysis. In addition, the thermal stability, crystallinity structure and surface morphology of synthesized polyamides were characterized via thermogravametric analysis(TGA), wide-angle X-ray diffraction analysis(WAXD) and scanning electron microscopy(SEM). Also, the corrosion inhibition behavior of selected examples of polyamides was investigated; the inhibitive effect of the investigated polymers for carbon steel in 1.0 mol·L~(-1) HCl was studied using potentiodynamic polarization(PDP) and electrochemical impedance spectroscopy(EIS) methods. PDP results displayed that the polyamides containing thieno[2,3-b]thiophene moiety can be as mixed-type inhibitors. The inhibition efficiency(P, %) was found to be in the range from 67.13% to 96.01%. There is an increase in P by the synthesized polymers in comparison to the starting monomer.The adsorption of these polymers was found to obey Langmuir adsorption isotherm.