排序方式: 共有10条查询结果,搜索用时 15 毫秒
1
1.
The Baylis-Hillman (BH) reaction plays a fascinating role in the field of synthetic and medicinal chemistry. BH adducts and their derivatives have been used as crucial synthons for the synthesis of various pharmaceutically useful natural products and compounds with carbocyclic or heterocyclic frameworks. This digest letter aims to discuss some key ideas for the synthesis of biologically active scaffolds using BH reaction and raise the awareness of this emerging research domain in modern drug discovery. In this review, we will present and discuss recent reports of various biologically active scaffolds derived from BH reaction, and their reported biological activities. 相似文献
2.
In the present work, the effect of longitudinal magnetic field on wave dispersion characteristics of equivalent continuum structure (ECS) of single-walled carbon nanotubes (SWCNT) embedded in elastic medium is studied. The ECS is modelled as an Euler–Bernoulli beam. The chemical bonds between a SWCNT and the elastic medium are assumed to be formed. The elastic matrix is described by Pasternak foundation model, which accounts for both normal pressure and the transverse shear deformation. The governing equations of motion for the ECS of SWCNT under a longitudinal magnetic field are derived by considering the Lorentz magnetic force obtained from Maxwell’s relations within the frame work of nonlocal elasticity theory. The wave propagation analysis is performed using spectral analysis. The results obtained show that the velocity of flexural waves in SWCNTs increases with the increase of longitudinal magnetic field exerted on it in the frequency range; 0–20 THz. The present analysis also shows that the flexural wave dispersion in the ECS of SWCNT obtained by local and nonlocal elasticity theories differ. It is found that the nonlocality reduces the wave velocity irrespective of the presence of the magnetic field and does not influences it in the higher frequency region. Further it is found that the presence of elastic matrix introduces the frequency band gap in flexural wave mode. The band gap in the flexural wave is found to independent of strength of the longitudinal magnetic field. 相似文献
3.
Garg Bhagwan S. Bhojak Narendar Dwivedi Poonam Kumar Vinod 《Transition Metal Chemistry》1999,24(4):463-466
The bidentate ligands, 2-[(N-acetyl)aminopyridine] (AAPH, A) and 2-[(N-benzoyl)aminopyridine] (BAPH, B) have been used to synthesize copper(II) complexes including an exogenous ligand X (X = AcO–, HCO2
–, N3
– and benzimidazole). The complexes were characterized by elemental analysis, electronic and vibrational spectroscopy, magnetic and e.s.r. studies. E.s.r. parameters and visible spectra indicated that all the complexes are monomers and exist in distorted octahedral geometry except for benzimidazole. With benzimidazole as an exogenous ligand, a five coordinate complex is formed. 相似文献
4.
Singh BK Bhojak N Mishra P Garg BS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(4):758-765
Complexes of Cu(II) with bioactive carboxyamide ligands N',N'-bis(3-carboxy-1-oxoprop-2-enyl)2-amino-N-arylbenzamidine, N',N'-bis(3-carboxy-1-oxopropanyl)2-amino-N-arylbenzamidine and N',N'-bis(3-carboxy-1-oxophenelenyl)2-amino-N-arylbenzamidine have been synthesized and characterized by various physico-chemical techniques. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML complexes. Vibrational spectra indicate coordination of amide and carboxylate oxygen of the ligands along with water molecules. Electronic spectra and magnetic susceptibility measurements reveal octahedral geometry for Cu(II) complexes. The EPR of the reported complex show g( parallel)>g( perpendicular)>2.0023 and G value within the range 2.08-4.49 are consistent with [Formula: see text] ground state in an octahedral geometry. The voltammogram of the copper(II) complex shows a quasi-reversible redox process and a simple one electron process assignable to the Cu(II)/Cu(I) couple. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The bio-efficacy of the ligands and its copper complexes have been examined against the growth of bacteria and pathogenic fungi in vitro to evaluate their antimicrobial potential. The results indicate that the ligand and its metal complexes possess notable antimicrobial properties. 相似文献
5.
Satish Babu Kodali Narendar Reddy Jakku Chinna Rajanna Kamatala Rajeshwar Rao Yerraguntla 《国际化学动力学杂志》2020,52(3):167-177
Bronsted acid catalyzed oxidation of certain sugar alcohols (polyols) has been studied by quinolinium dichromate (QDC) using aqueous sulfuric, perchloric, and hydrochloric acids at different temperatures. At constant acidity, reaction kinetics revealed the second-order kinetics with a first order in [Alcohol] and [QDC]. Zucker-Hammett, Bunnett, and Bunnett-Olsen criteria were used to analyze acid-dependent rate accelerations. Bunnett-Olsen plots of (log k + Hν) versus (Hν + log [H+]), and (log k) versus (Hν + log [H+]) afforded slope values (ϕ and ϕ*, respectively) > 0.47, suggesting that a water molecule acts as a prton transfer agent in the slow step of the mechanism in the oxidation of alcohols by QDC in the presence of aqueous sulfuric, perchloric, and hydrochloric acids. 相似文献
6.
