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71.
Li-NH3 reduction of 1α-Ethynyl-1β-hydroxy-6-oxo-8a-methyl-1,2,3,4,6,7,8,8a octahydronaphthalene 5 furnishes, in addition to reported products, the tricyclic compound . 相似文献
72.
Lourdusamy Emmanuvel Suryavanshi Gurunath Swaminathan Sivaram 《Tetrahedron letters》2006,47(28):4793-4796
A new reagent system consisting of NaIO4/KI/NaCl in aq AcOH has been found to be effective in iodinating a variety of activated aromatic substrates via in situ-generated iodine monochloride, to furnish iodoaromatics in excellent yields. This iodination procedure has been applied successfully for a cost-effective synthesis of 3,3′-diaminobenzidine, a key intermediate for preparing proton conducting membranes for fuel cell applications, with high yield and a purity of 99.7%. 相似文献
73.
74.
75.
The title compound has been synthesised via an alkylation, Wittig-Horner reaction sequence, Michael addition of several active methylene substrates with compound 1 has been carried out. 相似文献
76.
Whitney's theorem on 2-isomorphism characterizes the set of graphs having the same cycles as a given graph, where a cycle is regarded as a set of edges. In this paper, vertex 2-isomorphism is defined and used to prove a vertex analogue of Whitney's theorem. The main theorem states that two connected graphs have the same set of cycles, where a cycle is now regarded as a set of vertices, if and only if one can be obtained from the other by a sequence of simple operations. © 1992 John Wiley & Sons, Inc. 相似文献
77.
We consider the analogy between torsion line defects and vortex lines in a superconductor to suggest that the electric charge and masses of elementary particles may have a geometrical origin. Just as the field vanishes everywhere in a superconductor except along the vortex line, where the flux is confined, we have the torsion being concentrated only along the topological defects, giving rise to charge as well as mass. The mass is related to the string tension (c
2/G) and charge is connected with the gravitational permeability (G/c
2), both induced by torsion. 相似文献
78.
Israel V. Muthu Vijayan Enoch Meenakshisundaram Swaminathan 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3):149-154
The absorption and fluorescence spectral characteristics of 2-aminodiphenylsulphone (2ADPS) have been investigated in the presence of β-cyclodextrin (β-CDx) in water. Dual emission is observed upon the complexation of 2ADPS in β-CDx. The stoichiometry of the host:guest inclusion complex is found to be 2:1. Steady state and time-resolved fluorescence spectral analysis support the formation of 2:1 complex between β-CDx and 2ADPS. The large enhancement in fluorescence intensity of twisted intramolecular charge transfer (TICT) band in aqueous β-CDx solution is due to the decrease in non-radiative processes. The ground and the excited state pKa values for the monocation-neutral equilibrium of 2ADPS in β-CDx are found to be different from the pKa values in aqueous solution. In the presence of β-CDx, 2ADPS is found to be less basic in the ground and the excited states. 相似文献
79.
Rudhramyna GnaneshwarPrakash P. Wadgaonkar Swaminathan Sivaram 《Tetrahedron letters》2003,44(32):6047-6049
The Michael addition of a β,β-dimethyl substituted silyl ketene acetal [Me2CC(OMe)OSiMe3] to α,β-unsaturated ketones, namely, 2-cyclopentenone, 2-cyclohexenone, 3-methyl-2-cyclohexenone, isophorone, methyl vinyl ketone and mesityl oxide occurs smoothly in the presence of the nucleophilic catalyst, tetra-n-butyl ammonium bibenzoate (TBABB) in THF giving the corresponding 1,4-adducts in excellent yields. 相似文献
80.
A new model for the aether is suggested according to which it is a superfluid state of fermion and antifermion pairs, describable by a macroscopic wave function. The vacuum state of this superfluid pervades the entire universe and may account for the missing matter. The visible matter in the universe appears as excitations from the underlying superfluid vacuum. 相似文献