ChemInform Abstract: Sodium Perborate/Acetic Anhydride: A Convenient Reagent for the Conversion of Cyclic Acetals to Esters

A facile oxidative cleavage of cyclic acetals to their respective esters using an inexpensive reagent system, sodium perborate/acetic anhydride is described.

Reactivity of some tetra substituted furans and thiophenes towards BF3-Et(2)O catalysed Diels-Alder reaction

Some tetra substituted furans and thiophenes were reacted with methyl acrylate under BF3-etherate catalysed Diels-Alder conditions. While the derivatives of furan underwent Diels-Alder reaction in a facile manner, an observation of 2,5-dimethyl-3,4-dianisylthiophene undergoing Diels-Alder reaction with methyl acrylate is remarkable. (C) 1997, Elsevier Science Ltd.

Dendritic encapsulation of amino acid-metal complexes. Synthesis and studies of dendron-functionalized L-tyrosine-metal (Zn-II, Co-II) complexes

This paper describes the synthesis, characterization and studies of dendrimers possessing an amino acid-metal complex as the core. Using Frechet-type polyaryl ether dendrons, L-tyrosine-metal (Zn-II and Co-II) complex cored dendrimers of 0-4 generations were synthesized. The metal complexation of the tyrosine unit at the focal point of these dendrons took place smoothly, in excellent yields, even though the sizes of the dendrons increase as the generations advance. Spectrophotometric titrations with CoII metal ion confirmed the formation of a 2 : 1 dendritic ligand to metal complex and the existence of a pseudotetrahedral geometry at the metal centre is also inferred. Cyclic voltammetric studies of dendrimer-Co-II complexes showed that while the electron transfer of Co-II to Co-I was facile for generations 0-2, such a process was difficult with generations 3 and 4, indicating a rigid encapsulation of the metal ion centre by proximal dendron groups. Further reduction of Co-I to Co-0 and the corresponding oxidation processes appear to be limited by adsorption at the surfaces of the electrodes.

Solution combustion synthesis of gamma(L)-Bi(2)MoO(6) and photocatalytic activity under solar radiation

The facile method of solution combustion was used to synthesize gamma(L)-Bi(2)MoO(6). The material was crystallized in a purely crystalline orthorhombic phase with sizes varying from 300 to 500 nm. Because the band gap was 2.51 eV, the degradation of wide variety of cationic and anionic dyes was investigated under solar radiation. Despite the low surface area (< 1 m(2)/g) of the synthesized material, gamma(L)-Bi(2)MoO(6) showed high photocatalytic activity under solar radiation due to its electronic and morphological properties. (C) 2011 Elsevier Ltd. All rights reserved.

Efficient syntheses of benzothiazepines as antagonists for the mitochondrial sodium-calcium exchanger: Potential therapeutics for type II diabetes

Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed.

Probing the mobility of lithium in LISICON: Li+/H+ exchange studies in Li2ZnGeO4 and Li2+2xZn1-xGeO4

We investigated Li+/H+ exchange in the lithium ion conductors (LISICONS) [ Li2+2xZn1-xGeO4; x = 0.5 ( I) and x = 0.75 (II)] and their parent, gamma-Li2ZnGeO4. Facile exchange of approximately 2x lithium ions per formula unit occurs with both the LISICONS in dilute acetic acid, while the parent material does not exhibit an obvious Li+/H+ exchange under the same conditions. The results can be understood in terms of lithium ion distribution in the crystal structures: the parent Li2ZnGeO4, where all the lithium ions form part of the tetrahedral framework structure, does not exhibit a ready Li+/H+ exchange; LISICONS, where lithium ions are distributed between framework ( tetrahedral) and nonframework sites, undergo a facile Li+/H+ exchange of the nonframework site lithium ions. Accordingly, Li+/H+ exchange in dilute aqueous acetic acid provides a convenient probe to distinguish between the mobile and the immobile lithium ions in lithium ion conductors.

Self-organization of multiple components in a steroidal hydrogel matrix: design, construction and studies on novel tunable luminescent gels and xerogels

The present work combines two rapidly growing research areas-functional supramolecular gels and lanthanide based hybrid materials. Facile hydrogel formation from several lanthanide(III) cholates has been demonstrated. The morphological and mechanical properties of these cholate gels were investigated by TEM and rheology. The hydrogel matrix was subsequently utilized for the sensitization of Tb(III) by doping a non-coordinating chromophore, 2,3-dihydroxynaphthalene (DHN), at micromolar concentrations. In the mixed gels of Tb(III)-Eu(III), an energy transfer pathway was found to operate from Tb(III) to Eu(III) and by utilizing this energy transfer, tunable multiple-color luminescent hydrogels were obtained. The emissive properties of the hydrogels were also retained in the xerogels and their suspensions in n-hexane were used for making luminescent coating on glass surface.

