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排序方式: 共有285条查询结果,搜索用时 62 毫秒
61.
Subhash P. Chavan Pallavi Sharma R. Sivappa Uttam R. Kalkote 《Tetrahedron letters》2006,47(52):9301-9303
An efficient utilisation of RCM leading to a convenient synthesis of a pentacyclic indole alkaloid is described. 相似文献
62.
Direct Conversion of Alcohols into Alkenes by Dehydrogenative Coupling with Hydrazine/Hydrazone Catalyzed by Manganese 下载免费PDF全文
Dr. Uttam Kumar Das Dr. Subrata Chakraborty Dr. Yael Diskin‐Posner Prof. David Milstein 《Angewandte Chemie (International ed. in English)》2018,57(41):13444-13448
We have developed unprecedented methods for the direct transformation of primary alcohols to alkenes in the presence of hydrazine, and for the synthesis of mixed alkenes by the reaction of alcohols with hydrazones. The reactions are catalyzed by a manganese pincer complex and proceed in absence of added base or hydrogen acceptors, liberating dihydrogen, dinitrogen, and water as the only byproducts. The proposed mechanism, based on preparation of proposed intermediates and control experiments, suggests that the transformation occurs through metal–ligand cooperative N?H activation of a hydrazone intermediate. 相似文献
63.
K Bhaumik 《Journal of chromatography. A》1991,571(1-2):37-46
A combination of DEAE-cellulose chromatography and reversed-phase high-performance liquid chromatography (HPLC) has been used to devise a method for generating large quantities of embryonic as well as fetal globin chains. The identity of these globin chains was further confirmed by their tryptic peptide mapping. This technique could, therefore, provide a reliable source for these polypeptides for both analytical and immunological purposes. Moreover, the study of human hemoglobin switching, particularly embryonic to fetal, has been greatly hampered by the absence of a suitable model. K562 cells, due to their potential for differential induction of embryonic and fetal hemoglobin synthesis, can thus be used for this purpose and the various hemoglobins produced can then be effectively monitored using this method. 相似文献
64.
An enantiospecific synthesis of (+)-isoparvifolinone and (−)-parvifoline, from naturally occurring (R)-(+)-citronellal, employing intramolecular Friedel-Crafts acylation as the key step, is described. 相似文献
65.
66.
Formal synthesis of (±)-camptothecin via CDE tricyclic lactone employing tandem Michael addition, Dieckmann condensation and addition-elimination reaction as key steps starting from glycinate is described. 相似文献
67.
Phase pure, stable nanocrystalline brushite particles with average diameter in the range of 23–87 nm were obtained by the
reverse microemulsion technique employing a mixture of surfactants (Aliquat 336 & Tween 80) as template directing agents,
and calcium nitrate tetrahydrate and biammonium hydrogen phosphate as precursors. Particle sizes and morphologies were tuned
by adjusting the reaction parameters, precursor concentration and temperature. FTIR, TEM, and XRD were used to characterize
morphological changes of as synthesized nanoparticles. FTIR and XRD analyses confirmed the formation of brushite nanoparticles.
Variations in the reaction temperature resulted in changes in the particle morphology and distribution. At high temperatures
(60°C), the sample exhibited high monodispersity and spherical morphology with the average grain size of 42 nm. At low temperatures
(6°C), nanoflakes were formed. The results suggest that a reverse microemulsion system provides facile media for control of
the phase and morphology of nanoscale calcium phosphate biominerals. A mechanism providing an insight into the formation of
brushite particles has also been proposed. 相似文献
68.
Dutta D Jana AD Debnath M Bhaumik A Marek J Ali M 《Dalton transactions (Cambridge, England : 2003)》2010,39(48):11551-11559
Two novel organic-inorganic hybrid tungsto- and molybdo-telurates having formula [{Na(4)(H(2)O)(14)}{Cu(gly)}(2)][TeMo(6)O(24)] (1){gly = glycine} and [{Cu(en)(2)}(3){TeW(6)O(24)}]·6H(2)O {en = ethyline-diamine} (2) based on Anderson type heteropolyoxometalates (POMs) have been synthesized and characterized by X-ray crystallography. Common structural feature of both 1 and 2 is the presence of a unique 1D open rack-like architecture, where the disc shaped Anderson POMs act as steps and cationic Cu-organic complexes act as handles of the rack. In 1 the independent structural unit is a 1D coordination polymer with the above mentioned rack type architecture, while in 2, these independent rack-like architectures are further extended to a 2D coordination polymer. Heterogeneous catalysis for the epoxidation of cyclohexene and styrene by complexes 1 and 2 showed very good catalytic efficiency resulting epoxides of ~60% yield, with dialcohol formed by the hydrolysis of epoxides, as the other major product (~28%). Cyclic voltammetric studies of [{Na(4)(H(2)O)(14)}{Cu(gly)}(2)][TeMo(6)O(24)] (1) in aqueous KCl solution indicates that the redox changes occur only on the copper centers and supported by carrying out parallel experiments on the precursors like ([Cu(gly)(2)](2+) and [TeMo(6)O(24)](6-), under the identical experimental conditions. The E(1/2) = 0.662, -0.142 and -0.332 V(vs. SCE) correspond to Cu(III) → Cu(II), Cu(II) → Cu(I) and Cu(I) → Cu(0) reductions, respectively. Thermal analyses reveal identical phase transition reactions with an exothermic peak in the DTA curve at 380 °C for 1 and an endothermic peak appears at comparatively higher temperature (408 °C) for 2 manifesting the higher stability of tungstane based POM over the molybdenum ones. EPR as well as magnetic moment results indicate that both the complexes 1 and 2 are paramagnetic with one unpaired electron per copper(II) ion. 相似文献
69.
P. Kumar S. Moorthy Babu S. Perero Rajamaniccam L. Sai I. Bhaumik S. Ganesamoorthy A. K. Karnal 《Pramana》2010,75(5):1035-1040
Congruent LiNbO3 single crystals with Ti ion dopants (2 and 5 mol%) were successfully grown by Czochralski technique in the automatic diameter
control facility. As-grown crystal boules were oriented into (0 0 1) direction cut and optically polished for all measurements.
Influence of Ti-ion incorporation into LiNbO3 was studied by core level XPS analysis. Powder X-ray diffraction studies were carried out on doped lithium niobate for phase
identification. High-resolution X-ray diffraction technique was used to study the crystalline quality through full-width at
half-maximum values. The refractive index values are more for doped samples than for pure sample as determined by prism coupling
technique with different laser sources. 相似文献
70.
Nicolas Droushiotis Mohd Hafiz Dzarfan Othman Uttam Doraswami Zhentao Wu Geoff Kelsall Kang Li 《Electrochemistry communications》2009,11(9):1799-1802
Novel CGO/NiO–CGO dual-layer hollow fibres (HFs) have been fabricated in a single-step co-extrusion and co-sintering process. LSCF–CGO cathodes layers were then deposited onto the dual-layer HFs to construct micro-tubular SOFCs. The NiO in the micro-tubular HF–SOFCs was reduced at 550 °C using hydrogen gas to form Ni anodes. Scanning electron microscope images showed that the dual-layer HFs have porous anodes and dense electrolyte layers. Preliminary measurements with a HF–SOFC fed with H2 and atmospheric oxygen, produced maximum power densities of 420 W m−2 and 800 W m−2 at 450 °C and 550 °C, respectively. 相似文献