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排序方式: 共有325条查询结果,搜索用时 31 毫秒
71.
Siva Kumar Talluri 《Tetrahedron》2007,63(39):9758-9763
An efficient enantioselective synthesis of (R)-selegiline has been achieved by two routes, via proline-catalyzed α-aminooxylation as well as α-amination of phenylpropanaldehyde as the key step. 相似文献
72.
A well‐defined triazole functionalized porous triazine based polymers act as solid heterogeneous catalyst after incorporating palladium oxide nanoparticles (PdO@TTAS) have been synthesized and thoroughly characterized by various techniques such as, FT‐IR, UV‐DRS, solid state 13C CP‐MAS, XPS, powder X‐ray diffraction, TGA, SEM and TEM analysis has been detailed illustrated. It is important to note that synthesized catalytic performance for carbonylation of aryl halides (X = I, Br) with EDC.HCl (N‐(3‐dimethylaminopropyl)‐N′‐ethylcarbodiimide hydrochloride), and formic acid was found to be an effective CO source in the presence of triethylamine as a base and DMF as a solvent medium at 80 °C for about 3 hr. The PdO@TTAS catalyst exhibits superior catalytic performance and along with good yield (up to 90%). Moreover, studying the heterogeneity and reusability of the environmentally friendly solid catalyst can be easily separated by simple filtration and then recycled for several times. In this reaction method, we avoided ligand, additive, promoters and CO gas, due to additional problem arise by using gaseous CO, highly toxic greenhouse gases and high pressurized reaction setup. 相似文献
73.
Leela Prasad Kowtharapu Naresh Kumar Katari Christian A Sandoval Siva Krishna Muchakayala Vijay Kumar Rekulapally 《Journal of separation science》2022,45(10):1711-1726
Serotonin receptor antagonist drug Ondansetron hydrochloride injectable formulation containing all related substances was identified and quantified by a single, simple, sensitive, eco-friendly, and green high-performance liquid chromatography method. The disseverment of all impurities was achieved with the Discovery Cyano (250 × 4.6) mm, 5 μm column. The gradient program was composed of pH 5.7 phosphate buffer as mobile phase A and acetonitrile as mobile phase B. The flow rate, column compartment temperature, and detection wavelengths were 0.9 mL/min, 30°C, and 216 nm, respectively. The method was validated as per current regulatory guidelines. The obtained %relative standard deviation for the precision results was between 0.55 and 2.72% for all impurities. The correlation coefficient values from the linearity experiment for impurities and analyte were more than 0.995. The accuracy results were obtained between 88.4 and 113.0% for all impurities. Both sample and standard solutions showed 24 h stability at benchtop and refrigerator conditions. All impurities and analytes met the specificity and mass balance for all forced degradation conditions. Quality-by-design-based design of experiments was utilized to establish the method's robustness. Method greenness was assessed by using the current advanced tool green analytical procedure index, National Environmental Methods Index, and analytical eco-scale. 相似文献
74.
R. K. Sankaranarayanan S. Siva A. Antony Muthu Prabhu N. Rajendiran 《Journal of inclusion phenomena and macrocyclic chemistry》2010,67(3-4):461-470
Effect of β-cyclodextrin (β-CD) on the absorption and fluorescence spectra of 3,4,5-trihydroxybenzoic acid (THB) have been studied buffer solutions of different pHs (pH ~1, pH ~7 and pH ~10). The study reveals that in all the above pHs THB forms 1:1 inclusion complex. The hydroxyl groups are present in the interior part of the β-CD cavity and carboxyl group is present in the hydrophilic part of the β-CD cavity. Dual luminescence is observed at pH ~1 and pH ~7 solutions which shows that intramolecular charge transfer present at these pH. The broad spectral maximum at pH ~10 indicates that intramolecular proton transfer is present in THB. 相似文献
75.
Reddy SL Reddy NC Reddy GS Reddy BJ Frost RL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(3-4):684-688
Clinohumite, a humite group mineral, originated from Pamir Mountains, USSR, is used in the present work. Optical absorption, electron paramagnetic resonance (EPR), near infrared (NIR) and M?ssbauer techniques are used in the characterization of the mineral sample. The optical absorption spectrum indicates that Fe(II) impurity is present in two sites with distorted octahedral structure. NIR results are attributed to water fundamentals. EPR studies on powder sample confirm the presence of Mn(II) in three different sites and also an iron impurity. M?ssbauer studies confirm the presence of iron impurity in two different sites. 相似文献
76.
The first stereoselective total synthesis of the natural cryptopyranmoscatone B1 has been accomplished from 3,4,6-tri-O-acetyl-d-glucal. In addition to the double cross-metathesis reaction, a tandem nucleophilic addition-diastereoselective reduction of an in situ generated oxocarbenium cation have been used as key steps to assemble the glycoside moiety of the target molecule. 相似文献
77.
Krishna B. Athreya Siva R. Athreya Srikanth K. Iyer 《Proceedings Mathematical Sciences》2010,120(3):363-385
This paper studies: (i) the long-time behaviour of the empirical distribution of age and normalized position of an age-dependent
critical branching Markov process conditioned on non-extinction; and (ii) the super-process limit of a sequence of agedependent
critical branching Brownian motions. 相似文献
78.
On a bounded C
2-domain
we consider the singular boundary-value problem 1/2u=f(u) in D, u
D
=, where d3, f:(0,)(0,) is a locally Hölder continuous function such that f(u) as u0 at the rate u
–, for some (0,1), and is a non-negative continuous function satisfying certain growth assumptions. We show existence of solutions bounded below by a positive harmonic function, which are smooth in D and continuous in
. Such solutions are shown to satisfy a boundary Harnack principle. 相似文献
79.
Summary Selenito manganese(III) complexes of the type MMn(SeO3)2 · × H2O (where M = H+, NH
4
+
, K+, Rb+ and Cs+) have been prepared, Magnetic measurements show all these complexes to be of high spin d4 type, On the basis of their i.r. and electronic spectral studies and other properties, a polymeric octahedral structure involving bridging oxygen atoms has been suggested. 相似文献
80.