Oxidation of Hydrazides Using Sodium Perborate: Formation of N,N-Diacylhydrazines

Substituted aromatic hydrazides react very smoothly with sodium perborate in glacial acetic acid at room temperature to give N, N′-diacylhydrazines in excellent yields and purity.     

Activation of pig liver esterase in organic media with organic polymers: application to the enantioselective acylation of racemic functionalized secondary alcohols

Pig liver esterase (PLE) shows practically no activity in acylation of alcohols with vinylic esters in organic solvents. However, addition of methoxypoly(ethylene glycol) (MPEG), bovine serum albumin (BSA), TentaGelAmino resin (TGA), or aminomethyl polystyrene (AMPS) confers activity to PLE in acylation of alcohols with vinyl propionate in organic solvents of low water content. Polymer-activated PLE showed high enantioselectivities (E > 100) in the acylation of racemic 1-alkoxy-, 1-ethylsulfanyl-, and 1-fluoro-3-aryl-2-propanols as well as racemic 1-phenoxy-2-propanol and racemic 1-methoxy-2-phenoxy-2-propanol. The synthetic utility of polymer-activated PLE has been demonstrated by the gram-scale resolution of 1-methoxy-3-phenyl-2-propanol, 1-ethylsulfanyl-3-phenyl-2-propanol, 1-methoxy-3-p-methoxyphenyl-2-propanol, 1-fluoro-3-phenyl-2-propanol, and 1-methoxy-3-phenoxy-2-propanol. In PLE-catalyzed acylation of alcohols with vinyl propionate, acetaldehyde and propionic acids, both being detrimental to the enzyme, are formed as byproducts. In addition, the water content of the system, which is critical for the activity of pig liver esterase, is lowered because of a competing enzymatic hydrolysis of the acyl donor. The polymers TGA, BSA, and AMPS not only scavenge the aldehyde and the acid through imine formation and neutralization, respectively, but replenish at least in part also the water consumed in the competing hydrolysis of the acyl donor. A recovery of PLE together with the polymer was achieved without major loss of activity through their immobilization on a water-saturated polyaramide membrane, which occurs spontaneously in organic solvents.     

Interaction of Valdecoxib with β-cyclodextrin: Experimental and Molecular Modeling Studies

This study aimed to investigate the effect of β-cyclodextrin on aqueous solubility and dissolution rate of valdecoxib and also to get an insight of molecular interactions involved in formation of valdecoxib‐β-cyclodextrin inclusion complex. Phase solubility analysis indicated complex with possible stoichiometry of 1:1 and a stability constant of 234.01 M⁻¹. Thermodynamic studies in water indicated exothermic nature of inclusion complexation.␣Valdecoxib‐β-cyclodextrin complexes (1:1 M) were prepared by kneading method, solution method and␣freeze–drying method. The complex was characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (P-XRD), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance␣(¹H-NMR) spectroscopy. Molecular modeling was used to help establish the mode of interaction of β-cyclodextrin with valdecoxib. ¹H-NMR analysis suggested that the unsubstituted phenyl ring of valdecoxib display favorable interaction with the hydrophobic cavity of β-cyclodextrin, which was confirmed by molecular dynamic simulations. An inclusion complex model has been established for explaining the observed enhancement of solubility of valdecoxib in water by β-cyclodextrin. Dissolution studies in water showed that the valdecoxib in freeze-dried complex dissolved much faster than the uncomplexed drug and physical mixture. This improvement in dissolution rate is attributed to the increased solubility and wettability due to encapsulation along with decreased crystallanity caused by complex formation, which is evident by DSC and P-XRD studies.     

Copper Oxide Nanoparticles: Synthesis,Characterization and Their Antibacterial Activity

Copper oxide nanoparticles were prepared by electrochemical reduction method using tetra butyl ammonium bromide (TBAB) as structure directing agent in an organic medium viz. tetra hydro furan (THF) and acetonitrile (ACN) in 4:1 ratio by optimizing current density and molar concentration of the ligand. The reduction process takes place under inert atmosphere of nitrogen over a period of 2 h. Such nanoparticles are prepared using simple electrolysis cell in which the sacrificial anode as a commercially available copper metal sheet and platinum (inert) sheet act as a cathode. The parameters such as current density, solvent polarity, distance between electrodes, and concentration of stabilizers are used to control the size of nanoparticles. The synthesized copper oxide nanoparticles were characterized by using UV–Visible, FT-IR, XRD, SEM–EDS and TEM analysis techniques. The nanoparticles were tested for antibacterial activity against human pathogens like Escherichia coli (E. coli) and Staphylococcus strains and which was proved to be excellent.     

Mössbauer study of Al and Cr co-substituted Yttrium iron garnets

The Mössbauer spectra of Y₃Al _x Cr _X Fe_5???2x O₁₂ (x?=?0.0 to 0.6) measured at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at the octahedral (a) and the tetrahedral (d) sites for x?≤ 0.6. The isomer shifts (δ) and quadrupole splitting (ΔE_Q) indicate the presence of high spin Fe³⁺ ions in the tetrahedral (d) and octahedral (a) sites, typical of yttrium of yttrium iron garnet structure. Mössbauer results have shown that Al³⁺, enters a-sites only but Cr³⁺ enters both a-and d-sites.     

Cation distribution by Rietveld,spectral and magnetic studies of chromium-substituted nickel ferrites

Ultrafine crystals of chromium-substituted nickel ferrite were prepared by wet chemical co-precipitation method using sulphates of respective metal ions. Formation of these materials has been confirmed by X-ray powder diffraction method. The fine crystal nature of these materials is evidenced from scanning electron microscope (SEM). Cation distribution has been investigated using X-ray diffraction technique. Cation distribution indicates that chromium occupy octahedral site for all the values of composition x. The saturation magnetization and magneton number both are decreasing with increase of chromium concentration x. The decrease in saturation magnetization and magneton number is attributed to the substitution of the Cr³⁺ ions. Curie temperature (T _C ) from susceptibility plot is found to decrease with Cr concentration x. Curie temperature of all the compositions are also obtained theoretically and it agrees with observed Curie temperature.     

Preparation of silicon-containing polymers. I. Polyimides from dianhydrides and organosilicon diisocyanates

New silicon-containing polyimides have been prepared by the reaction of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with organosilicon diisocyanates having the following general structure: where R₁ = R₂ = ? CH₃ and ? C₆H₅. Thermal properties of these polyimides were studied were by TG, DTA, and DTG.     

Efficient sonochemical protocol for the facile synthesis of dipyrimido-dihydropyridine and pyrimido[4,5-d]pyrimidines in aqueous β-cyclodextrin

An economical and efficient synthesis of dipyrimido-dihydropyridines and pyrimido[4,5-d]pyrimidines is described using greener and recyclable β-cyclodextrin as a supramolecular catalyst in aqueous medium. The remarkable features of this method are mild reaction conditions, short reaction times, easy workup procedure, recyclability of the catalyst, and excellent yields of the products. The highly functional group tolerance and shorter reaction times make this method suitable for the synthesis of dihydropyridine and pyrimido[4,5-d]pyrimidine derivatives with a wide substitution pattern.