Organic syntheses on an icosahedral borane surface: closomer structures with twelvefold functionality

The syntheses of a series of novel ester-linked derivatives of the icosahedral [closo-B12(OH)12]2- boron cluster (closomer esters) are described using several synthetic methods. The reaction of bis(tetrabutylammonium)-closo-dodecahydroxy-dodecaborate, [NBu4]2 1, with carboxylic acid chlorides and anhydrides, vinyl esters with a Y5(OiPr)13O catalyst and 1,1'-carbonyldiimidazole-activated carboxylic acids yields the corresponding dianionic dodeca-ester closomers. The method using 1,1'-carbonyldiimidazole-activated carboxylic acids may be employed as a general synthetic strategy. The use of elevated reaction temperatures, achievable under pressure, to expedite syntheses is described. An attractive methodology using immobilized scavenger reagents for the expeditious purification of the closomer esters was employed. The developed methodology is compatible with a variety of peripheral functional groups attached to the termini of densely packed, carboxylate ester-linked radial arms bonded to the icosahedral borane surface. A closomer ester having twelve terminal amino groups was prepared, and without isolation, fully acetylated in good yield.     

INAA and ETAAS of toxic element content of fruits harvested and consumed in Pakistan

Instrumental neutron activation analysis (INAA) and electro-thermal atomic absorption spectrometry (ETAAS) were employed to determine the toxic elements in fourteen fruits harvested in Pakistan. As, Br, Hg, Sb and Se were determined using INAA. Cadmium and Pb were determined using ETAAS. The intake levels of all toxic elements have been calculated. The data show that dates supply the maximum amount of most of the toxic elements. Peels of apple and pear have also been investigated and were found to contain higher concentration of toxic elements than their edible parts. The reliability of the techniques has been established by the use of standard reference materials. This study shows that all investigated fruits cultivated and consumed in Pakistan are safe for human consumption.     

A new tetradentate N2O2-type Schiff base ligand. Synthesis, extractive properties towards transition metal ions and X-ray crystal structure of its nickel complex

A new tetradentate N₂O₂-type Schiff base, bis(2-hydroxypropiophenone)-1,2-propanediimine (L), was synthesized by the reaction of 1,2-propanediamine with 2-hydroxypropiophenone in EtOH. The Schiff base is able to extract Co^II, Ni^II, Cu^II and Zn^II ions in aqueous NaNO₃ media into a CH₂Cl₂ organic phase via a cation exchange mechanism. The observed extraction order was as follows: Cu^II > Ni^II > Co^II > Zn^II. Reaction of nickel acetate with the Schiff base in EtOH afforded the neutral complex Ni · L. Single crystals of this complex were obtained from mixed CHCl₃-EtOH (3:1) solvent and its structure was determined by X-ray diffraction. Crystal data for Ni · L · CHCl₃: triclinic, space group Pī, with a = 9.005(2) Å, b = 9.625(2) Å, c = 14.212(4) Å, V = 1136.8(5) ų, α = 106.06(2)°, β = 106.06(2), γ = 105.10(2)°, and Z = 2. A near square planar structure is observed for the studied complex.     

A Short Synthesis of Natural Isocoumarin Glucoside Delphoside

A simple synthesis of delphoside, 3-methyl-6-hydroxy-8-O-β-D-glucopyranosyloxy isocoumarin (1), isolated from Delphinium spp. is described. 3,5-Dimethoxyhomophthalic anhydride (2) on treatment with acetyl chloride in the presence of 1,1,3,3-tetramethylguanidine (TMG) and triethyl amine afforded the 6,8-dimethoxy-3-methylisocoumarin (3). Regioselective demethylation of the latter furnished 8-hydroxy-6-methoxy-3-methylisocoumarin (4). Glycosylation with O-(2,3,4,6-tetra-O-acetyl-D-glucopyranosyl)trichloroacetimidate in presence of catalytic amount of boron trifluoride etherate followed by deacetylation using 5% potassium carbonate afforded 3-methyl-6-methoxy-8-O-β-D-glucopyranosyloxyisocoumarin (6) that was finally demethylated to yield delphoside 1.     

