Diastereodivergent Catalysis Using Modularly Designed Organocatalysts: Synthesis of both cis‐ and trans‐Fused Pyrano[2,3‐b]pyrans

Both enantiomers of cis‐ and trans‐fused 3,4,4a,8a‐tetrahydro‐2H,5H‐pyrano[2,3‐b]pyran‐7‐carboxylates have been obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse‐electron‐demand hetero‐Diels–Alder/oxa‐Michael reaction catalyzed by modularly designed organocatalysts (MDOs). Diastereodivergence was achieved in these reactions through the direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self‐assembled from both enantiomers of proline and cinchona alkaloid thiourea derivatives.     

Finite size effects on the structural and magnetic properties of sol–gel synthesized NiFe2O4 powders

Nanoparticles of nickel ferrite have been synthesized by the sol–gel method and the effect of grain size on its structural and magnetic properties have been studied in detail. X-ray diffraction (XRD) studies revealed that all the samples are single phasic possessing the inverse spinel structure. Grain size of the sol–gel synthesized powders has been determined from the XRD data and the strain graph. A grain size of 9 nm was observed for the as prepared powders of NiFe₂O₄ obtained through the sol–gel method. It was also observed that strain was induced during the firing process. Magnetization measurements have been carried out on all the samples prepared in the present series. It was found that the specific magnetization of the nanosized NiFe₂O₄ powders was lower than that of the corresponding coarse-grained counterparts and decreased with a decrease in grain size. The coercivity of the sol–gel synthesized NiFe₂O₄ nanoparticles attained a maximum value when the grain size was 15 nm and then decreased as the grain size was increased further.     

Facile One‐Step Conversion of Ketones into α‐Azidoketones using [Hydroxy(tosyloxy)iodo]benzene and Sodium Azide in the Presence of a Phase‐Transfer Catalyst under Solvent‐Free Conditions

We have described a one‐step, solvent‐free synthesis of α‐azidoketones from the corresponding ketones that requires relatively benign [hydroxy(tosyloxy) iodo]‐benzene reagent, sodium azide, and phase‐transfer catalyst at room temperature. Generality of the protocol has been demonstrated by synthesizing various α‐azidoketones high in yield and purity within a short time.     

Laser-induced thermal lens study of the role of morphology and hydroxyl group in the evolution of thermal diffusivity of copper oxide

The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens (TL) technique. For this purpose, the decomposition of Cu(OH)₂ into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications, from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid's thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.     

Effect of plant extracts on book deteriorated fungal species

Abstract

The aim of the study was to evaluate the effect of leaf extracts of four plants against some isolated fungal species from deteriorated books. Aqueous, methanol and chloroform extracts of selected plant species were screened in vitro for their antifungal activity against some book deteriorating fungal species. Fifteen species belonging to 09 genera were isolated and identified from infested books in library. Aqueous and solvent extracts of leaves of Azadiracta indica, Callistemon citrinus, Eucalyptus lanceolatus and Pongamia pinnata were tested against some dominant fungal species viz. Chaetomium spiralis, Alternaria alternata, Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus and Rhizopus stolonifer. Solvent extracts exhibited potent inhibitory activity than aqueous extracts. However, these plant extracts exhibited moderate activity against A. flavus, C. spiralis, R. stolonifer and A. alternata.     

Reversed-phase chiral HPLC and LC/MS analysis with tris(chloromethylphenylcarbamate) derivatives of cellulose and amylose as chiral stationary phases

