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41.
Indira Fabre Niklas von Wolff Dr. Gaëtan Le Duc Dr. Emmanuel Ferrer Flegeau Dr. Christian Bruneau Prof. Pierre H. Dixneuf Dr. Anny Jutand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7595-7604
The activation of the C? H bond of 1‐phenylpyrazole ( 2 ) and 2‐phenyl‐2‐oxazoline ( 3 ) by [Ru(OAc)2(p‐cymene)] is an autocatalytic process catalyzed by the co‐product HOAc. The reactions are indeed faster in the presence of acetic acid and water but slower in the presence of a base K2CO3. A reactivity order is established in the absence of additives: 2‐phenylpyridine>2‐phenyl‐2‐oxazoline>1‐phenylpyrazole (at RT). The accelerating effect of added acetate ions reveals an intermolecular deprotonation after C? H bond activation by a cationic RuII center (SE3 mechanism). The reactions of 1‐phenylpyrazole and 2‐phenyl‐2‐oxazoline first lead to the neutral cyclometalated complexes A2 and A3 ligated by one acetate. The latter dissociate to the cationic complexes B2 + and B3 + , respectively, and acetate. A slow incorporation of one or two D atoms into 2 , 3 , and 2‐phenylpyridine ( 1 ) was observed in the presence of deuterated acetic acid. The “reversibility” of the C? H bond activation/deprotonation takes place from the cationic complexes B n + (n=1–3). They are also involved in oxidative additions to PhI, which are rate‐determining and lead to the mono‐ and bis‐phenylated products at high temperatures. A general mechanism is proposed for the arylation of arenes 1–3 catalyzed by [Ru(OAc)2(p‐cymene)]. In contrast, the reaction of Pd(OAc)2 with 2‐phenylpyridine ( 1 ), is much faster: Pd(OAc)2>[Ru(OAc)2(p‐cymene)]. Since the kinetics is not affected by added acetates, the reaction proceeds through a CMD mechanism assisted by a ligated acetate (intramolecular process) and is irreversible. A bis‐cyclometalated PdII^PdII dimer D′1 is formed whose bielectronic electrochemical oxidation leads to a [PdIII^PdIII]2+ dimer, in agreement with the result of a reported chemical oxidation used in arene functionalizations catalyzed by Pd(OAc)2. 相似文献
42.
Fluorescence spectroscopic studies on binding of a flavonoid antioxidant quercetin to serum albumins
Beena Mishra Atanu Barik K. Indira Priyadarsini Hari Mohan 《Journal of Chemical Sciences》2005,117(6):641-647
Binding of quercetin to human serum albumin (HSA) was studied and the binding constant measured by following the red-shifted
absorption spectrum of quercetin in the presence of HSA and the quenching of the intrinsic protein fluorescence in the presence
of different concentrations of quercetin. Fluorescence lifetime measurements of HSA showed decrease in the average lifetimes
indicating binding at a location, near the tryptophan moiety, and the possibility of fluorescence energy transfer between
excited tryptophan and quercetin. Critical transfer distance (R
o
) was determined, from which the mean distance between tryptophan-214 in HSA and quercetin was calculated. The above studies
were also carried out with bovine serum albumin (BSA). 相似文献
43.
44.
Suárez-Castillo OR Meléndez-Rodríguez M Beiza-Granados L Cano-Escudero IC Morales-Ríos MS Joseph-Nathan P 《Natural product communications》2011,6(4):451-456
An efficient route to natural occurring methyl 6-bromoindolyl-3-acetate 1c from methyl indolyl-3-acetate 3 was achieved in 3 steps and 68% overall yield. Thus, in order to regioselectively brominate 3 at the C6-position, introduction of electron withdrawing substituents at N1 and C8 was affected to give intermediate 4 in 82% yield. Bromination of 4 with 8 equiv of bromine in CCl4 and washings with aqueous Na2SO3 gave 5 in 86% yield, which was N- and C-decarbomethoxylated by treatment with NaCN in DMSO, affording 1c in 97% yield. The regioselectivity of bromination was evidenced by NMR spectroscopy and X- ray diffraction analysis. 相似文献
45.
Gupta SC Prasad S Kim JH Patchva S Webb LJ Priyadarsini IK Aggarwal BB 《Natural product reports》2011,28(12):1937-1955
Curcumin (diferuloylmethane), the active ingredient in turmeric (Curcuma longa), is a highly pleiotropic molecule with anti-inflammatory, anti-oxidant, chemopreventive, chemosensitization, and radiosensitization activities. The pleiotropic activities attributed to curcumin come from its complex molecular structure and chemistry, as well as its ability to influence multiple signaling molecules. Curcumin has been shown to bind by multiple forces directly to numerous signaling molecules, such as inflammatory molecules, cell survival proteins, protein kinases, protein reductases, histone acetyltransferase, histone deacetylase, glyoxalase I, xanthine oxidase, proteasome, HIV1 integrase, HIV1 protease, sarco (endo) plasmic reticulum Ca(2+) ATPase, DNA methyltransferases 1, FtsZ protofilaments, carrier proteins, and metal ions. Curcumin can also bind directly to DNA and RNA. Owing to its β-diketone moiety, curcumin undergoes keto-enol tautomerism that has been reported as a favorable state for direct binding. The functional groups on curcumin found suitable for interaction with other macromolecules include the α, β-unsaturated β-diketone moiety, carbonyl and enolic groups of the β-diketone moiety, methoxy and phenolic hydroxyl groups, and the phenyl rings. Various biophysical tools have been used to monitor direct interaction of curcumin with other proteins, including absorption, fluorescence, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy, surface plasmon resonance, competitive ligand binding, Forster type fluorescence resonance energy transfer (FRET), radiolabeling, site-directed mutagenesis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), immunoprecipitation, phage display biopanning, electron microscopy, 1-anilino-8-naphthalene-sulfonate (ANS) displacement, and co-localization. Molecular docking, the most commonly employed computational tool for calculating binding affinities and predicting binding sites, has also been used to further characterize curcumin's binding sites. Furthermore, the ability of curcumin to bind directly to carrier proteins improves its solubility and bioavailability. In this review, we focus on how curcumin directly targets signaling molecules, as well as the different forces that bind the curcumin-protein complex and how this interaction affects the biological properties of proteins. We will also discuss various analogues of curcumin designed to bind selective targets with increased affinity. 相似文献
46.
