Benzotriazole: an efficient ligand for the copper-catalyzed N-arylation of indoles

A general, efficient, and inexpensive method for the N-arylation of indoles using a catalytic system derived from CuI and benzotriazole is reported. Selective mono N-arylation of indoles with ortho-dihaloarenes has also been successfully achieved in good yields using this protocol.     

Silicate Cross‐Linked Bio‐Nanocomposite Hydrogels from PEO and Chitosan

The compositions and the multi phase structures of bio‐nanocomposite hydrogels made from silicate cross‐linked PEO and chitosan are related to some of their physical and biological properties. The gels are injectable and self‐healing because the cross‐linking is physical and reversible under deformation. The presence of chitosan aggregates affects the viscoelastic properties and reinforces the hydrogel network. The chitosan adds advantageous properties to the hydrogel such as enhanced cell spreading and adhesion. In vitro biocompatibility data indicate that NIH 3T3 fibroblasts grow and proliferate on the bio‐nanocomposite hydrogel as well as on hydrogel films.

     

Isolation and Crystal Structure of 6α,7α-Epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide monohydrate-A Withasteroid from Withania somnifera Leaves

Abstract  

(5R,6S,7S,8S,9S,10R,13S,14S,17S,20R,22R)-6α,7α-epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide has been isolated from Withania somnifera leaves. Three-dimensional X-ray intensity data were collected at 293 K on Bruker CCD area-detector diffractometer equipped with graphite-monochromated MoKα radiation (λ = 0.71073 ?). The compound crystallizes in monoclinic space group P21 with unit cell parameters: a = 6.4540(2), b = 11.3656(4), c = 17.4982(5) ?, β = 90.730 ^o(2), Z = 2. The crystal structure was refined to a final R-value of 0.0419 for 6122 observed reflections. One water solvent molecule was observed. All the rings of the steroid skeleton are trans connected. Rings A and B exists in a half-chair conformation, ring C a chair, and five membered ring D is intermediate between half-chair and envelope. The δ-lactone ring E adopts a distorted sofa conformation. The characteristic pattern observed in the packing diagram is the appearance of twisted chains of molecules. The packing of the molecules in the crystal is stabilized by intra- and intermolecular O–H···O and C–H···O interactions.     

Polyene photoisomerization rates: are they distinct in aqueous block copolymer micellar solutions and gels?

Photoisomerization of 3,3'-diethyloxadicarbocyanine iodide (DODCI) has been investigated in water, 5% and 30% aqueous triblock copolymer, poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20 (P123) by measuring the fluorescence quantum yields and lifetimes in the temperature range 293-318 K. Reports available in literature indicate that 5% aqueous P123 exists as micellar solution, whereas 30% aqueous P123 forms gel due to micelle-micelle entanglement. This study has been undertaken to find out how the polyene photoisomerization rates are influenced in the sol and gel phases. It has been observed that 60%-70% of DODCI is located in the palisade layer of the micelles in the sol as well as gel phases and the photoisomerization rate of this component is identical in both the phases at a particular temperature. The remainder of the probe is located in the interfacial region and isomerization rates of this fraction are slower by a factor of 1.4-1.1 in the gel phase compared with the micellar solution. The retardation of the isomerization rate in the gel phase has been explained on the basis of enhancement in the friction experienced by the probe due to micelle-micelle entanglement at the interface. Compared to the isomerization rates in water, the rates of photoisomerization of DODCI located in the palisade layer, interfacial region of micellar solution, and interfacial region of the micelles in the gel phase are slower by factors of 3.5, 1.5-1.9, and 2, respectively. The outcome of this study validates the point that in organized media photoisomerization rates are sensitive to the localized friction, which is not uniform unlike in a homogeneous solution.     