Complexation of (trimethylphosphine)gold(I) with Selenones

Mixed ligand complexes of gold(I) with various selenones and Me₃P, [Me₃PAuSe=C<]Cl, have been prepared and characterized by elemental analyses, i.r. and n.m.r. methods. A decrease in the i.r. frequency of the >C=Se mode of selenones upon complexation is indicative of selenone binding to gold(I) via a selenone group. An upfield shift in ¹³C-n.m.r. for the >C=Se resonance of selenones and downfield shifts in ³¹P-n.m.r. for Me₃P moiety are consistent with the selenium coordination to gold(I). The steric effect as well as the basicity of Me₃PAu⁺ plays a significant role in bonding with Se-containing ligands compared to the Et₃PAu⁺ and Ph₃PAu⁺ complexes.     

Synthesis of novel spiro-[3H-indole-3,3′-[1,2,4]triazolidine]-2-ones via azomethine imines

Novel spiroindoles 5 are prepared easily via a one-pot, 1,3-dipolar cycloaddition reaction of azomethine imines with isatin imines under thermal conditions.     

Synthesis,spectroscopic characterization,and computed optical analysis of green fluorescent cyclohexenone derivatives

Cyclohexenone containing chalcones core is one important class of materials, which exhibit high nonlinear optical (NLO) responses and good crystallizability. The present study reports the successful development of six new fluorescent cyclohexenone derivatives (CDs) via conventional Robinson annulation method. The molecular structures of these newly synthesized CDs were confirmed by using various analytical techniques such as ¹H NMR, ¹³C NMR, FTIR, EIMS, UV–Vis spectroscopy and single crystal X‐ray diffraction. The crystallographic data revealed that the spatial structure of the representative CD (4BE) belongs to monoclinic, P2₁/c space group. The results from luminescence studies show that the CDs molecules apparently emit intense green light at room temperature in aqueous media. The relative polarity and molecular chemical stability of the CDs molecules were predicted by measuring the molecular electrostatic potential and frontier molecular orbital energy. In addition, the UV–Vis spectra, transition character and electronic structures of these CDs were computed by using quantum chemical methodology. It was interesting to note that the values of computed and experimental electronic transitions (λ_max) were in good agreement and these CDs display high hyperpolarizability (β) values. The present work will be helpful for systematical understanding of the structures and the optical properties of CDs for studying the structure–activity relationship that will suggest their potential application in photonic devices. Copyright © 2015 John Wiley & Sons, Ltd.     

Solution of nonlinear weakly singular Volterra integral equations using the fractional‐order Legendre functions and pseudospectral method

In this article, our main goal is to render an idea to convert a nonlinear weakly singular Volterra integral equation to a non‐singular one by new fractional‐order Legendre functions. The fractional‐order Legendre functions are generated by change of variable on well‐known shifted Legendre polynomials. We consider a general form of singular Volterra integral equation of the second kind. Then the fractional Legendre–Gauss–Lobatto quadratures formula eliminates the singularity of the kernel of the integral equation. Finally, the Legendre pseudospectral method reduces the solution of this problem to the solution of a system of algebraic equations. This method also can be utilized on fractional differential equations as well. The comparison of results of the presented method and other numerical solutions shows the efficiency and accuracy of this method. Also, the obtained maximum error between the results and exact solutions shows that using the present method leads to accurate results and fast convergence for solving nonlinear weakly singular Volterra integral equations. Copyright © 2015 John Wiley & Sons, Ltd.     

Using generating functions to convert an implicit (3,3) finite difference method to an explicit form on diffusion equation with different boundary conditions

In this article, our main goal is to develop an idea to convert an implicit (3,3) ??-scheme finite difference method to an explicit form for both linear and nonlinear diffusion equations and also for nonlinear advection-diffusion equation with different boundary conditions. Accordingly, we assist power series generating functions which are a routine method in discrete mathematics. Also, the stability analysis of ??–scheme to implement in nonlinear advection–diffusion equation has been investigated. Finally, the new approach has been implemented for Fisher, reaction–diffusion, Burgers and coupled Burgers equations as test problems to verify the ability and efficiency of the method proposed in this paper.     

Application of SBA-Pr-SO<Subscript>3</Subscript>H as a nanoreactor in the one-pot synthesis of spiroquinazolinones

An efficient method for the synthesis of spiroquinazolinones was developed using isatoic anhydride, hydrazides and cyclic ketones, through a rapid one-pot three-component reaction in the presence of SBA-Pr-SO₃H under solvent-free conditions. SBA-Pr-SO₃H was an efficient heterogeneous nanoreactor with a pore size of 6 nm which can be easily handled and removed from the reaction mixture by simple filtration and can be reused several times without any loss of activity. The main advantages of using this nanoreactor are high product yields, being environmentally benign, short reaction times, and easy handling.