排序方式: 共有47条查询结果,搜索用时 15 毫秒
31.
《Journal of Coordination Chemistry》2012,65(16-18):2787-2799
AbstractMononuclear trans-Pd(II)–NHC complexes (where NHC?=?N-heterocyclic carbene) bearing asymmetrically substituted NHC-ligand have been synthesized via transmetalation reaction between Ag(I)–NHC complexes and [Pd(NCCH3)2Cl2]. The NHC precursors are accessible in two steps by N-n-alkyl reactions of benzimidazole. The resultant benzimidazolium salts were deprotonated with Ag2O by in situ deprotonation to facilitate the formation of mononuclear Ag(I)–NHC complexes. Single-crystal structural study for Pd(II)–NHC shows that the palladium(II) ion exhibits a square-planar geometry of two NHC ligands and two chloride ions. The cytotoxicity study was investigated against breast cancer cell line (MCF-7). The Ag(I)–NHC complexes exhibit better activities than their corresponding Pd(II)–NHC complexes, whereas all benzimidazolium salts are inactive toward MCF-7 cancer cell line. 相似文献
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33.
Poly(phenylene) and m‐Terphenyl as Powerful Protecting Groups for the Preparation of Stable Organic Hydroxides
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Andrew G. Wright Thomas Weissbach Prof. Steven Holdcroft 《Angewandte Chemie (International ed. in English)》2016,55(15):4818-4821
Four benzimidazolium hydroxide compounds, in which the C2‐position is attached to a phenyl group possessing hydrogen, bromine, methyl groups, or phenyl groups at the ortho positions, are prepared and investigated for stability in a quantitative alkaline stability test. The differences between the stability of the various protecting groups in caustic solutions are rationalized on the basis of their crystal structures and DFT calculations. The highest stability was observed for the m‐terphenyl‐protected benzimidazolium, showing a half‐life in 3 m NaOD/CD3OD/D2O at 80 °C of 3240 h. A high‐molecular‐weight polymer analogue of this model compound is prepared that exhibits excellent mechanical properties, high ionic conductivity and ion‐exchange capacity, as well as remarkable hydroxide stability in alkaline solutions: only 5 % degradation after 168 h in 2 m KOH at 80 °C. This is the most stable hydroxide‐conducting benzimidazolium polymer to date. 相似文献
34.
F. Doǧan S. Gülcemal M. Yürekli B. Çetinkaya 《Journal of Thermal Analysis and Calorimetry》2008,91(2):395-400
The imidazolinium and benzimidazolium bromide salts with pentafluor substituents on N atom were synthesized. The structures
of imidazolinium and benzimidazolium bromide salts obtained were conformed by 1H and 13C NMR, 19F NMR and elemental analysis. It was found that pyrolytic decomposition occurs with melting in salts. The imidazolinium and
benzimidazolium bromide salts were studied by TG-DTG and DTA from ambient temperature to 1000°C in nitrogen atmosphere. The
decomposition occurred mainly in one stage and the values of activation energy E, frequency factor A, reaction order n, enthalpy change ΔH
#, entropy change ΔS
# and Gibbs free energy ΔG
#, of the thermal decomposition were calculated by means of Coats-Redfern (CR), MacCallum-Tanner (MC) and van Krevelen (vK)
methods. The activation energy value obtained by CR and MC methods were in good agreement with each other while those obtained
by vK were found to be 10–12 kJ mol−1 larger. 相似文献
35.
Beatrice-Cristina Ivan Florea Dumitrascu Adriana Iuliana Anghel Robert Viorel Ancuceanu Sergiu Shova Denisa Dumitrescu Constantin Draghici Octavian Tudorel Olaru George Mihai Nitulescu Mihaela Dinu Stefania-Felicia Barbuceanu 《Molecules (Basel, Switzerland)》2021,26(21)
A series of new pyrrole derivatives were designed as chemical analogs of the 1,4-dihydropyridines drugs in order to develop future new calcium channel blockers. The new tri- and tetra-substituted N-arylpyrroles were synthesized by the one-pot reaction of 1-methyl-3-cyanomethyl benzimidazolium bromide with substituted alkynes having at least one electron-withdrawing substituent, in 1,2-epoxybutane, acting both as the solvent and reagent to generate the corresponding benzimidazolium N3-ylide. The structural characterization of the new substituted pyrroles was based on IR, NMR spectroscopy as well as on single crystal X-ray analysis. The toxicity of the new compounds was assessed on the plant cell using Triticum aestivum L. species and on the animal cell using Artemia franciscana Kellogg and Daphnia magna Straus crustaceans. The compounds showed minimal phytotoxicity on Triticum rootlets and virtually no acute toxicity on Artemia nauplii, while on Daphnia magna, it induced moderate to high toxicity, similar to nifedipine. Our research indicates that the newly synthetized pyrrole derivatives are promising molecules with biological activity and low acute toxicity. 相似文献
36.
Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by 1H-NMR, 13C-NMR, FTIR, single crystal x-ray crystallography and elemental analysis. A proof-of-principle non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using 1H-NMR titration. 相似文献
37.
Palladium(II)‐N‐Heterocyclic Carbene Complexes: Efficient Catalysts for the Direct C‐H Bond Arylation of Furans with Aryl Halides
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This paper contains the synthesis and characterization of the seven new benzimidazolium salts and their corresponding new palladium(II)‐NHC complexes with the general formula [PdX2(NHC)2], (NHC = N‐heterocyclic carbene, X = Cl or Br), and also their catalytic activity in direct C‐H bond arylation of 2‐substituted furan derivatives with aryl bromides and aryl chlorides. Under the optimal conditions, these palladium(II)‐NHC complexes showed the good catalytic performance for the direct C‐H bond arylation of 2‐substituted furans with (hetero)aryl bromides, and with readily available and inexpensive aryl chlorides. The C‐H bond arylation regioselectively produced C5‐arylated furans by using 1 mol% of the palladium(II)‐NHC catalysts in moderate to high yields. 相似文献
38.
《应用有机金属化学》2017,31(10)
A series of symmetrically n ‐alkyl‐substituted mono benzimidazolium salts with steady increase in n ‐alkyl chain length have been prepared by stepwise N ‐alkylation resulting in salts ( 1 – 8 ). The mono N‐heterocyclic carbene (NHC)–Ag(I) complexes ( 9 – 16 ) derived from the respective salts were readily accessible by in situ deprotonation using Ag2O. All the salts and the complexes were characterized using Fourier transform infrared, 1H NMR, 13C NMR and elemental analyses. Furthermore, the structures of salts 3 and 7 and complex 16 were elucidated using X‐ray crystallography, which established that this mono NHC–Ag(I) complex has a linear bis‐carbene arrangement (C2–Ag). The proligands and the respective Ag(I) complexes were studied for their in vitro anticancer potential against human colon cancer cell line (HCT‐116) using 5‐fluorouracil as a standard. From the IC50 values of all the tested compounds, it can be postulated that there is an influential relationship between the increase in chain length of the wingtip n ‐alkyl groups and the anticancer potential. The proligands 4 – 8 and their respective complexes 12 – 16 with long n ‐alkyl chain lengths (n = 6–10) showed better IC50 values (0.3–3.9 μM) than the standard drug with the complexes displaying markedly better antiproliferation activity against HCT‐116 cell line than the respective proligands and the standard drug (IC50 = 10.2 μM). 相似文献
39.
A comparative study of hydroxyl‐ and carboxylate‐functionalized imidazolium and benzimidazolium salts as precursors for N‐heterocyclic carbene ligands
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The preparation of imidazolium and benzimidazolium salts with hydroxyl or carboxylate functions has been achieved using straightforward synthetic pathways. These salts in combination with palladium(II) acetate give active catalytic systems for Suzuki reaction. A comparative study has been performed, which has revealed that both the heterocycle and the functional group are important for the catalytic activity and stability of the catalyst. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
40.
Bis‐benzimidazolium salt 1 was prepared via a series of reactions using 2,2′‐diphenol as starting material. Compound 2 was afforded through the intramolecular C? C coupling reaction of 1 under the catalysis of Pd(OAc)2. The structure of 2 is characterized through X‐ray diffraction analyses, 1H NMR and 13C NMR. In 2 , two boat‐like seven‐membered rings are contained, where the C? C bond distance newly formed is 1.461(5) Å, and it is between regular C? C single bond (1.54 Å) and C?C double bond (1.34 Å). This shows that new C? C bond has partial double‐bond character. In the crystal packing of 2 , the 2D supramolecular layers are formed via C? H···F hydrogen bond. 相似文献