Experimental investigation on circumferential and axial temperature gradient over fuel channel under LOCA

In a nuclear reactor temperature rises drastically in fuel channels under loss of coolant accident due to failure of primary heat transportation system. Present investigation has been carried out to capture circumferential and axial temperature gradients during fully and partially voiding conditions in a fuel channel using 19 pin fuel element simulator. A series of experiments were carried out by supplying power to outer, middle and center rods of 19 pin fuel simulator in ratio of 1.4:1.1:1. The temperature at upper periphery of pressure tube (PT) was slightly higher than at bottom due to increase in local equivalent thermal conductivity from top to bottom of PT. To simulate fully voided conditions PT was pressurized at 2.0 MPa pressure with 17.5 kW power injection. Ballooning initiated from center and then propagates towards the ends and hence axial temperature difference has been observed along the length of PT. For asymmetric heating, upper eight rods of fuel simulator were activated and temperature difference up-to 250 °C has been observed from top to bottom periphery of PT. Such situation creates steep circumferential temperature gradient over PT and could lead to breaching of PT under high pressure.     

Mass transfer to tubular electrodes: ECE process

The mathematical model of mass transport for linear sweep voltammetry under hydro-dynamic conditions at tubular electrodes has been studied for ECE processes in which an irreversible chemical reaction is coupled between two reversible charge transfer reactions. The resulting boundary value problem is converted into system of two integral equations, which is solved numerically. The effects of axial flow rate, scan rate, potential difference, variation of chemical reaction rate and the effect of the ratio of number of electrons (n ₂/n ₁) involved in two charge transfer reactions on CV-voltammograms are investigated and shown graphically.     

Ionization states of cosmic rays:Anuradha (IONS) experiment in Spacelab-3

The measurements of the ionization states, composition, energy spectra and spatial distribution of heavy ions of helium to iron of energies 10–100 MeV/amu in the anomalous cosmic rays are of major importance in understanding their origin which is unknown at present.Anuradha (IONS) cosmic ray experiment in Spacelab-3 was designed to determine the above properties in near earth space and this had a highly successful flight and operations aboard the shuttle Challenger at an orbital altitude of 352 km during 29 April to 6 May 1985. The instrument employs solid state nuclear track detectors (CR-39) of high sensitivity and large collecting area of about 800 cm² and determines the arrival time information of particles with active elements. Experimental methods, flight operations and preliminary results are briefly described. Initial results indicate that relatively high fluxes of low energy cosmic ray α-particles, oxygen group and heavier ions were obtained. The flight period corresponded to that of quiet Sun and the level of solar activity was close to solar minimum. It is estimated that about 10,000 events of low energy cosmic ray alpha particles with time annotation are recorded in the detector together with similar number of events of oxygen and heavier ions of low energy cosmic rays. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

Synthesis of Cysteine-Functionalized Silver Nanoparticles Using Green Tea Extract with Application for Lipase Immobilization

The application of cysteine-capped silver nanoparticles synthesized using green tea as the reducing agent to immobilize lipase has been reported in the present work. The reducing property of green tea is due to the presence of polyphenolic compounds in its extract which are not oxidized at ambient atmospheric conditions and hence is a suitable reducing agent for green synthesis of nanoparticles. Cysteine-capped silver nanoparticles were synthesized under alkaline conditions by reducing the silver salt by green tea extract in the presence of cystine. Various parameters such as the cystine concentration, pH, temperature, and amount of reducing agent were standardized and their effect on the synthesis process has been initially evaluated by surface plasmon resonance peak analysis. Furthermore, the synthesized nanoparticles were also characterized using X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The particle size analysis revealed the average size of the particles to be around 20?nm. The glutaraldehyde-deactivated amino group on cysteine-capped nanoparticles was used to immobilize lipase on its surface. Both crude and immobilized lipases were checked for activity and protein content under standard assay conditions and their activity was found to be 37.7 and 24.9?U?mL^?1, respectively. The lipase nanoparticle bioconjugates exhibited a good shelf life of 60 days with a marginal decrease in activity. The bioconjugates showed 15% loss in its initial activity at the end of five reusability cycles. This immobilized reusable system has the potential to be utilized for various applications pertaining to the exploitation of lipase in various industries.     

A general and efficient CuI/BtH catalyzed coupling of aryl halides with thiols

We report an exceptionally mild, general and efficient copper catalyzed cross coupling reaction of aryl bromides and thiols using 0.5 mol % CuI and 1 mol % benzotriazole. Experimental simplicity, generality, functional group tolerance and low cost of the catalyst are advantages of the protocol.