Crystallographic report: The crystal structure of bis‐(3,3‐dimethyl‐3,4‐dihydro‐2H‐1‐thia‐4a,9‐diaza‐3‐sila‐fluorene) silver nitrate

The title compound is a silver nitrate complex with two molecules of 2‐mercaptobenzimidazole derivative. The silver atom lies on an inversion centre of the crystal lattice; nitrogen of the nitrate anion is in another inversion centre. Bond length Ag(1)? N(7) is 2.087(3) Å. Copyright © 2005 John Wiley & Sons, Ltd.     

Crystallographic report: The crystal structure of 2‐benzo[b]thienylgermatrane

The germanium atom is penta‐coordinated and adopts trigonal bipyramidal geometry. The 2‐benzo[b]thienyl group and the nitrogen atom each occupy an apical position with the transannular N → Ge bond distance being 2.180(4) Å. Copyright © 2003 John Wiley & Sons, Ltd.     

A versatile copper-catalyzed coupling reaction of pyridin-2(1H)-ones with aryl halides

A robust method has been developed to couple a wide variety of pyridin-2-ones and aryl halides. This C-N bond forming reaction makes use of catalytic copper(I) iodide and the ligand 8-hydroxyquinoline. These conditions tolerate a wide degree of functionality on both the aryl halide and pyridin-2-one reactants and have resulted in numerous examples being synthesized.     

Synthesis and neurotropic activity of silyl propargyl alcohols and sulfides

New silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols were synthesized using phase‐transfer catalytic and organometallic methods. These compounds were tested for acute toxicity and neurotropic activity in the pentylenetetrazole test, and for phenamine hypothermia, phenamine hyperactivity and passive avoidance response tests. We have found that the silyl propargyl alcohols and sulfides are low toxicity compounds, the LD₅₀ being 700–1300 mg kg^?1. In the PAR test, the synthesized compounds exerted some memory‐improving activity. For di‐1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)methyl(3‐iodopropyl)silane ( 16 ) the effect was statistically significant and amounted to 250% of the control level. In the pentylenetetrazole test, all compounds possessed anticonvulsant activity, the most active compounds being 3‐(benzoxazolylthio)‐1‐propynyl(trimethyl)silane ( 6 ) and di‐[2‐(1‐hydroxycyclohexyl)ethynyl]methyl(3‐iodopropyl)silane ( 17 ). The phenamine‐induced hyperactivity was significantly elevated after treatment with (3‐trimethylsilyl‐2‐propynyl)thiobenzene ( 1 ) or di‐[1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)diphenylsilane ( 12 ). Our data show that these silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols possess certain memory improving and anticonvulsant activity that should be studied in detail to evaluate the receptor systems involved. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis of unsymmetric diynes by palladium and cesium fluoride catalyzed coupling of terminal bromoalkynes with alkynylstannane

The Stille reaction of unsymmetric diynes from terminal bromoalkynes with alkynylstannane in the presence of palladium catalyst and cesium fluoride was studied. The system (bromoalkyne: PhC≡CSnMe₃:Pd₂(dba)₃:PPh₃:CsF:18‐crown‐6) = (1:1:0.015:0.06:2.2:0.1) in toluene at reflux temperature was found to be the most favored. Products were obtained in 31–100% yields. Correlations between calculated electron density, dipole moments and ¹³C NMR spectral data of synthesized bromoacetylenes and diynes have been carried out. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and cytotoxic activity of silacycloalkyl‐substituted heterocyclic aldehydes and their thiosemicarbazones

A series of 5‐[1‐methylsilacyclo‐pentyl/‐hexyl]‐2‐furfural, 5‐[1‐methylsilacyclo‐pentyl/‐hexyl]‐2‐thiophene carbaldehyde and 1,1‐bis(5‐formyl‐2‐furyl)silacyclo‐pentane/‐hexane and their thiosemicarbazones has been synthesized and subjected to antitumour assay. The effects of the substituents and the heterocycle were examined to establish structure–activity relationships. Thiosemicarbazones of 5‐(1‐methylsilacyclohexyl)furfural and 5‐(1‐methylsilacyclopentyl)furfural were very active (1.0–4.0 µg ml^?1) in vitro against human fibrosarcoma HT‐1080 and mouse hepatoma MG‐22A cells. At the same time, they were less toxic for normal fibroblasts 3T3. All compounds synthesized exhibited low or moderate toxicity (LD₅₀ 152–1904 mg kg^?1). Copyright © 2005 John Wiley & Sons, Ltd.     

Matched asymptotic expansions in nonlinear fracture mechanics—III. In-plane loading of an elastic perfectly-plastic symmetric specimen

The matched expansion method, introduced by the authors in two earlier papers (1976) devoted to mode III loading, is applied to the practically important case of mode I loading of a symmetric specimen. The method allows the linear elastic far-field to be considered separately from the elasto-plastic near-tip field, except for coupling through a set of parameters that are determined explicitly in the matching. The effects of the plasticity are thus found, once and for all, from the solution of a set of standard elasto-plastic problems for a semi-infinite crack in an infinite body, whose properties may be tabulated. The solution for any particular specimen geometry and loading then follows from a small set of linear elastic solutions for the specimen, which define, through coefficients γ_ij appearing in their near-tip expansions, all the parameters in the “inner” and “outer” solutions. The effects of plasticity appear in these parameters only through a set of constants C_ti that define the far-field expansions of the “inner” (near-tip) solutions: they are material constants, depending upon the constitutive relation for the material, but not upon specimen geometry and loading. The J-integral, being obtainable from the far-field, is expressed as an explicit asymptotic series in the loading parameter ε, whose coefficients are given as functions of the “elastic” parameters γ_ij and the material constants C_i. It is demonstrated that a plastic-zone correction term, r_y, can be chosen to yield a two-term asymptotic expansion for J; the value of r_y depends upon the yielding model only through the constant C₁.The Dugdale (1960) model of yielding is treated, as a simple example for which all calculations can be performed analytically, and for which exact solutions are available for comparison.Finally, the near-tip solutions are constructed for a material obeying the Mises yield criterion and associated flow-rule, using a specially developed finite element program. The first eight of the constants C_i are tabulated, which suffice to define the J-integral up to terms of order ε⁶ (where ε is a loading parameter) and some representative near-tip features are displayed graphically. The computed value of C₁ shows that the conventionally adopted value for the plastic-zone correction r_y is too large by a factor of roughly 2.8, if it is to yield a genuine asymptotic estimate for J. As an example, the “elastic” parameters γ_ij are found, from a boundary collocation program, for a centre-cracked square plate subjected to tensile loading; and a plot of J versus load, and the plastic-zone shape at a particular load level, are displayed.     

Synthesis and Neurotropic Activity of 5-Substituted Furfural Thiosemicarbazones

Abstract

5-Substituted-2-furaldehyde thiosemicarbazones were prepared from furfurals and thiosemicarbazide using the condensation method. The neurotropic activity of the synthesized thiosemicarbazones has been evaluated. The majority of the compounds examined has been shown to possess high or medium neurotropic activity of the depressant type. Structure-activity relationships of the titled compounds have been studied as well.