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1.
[reaction: see text] Palladium-catalyzed directed C-H activation/oxygenation reactions have been explored in a series of meta-substituted aryl pyridine and aryl amide derivatives. These transformations tolerate a diverse array of electron-donating and electron-withdrawing meta-substituents and generally proceed with high levels of regioselectivity for functionalization of the less sterically hindered ortho-C-H bond. 相似文献
2.
Navamoney Arulsamy Chepuri R. K. Rao Panthappally S. Zacharias 《Transition Metal Chemistry》1991,16(6):606-609
Summary Condensations of Cu(L-ser)2 and Cu(L-thr)2 (where L-ser=L-serinato anion and L-thr=L-threoninato anion) with formaldehyde at pH 4.5 yield two new optically active products:bis[L-(oxazolidine-4-carboxylato)]-copper(II) monohydrate (1) andbis[L-(N-hydroxymethyl-5-methyloxazolidine-4-carboxylato)]copper(II) dihydrate (2), respectively. Cu(D-ser)2 and Cu(D-thr)2 also undergo similar reactions. The new products are different from the products obtained from Cu(DL-ser)2 and Cu(DL-thr)2, and a mechanism has been suggested to explain the stereospecificity of these conversions. Condensation of Cu(L-ser)2 with formaldehyde and ammonia at pH 4.5 yields the new product, [3N,7N-(1,3,5,7-tetraazabicyclo-[3.3.1]nonyl)di(hydroxymethyl)-acetato]copper(II), (3). The compexes have been characterized by analytical and by i.r. electronic and c.d. spectral data. Complexes (1) and (2) undergo a reversible CuII/CuI redox process in aqueous media at –0.18 Vversus s.c.e.; complex (3) exhibits irreversible CuII/CuI reduction at –0.49 V confirming the presence of a rigid pentamethylenediaza-bridged ligand system. 相似文献
3.
4.
This paper describes a method for nickel catalyzed intramolecular C–H arylation using aryl pivalates as electrophiles. The transformation is efficient for the synthesis of diverse electronically and sterically differentiated dibenzofurans. Additionally, the method could be expanded toward the synthesis of carbazoles. Preliminary mechanistic studies of the transformation are also described. 相似文献
5.
S. Chitra P. Kalyani T. Mohan M. Massot S. Ziolkiewicz R. Gangandharan M. Eddrief C. Julien 《Ionics》1998,4(1-2):8-15
A moderate-temperature method of preparation of the spinel LiMn2O4 was developed around 500 °C. Physical features of the products were identified by X-ray photoelectron spectroscopy, X-ray
diffractometry, Raman scattering and FTIR spectroscopy. The electronic conductivity of LiMn2O4 has been studied as a function of annealing temperature. The product LiMn2O4 is identified as a micron-sized powder and analysis of the local environment is in good accordance with the classical structural
model of Fd3m space group. LiMn2O4 exhibits an electrical conductivity of 1.9×10−5 S/cm at room temperature with an activation energy of 0.16 eV which corresponds to an electron hopping mechanism between
the two charge states of Mn3+ and Mn4+ ions. A first-order phase transition is observed at 292 K. 相似文献
6.
7.
We present a highly selective and sensitive method for the determination of cysteine (Cys) and related aminothiols that play important roles in health and disease. The key step in the analysis is treatment with 1,1′-thiocarbonyldiimidazole (TCDI) that rapidly and quantitatively reacts with both the amino and thiol groups to form stable cyclic dithiocarbamates with intense UV absorption. Cys, homocysteine (hCys), and cysteinylglycine in plasma (75 μl), urine (100 μl), or cerebrospinal fluid (100–500 μl) were determined by separating and measuring their cyclic derivatives by a high performance liquid chromatograph (HPLC) connected to a UV detector. The chromatograms obtained using TCDI contained fewer and better-resolved peaks than those produced by less selective reagents used previously. Using chemically similar 2-methylcysteine as the internal standard, high repeatability (variation of less than 5%) and adequate sensitivity to detect small increments (10–20%) in the concentrations of cysteinylglycine and hCys were achieved. The HPLC method can also be modified to measure
-penicillamine (greater than 0.8 μM) in plasma (50 μl) providing a potential method to monitor plasma levels of this drug in patients. 相似文献
8.
Shankaraiah Malthum Naveen Polkam Tejeswara Rao Allaka Kalyani Chepuri Jaya Shree Anireddy 《Tetrahedron letters》2017,58(44):4166-4168
We present a convenient route for the synthesis of C6-amino-C5′-N-cyclopropyl carboxamido-C2-alkynylated purine nucleoside analogues 11a–g via Sonogashira coupling reaction. The nine step synthesis is easy to perform, employing commercially available reagents. Compound 9 is used as key intermediate for the synthesis of analogues 11a–g. Synthetic intermediates and final products are appropriately characterized by IR, 1H NMR, 13C NMR and Mass. The modified nucleoside analogues 11a–g is evaluated for in vitro anticancer activity against MDA-MB-231 and Caco-2 cell lines. Screening data reveals that compounds 11b and 11e displayed potent IC50 value of 7.9, 6.8 µg/mL respectively against MDA-MB-231 and of 7.5, 8.3 µg/mL respectively against Caco-2 than the standard drug doxorubicin, thus establishing the potential anti-cancer properties of these newer derivatives. 相似文献
9.
Exact solutions of the field equations of Nordtvedt’s theory for spatially flat FRW models with constant deceleration parameter
have been obtained. Singular solutions with (i) power-law (ii) exponential expansion have been studied in Nordtvedt’s theory
where the coupling parameterω is a function of the scalar fieldφ. 相似文献
10.
Kalyani Desikan 《General Relativity and Gravitation》1997,29(4):435-443
The effect of bulk viscosity, with a time varying bulk viscous coefficient, on the evolution of frw models is investigated in the context of open thermodynamic systems, which allows for particle creation. It is seen that, by choosing an appropriate function for particle creation, the models presented exhibit non-singular beginnings. 相似文献