Narendar Dudhipala Swetha Ettireddy Ahmed Adel Ali Youssef Goverdhan Puchchakayala 《Molecules (Basel, Switzerland)》2021,26(24)
Irbesartan (IR) is an angiotensin II receptor antagonist drug with antihypertensive activity. IR bioavailability is limited due to poor solubility and first-pass metabolism. The current investigation aimed to design, develop, and characterize the cyclodextrin(s) (CD) complexed IR (IR-CD) loaded solid lipid nanoparticles (IR-CD-SLNs) for enhanced solubility, sustained release behavior, and subsequently improved bioavailability through oral administration. Based on phase solubility studies, solid complexes were prepared by the coacervation followed by lyophilization method and characterized for drug content, inclusion efficiency, solubility, and in vitro dissolution. IR-CD inclusion complexes demonstrated enhancement of solubility and dissolution rate of IR. However, the dissolution efficiency was significantly increased with hydroxypropyl-βCD (HP-βCD) inclusion complex than beta-CD (βCD). SLNs were obtained by hot homogenization coupled with the ultrasonication method with IR/HP-βCD inclusion complex loaded into Dynasan 112 and glycerol monostearate (GMS). SLNs were evaluated for physicochemical characteristics, in vitro release, differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD), and physical stability at room temperature for two months. The optimized SLNs formulation showed particle size, polydispersity index, zeta potential, assay, and entrapment efficiency of 257.6 ± 5.1 nm, 0.21 ± 0.03, −30.5 ± 4.1 mV, 99.8 ± 2.5, and 93.7 ± 2.5%, respectively. IR-CD-SLN and IR-SLN dispersions showed sustained release of IR compared to the IR-CD inclusion complexes. DSC results complimented PXRD results by the absence of IR endothermic peak. Optimized IR-CD complex, IR-SLN, and IR-CD-SLN formulations were stable for two months at room temperature. Thus, the current IR oral formulation may exhibit improved oral bioavailability and prolonged antihypertensive activity, which may improve therapeutic outcomes in the treatment of hypertension and heart failure. 相似文献
7.
Formation of MgxNbyOx+y through the Mechanochemical Reaction of MgH2 and Nb2O5, and Its Effect on the Hydrogen‐Storage Behavior of MgH2
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. D. Pukazhselvan Dr. José Perez Dr. Narendar Nasani Dr. Igor Bdikin Dr. Andrei V. Kovalevsky Dr. Duncan Paul Fagg 《Chemphyschem》2016,17(1):178-183
The present study aims to understand the catalysis of the MgH2–Nb2O5 hydrogen storage system. To clarify the chemical interaction between MgH2 and Nb2O5, the mechanochemical reaction products of a composite mixture of MgH2+0.167 Nb2O5 was monitored at different time intervals (2, 5, 15, 30, and 45 min, as well as 1, 2, 5, 10, 15, 20, 25, and 30 h). The study confirms the formation of catalytically active Nb‐doped MgO nanoparticles (typically MgxNbyOx+y, with a crystallite size of 4–8 nm) by transforming reactants through an intermediate phase typified by Mgm?xNb2n?yO5n?(x+y). The initially formed MgxNbyOx+y product is shown to be Nb rich, with the concentration of Mg increasing upon increasing milling time. The nanoscale end‐product MgxNbyOx+y closely resembles the crystallographic features of MgO, but with at least a 1–4 % higher unit cell volume. Unlike MgO, which is known to passivate the surfaces in MgH2 system, the Nb‐dissolved MgO effectively mediates the Mg–H2 sorption reaction in the system. We believe that this observation will lead to new developments in the area of catalysis for metal–gas interactions. 相似文献
8.
Nasani Narendar 《Tetrahedron letters》2009,50(36):5159-9410
We have developed an efficient method for the preparation of enantiopure N-aryl-α-amino acids via copper-catalyzed N-arylation of α-amino acids and aryl halides under microwave irradiation. This protocol only needs less than 30 min to obtain the products, which are far superior to those obtained under conventional heating. 相似文献
9.
G. Krishnaiah B. Sandeep D. Kondhare K.C. Rajanna J. Narendar Reddy Y. Rajeshwar Rao P.K. Zhubaidha 《Tetrahedron letters》2013,54(7):703-706
Transesterification of β-ketoesters with various alcohols has been studied under conventional and non-conventional conditions using desktop chemicals such as Mn(II) salts as catalysts. These methods offered transesterification of β-ketoesters in good yields with dramatic rate accelerations and reduced reaction times. The developed protocols under nonconventional methods such as sonication and microwave irradiation are highly promising compared with the existing procedures. 相似文献
10.
R. Narendar 《International Journal of Polymer Analysis and Characterization》2013,18(5):369-376
Multilayered coir pith/nylon fabric/epoxy hybrid composites were fabricated by the hand lay-up technique. Coir pith was subjected to chemical treatment before processing and the volume fraction of coir pith was maintained in the range of 60–65%. The effect of treatment was analyzed by SEM and optical microscopy. The effects of layering and treatment on the mechanical and water transport nature of composite were analyzed. The mechanical properties of the composite decreased on exposure to water. However, the retention of impact strength increased with chemical treatment of coir pith. 相似文献
1