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991.
Gowravaram Sabitha Chintam Nagendra ReddyAtla Raju Jhillu Singh Yadav 《Tetrahedron: Asymmetry》2011,22(4):493-498
A highly stereoselective synthesis of the naturally occurring lactone (−)-spicigerolide has been achieved utilizing OsO4-catalyzed dihydroxylation, CBS, Lindlar’s reductions, Still-Gennari, and Grignard reactions as the key reaction steps. 相似文献
992.
P. Ashok Yadav G. Suresh K. Rajendra Prasad M. Suri Appa Rao K. Suresh Babu 《Tetrahedron letters》2012,53(7):773-777
Two novel phragmalin type limonoids have been isolated from the bark of Soymida febrifuga and their structures were fully established on the basis of spectroscopic (especially 2D NMR) and spectrometric (mass spectrometry) data, respectively. These novel secondary metabolites possessed β-furyl ring and an ortho ester functionality and their biosynthetic origin was proposed to be the phragmalin-type limonoids. 相似文献
993.
994.
995.
Manjula Singh Arvind K. Yadav Lal Dhar S. Yadav R.K.P. Singh 《Tetrahedron letters》2018,59(5):450-453
A convenient, highly selective and metal-free synthesis of sulfoxides from alkenes and thiols using NHPI as an inexpensive and reusable organophotoredox catalyst is reported. The protocol involves radical thiol-ene/oxidation reaction cascade and utilizes visible light and air (O2) as inexpensive, readily available, non-toxic and eco-sustainable reagents to afford up to 96% yields of the product at room temperature. 相似文献
996.
A simple three step synthesis of 4-alkyl-γ-butanolides as flavoring compounds from chiral propargyl alcohols is described. 相似文献
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998.
JPC – Journal of Planar Chromatography – Modern TLC - Premna integrifolia is an important constituent of the famous herbal formulation “Dashmool” of the Indian Ayurvedic... 相似文献
999.
Amarjeet Yadav 《Molecular physics》2014,112(8):1063-1070
Polycyclic aromatic hydrocarbons (PAHs) form an important class of molecules as they are ubiquitous, pollute air and cause severe health problems. Lowest vertical π–π* singlet–singlet or triplet–triplet excitation energies and corresponding oscillator strengths were studied for several linear and two-dimensional PAHs employing time-dependent density functional theory. Excited-state electron density, molecular electrostatic potential (MEP) and spin density distributions in the PAHs, along with ground-state chemical hardness, were also studied. It has been found that, generally, excitation energies and oscillator strengths decrease with increase in PAH size, and excitation energies and chemical hardness are strongly linearly correlated. Enhanced electron density edge effect, which was found to occur in the ground states of the molecules, continues to hold in their excited states also. A strong similarity between the ground and π–π* excited-state MEP maps suggests that σ electrons are the main contributors to the enhanced electron density at the edges. Due to their strong electronic absorption transitions in the visible and infrared regions, the PAHs can be used for harnessing solar energy efficiently. 相似文献
1000.
The ultrasonic attenuation and acoustic coupling constants due to phonon–phonon interaction and thermoelastic relaxation mechanisms have been studied for longitudinal and shear waves in B1 structured neptunium monochalcogenides NpX (X: S, Se, Te) along 〈1 0 0〉 direction in the temperature range 100–300 K. The second and third order elastic constants (SOEC and TOEC) of the chosen monochalcogenides are also computed for the evaluation of ultrasonic parameters. The ultrasonic attenuation due to phonon–phonon interaction process is predominant over thermoelastic relaxation process in these materials. The ultrasonic attenuation in NpTe has been found lesser than other materials NpS, NpSe and GdY (Y: P, As, Sb and Bi). The semiconducting or semimetallic nature of neptunium monochalcogenides can be well understood with the study of thermal relaxation time. Total ultrasonic attenuation in these materials is found to be quadratic function of temperature. The nature of NpTe is very similar to semimetallic GdP. The mechanical and ultrasonic study indicates that NpTe is more reliable, perfect, flawless material. 相似文献