Samples of polystyrene films were irradiated under vacuum at room temperature with 58Ni7+ (86 MeV) ion with fluences ranging from 1 × 1011 to 1 × 1013 ions cm−2. Ion induced structural modifications were studied by means of atomic force microscopy atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visible absorption spectroscopy (UV-Vis) and Fourier transform infrared spectroscopy (FTIR) techniques. Atomic force microscopy shows that the root mean square (RMS) roughness of the irradiated polystyrene surface increases with the increment of ion fluence. XRD analysis reveals that in addition to the increase of amorphization of polymer with the increase of ion fluence there is also an increase of ordering (to a small extent) in some of the micro-domains. These results have further been supported by the study of optical and chemical analysis. The analysis of present study shows that the increase of full width at half maximum (FWHM) of first peak of XRD spectra, decrease of optical band gap and the formation of new alkyne group may be attributed to the increase of amorphization of polystyrene. Similarly, sharpening of second X-ray diffraction peak, decrease of Urbach’s energy and increase in the absorbance ratio of I1222/I1183 may be owed to the increase of ordering in some domains. 相似文献
47.
In this paper, we establish the approximate controllability results for a non-autonomous functional differential equation using the theory of linear evolution system, Schauder fixed point theorem, and by making use of resolvent operators. The results obtained in this paper, improve the existing ones in this direction, to a considerable extent. An example is also given to illustrate the abstract results. 相似文献
48.
Indira S. Vinoth G. Bharathi M. Ramachandran R. Shanmuga Bharathi K. 《Research on Chemical Intermediates》2021,47(7):3051-3065
Research on Chemical Intermediates - A new class of mixed ligand complexes, [M(L)(phen)2], using a bidentate bischlorophenol ligand H2L (2,2′-methylenebis(4-chlorophenol)) and phenanthroline... 相似文献
49.
Transition‐Metal‐Free α‐Arylation of Enolizable Aryl Ketones and Mechanistic Evidence for a Radical Process 下载免费PDF全文
Martin Pichette Drapeau Indira Fabre Dr. Laurence Grimaud Dr. Ilaria Ciofini Prof. Dr. Thierry Ollevier Dr. Marc Taillefer 《Angewandte Chemie (International ed. in English)》2015,54(36):10587-10591
The α‐arylation of enolizable aryl ketones can be carried out with aryl halides under transition‐metal‐free conditions using KOtBu in DMF. The α‐aryl ketones thus obtained can be used for step‐ and cost‐economic syntheses of fused heterocycles and Tamoxifen. Mechanistic studies demonstrate the synergetic role of base and solvent for the initiation of the radical process. 相似文献
50.
K. Indira Priyadarsini T. P. A. Devasagayam M. N. A. Rao S. N. Guha 《Radiation Physics and Chemistry》1999,54(6):147-558
Free radical reactions of dehydrozingerone (DZ), a methoxy phenol, were studied at dfferent pHs with a variety of oxidants using nanosecond pulse radiolysis technique. Hydroxyl radical (OH) reaction with the phenolic form at pH 6 led mainly to the formation of an OH-adduct absorbing at 460 nm in addition to a minor oxidation product. On the other hand, at pH 10 with the deprotonated phenoxide ion, the only reaction observable was oxidation generating a phenoxyl radical absorbing at 360 nm. HPLC analysis indicated formation of two different products at pH 6 from addition and oxidation reactions, whereas at pH 10, only the oxidation product was detectable. Reactions of more specific secondary oxidizing radicals, N3√, Br√, Br−2√ and Tl(II) with DZ gave rise to the phenoxyl radical over the entire pH range. DZ in the phenoxide ion form reacted with nitrogen dioxide and trichloromethyl peroxyl radicals with rate constants 6×108 and 8.8×108 dm3 mol−1 s−1 respectively leading to the phenoxyl radicals. The DZ phenoxyl radical reacted with trolox C (an analogue of -tocopherol) with a rate constant of 8.3×107 dm3 mol−1 s−1. One electron reduction potential of the DZ phenoxyl radical at pH 6 was determined to be +1.1 V vs NHE using N3√/N−3 as the standard couple. 相似文献