Structural Elucidation and Position Identification of Cu(II) ion in Hexaaquazinc(diaquabismalonto)zincate: Single Crystal EPR and Optical Studies

Journal of Cluster Science - Single crystal electron paramagnetic resonance (EPR), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) and UV–Visible (UV–Vis)...     

Synthesis of novel quinoline analogues of nimesulide: An unusual observation

Reduction of nimesulide followed by treating the N‐acyl derivative of resulting arylamine with Vilsmeier‐Haack reagent provided novel 2‐chloro‐3‐formylquinoline derivatives. The construction of quinoline ring using Vilsmeier‐Haack reagent afforded an unexpected compound, N‐(2‐chloro‐3‐formyl‐7‐phenoxy quinolin‐6‐yl)formamide, in addition to the expected product. The structure of this unexpected quinoline derivative was established via single‐crystal X‐ray analysis and its formation could be explained by an unprecedented N‐S bond cleavage under Vilsmeier‐Haack reaction conditions. The 2‐chloro‐3‐formylquinoline derivatives obtained were converted to a number of corresponding Schiff bases with potential pharmacological importance. J. Heterocyclic Chem., 2011.     

High-pressure study of lithium azide from density-functional calculations

The structural, electronic, optical, and vibrational properties of LiN(3) under high pressure have been studied using plane wave pseudopotentials within the generalized gradient approximation for the exchange and correlation functional. The calculated lattice parameters agree quite well with experiments. The calculated bulk modulus value is found to be 23.23 GPa, which is in good agreement with the experimental value of 20.5 GPa. Our calculations reproduce well the trends in high-pressure behavior of the structural parameters. The present results show that the compressibility of LiN(3) crystal is anisotropic and the crystallographic b-axis is more compressible when compared to a- and c-axes, which is also consistent with experiment. Elastic constants are predicted, which still awaits experimental confirmation. The computed elastic constants clearly show that LiN(3) is a mechanically stable system and the calculated elastic constants follow the order C(33) > C(11) > C(22), implying that the LiN(3) lattice is stiffer along the c-axis and relatively weaker along the b-axis. Under the application of pressure the magnitude of the electronic band gap value decreases, indicating that the system has the tendency to become semiconductor at high pressures. The optical properties such as refractive index, absorption spectra, and photoconductivity along the three crystallographic directions have been calculated at ambient as well as at high pressures. The calculated refractive index shows that the system is optically anisotropic and the anisotropy increases with an increase in pressure. The observed peaks in the absorption and photoconductivity spectra are found to shift toward the higher energy region as pressure increases, which implies that in LiN(3) decomposition is favored under pressure with the action of light. The vibrational frequencies for the internal and lattice modes of LiN(3) at ambient conditions as well as at high pressures are calculated from which we predict that the response of the lattice modes toward pressure is relatively high when compared to the internal modes of the azide ion.     

Baylis-Hillman acetates in organic synthesis: A simple two-step strategy for oxindole-spiro-α-arylidene-γ-butyrolactone framework

A facile, convenient, and two step strategy for synthesis of spirooxindoles containing α-arylidene-γ-butyrolactone moiety has been developed via monoalkylation of 2-oxindoles with Baylis-Hillman acetates followed by the spirolactonization of the resulting cinnamic esters on treatment with phenyliodine (III) bistrifluoroacetate (PIFA).     

Anti and gauche conformers of an inorganic butane analogue, NH3BH2NH2BH3

The crystal structures of an inorganic butane analogue, NH(3)BH(2)NH(2)BH(3) (DDAB), were determined using single crystal X-ray diffraction, revealing both anti and gauche conformations. The anti conformation is stabilized by intermolecular dihydrogen bonds in the crystal whereas two gauche conformations of DDAB observed in its 18-crown-6 adducts are stabilized by an intramolecular dihydrogen bond. The two gauche conformations show rotational isomerization but whether they are a pair of enantiomers is yet to be defined.     

Synthesis and characterization of new poly(azomethine ester)s having phenylthiourea units

New polyesters having azomethine and phenylthiourea groups in the polymer backbone were synthesized by interfacial polycondensation method. The dihydroxy monomer N-(4-hydroxy-3-methoxybenzal) N′-(4′-hydroxyphenyl)thiourea was condensed with six diacid chlorides: terephthaloyl, isophthaloyl, azeloyl, suberoyl, pimeloyl and adipolyl chlorides. The resulting polyesters were characterized by viscosity, IR, NMR and TGA analysis. The wholly aromatic poly(azomethine ester) derived from terephthaloyl chloride when blended with polyaniline/NH₄OH, polyaniline/HCl and pure polyaniline shows conductance in the range 3.2 × 10⁻³-0.91 × 10⁻¹ S cm⁻¹.     

Spin-lattice relaxation studies on semiquinone ions

Electron spin-lattice relaxation times ofp-benzosemiquinone, durosemiquinone and 2, 5 ditertiary butyl-p-benzosemiquinone ions have been measured by the pulsed saturation recovery technique. The relaxation times of the different hyperfine components of a semiquinone ion are the same within the limits of experimental error in disagreement with the findings of Schreurs and Fraenkel. The dependence of T₁ on viscosity does not follow the BPP’s theory.     

Quasiparticle band structure and optical properties of NH3BH3

The quasiparticle band structure of the low temperature orthorhombic phase of NH₃BH₃ is studied by using the GW approximation. It is found that NH₃BH₃ is an insulator with a value of the band gap of 5.90 eV with GGA and of 9.60 eV with the GW approximation. Then, the optical properties of NH₃BH₃ are obtained by the calculation of the dielectric function, corrected by a scissor shift operation corresponding to the GW correction on the band gap. Also, the optical anisotropy in NH₃BH₃ is analyzed through the refractive index and static dielectric constants along the different crystallographic directions. Finally, it is found that the energy loss function has a prominent peak at 22.26 eV; at these frequencies (above 22.26 eV) NH₃BH₃ becomes transparent. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

First Total Synthesis of Bauerine C

The first total synthesis of Bauerine C, a unique indoloquinazoline alkoloid, has been achieved from readily available 2,3‐dichloroaniline. The key step is the Japp–Klingmann condensation between 2,3‐dichloroaniline and ethyl‐2‐acetyl‐5‐phthalimido pentanoate to get 3‐[(2,3‐dichlorophenyl)‐hydrozono]‐pipiridin‐2‐one, which cyclizes to 7,8‐dichloro‐2,3,4,9‐tetrahydro‐β‐carbolin‐1‐one, which can be methylated by dimethyl sulphate to give 7,8‐dichloro‐9‐methyl 2,3,4,9‐tetrahydro‐β‐carbolin‐1‐one. This N‐methyl derivative is then subjected to dehydrogenation with 2,3‐dichloro‐5,6‐dicayano‐1,4‐benzoquinone (DDQ) to give the target compound Bauerine C.