Oxidative cyclisation of chalcones with thallium(III)nitrate: Synthesis of (Z)-2-phenylmethylene-7-nitro-3(2H)-benzofuranones

Oxidation of 2-hydroxy-3-nitrochalcones with thallium(III) nitrate gives (Z)-2-phenylmethylene-7-nitrobenzofuran-3(2H)-one derivatives, rather than the more usual 1,2-diaryl-3,3-dimethoxypropan-1-ones or the corresponding isoflavones.

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Oxydative Cyclisierung von Chalconen mit Thallium(III)nitrat: Synthese von (Z)-2-Phenylmethylen-7-nitro-3(2H)-benzofuranonen (Kurze Mitteilung)

Zusammenfassung Die Oxidation von 2-Hydroxy-3-nitrochalconen mit Thallium(III)nitrat ergab (Z)-2-Phenylmethylen-7-nitro-3(2H)-benzofuranon-Derivate und nicht die üblichen 1,2-Diaryl-3,3-dimethoxypropan-1-one bzw. die entsprechenden Isoflavone.

     

Coimmobilization of urease and glutamate dehydrogenase in electrochemically prepared polypyrrole-polyvinyl sulfonate films

Immobilization of urease and glutamate dehydrogenase enzymes in electrochemically prepared polypyrrole-polyvinyl sulfonate films (PPY-PVS) was carried out using physical adsorption and electrochemical entrapment techniques. Detailed studies on optimum pH, Fourier transform infrared spectroscopy, cyclic voltammetry, and scanning electron microscopy of the enzymes in the immobilized state were conducted. The value of the apparent Michaelis-Menten constant was experimentally determined to be 2.5 and 2.7 for physically adsorbed and electrochemically entrapped urease in PPY-PVS films, respectively.     

Cation complexation with p-tert-butylcalix[5]arene pentacarboxylic acid derivative: an allosteric regulation of the first metal ion for stepwise extraction of the second ion

A calix[5]arene based solvent extraction reagent 3, appending carboxylic acid groups at the lower rim, has been developed and its complexation behavior towards some transition metal ions has been studied. The host 3 can selectively and quantitatively extract Pb(II) ions above pH 1.8 while other divalent ions such as Cu(II), Zn(II), Co(II), Ni(II) are extracted quantitatively only above pH 3.0. The outstanding Pb(II) selectivity of 3 comes from the size fit complementarity effect of the Pb(II) ion in the calix[5]arene cavity. One molecule of 3 extracts two Pb(II) ions in a stepwise manner. The first Pb(II) ion is extracted into the deep cavity of the calix[5]arene defined by phenoxy oxygen atoms. The first complexed Pb(II) ion acts as a template to bring the host into a cone conformation and induces a positive allosteric effect for the extraction of the second Pb(II) ion at an oxygen rich coordinating site composed of carboxyl groups. Both the Pb(II) ions are extracted through an ion exchange mechanism and the electroneutral complex in the organic phase is formed by the release of an equivalent number of hydrogen ions into aqueous solution. The loaded Pb(II) is easily back-extracted from Pb(II)-complexed 3 using dilute acid solution.     

A higher order finite element method with modified graded mesh for singularly perturbed two-parameter problems

This paper presents a modified graded mesh for singularly perturbed two-parameter problems. The mesh is generated recursively using Newton's algorithm and some implicitly defined function. The problem is solved numerically using the finite element method based on higher order polynomials of degree p≥1. We prove parameter uniform convergence of optimal order in ε-weighted energy norm. A test example is taken to compare the proposed graded mesh with others found in the literature.     

A time-delay model for the effect of toxicant in a single species growth with stage-structure

In this paper, we investigate a single-species growth model with stage-structure consisting of immature and mature stages for the effects of toxicants with constant maturation time-delay. We study the dynamics of our model in three cases: an instantaneous emission of toxicant, a constant emission of toxicant, and a periodic emission of toxicant into the environment. We present results on positivity and boundedness of all solutions under appropriate conditions. The model equations are analyzed mathematically with regard to the nature of equilibria and their stabilities using the theory of nonlinear differential equations and computer simulations. It is shown that under suitable conditions, there exists a globally asymptotically stable positive equilibrium. It is concluded from the analysis that as the concentration of toxicant in the environment increases, equilibrium densities of both immature and mature populations decrease. It is also noted that the effects of toxicants are more on the equilibrium level of immature population in comparison to the mature population.     

Analysis of the factorization method for elliptic differential equations

This paper presents a numerical analysis of the method of factorization for elliptic boundary value problems. A second-order elliptic boundary value problem is transformed into a decoupled system of first-order initial value problems. This elaborates the decoupled system’s occupying operator, the solution of the problem, and the affine part of the operator. The solution of the problem is thus obtained by solving the factorized system using the finite-element method. A comparative study is made with the help of an example that illustrates many of its properties.     

The effect of nitro groups on oxidative cyclisation of chalcones by thallium(III) nitrate(TTN)

2′-Hydroxy-3′-nitrochalcones on oxidation with thallium(III) nitrate do not give rearranged intermediates that can give isoflavones, instead cyclisation gives benzyl-idenebenzofuran-3(2H)-one derivatives.     

Variable Ag—O bonding patterns in silver cyclic amide tri-aryl-phosphine complexes

The solid-state structures of five new tri-arylphosphine silver cyclic amide complexes having a systematic variation in the ring structures have been resolved. Normal Ag—N bonding and variable, weaker Ag—O bonding interactions, which can be attributed to the ring modifications, form the basis of the bonding patterns. Reported here are the solid-state structures of silver complexes of tri-arylphosphine derivatives of silver 1(2H)-phthalazinone, silver phthalimide, silver 1,2,3-benzotriazin-4(3H)-one, silver 2H-1,3-benzoxazine-2,4(3H)-dione and silver 2,3-dihydro-1,4-phthalazine- dione. The unit cell parameters are: P-1, a = 11.179(2) ?, b = 15.508(3) ?, c = 22.636(5) ?, α = 104.30(3)°, β = 95.39(3)°, γ = 94.62(3)°; C2/c, a = 17.3600(8) ?, b = 15.4930(8) ?, c = 15.0760(7) ?, β = 113.911(2)°; P-1, a = 11.0656(2) ?, b = 11.9447(2) ?, c = 17.4764(3) ?, α = 79.5254(9)°, β = 80.2877(9)°, γ = 68.9136(7)°; P-1, a = 10.5743(4) ?, b = 11.8439(4) ?, c = 19.0110(8) ?, α = 102.4280(13)°, β = 104.0330(12)°, γ = 100.2520(18)°, P-1, a = 13.6908(3) ?, b = 16.2230(4) ?, c = 18.3678(7) ?, α = 86.8920(10)°, β = 69.5290(10)°, γ = 70.7840(10)°, respectively. Four of the complexes include ligand chelation by Ag—O bonding to the adjacent carbonyl in addition to the main Ag—N connection.     

New materials with novel topologies. Synthesis and characterisation of telomers and polymers with ribbon topology

The five, seven and nine ring analogues of thianthrene have been made as model compounds for ribbon polymers based on the structural motif shown below. The smaller molecules are soluble and readily characterised but the nine ring model compound and polymers based on this structural motif are insoluble and intractable. Analogues of the model compounds and polymers which carry decyl substituents are soluble upto species having about seventy rings.