Synthesis and Crystal Structure of 2-Amino-4,6,6-trimethyl-cyclohex-2-en-1,1,3,4(S)-tetracarbonitrile

Abstract  

Crystal structure analysis of the novel 2-amino-4,6,6-trimethyl-cyclohex-2-en-1,1,3,4(S)-tetracarbonitrile, obtained in 70% yield, by the Bi(OTf)₃ catalyzed reaction of acetone and malononitrile, at room temperature, is described. For the first time Bi(OTf)₃–Et₃N has been used in this inverse electron demand Diels–Alder cycloaddition reaction involving the participation of carbonitrile π-bond. The structure of the molecule was established by spectral analysis and X-ray diffraction studies. The compound crystallizes in the monoclinic space group P2₁/n with unit cell parameters: a = 8.0580 (17), b = 13.038 (3), c = 12.641 (3) ?, β = 101.883 (4)°, Z = 4. The crystal structure was solved by direct methods and refined to R = 0.0506 for 2,456 observed reflections. The cyclohexene ring of the molecule adopts a distorted sofa conformation. The molecules in the unit cell are arranged in layers. The crystal structure in stabilized by C–H⋯N and N–H⋯N interactions.     

Synthesis of some new substituted oxiranes from 4′-hydroxy-3′,5′-dinitrochalcones and their sulfanilic acid-catalyzed aminolysis

A new series of (4′-hydroxy-3′,5′-dinitrophenyl) (3-aryloxiran-2-yl) methanone derivatives has been synthesized by the reaction of 4′-hydroxy-3′,5′-dinitro-substituted chalcones and alkaline H₂O₂. The resulted oxiranes on sulfanilic acid-catalyzed aminolysis afforded 2-hydroxy-1-(4′-hydroxy-3′,5′-dinitrophenyl)-3-aryl-3-(arylamino) propan-1-one derivatives. The advantage of this environmentally benign safe protocol offers a simple reaction set-up, mild reaction conditions, high product yields and short reaction time. The catalyst was reused several times without significant loss of catalytic activity.     

Higher-Order Antibunching of Light in Seven-Photon Interaction Process

Journal of Russian Laser Research - We study higher-order antibunching of light and the possibility of observing it in all modes in two and three-photon absorption seven-photon interaction...     

Quenching of photoconductivity in Fe doped CdS thin films prepared by spray pyrolysis technique

Fe doped CdS films are prepared using spray pyrolysis technique. All the samples are found to be of single phase and crystallized in hexagonal lattice. The X-ray diffraction peaks position of Cd_1−xFe_xS shifts to higher angle with increasing Fe concentration indicating decrease in cell volume. The temperature dependence of resistivity follows Arrhenius behavior having lower activation energy with increasing Fe concentration in dark while there is a little variation in light. Pure CdS films are having large photoconductivity. Upon Fe incorporation, this photoconductivity gradually decreases and for concentration more than 20%, it is almost vanished. Note worthy observation is the changes seen in morphology with AFM, viz. nanorod features seen in CdS is changed to continuous nanorod like structures depicting signatures of Ostwald ripening.     

Modeling the spread of bird flu and predicting outbreak diversity

Avian influenza, commonly known as bird flu, is an epidemic caused by H5N1 virus that primarily affects birds like chickens, wild water birds, etc. On rare occasions, these can infect other species including pigs and humans. In the span of less than a year, the lethal strain of bird flu is spreading very fast across the globe mainly in South East Asia, parts of Central Asia, Africa and Europe. In order to study the patterns of spread of epidemic, we made an investigation of outbreaks of the epidemic in one week, that is from February 13–18, 2006, when the deadly virus surfaced in India. We have designed a statistical transmission model of bird flu taking into account the factors that affect the epidemic transmission such as source of infection, social and natural factors and various control measures are suggested. For modeling the general intensity coefficient f(r), we have implemented the recent ideas given in the article Fitting the Bill, Nature [R. Howlett, Fitting the bill, Nature 439 (2006) 402], which describes the geographical spread of epidemics due to transportation of poultry products. Our aim is to study the spread of avian influenza, both in time and space, to gain a better understanding of transmission mechanism. Our model yields satisfactory results as evidenced by the simulations and may be used for the prediction of future situations of epidemic for longer periods. We utilize real data at these various scales and our model allows one to generalize our predictions and make better suggestions for the control of this epidemic.     

Solvothermally synthesized europium-doped CdS nanorods: applications as phosphors

To exploit the photoluminescent behavior of CdS at nanoscale with different doping concentration of europium—a rare earth element, we report the synthesis of Eu-doped CdS nanorods by using low temperature solvothermal process by using ethylenediamine. The outcomes can have future applications as phosphors, photovoltaic cells, lasers, light emitting diodes, bio-imaging, and sensors. The doping was confirmed by electron dispersive spectroscopy supported by X-ray diffraction. From scanning electron microscopy and transmission electron microscopy analysis it was observed that the average diameter of the Cd_1−x Eu _x S nanorods is about 10–12 nm having lengths in the range of 50–100 nm. UV–Visible spectroscopy study was carried out to determine the band gap of the nanorods and the absorbance peaks showed blue shift with respect to the bulk CdS. The blue shift was also observed as the doping concentration of Eu increases. From photoluminescence (PL) studies at λ_ex = 450 nm, peaks at 528 and 540 nm were observed due to CdS, peak at 570 nm is due to defects related transitions, while the peak at 613 nm is due to Eu. As the doping concentration of Eu is increased the intensity of the luminescent peak at 613 nm is increased. Thermogravimetric analysis showed the nanorods are thermally stable up to 300 °C. The traces of impurities adsorbed on the nanorods were confirmed by Fourier transform infrared spectroscopy.     

Synthesis of tetrahydropyrimidino[4,3‐a]isoquinolines via regiospecific N‐alkylation‐annulation of 4‐aryldihydropyrimidinones

4‐Aryldihydropyrimidinones were obtained in excellent yields via solid‐phase Biginelli reaction of arylaldehydes, β‐ketoester and urea, using bismuth nitrate, immobilized on Al₂O₃ as catalyst. Subsequently, the products were converted into corresponding tetrahydropyrimidino[4,3‐a]isoquinolines (69–73% yield) by one‐pot regiospecific N‐alkylation‐annulation reaction using sodium hydride and dimethylaminopyridine. J. Heterocyclic Chem., (2011).     

Spatiotemporal pattern formation in a diffusive predator-prey system: an analytical approach

In this paper, we propose and analyse a mathematical model to study the mathematical aspect of reaction diffusion pattern formation mechanism in a predator-prey system. An attempt is made to provide an analytical explanation for understanding plankton patchiness in a minimal model of aquatic ecosystem consisting of phytoplankton, zooplankton, fish and nutrient. The reaction diffusion model system exhibits spatiotemporal chaos causing plankton patchiness in marine system. Our analytical findings, supported by the results of numerical experiments, suggest that an unstable diffusive system can be made stable by increasing diffusivity constant to a sufficiently large value. It is also observed that the solution of the system converges to its equilibrium faster in the case of two-dimensional diffusion in comparison to the one-dimensional diffusion. The ideas contained in the present paper may provide a better understanding of the pattern formation in marine ecosystem.