Three polysaccharide-derived chiral stationary phases (CSP) were evaluated for the resolution of more than 200 racemic compounds of pharmaceutical interest in the reversed-phase (RP) separation mode. The population of test probes was carefully evaluated in order to insure that it covers as completely as possible all structural diversity of chiral pharmaceuticals. RP showed the highest potential for successful chiral resolution in HPLC and LC/MS analysis when compared to normal phase and polar organic separation modes. Method development consisted of optimizing mobile phase eluting strength, nature of organic modifier, nature of additive and column temperature. The newer CSPs, cellulose tris(3-chloro-4-methylphenylcarbamate) and amylose tris(2-chloro-5-methylphenylcarbamate), were compared to the commonly used cellulose tris(3,5-dimethylphenylcarbamate) in regards to their ability to provide baseline resolution. Comparable success rates were observed for these three CSPs of quite complimentary chiral recognition ability. The same method development strategy was evaluated for LC/MS analysis. Diethylamine as additive had a negative effect on analyte response with positive ion mode electrospray (ESI⁺) MS(/MS) detection, even at very low concentration levels (e.g., 0.025%). Decreasing the organic modifier (acetonitrile or methanol) content in the mobile phase often improved enantioselectivity. The column temperature had only a limited effect on chiral resolution, and this effect was compound dependent. Ammonium hydrogencarbonate was the preferred buffer salt for chiral LC with ESI⁺ MS detection for the successful separation and detection of most basic pharmaceutical racemic compounds. Ammonium acetate is a viable alternative to ammonium hydrogencarbonate. Aqueous formic acid with acetonitrile or methanol can be successfully used in the separation of acidic and neutral racemates. Cellulose tris(3-chloro-4-methylphenylcarbamate) and amylose tris(2-chloro-5-methylphenylcarbamate) emerge as CSPs of wide applicability in either commonly used separation modes rivaling such well established CSPs as cellulose tris(3,5-dimethylphenylcarbamate). Screening protocols including these two new CSPs in the preferentially screened set of chiral columns have higher success rates in achieving baseline resolution in shorter screening time.     

Multi-Hamiltonian structure of kdv hierarchy by Drienfeld-Sokolov formalism

Conserved quantities and the multi-Hamiltonian structure for the integrable coupled kdv system which is associated with the isospectral flow [(∑ _i=0 ^N−1 ε _i λ ⁱ )∂² + ∑ _i=0 ^N−l V ₁λ ⁱ ]φ=λ ^N φ are deduced by the Drienfeld-Sokolov formalism.     

Synthesis,characterization, and thermal property of phosphate-based cobalt mixture of non-calcined,calcined, and composite material

Monatshefte für Chemie - Chemical Monthly - The phosphate-containing cobalt mixtures of non-calcined, calcined, and composite materials were synthesized in atmospheric conditions and...     

The Assessment of Phytoremediation Potential of Invasive Weed Amaranthus spinosus L.

Presently the environment is heavily polluted by various toxic metals, which creates danger for all living beings. Heavy metals are toxic above certain threshold levels. Phytoremediation is an emerging technology which is quite a novel technique of cleaning polluted sites through the use of plants. Phytoremediation methods are comparatively cheap and ecologically advantageous, compared to conventional and physicochemical methods like precipitation, evaporation and chemical reduction. In this respect, plants can be compared to solar-driven pumps capable of extracting and concentrating certain elements from their environment. Amaranthus spinosus, an invasive weed seen on road sides and bare land belonging to the family Amaranthaceae, was selected for the present study. A greenhouse experiment was conducted and consisted of a range-finding test and definitive test for various concentrations of heavy metals Cu, Zn, Cr, Pb and Cd. Plants were grown in soil treated with different concentration of metals depending upon the threshold level. The bio-organics of the plant such as soluble sugar, protein, lipid, phenol, amino acid and photosynthetic pigments were estimated after 30?days of treatment. The bio-organics showed profound variation in response to accumulation of heavy metals. Accumulation of Cu, Pb and Cd was high in the roots followed by stem and leaves and that of Zn and Cr remained high in aerial parts. A steady increase was noticed in the bioaccumulation of copper, zinc and cadmium on enhancing the concentration of the corresponding metal in the soil. The bioconcentration factor and translocation factor were above unity in most of the treatments and increased as the concentration of treatment increased which indicated that A. spinosus is a potential agent for heavy metal accumulation and translocation.