Efficient Oxidation of Hantzsch 1,4-Dihydropyridines with Nicotinium Dichromate

A convenient method for the oxidation of various 4-substituted Hantzsch 1,4-dihydropyridines with nicotinium dichromate (NDC) in refluxing acetonitrile is reported. The yields obtained are excellent.     

2-Hydroxyethylammonium acetate: A reusable task-specific ionic liquid promoting one-pot,three-component synthesis of 2-amino-3,5-dicarbonitrile-6-thio-pyridines

2-Hydroxyethylammonium acetate (2-HEAA) as a task-specific ionic liquid, efficiently promotes one-pot three-component reaction of aryl/heteroaryl/alkyl aldehydes with aryl/alkyl thiols and malononitrile at room temperature. This protocol offers several advantages such as using a reusable and cost-effective ionic liquid, being amenable to scale-up and produces the corresponding 2-amino-3,5-dicarbonitrile-6-thio-pyridines in a short reaction time (5 min) and in good to high yields.     

Glass transition phenomena in two-component plastic crystals: study of hexasubstituted benzenes

We have critically examined the relaxation that is known to occur in the crystalline phase of pentachloronitrobenzene (PCNB) and 2,3,4,5,6-pentabromotoluene using dielectric spectroscopy and differential scanning calorimetry (DSC). Within the resolution of our experimental setup, a relaxation process similar to that of the primary (or alpha-) relaxation is found. A slight deviation from Arrhenius behavior is noticed only in the vicinity of the glass transition temperature (T(g)). This deviation and a small steplike change found in the DSC scans at T(g) indicates that the "fragility" of these plastic crystals is rather low. However, in PCNB, the dielectric strength (Deltaepsilon) of the above said alpha-process did not change appreciably with temperature, and, interestingly, a small addition of an impurity such as pentachlorobenzene (PCB) to the molten state of PCNB drastically lowered the dielectric strength and the calorimetric signature of glass transition phenomena in the DSC data at T(g). The room-temperature powder X-ray diffraction measurements in combination with the DSC data in the melting temperature region did not indicate any observable change in the crystalline structure. A residual alpha-process with no significant change in the shape of the dielectric spectrum indicates that the hindrance to the rotational motion of PCNB molecules is caused by the presence of a small number of PCB molecules in the crystalline lattice of PCNB over a certain region. Outside of this region, the original PCNB disordered phase is preserved, which is the origin of the residual alpha-process. With a further increase in PCB concentration, the alpha-process, characteristic of pure PCNB, vanishes, and instead another relaxation develops. This process is explained with the help of a solid-liquid phase diagram of the alpha-process of the plastic phase of 2:1 and 1:2 compound formations, which are stable below 386 +/- 1 and 366 +/- 1 K, respectively.     

Synthesis of 4-alkylaminoimidazo[1,2-a]pyridines linked to carbamate moiety as potent α-glucosidase inhibitors

Molecular Diversity - In this work, various imidazo[1,2-a]pyridines linked to carbamate moiety were designed, synthesized, and evaluated for their α-glucosidase inhibitory activity. Among...     

Three-dimensional free vibration analysis of four-parameter continuous grading fiber reinforced cylindrical panels resting on Pasternak foundations

This research investigates three-dimensional free vibration analysis of four-parameter continuous grading fiber reinforced (CGFR) cylindrical panels resting on Pasternak foundations by using generalized power-law distribution. The functionally graded orthotropic panel is simply supported at the edges, and it is assumed to have an arbitrary variation of matrix volume fraction in the radial direction. A four-parameter power-law distribution presented in literature is proposed. Symmetric and asymmetric volume fraction profiles are presented. Suitable displacement functions that identically satisfy the boundary conditions at the simply supported edges are used to reduce the equilibrium equations to a set of coupled ordinary differential equations with variable coefficients, which are solved by generalized differential quadrature method, and natural frequency is obtained. The fast rate of convergence of the method is demonstrated, and to validate the results, comparisons are made with the available solutions for functionally graded isotropic shells with/without elastic foundations. The effect of the elastic foundation stiffness parameters and various geometrical parameters on the vibration behavior of the CGFR cylindrical panels is investigated. This work mainly contributes to illustrate the influence of the four parameters of power-law distributions on the vibration behavior of functionally graded orthotropic cylindrical panels resting on elastic foundation. This paper is also supposed to present useful results for continuous grading of matrix volume fraction in the thickness direction of a cylindrical panel on elastic foundation and comparison with similar discrete laminated composite cylindrical panel.     

