排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
2.
S. M. Islam Sanchita Mondal Anupam Singha Roy Paramita Mondal Manir Mobarak Dildar Hossain Palash Pandit 《Transition Metal Chemistry》2010,35(3):305-313
A polymer-anchored Pd(II) Schiff base complex has been synthesized by reacting a polymeric amine with 2-pyridinecarboxaldehyde
to get the polymer-anchored Schiff base, which was then reacted with palladium acetate. The catalyst was characterized by
physicochemical and spectroscopic methods. It shows excellent catalytic activity in the Sonogashira coupling of phenylacetylene
with aryl halides using triethylamine as a base and copper iodide as a co-catalyst in water under open air at 70 °C. We have
also studied the effects of base and solvent on the coupling reaction. Sonogashira reactions of phenylacetylene with a variety
of functionalized aryl halides were performed under the optimized reaction conditions. This catalyst gives excellent yields
without the use of phosphine ligands. Further experiments showed that the catalyst can be used five times without much loss
in the catalytic activity. 相似文献
3.
Manirul?IslamEmail author Dildar?Hossain Paramita?Mondal Kazi?Tuhina Anupam?Singha?Roy Sanchita?Mondal Manir?Mobarak 《Transition Metal Chemistry》2011,36(2):223-230
A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical
and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates
including alkenes and alcohols using H2O2 as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate
to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between
the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out. 相似文献
4.
A new cucurbitacin glucoside 2-O-beta-D-glucopyranosyl-16alpha-20R-dihydroxy-cucurbita-1,5,23E,25(26)-tetraen-3,11,22-trione (1) has been isolated from the methanolic extract of the fruits of Citrulluscolocynthis. The structure has been assigned on the basis of spectral analysis including 1D and 2D NMR techniques. In addition 2-O-beta-D-glucopyranosyl-cucurbitacin B (arvenin I) (2) and 2,25-di-O-beta-D-glucopyranosyl-cucurbitacin L (3) are reported for the first time from this species. 相似文献
5.
Manirul Islam Sanchita Mondal Paramita Mondal Anupam Singha Roy Dildar Hossain Manir Mobarak 《Transition Metal Chemistry》2011,36(1):1-11
Two copper complexes were synthesized from macroporous chloromethylated polystyrene beads. The first one was prepared by sequential
attachment of imidazole and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer, and the second one
was prepared from 4-vinylpyridine and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer. These catalysts
showed excellent catalytic activity in O-arylation reaction of aryl halides with phenol in dimethylsulfoxide using potassium
carbonate at 130 °C under open air conditions to give diaryl ethers in high yields. Less reactive aryl bromides and aryl chlorides
have also been shown to react with phenols to give good yields of the diaryl ethers. The effects of various parameters such
as solvent, catalyst from different copper salt and base on the reaction system were studied. The reaction is applicable to
a wide variety of substituted aryl halides and phenols with different steric and electronic properties. These catalysts were
recovered by simple filtration, and the reusability experiments showed that these catalysts can be used five times without
much loss in the catalytic activity. 相似文献
6.
Two new ursene-type triterpenes, nudicauline A and nudicauline B, have been isolated from Launaea nudicaulis. Their structures have been assigned as 3beta-hydroxy-urs-11-ene (1) and 3beta-acetyl-urs-11-ene (2), respectively, by extensive NMR studies. In addition, olean-11,13(18)-diene (3), 3beta-hydroxy-13(28)-epoxy-urs-11-ene (4) and 3-keto-13(28)-epoxy-urs-11-ene (5) are also reported for the first time from this species. 相似文献
7.
Shohel Ahme Md. Kamrujjaman Sumaiya Rahman 《Journal of Applied Analysis & Computation》2020,10(5):1800-1822
This paper deals with a nonlinear model of the viral dynamics which describes the interactions between the human immune system and the virus. The novelty of this work is the introduction of combined treatments in the dynamics to modify the model. We investigate the qualitative behavior of the model and find a threshold parameter that guarantees the asymptotic stability of the equilibrium points, this parameter is known as the basic reproduction number. We estimated the parameters of the model by least-squares minimization between the numerical solution of the system and clinical data of cell cultures. It is also demonstrated that critical drug efficacy in terms of the model parameter is greatly useful to curtail the spreading of the disease. 相似文献
8.
Manirul Islam Sanchita Mondal Mobarak Manir Anupam Singha Roy Paromita Mondal Dildar Hossain 《中国化学》2010,28(10):1810-1820
Polymer anchored Cu(II) Schiff base complexes have been prepared and characterized by using scanning electron microscope (SEM), elemental analysis, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), spectrometric methods like diffuse reflectance spectra of solid (DRS) and fourier transform infrared spectroscopy (FTIR). These catalysts show excellent catalytic activity in the O‐arylation reaction of aryl halides with phenol in acetonitrile using Cs2CO3 at 70°C under an open air condition to give diaryl ethers in high yields. The effects of various parameters such as solvent, catalyst from different copper salt and base on the reaction system have been studied. The reaction is applicable to a wide variety of substituted aryl halides and phenols with different steric and electronic properties. These catalysts are recovered by simple filtration and the reusability experiments show that these catalysts can be used five times without much loss in the catalytic activity. 相似文献
9.
Dildar Ahmed Khaizran Fatima Ramsha Saeed Rashid Masih 《Natural product research》2016,30(17):2012-2016
Carissa opaca is a shrub known for its variety of medicinal applications. This study reports isolation and identification of four chemical compounds from its roots for the first time. The methanolic extract of the roots was fractionated into various solvents with increasing polarity. Chloroform fraction was subjected to column and thin layer chromatography to ultimately yield 2H-cyclopropanaphthalene-2-one, 7-hydroxy-6-methoxy-2H-1-benzopyran-2-one, 3-(4-methoxyphenyl)-2,6-dimethylbenzofuran and 5(1H)-azulenone, 2,4,6,7,8,8a-hexahydro-3,8-dimethyl-4-(1-methylethylidene)-,(8S-cis). They were identified by GC–MS analysis. The compounds exhibited considerable antimicrobial activities against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus niger with zones of inhibition ranging from 10 to 13 mm as compared to the standard drug amoxicillin with zones of inhibition 13–17 mm under the similar conditions. In conclusion, the roots of C. opaca can provide new leads for future antimicrobial drugs. 相似文献
10.