Iodine-Catalyzed Amination of Benzoxazoles: A Metal-Free Route to 2-Aminobenzoxazoles under Mild Conditions

A facile metal-free route of oxidative amination of benzoxazole by activation of C-H bonds with secondary or primary amines in the presence of catalytic iodine in aqueous tert-butyl hydroperoxide proceeds smoothly at ambient temperature under neat reaction condition to furnish the high yield of the aminated product. This user-friendly method to form C-N bonds produces tertiary butanol and water as the byproduct, which are environmentally benign. The application of the methodology is demonsrated by synthesizing therapeutically active benzoxazoles.

Sol-Gel Transition in Dispersions of Layered Double-Hydroxide Nanosheets

Surfactant-intercalated layered double-hydroxide solid Mg-Al LDH-dodecyl sulfate (DDS) undergoes rapid and facile delamination to its ultimate constituent, single sheets of nanometer thickness and micrometer size, in a nonpolar solvent such as toluene to form stable dispersions. The delaminated nanosheets are electrically neutral because the surfactant chains remain tethered to the inorganic layer even on exfoliation. With increasing volume fraction of the solid, the dispersion transforms from a free-flowing sol to a solidlike gel. Here we have investigated the sol-gel transition in dispersions of the hydrophobically modified Mg-Al LDH-DDS in toluene by rheology, SAXS, and (1)H NMR measurements. The rheo-SAXS measurements show that the sharp rise in the viscosity of the dispersion during gel formation is a consequence of a tactoidal microstructure formed by the stacking of the nanosheets with an intersheet separation of 3.92 nm. The origin and nature of the attractive forces that lead to the formation of the tactoidal structure were obtained from 1D and 2D (1)H NMR measurements that provided direct evidence of the association of the toluene solvent molecules with the terminal methyl of the tethered DDS surfactant chains. Gel formation is a consequence of the attractive dispersive interactions of toluene molecules with the tails of DDS chains anchored to opposing Mg-Al LDH sheets. The toluene solvent molecules function as molecular ``glue'' holding the nanosheets within the tactoidal microstructure together. Our study shows how rheology, SAXS, and NMR measurements complement each other to provide a molecular-level description of the sol-gel transition in dispersions of a hydrophobically modified layered double hydroxide.

Synthesis of 2-Deoxy-2-C-alkyl Glycal and Glycopyranosides from 2-Hydroxy Glycal Ester

A method to convert 2-hydroxy glycol ester to the corresponding corresponding 2-deoxy-2-C-alkyl glycol in a facile manner, through key reactions including (i) C-allylation at C-1, (ii) Wittig reaction, and (iii) Cope rearrangement of a 1,5-diene derivative, is reported. The alpha-anomer of the 1,5-diene derivative underwent Cope rearrangement to afford 2-deoxy-2-C-glycal derivative, whereas the beta-anomer was found to be unreactive. Employing this sequence, was transformed to 3,4,6-tri-O-benzyl-2-deoxy-2-C-alkyl-1,5-anhydro-D-arabino-hex-1-enitol. 2-Deoxy-2-C-alkyl glycol derivative is a suitable glycosyl donor to prepare 2-deoxy-2-C-alkyl glycosides, mediated through haloglycosylation and a subsequent dehalogenation. A number of 2-deoxy-2-C-alkyl glycosides, with both glycosyl and nonglycosyl moieties at the reducing end, are thus prepared from the glycol.

Self-Assembly of Manganese(I)-Based Molecular Squares: Synthesis and Spectroscopic and Structural Characterization

Syntheses of manganese(I)-based molecular squares have been accomplished in facile one-pot reaction conditions at room temperature. Self-assembly of eight components has resulted in the formation of M4L4-type metallacyclophanes [Mn(CO)(3)Br(mu-L)(4) (1-3) using pentacarbonylbromomanganese as metal precursor and rigid azine ligands such as pyrazine, 4,4'-bipyridine, and trans-1,2-bis(4pyridyl)ethylene, respectively, as bridging ligands. The metallacyclophanes have been characterized on the basis of IR, NMR, and UV-vis spectroscopic techniques and single-crystal X-ray diffraction methods.