Prediction of long and short time rheological behavior in soft glassy materials

We present an effective time approach to predict long and short time rheological behavior of soft glassy materials from experiments carried out over practical time scales. Effective time approach takes advantage of relaxation time dependence on aging time that allows time-aging time superposition even when aging occurs over the experimental time scales. Interestingly, experiments on a variety of soft materials demonstrate that the effective time approach successfully predicts superposition for diverse aging regimes ranging from subaging to hyperaging behaviors. This approach can also be used to predict behavior of any response function in molecular as well as spin glasses.     

Quasi-exactly solvable decatic model description of nuclei near the X(5) critical point

The Bohr Hamiltonian with axially deformed shape confined in a quasi-exactly solvable decatic β-part potential is studied.It is shown that the decatic model can well reproduce the X(5)model results as far as the energy ratios in the ground and beta band and related B(E2)values are concerned.Fitting results to the low-lying energy ratios and relevant B(E2)values of even-even X(5)candidates ¹⁵⁰Nd,¹⁵⁶Dy,¹⁶⁴Yb,¹⁶⁸Hf,¹⁷⁴Yb,^176,178,180Os,and ^188,190Os show that the decatic model provides the best fitting results for the energy ratios,while the X(5)model is the best at reproducing the B(E2)values of these nuclei,in which the beta-bandhead energy is lower than that of the gamma band.While for even-even nuclei,such as ^154,156,158Gd,with bandhead energies of the beta and gamma bands more or less equal within the X(5)critical point to the axially deformed region,our numerical analysis indicates that the decatic model is better than the X(5)model in describing both the low-lying level energies and related B(E2)values.     

Organocatalysis in aqueous micellar medium: a new protocol for the synthesis of [1,2,4]-triazolyl-thiazolidinones

A new environmentally friendly methodology for the efficient synthesis of biologically significant triazole thiazolidinone hybrids in aqueous medium, using acetic acid as an organocatalyst in the presence of cetyltrimethylammonium bromide (CTAB) surfactant has been developed for the first time. The effect of several surfactants on the yield and completion time of the reaction was investigated and it was found that the use of CTAB at 60 °C gave the best results (79–96% in 20 min–35 min) for the synthesis of the target compounds.     

Electrospun polystyrene fibers for HIV entrapment

The high versatility and ease of electrospinning of polymer solutions have recently resulted in electrospun fibers, which are of interest for a wide variety of chemical and biomedical applications. This is partially due to the high surface area of the fibers, which is attractive for the detection and capture of (bio)chemicals. In the present work, polystyrene (PS) fibers were electrospun and coated with cationic poly(allylamine hydrochloride) (PAH) or anionic dextran sulfate sodium (DSS). The fibers were physicochemically characterized. Upon incubation in a dispersion of inactivated HIV‐1, avid binding of HIV to all types of fibers occurred. By atomic force microscopy and spatial selective photobleaching, the binding of the inactivated HIV‐1 particles to the fibers could be confirmed. Interestingly, all fibers, especially the DSS‐coated and PAH‐coated ones, resulted in a significant reduction of infection of CD4⁺ TZMbl cells by replication‐competent HIV‐1. On top, DSS‐coated PS fibers were not toxic for vaginal epithelial cells, which may make these fibers of potential interest to inhibit HIV infection in the context of topical prevention. Copyright © 2014 John Wiley & Sons, Ltd.     

SU(3) monopole of unit charge

We present an explicitSU(3) monopole solution of unit charge constructed using the (ADHMN) construction.