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981.
982.
R.B. Yadav 《Solid State Communications》1983,47(4):267-268
The probabilities for recoilless resonant absorption of 23.8 keV γ-rays by 119Sn in matrices of vanadium, platinum and niobium have been calculated in the temperature ranges 80–400 K. The calculated results show a good agreement with the experimental data. 相似文献
983.
The review covers the phytochemistry and pharmacology of furanoflavonoids describing 291 compounds and containing 228 references. 相似文献
984.
The diastereoselectivities of tricyclo(5.2.1.0(2,6))decan-10-one and its derivatives are controlled by antiperiplanar and vicinal sigma --> piC=O interactions rather than the hyperconjugation effects as reported previously. 相似文献
985.
Phase diagram studies in two-surfactant ternary systems employing positron annihilation spectroscopy
Positron annihilation lifetime parameters in condensed media are sensitive to structural and conformational changes. This property has been exploited to study the phase diagrams of two ternary cationic surfactant systems. Positron lifetime measurements were performed in cetyltrimethylammonium bromide (CTAB)/water/hexanol and tetradecyltrimethylammonium bromide (TTAB)/water/pentanol systems having varying concentrations of hexanol and pentanol respectively. For both the systems, changes were observed in the positron lifetime parameters whenever a phase transformation occurred. The various phase boundaries demarcated by this technique agrees well with those obtained by other conventional techniques. Besides this, the present work suggests the existence of two kinds of lamellar structures referred to as DI and DII phases in both the systems, which were otherwise considered to be a single D phase by other conventional techniques. The existence of such lamellar structures has been demonstrated by a change in the trend of o-Ps lifetime when the system passes from one type of lamellar structure to the other type. The results of these investigations are presented. 相似文献
986.
987.
Dhananjay Yadav Gaurav Shukla Monish A. Ansari Abhijeet Srivastava Maya Shankar Singh 《Tetrahedron》2018,74(40):5920-5931
An operationally simple and efficient one-pot method for the synthesis of 1-aroyl (or alkanoyl)-2-thioalkyl-3-aryl (or alkyl)-3H-benzo[e]indole-4,5-diones and naphtho[2,1-b]thiophene-4,5-diones has been devised by copper-catalyzed cross-coupling of α-oxoketene N,S-acetals/β-ketothioamides with α-/β-naphthols in open air for the first time. The key to the success of this transformation is the room temperature oxidation of α-/β-naphthol to 1,2-naphthoquinone as a reactive species, which undergoes formal [3 + 2] annulation with α-oxoketene N,S-acetals/β-ketothioamides via cascade sequence of Michael addition/tautomerization/oxidation/cyclization/aromatization reactions, enabling addition of a pyrrole/thiophene ring onto naphthoquinone moiety. Further, benzo[e]indole-4,5-diones were transformed to pentacyclic fused phenazine derivatives under solvent-free conditions. Based on our experimental outcomes, a tentative mechanistic rationale for this chemoselective protocol is proposed, which is well validated and supported by the control experiments. 相似文献
988.
Manjula Singh Arvind K. Yadav Lal Dhar S. Yadav Rana Krishna Pal Singh 《Tetrahedron letters》2018,59(33):3198-3201
A convenient and straightforward synthesis of 6-sulfonylated phenanthridines via silver-catalyzed sequential radical insertion, cyclization and aromatization of 2-isocyanobiphenyls is reported. The protocol does not require a phenanthridine scaffold as a substrate and presents a highly regioselective synthesis of 6-alkyl/arylsulfonyl phenanthridines. The protocol utilizes readily available and easy to handle sodium sulfinates as sulfonating agents and potassium persulfate as an oxidant to afford good to excellent yields of the desired products in a one-pot operation at room temperature. 相似文献
989.
Gavireddy Chaithanya Kumar Katta Muralikrishna Vavilapalli Satyanarayana Chintakrinda Suresh Kumar Jhillu Singh Yadav 《Tetrahedron letters》2018,59(5):454-456
A synthetic approach toward the phostriecin, an antitumor natural product is described. The key features of the present synthesis are Wittig reaction, synthesis of homoallylic alcohol using Brown’s protocol (alkoxyallylboration) and RCM for the creation of unsaturated lactone moiety of phostriecin. 相似文献
990.
The present work concerns with the investigation of the effect of dispersion of Silica (SiO2) nanoparticles (NPs) in host ferroelectric liquid crystal (FLC) KCFLC10S on the dielectric and electro-optical properties and ultraviolet-visible (UV-VIS) absorption spectra of the pristine and dispersed systems. We have found that the dispersion of SiO2 NPs in the host FLC strongly influences the various properties of dispersed systems. No evidence of aggregates and clumps in the dispersed system has been observed. Due to SiO2 NPs dispersion, a rapid decrease in dielectric permittivity ε’, increase in conductivity σ with frequency, increase in spontaneous polarisation Ps and decrease in switching time with bias voltage have been observed. Based on the absorption spectra, we have also made an attempt to link the electro-optical and dielectric response with the mechanism of FLC–NPs interactions. 相似文献