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...     

Mild and Highly Efficient Stereoselective Synthesis of 2,3‐Unsaturated Glycopyranosides using La(NO3)3 · 6H2O as a Catalyst: Ferrier Rearrangement

A mild and highly efficient stereoselective reaction of 3,4,6‐tri‐O‐acetyl‐d‐glucal with a variety of nucleophiles, viz. alcohols, phenols, thiols, thiophenols, and allyl trimethyl silane (TMS), in the presence of 5 mol% of lanthanum(III) nitrate hexahydrate under solvent‐free conditions yielded the corresponding 2,3‐unsaturated glycopyranosides (pseudoglycals) in excellent yields.     

Lanthanum(III) Nitrate Hexahydrate: A Versatile Reagent for the Synthesis of Bis(indolyl) Methanes under Solvent‐Free Conditions

A mild and efficient synthesis of bis(indolyl) methanes by the reaction of indoles with various aldehydes at room temperature in the presence of a catalytic amount of a La(NO₃)₃ · 6H₂O afforded the corresponding bis(indolyl) methanes in excellent yields under solvent‐free conditions.     

Metal‐like Ductility in Organic Plastic Crystals: Role of Molecular Shape and Dihydrogen Bonding Interactions in Aminoboranes

Ductility is a common phenomenon in many metals but is difficult to achieve in molecular crystals. Organic crystals bend plastically on one or two face‐specific directions but fracture when stressed in any other arbitrary directions. An exceptional metal‐like ductility and malleability in the isomorphous crystals of two globular molecules, BH₃NMe₃ and BF₃NMe₃, is reported, with characteristic tensile stretching, compression, twisting, and thinning. The mechanically deformed samples, which transition to lower symmetry phases, retain good long‐range order amenable to structure determination by single‐crystal X‐ray diffraction. Molecules in these high‐symmetry crystals interact through electrostatic forces (B^??N⁺) to form columnar structures with multiple slip planes and weak dispersive forces between columns. On the other hand, the limited number of facile slip planes and strong dihydrogen bonding in BH₃NHMe₂ negates ductility. Our study has implications for the design of soft ferroelectrics, solid electrolytes, barocalorics, and soft robotics.     

A new bis-andrographolide ether from Andrographis paniculata nees and evaluation of anti-HIV activity

Novel bis-andrographolide ether (1) and six known compounds andrographolide, 14-deoxy-11,12-didehydroandrographolide, andrograpanin, 14-deoxyandrographolide, (+/-)-5-hydroxy-7,8-dimethoxyflavanone, and 5-hydroxy-7,8-dimethoxyflavone have been isolated from the aerial parts of Andrographis paniculata and their structures were established by spectral data. All the isolates were tested for the anti-HIV and cytotoxic activity.     

Synthesis, characterization and coordination properties of bis(alkyl)selenosalen ligands

New bis (alkyl) selenosalen podand ligands having Se2N2 donor sites have been synthesized by the condensation of unsymmetrical o-formylphenyl alkyl selenide (1-3) with ethylenediamine. The reaction of bis(alkyl)selenosalen podands with Pd(II) and Pt(II) afforded selenoether-selenolate coordination complexes 7-10via cleavage of one of the two Se-C(alkyl) bonds of bis(alkyl)selenosalen podands upon complexation. DFT calculations revealed that the cleavage of Se-C(alkyl) bonds occurred possibly via S(N)2 mechanism instead of a sequence of oxidative addition and reductive elimination reactions. The spectral data and elemental analyses confirmed the formation of selenoether-selenolate complexes. The structures of the podands N,N'-bis[(2-methylseleno)phenylmethylene]-1,2-ethanediamine (4), N,N'-bis[(2-decylseleno)phenylmethylene]-1,2-ethanediamine (5) and the selenoether-selenolate complex 8 have been determined by single crystal X-ray diffraction analysis. The crystal structure of 5 showed SeH interaction with a ladder like 3D supramolecular arrangement via interdigitation of long alkyl chains. Comparison of crystal packing of podands 4 and 5 indicates that the alkyl chain length has significant impact on the crystal packing. The platinum selenolate complex 8 shows a square planar arrangement around the Pt centre, where the Se atoms in the selenolate and the selenoether have nearly equal Pt-Se bond length.     

A new three-component reaction: green synthesis of novel isoindolo[2,1-a]quinazoline derivatives as potent inhibitors of TNF-α

Concurrent construction of five and six membered fused N-heretocyclic ring was achieved via a conceptually new three-component reaction affording 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones as novel inhibitors of TNF-αin vitro. This represents one of the few examples of direct TNF-α inhibition by small molecules.     

A mild and efficient synthesis of chiral tetrahydroquinolino pyranose derivatives catalyzed by lanthanum(iii) nitrate hexahydrate

A mild and highly efficient synthesis of chiral tetrahydroquinolino pyranose derivatives is described. The reaction of a chiral α,β‐unsaturated aldehyde containing a hydroxyl group with different aryl amines using lanthanum(III) nitrate hexahydrate as a catalyst afforded corresponding chiral tetrahydroquinolinated pyranosides in excellent yields. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:429–433, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20441     

Tri­phenyl(3,4,5‐tri­iodo­phenyl)­methane

The crystal structure of the title compound, alternatively called 1,2,3‐triiodo‐5‐(triphenylmethyl)benzene, C₂₅H₁₇I₃, is analysed in terms of I⋯I and I⋯π interactions and the herring‐bone T motif between phenyl groups. There are two mol­ecules in the asymmetric unit, denoted A and B. Inversion‐related A mol­ecules are connected via an I⋯π interaction (3.641 Å, to a C—C bond mid‐point) to form an I⋯π dimer, and these dimers are connected through symmetry‐independent B mol­ecules via I⋯I [3.5571 (15) Å] and I⋯π (3.561 Å, to a C—C bond mid‐point) interactions.     

Comparative assessment of two sequential chemical extraction schemes for the fractionation of cadmium, chromium, lead and zinc in surface coastal sediments

Two existing sequential chemical extraction schemes, involving respectively five and six leaching steps with solutions of increasing dissolving power, were compared. The methods have been applied to surface sediment samples collected in a marine estuary zone potentially exposed to contamination arising from nearby industrial activities. A certified reference material (MURST-ISS-A1) consisting of an Antarctic bottom sediment for which no information regarding phase dependent concentration is available, was also analyzed. In order to evaluate the partition of metals among different geochemical forms, the concentrations of cadmium, chromium, lead and zinc were measured in the liquid extracts by Zeeman-corrected flame atomic absorption and by inductively coupled plasma-atomic emission spectrometry. The total metal concentrations were determined after strong acid attack, and the adequacy of this total digestion/dissolution technique was verified by its application to the reference material. Comparison of total metal concentrations with the sum of concentrations associated with the individual phases was employed to assess possible analyte losses or contaminations. Precisions for both sequential procedures were comparable, but some inconsistencies in mass balances were found in one of the samples for the distribution of Zn in the soluble/exchangeable fractions and for Cd in the bound to carbonates form. In addition, the six steps procedure produced lower concentration values in the case of elements associated to the residual fraction. For the five steps method mass balances showed acceptable agreement, with average recoveries in the 87 to 106% range. On the whole, differences in metal distributions were observed, being more marked for the bottom sediment. Significant proportions of the studied elements, with the exception of Cr, were found as easily extractable forms. X-ray diffraction and petrographic observation of the surface sediments allowed qualitative correlation between the leaching results obtained and the presence of defined geochemical phases.