Oxidative Dearomatization: Synthesis of Functionalized Bicyclo[2.2.2]octenones,Sigmatropic Shift in Excited State,and Radical-Induced Cleavage of Cyclopropane Ring

Synthesis of novel bicyclo[2.2.2]octenones endowed with a β,γ-enone system in which γ-carbon is substituted with an electron-withdrawing group from simple aromatics is described. Oxa-di-pi-methane reaction of bicyclo[2.2.2]octenones to functionalized bicyclo[3.3.0]octanes and their transformation to bicyclo[3.2.1]octane framework are also presented.     

Microwave-assisted Vilsmeier-Haack synthesis of Pyrazole-4-carbaldehydes

The synthesis of 4-formylpyrazoles using Vilsmeier-Haack reagent is a common protocol in pyrazole chemistry. An efficient microwave-assisted synthesis of 4-formylpyrazoles by employing Vilsmeier-Haack reagent (OPC-VH) derived from phthaloyl dichloride/dimethylformamide has been described. This method offers the advantages of operational simplicity, avoiding the use of POCl₃ as toxic reagents and reuse of the by-product in the preparation of phthaloyl dichloride.     

Plasmonic giant quantum dots: hybrid nanostructures for truly simultaneous optical imaging,photothermal effect and thermometry

Hybrid semiconductor–metal nanoscale constructs are of both fundamental and practical interest. Semiconductor nanocrystals are active emitters of photons when stimulated optically, while the interaction of light with nanosized metal objects results in scattering and ohmic damping due to absorption. In a combined structure, the properties of both components can be realized together. At the same time, metal–semiconductor coupling may intervene to modify absorption and/or emission processes taking place in the semiconductor, resulting in a range of effects from photoluminescence quenching to enhancement. We show here that photostable ‘giant’ quantum dots when placed at the center of an ultrathin gold shell retain their key optical property of bright and blinking-free photoluminescence, while the metal shell imparts efficient photothermal transduction. The latter is despite the highly compact total particle size (40–60 nm “inorganic” diameter and <100 nm hydrodynamic diameter) and the very thin nature of the optically transparent Au shell. Importantly, the sensitivity of the quantum dot emission to local temperature provides a novel internal thermometer for recording temperature during infrared irradiation-induced photothermal heating.     

Optimal control of effort of a stage structured prey–predator fishery model with harvesting

This paper describes a prey–predator fishery model with stage structure for prey. The adult prey and predator populations are harvested in the proposed system. The dynamic behavior of the model system is discussed. It is observed that singularity induced bifurcation phenomenon is appeared when variation of the economic interest of harvesting is taken into account. We have incorporated state feedback controller to stabilize the model system in the case of positive economic interest. Fishing effort used to harvest the adult prey and predator populations is used as a control to develop a dynamic framework to investigate the optimal utilization of the resource, sustainability properties of the stock and the resource rent earned from the resource. Pontryagin’s maximum principle is used to characterize the optimal control. The optimal system is derived and then solved numerically using an iterative method with Runge–Kutta fourth-order scheme. Simulation results show that the optimal control scheme can achieve sustainable ecosystem.     

A New Sodium Borate: Na[B6O8(OH)3]·6H2O·H3BO3

The structure of [B₆H₉NaO₁₄, H₃BO₃, 6H₂O] was determined by single‐crystal X‐ray diffraction and further analyzed by FTIR spectroscopy and differential thermal/thermogravimetric analysis. The asymmetric unit contains Na–O polyhedra (distorted octahedron), [B₆O₈(OH)₃]^– fundamental building blocks, one free water molecule and one free H₃BO₃ molecule. In the hexaborate anion, three B₃O₃ rings are linked by a common oxygen atom with five trigonal and one tetrahedral boron atoms. The hexaborate group is also linked to the oxygenated environment of the sodium atom by three other six‐membered rings, each of which involve two boron atoms, three oxygen atoms, and sodium as the joint atom.     

A Rapid Densitometric TLC Method for Simultaneous Analysis of Costunolide and Dehydrocostus Lactone in Saussurea Costus

Costunolide and dehydrocostus lactone are two guianolide sesquiterpene lactones present in abundance in Saussurea costus, a plant popularly known as `costus' and renowned throughout the world for its medicinal properties. A simple densitometric TLC method for simultaneous quantification of costunolide and dehydrocostus lactone, without derivatization, has been developed as an alternative to gas chromatography. The method enables rapid, sensitive, and reproducible simultaneous analysis of a variety of samples. The method was validated for precision, repeatability, and accuracy in accordance with ICH guidelines. Amounts of costunolide and dehydrocostus lactone in different samples of costus, estimated by use of this method, were in the range 0.46 to 1.00% and 0.81 to 1.21%, respectively. The proposed method is simple, precise, specific, sensitive, and accurate and can be used by the herbal drug industry for routine quality control of the crude drug costus.     

Electrochemically generated tungsten‐based active species as catalysts for metathesis‐related reactions: 2. Ring‐opening metathesis polymerization of norbornene

The present work reports the application of the WCl₆–e^?–Al–CH₂Cl₂ catalyst system to the ring‐opening metathesis polymerization of norbornene. Analysis of the polynorbornene microstructure by means of ¹H and ¹³C NMR spectroscopy indicates that the polymer contains a mainly cis stereoconfiguration of the double bonds (σ_c = 0.61) and a blocky distribution (r_tr_c > 1) of cis and trans double bonds (r_tr_c = 3.37). This catalytic system is reluctant to facilitate the competing addition reactions of cycloalkenes while proceeding with the polymerization reactions with good conversions and at short periods. Copyright © 2004 John Wiley & Sons, Ltd.     

Magnetic proximity effect in the topological insulator BiSbTeSe2

Magnetic proximity effects can lead to novel phenomena in the transport properties of topological insulators. In this study, we demonstrate a characteristic fourfold symmetry in the angular dependence of magnetoresistance in the topological insulator BiSbTeSe₂ exfoliated onto magnetic insulator yttrium iron garnet substrates. The observed symmetry is seen to arise when the external magnetic field is in‐plane to the current direction and gets enhanced at large field magnitudes. Increasing the temperature and current density diminishes the fourfold symmetry. The symmetry seems to be a signature of the proximity effect from the underlying magnetic substrate on BiSbTeSe₂. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)