Electrochemical Detection of Bisphenol A Using Graphene-Modified Glassy Carbon Electrode

Graphene's nano-dimensional nature and excellent electron transfer properties underlie its electrocatalytic behavior towards certain substances. In this light, we have used graphene in the electrochemical detection of bisphenol A. Graphene sheets were produced via soft chemistry route involving graphite oxidation and chemical reduction. X-ray diffraction, Fourier transform infra-red (FT-IR) and Raman spectroscopy were used for the characterization of the as-synthesized graphene. Graphene exhibited amorphous structure in comparison with pristine graphite from XRD spectra. FTIR showed that graphene exhibits OH and COOH groups due to incomplete reduction. Raman spectroscopy revealed that multi-layered graphene was produced due to low intensity of the 2D-peak. Glassy carbon electrode was modified with graphene by a simple drop and dry method. Cyclic voltammetry was used to study the electrochemical properties of the prepared graphene-modified glassy carbon electrode using potassium ferricyanide as a redox probe. The prepared graphene- modified glassy carbon electrode exhibited more facile electron kinetics and enhanced current of about 75% when compared to the unmodified glassy carbon electrode. The modified electrode was used for the detection of bisphenol A. Under the optimum conditions, the oxidation peak current of bisphenol A varied linearly with concentration over a wide range of 5 x 10(-8) mol L-1 to 1 x 10(-6) mol L-1 and the detection limit of this method was as low as 4.689 x 10(-8) M. This method was also employed to determine bisphenol A in a real sample

Tailoring the Magnetic and Optical Characteristics of Nanocrystalline BiFeO3 by Ce Doping

The Ce-doped BiFeO3 (BFO) nanoparticles (NPs) were synthesized using a facile solgel route with varying Ce concentrations in the range of 15 mol%. Ferroelectric transition temperature was found to shift from 723 degrees C +/- 5 degrees C for pristine BFO NPs to 534 degrees C +/- 3 degrees C for 5 mol% Ce-doped BFO NPs. UVVis absorption spectra of BFO NPs showed a significant blue shift of similar to 100 nm on Ce doping. The Fourier transformed infrared (FTIR) spectrum centered similar to 550 cm(-1) becomes considerably broadened on Ce doping which is due to additional closely spaced vibrational peaks as revealed by the second derivative FTIR analysis. High-frequency EPR measurements indicated that clustering occurs at high dopant levels, and that Fe is present as Fe(3+)corroborating Mossbauer measurements. The values of saturation and remanent magnetization for 3% Ce-doped BFO NPs are 3.03 and 0.49 emu/g, respectively, which are quite significant at room temperature, making it more suitable for technological applications.

Computational investigations on covalent dimerization/oligomerization of polyacenes: Is it relevant to soot formation?

We have postulated a novel pathway that could assist in the nucleation of soot particles through covalent dimerization and oligomerizations of a variety of PAHs. DFT calculations were performed with the objective of obtaining the relative thermal stabilities and formation probabilities of oligomeric species that exploit the facile dimerization that is known to occur in linear oligoacenes. We propose that the presence of small stretches of linear oligoacence (tetracene or longer) in extended PAH, either embedded or tethered, would be adequate for enabling the formation of such dimeric and oligomeric adducts; these could then serve as nuclei for the growth of soot particles. Our studies also reveal the importance of p-stacking interactions between extended aromatic frameworks in governing the relative stabilities of the oligomeric species that are formed. (c) 2012 Wiley Periodicals, Inc.

Enhancing the magnetic characteristics of BiFeO3 nanoparticles by Ca, Ba co-doping

Multiferroic nanoparticles (NPs) of pristine and Ca, Ba co-doped BiFeO3 were synthesized by a facile sal gel route. Co-doping was done by fixing the total dopant concentration at 5 mol% and then the relative concentrations of Ca and Ba was varied. Structural, optical and magnetic properties of the NPs were investigated using different techniques. UV-Vis absorption spectra of BiFeO3 NPs showed a substantial blue shift of similar to 100 nm (530 nm -> 430 nm) on Ca. Ba co-doping which corresponds to increase in band gap by 0.5 eV. Fe-57 Mossbauer spectroscopy confirmed that iron is present only in 3(+) valence state in all co-doped samples. The coercive field increased by 18 times for Bi0.95Ca0.01Ba0.04FeO3 samples, which is the maximum enhancement, observed amongst all the 5 mol% doped samples. At the equimolar (2.5 mol % each) concentration of co-dopants, the coercive field shows a significant enhancement of about 9 times (220 Oe -> 2014 Oe) with concomitant increase in saturation magnetization by 7 times. Thus, equimolar co-doping causes simultaneous enhancement of the twin aspects of magnetic properties thereby making them better suited for device applications. (C) 2012 Elsevier B.V. All rights reserved.