Copper dipyridine dichloride as a mild and efficient catalyst for a one pot condensation bigenelli reaction

The condensation reaction of aldehydes, β‐ketoesters and urea/thiourea in presence of a catalytic amount of CuPy₂Cl₂ complex proceeded under very mild reaction conditions in high yield (80‐90%).     

STUDY OF SH-WAVE PROPAGATION IN AN INITIALLY STRESSED TRICLINIC LAYER SANDWICHED BETWEEN TRANSVERSELY ISOTROPIC ELASTIC AND HETEROGENEOUS POROELASTIC HALF-SPACES

Journal of Applied Mechanics and Technical Physics - In this paper, SH-wave propagation in an initially stressed triclinic layer welded between two half-spaces is investigated. The upper half-space...     

Shape and topology optimization of an acoustic horn–lens combination

Using gradient-based optimization combined with numerical solutions of the Helmholtz equation, we design an acoustic device with high transmission efficiency and even directivity throughout a two-octave-wide frequency range. The device consists of a horn, whose flare is subject to boundary shape optimization, together with an area in front of the horn, where solid material arbitrarily can be distributed using topology optimization techniques, effectively creating an acoustic lens.     

One-pot multicomponent synthesis of novel 1-thiazolyl-5-coumarin-3-yl-pyrazole derivatives and evaluation of their cytotoxic activity

A series of novel 1-thiazolyl-5-coumarin-3-yl-pyrazole derivatives (4a–l) were synthesized via one-pot multicomponent reaction of 5-substituted salicylaldehydes (1a–c), 4-hydroxy-6-methyl-2H-pyran-2-one (2) and 2-hydrazinyl-4-arylthiazoles (3a–d) in acetonitrile using a catalytic amount of piperidine under reflux conditions. This multicomponent approach has advantages such as reduced reaction time and a high product yield percentage when compared with corresponding multistep approaches. All the synthesized compounds were evaluated for their cytotoxic activity against Hep G2 (hepatocellular liver carcinoma) and MCF-7 (breast cancer) cell lines and compared with the standard drug Doxorubicin. Among all the compounds, compounds 4d against Hep G2, 4k against MCF-7 and 4e against both Hep G2 & MCF-7 showed excellent cytotoxic activity.     

Synthesis of meso‐tetrakis(4‐chlorocoumarin‐3‐yl)porphyrins

meso‐Tetrakis(4‐chlorocoumarin‐3‐yl)porphyrins were prepared by condensation of corresponding 4‐chlorocoumarin‐3‐carboxaldehydes and pyrrole in the presence of trifluoro acetic acid (TFA) in dichloromethane followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). These porphyrins exhibited the atropisomerism due to ortho substituent of meso aryl groups. The atropisomers of meso‐tetrakis(4‐chloro‐6‐methylcoumarin‐3‐yl)porphyrin were separated and identified by ¹H‐nmr spectra. Zinc complexes of these porphyrins were synthesized and characterized by ms, ¹H nmr, ir and uv‐vis spectra.     

Synthesis of Novel Fused Thiazolo[3,2‐a]pyrimidin‐3‐ols and Evaluation for their Antibacterial Activity

A series of novel fused thiazolo[3,2‐a]pyrimidin‐3‐ol derivatives have been synthesized by reaction of fused pyrimidine‐thiones with 4‐substituted phenacyl bromide/3(2‐bromoacetyl)coumarin in refluxing acetic acid with good yields. All the synthesized compounds were confirmed by spectral studies and screened for their in vitro antibacterial activity against Staphylococcus aureus, Bacillus thuringiensis (Gram positive), Escherichia coli, and Klebsiella pneumoniae (Gram negative) bacterial strains. Activity results revealed that all the compounds were weak to good active against the tested bacterial strains on comparing with the standard drug gentamicin.     

Xanthan Sulfuric Acid: An Efficient Bio‐supported and Recyclable Solid Acid Catalyst for the Synthesis of 2‐Aryl Thiadiazolo Benzimidazoles

Xanthan sulfuric acid is an efficient solid acid catalyst for the preparation of 2‐aryl benzimidazoles in excellent yields. This method is applicable for the reaction of benzo[c][1,2,5]thiadiazole‐4,5‐diamine with aldehydes by simple physical grinding at room temperature. The salient features of the present methodology is cheaper process, easy synthesis of stable catalyst and the catalyst can be easily recycled without significant loss of activity.     

Role of entropy in the stability of cobalt titanates

The standard molar Gibbs free energy of formation of Co₂TiO₄, CoTiO₃, and CoTi₂O₅ as a function of temperature over an extended range (900 to 1675) K was measured using solid-state electrochemical cells incorporating yttria-stabilized zirconia as the electrolyte, with CoO as reference electrode and appropriate working electrodes. For the formation of the three compounds from their component oxides CoO with rock-salt and TiO₂ with rutile structure, the Gibbs free energy changes are given by:$\begin{array}{cc}\hfill & {\mathrm{\Delta }}_{\text{f}}{G}_{(\text{ox})}^{°}({\text{Co}}_2{\text{TiO}}_4)\pm 104/(\text{J}·{\text{mol}}^{-1})=-18865-4.108(T/\text{K})\hfill \\ \hfill & {\mathrm{\Delta }}_{\text{f}}{G}_{(\text{ox})}^{°}({\text{CoTiO}}_3)\pm 56/(J·{\text{mol}}^{-1})=-19627+2.542(T/\text{K})\hfill \\ \hfill & {\mathrm{\Delta }}_{\text{f}}{G}_{(\text{ox})}^{°}({\text{CoTi}}_2{O}_5)\pm 52/(\text{J}·{\text{mol}}^{-1})=-6223-6.933(T/\text{K})\hfill \end{array}$Accurate values for enthalpy and entropy of formation were derived. The compounds Co₂TiO₄ with spinel structure and CoTi₂O₅ with pseudo-brookite structure were found to be entropy stabilized. The relatively high entropy of these compounds arises from the mixing of cations on specific crystallographic sites. The stoichiometry of CoTiO₃ was confirmed by inert gas fusion analysis for oxygen. Because of partial oxidation of cobalt in air, the composition corresponding to the compound Co₂TiO₄ falls inside a two-phase field containing the spinel solid solution Co₂TiO₄–Co₃O₄ and CoTiO₃. The spinel solid solution becomes progressively enriched in Co₃O₄ with decreasing temperature.