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121.
Rukhsana I. Kureshy Manish Kumar Santosh Agrawal Noor-ul H. Khan Sayed H.R. Abdi Hari C. Bajaj 《Tetrahedron: Asymmetry》2010,21(4):451-456
Chiral Cr(III) salen complex 1 having t-Bu substituents at 3,3′ and 5,5′-positions was used as a catalyst for the highly enantioselective aminolytic kinetic resolution (AKR) of racemic trans epoxides with different anilines as nucleophile in the presence of different ionic liquids at rt. Excellent yields (>98%) of anti β-aminoalcohols with high enantioselectivity (ee >99%) was achieved in 4 h when [bmim]PF6 was used as the ionic liquid. The present ionic liquid mediated AKR process is recyclable (up to six cycles with no loss in performance) and is five times quicker than the homogeneous process utilizing conventional organic solvents. 相似文献
122.
Saravanan S Sadhukhan A Khan NU Kureshy RI Abdi SH Bajaj HC 《The Journal of organic chemistry》2012,77(9):4375-4384
Recyclable chiral amide-based organocatalyst 5 efficiently catalyzed asymmetric Strecker reaction of various aromatic and aliphatic N-benzhydrylimines with ethyl cyanoformate as cyanide source at -10 °C to give a high yield (95%) of α-aminonitriles with excellent chiral induction (ee, up to 99%) with the added advantage of recyclability. Based on experimental observations a probable mechanism was proposed for this reaction. This protocol with catalyst 5 was extended for the synthesis of (R)-phenylalanine and pharmaceutically important drug intermediate (R)-3-phenylpropane-1,2-diamine in high yield with high enantioselectivity. 相似文献
123.
Charu Dwivedi Naina Raje Manmohan Kumar A. V. R. Reddy P. N. Bajaj 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(1):131-136
The present work describes the application of radiotracer technique for studying uptake of arsenic on titanium hydroxide, commercial titanium dioxide (TiO2) powder (anatase) and synthesized mesoporous titania beads in acidic, neutral, and alkaline conditions. Sol–gel templating method was used to prepare titania–polysaccharide composites, with different polymer contents. Mesoporous titania was obtained by heat treatment of the composite beads in a controlled environment. The synthesis process was optimized, using thermogravimetry analysis. X-ray diffraction patterns confirmed the formation of anatase pure phase titania (TiO2) at 700 °C in different environments, and scanning electron microscopy studies confirmed uniform pore size distribution. The effect of surface area, polymer content and pH on uptake of arsenic(III) and (V) on the synthesized titania beads was also investigated. Arsenic(V) was found to be retained quantitatively on the titania beads synthesized from 0.8% polymer content titania–polymer composite precursor in neutral to alkaline conditions. Details of the results obtained are discussed. 相似文献
124.
Satheeshmanikandan RS Thappali Kanthikiran VS Varanasi Sridhar Veeraraghavan Swaroop Kumar VS Vakkalanka Mukkanti K 《Journal of mass spectrometry : JMS》2012,47(12):1612-1619
A sensitive and reliable high‐performance liquid chromatography–mass spectrometry (LC–MS/MS) was developed and validated for simultaneous quantification IC87114, roflumilast (RFM), and its active metabolite roflumilast N‐oxide (RFN) using tolbutamide as an internal standard. The analytes were extracted by using liquid–liquid extraction and separated on a reverse phase C18 column (50 mm × 3 mm i.d., 4.6 µ) using methanol: 2 mM ammonium acetate buffer, pH 4.0 as mobile phase at a flow rate 1 mL/min in gradient mode. Selective reaction monitoring was performed using the transitions m/z 398.3 > 145.9, 403.1 >186.9, 419.1 > 187.0 and 271.1 > 155.0 to quantify quantification IC87114, RFM, RFN and tolbutamide, respectively. The method was validated over the concentration range of 0.1–60 ng.mL?1 for RFM and RFN and 6 to 2980 ng.mL?1 for IC87114. Intra‐ and inter‐day accuracy and precision of validated method were within the acceptable limits of <15% at all concentrations. Coefficients of correlation (r2) for the calibration curves were >0.99 for all analytes. The quantitation method was successfully applied for simultaneous estimation of IC87114, RFM and RFN in a pharmacokinetic drug–drug interaction study in Wistar rats. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
125.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Katherine T. Flynn Nikesh H. Bajaj Yousef Bittar 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):973-976
Novel copolymers of trisubstituted ethylene monomers, alkoxy ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC6H4CH = C(CN)2 (where R is 2-methoxy, 3-methoxy, 4-methoxy, 2-ethoxy, 3-ethoxy, 4-ethoxy, 4-propoxy, 4-buthoxy, 4-hexyloxy) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers is 2-methoxy (1.5) > 4-ethoxy (1.0) > 4-methoxy (0.8) > 3-ethoxy (0.7) = 3-methoxy (0.7) > 4-hexyloxy (0.6) = 2-ethoxy (0.6) > 4-butoxy (0.5) = 4-propoxy (0.5). High T g of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 284–500°C range with residue (5–9% wt), which then decomposed in the 500–800°C range. 相似文献
126.
