A Fast and Highly Efficient Protocol for Reductive Amination of Aromatic Aldehydes Using NaBH4 and Isoxazole Amines in an Ionic Liquid Medium

Reductive amination of aromatic aldehydes using NaBH₄ and isoxazole amines is carried out in a Brønsted acidic ionic liquid 1‐methylimidazolium tetrafluoroborate [(HMIm)BF₄]. The ionic liquid plays dual roles of solvent as well as catalyst for the efficient transformation of aromatic aldehydes to heterocyclic substituted amines in excellent yields without any undesired side product formation. The newly synthesized compounds ( 3 , 6 and 7 ) were characterized by IR, ¹H NMR and mass spectral techniques.     

Dielectric Properties of Tin Oxide Thin Film Capacitors

Thin films of several thicknesses in the form of MIM structures are prepared from the powders of tin oxide (SnO₂) by thermal evaporation technique in a vacuum of 10⁻⁵ Torr. The dielectric properties of tin oxide film capacitors have been studied with temperatures varying from 77 to 400 K and also with frequency. At 77 K the values of capacitance and loss tangent are small for these films. With increasing temperature the values of capacitance and loss tangent increase. The capacitance-temperature plots show peak values of capacitance at 345 K for 1 kHz, 350 K for 2 kHz, 360 K for 5 kHz and 368 K for 10 kHz. These peak values of capacitance can be eliminated by repeated heating and cooling of the structures. The activation energy for the migration of charge carriers is calculated for tin oxide films and is found to be 0.13 eV. The results obtained on the dielectric properties of tin oxide thin films are presented and discussed.     

Enantioselective Desymmetrization of Curcumins with 3-Olefinic Oxindoles for the Synthesis of Spirocyclohexanoneoxindoles

An enantioselective desymmetrization of curcumins with 3-olefinic oxindoles involving a cascade double-Michael addition strategy provides direct access to spirocyclohexanone-oxindoles with complete regio- and diastereoselectivities and excellent enantioselectivities, besides good to excellent yields. The products possess three contiguous chiral centers and multiple reactive functionalities. The observed selectivities were rationalized by transitions state energy calculations at B3LYP//6-31g(d) level of DFT.     

Transport Properties of (NH4)2 CuCl4.2H2O Low Dimensional Single Crystals

The X‐ray diffraction and Infrared (IR) spectral studies of (NH₄)₂ CuCl₄.2H₂O single crystals reveals that these crystals contains tetragonal crystal structure with the unit cell dimensions of a = 7.58Å, c = 7.95Å, z= 2, β =90° and two water molecules in the unit cell. The temperature dependence of thermally stimulated depolarization current (TSDC) and dc electrical conductivity (σ) studies of this two‐dimensional (NH₄)₂ CuCl₄.2H₂O single crystal have been carried out in 77K–300K temperature region. The TSDC thermograph shows only one sharp peak at 248K with a peak current of 130nA, which is attributed to the Maxwell‐Wagner peak. The activation energy (U), relaxation time (τ) are calculated as 0.78eV and 3.44×10^‐15 s respectively. Dc electrical conductivity studies of these crystals show a first order phase transition at about 248K.     

Ageing effect on dielectric properties of SnO2, Sb2O3, and their mixed thin films

Thin films of various thicknesses in the form of MIM structures have been prepared from the powders of high purity of SnO₂, Sb₂O₃, and their mixed powders separately by the thermal evaporation technique in a vacuum of 10⁻⁵ Torr. The dielectric properties of these oxide thin films have been studied with ageing time and also with frequency at room temperature. The results obtained have shown that the capacitance and loss tangent of the structures initially fall off rapidly and thereafter they attain a constant value even after ageing the capacitors for about 20 days. The rapid fall of capacitance and loss tangent may be due to the rapid decrease in the density of defects due to ageing time. The results thus obtained on SnO₂, Sb₂O₃, and their mixed thin film capacitors are presented and discussed.