127.
Time-of-flight technique has been used to characterize supersonic beams of polyatomic molecules in terms of translational
and vibrational temperatures, various velocity parameters and speed ratio. Collision effectiveness and effective specific
heat ratio of polyatomic gases pertinent to jet expansion have also been determined and interpreted. 相似文献
128.
A hereditary model and a fractional derivative model for the dynamic properties of flexible polyurethane foams used in automotive seat cushions are presented. Non-linear elastic and linear viscoelastic properties are incorporated into these two models. A polynomial function of compression is used to represent the non-linear elastic behavior. The viscoelastic property is modelled by a hereditary integral with a relaxation kernel consisting of two exponential terms in the hereditary model and by a fractional derivative term in the fractional derivative model. The foam is used as the only viscoelastic component in a foam-mass system undergoing uniaxial compression. One-term harmonic balance solutions are developed to approximate the steady state response of the foam-mass system to the harmonic base excitation. System identification procedures based on the direct non-linear optimization and a sub-optimal method are formulated to estimate the material parameters. The effects of the choice of the cost function, frequency resolution of data and imperfections in experiments are discussed. The system identification procedures are also applied to experimental data from a foam-mass system. The performances of the two models for data at different compression and input excitation levels are compared, and modifications to the structure of the fractional derivative model are briefly explored. The role of the viscous damping term in both types of model is discussed. 相似文献
129.
Halpern-Manners NW Paulsen JL Bajaj VS Pines A 《The journal of physical chemistry. A》2011,115(16):4023-4030
Many NMR and MRI methods probe fluid dynamics within macro- and mesoporous materials, but with few exceptions, they report on its macroscopically averaged properties. MRI methods are generally unable to localize microscopic features of flow within macroscopic samples because the fraction of the enclosing detector volume occupied by these features is so small. We have recently overcome this problem using remotely detected MRI velocimetry, a technique in which spatial, chemical, and velocity information about elements of the flow is encoded with a conventional NMR coil and detected sensitively at the sample outflow by a volume-matched microdetector. Here, we apply this method to microporous model systems, recording MRI images that correlate local velocity, spin relaxation, and time-of-flight in microscopic resolution and three spatial dimensions. Our results illustrate that remotely detected MRI is an effective approach to elucidate flow dynamics in porous materials including bead pack microreactors and chromatography columns. 相似文献
130.
Khan NU Pandya N Prathap KJ Kureshy RI Abdi SH Mishra S Bajaj HC 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,81(1):199-208
Chiral Schiff base ligands (S)-H(2)L and (R)-H(2)L and their complexes (S-Ni-L, R-Ni-L, S-Cu-L, R-Cu-L, S-Zn-L and R-Zn-L) were synthesized, characterized and examined for their DNA binding, antioxidant and antibacterial activities. The complexes showed higher binding affinity to calf thymus DNA with binding constant ranging from 2.0×10(5) to 4.5×10(6) M(-1). All the complexes also exhibited remarkable superoxide (56-99%) and hydroxyl scavenging (45-89%) activities as well as antibacterial activities against gram (+) and gram (-) bacteria. However, none of the complexes showed antifungal activity. Conclusively, S enantiomers of the complexes were found to be relatively more efficient for DNA interaction, antioxidant and antibacterial activities than their R enantiomers. This study reveals the possible utilization of chiral Schiff base complexes for pharmaceutical applications. 相似文献