Efficient synthesis and structure peculiarity of macrocycles with bi-indolizinylquinoxalinone moieties

Monoindolizinylquinoxalinepodands, easily available from indolizinylquinoxalines and various dihalides, undergo smooth oxidative dimerization in the presence of molecular iodine to afford corresponding macrocycles in good yields in a short reaction time. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical. In solution the title macrocycles exist in an equilibrium of several conformations arising from restricted rotation around the Ind–Qx bonds (ca. C₂ symmetrical and nonsymmetrical forms). The population of the forms and exchange rate between them depends strongly on the spacer type (length).     

Critical Comment on “Numerical solution of Bloch–Gruneisen function to determine the contribution of electron–phonon interaction in polycrystalline MgB2 superconductor” by Intikhab A. Ansari [Physica C: Superconductors, 470 (2010) 508–510]

We present critical comments on the recent paper [Intikhab A. Ansari, Physica C: Superconductors, 470 (2010) 508] concerning numerical methods for solving Bloch–Gruneisen function and its applications to MgB₂ superconductor. It is demonstrated that the presented in this work the formulas and examples are not original and they are quite identical the formulas already established in our article [B.A. Mamedov, I.M. Askerov, Physics Letters A, 362 (2007) 324].     

Asymmetrical [4+2]-Cycloaddition of (-)-Menthyl Acrylate and (-)-Menthyl Methacrylate to Cyclopentadiene in the Presence of BBr3

An asymmetrical synthesis of bicyclo[2.2.1]hept-2-enes is described performed by [4+2]-cyclo-addition of (-)-menthyl acrylate, (-)-menthyl methacrylate to cyclopentadiene in the presence of BBr₃.The effect of different factors on isomer composition, yield, and enantiomeric purity of the compoundsobtained was investigated. Kovatch indices were determined and boiling points were estimated with the use of gas-liquid chromatography.     

Asymmetric Diels-Alder reaction of 1,3-butadienes with (−)-dimenthyl fumarate in the presence of BBr<Subscript>3</Subscript> and BBr<Subscript>3</Subscript>·OEt<Subscript>2</Subscript>

Asymmetric synthesis of substituted cyclohexenes was performed by [4+2]-cycloaddition of (-)-dimenthyl fumarate to 1,3-butadienes in the presence of BBr₃ and BBr₃·OEt₂. The latter are efficient catalysts for this reaction. The effect of various factors on the chemical and optical yield of compounds synthesized was studied. The lowering of the reaction temperature to ?70°C favors increase in the enantiomeric purity of products up to 81%. The overall yield of adducts grows with temperature and catalyst amount. The solvent character insignificantly affects the overall and optical yield of compounds obtained.     

Impact of Co Atoms on the Electronic Structure of Bi2Te3 and MnBi2Te4 Topological Insulators

Journal of Experimental and Theoretical Physics - This work is devoted to an experimental investigation of the electronic structure of the surface of topological insulators of various stoichiometry...     

Fully analytical evaluation of optical gain coefficient in bulk semiconductors in quasi-equilibrium free-carrier approximation

In this letter, a new analytical method is presented to calculate of the semiconductor optical gain coefficient. This method is particularly suitable for theoretical analyses to determine the dependence of semiconductor gain on the total carrier density and temperature in the semiconductor lasers. Also, the optical gain functions for semiconductor optical gain coefficient are presented analytically. The analytical evaluation is verified with numerical methods, which illustrates the accuracy of these obtained analytical expressions.     

Cycloalkyldecalins as components of jet fuels

The possibility of obtaining cycloalkyldecalins by the alkylation of 1–and 2–methylnaphthalenes by cycloolefins with subsequent hydrogenation of methylcycloalkylnaphthalenes was studied. Physicochemical parameters of reaction products were determined, and their structure was defined on the basis of IR and NMR spectra.     

Calculation of three-center nuclear attraction integral over Slater type orbitals in molecular coordinate system using Löwdin <Emphasis Type="Italic">α</Emphasis>-radial function and Guseinov’s two-center charge density expansion formulae

Using Löwdin α-radial function and the Guseinov’s charge density expansion formulae, the calculation of the three-center nuclear attraction integrals over Slater type orbitals in molecular coordinate system is performed. The proposed algorithm is especially useful for computation of multicenter-multielectron integrals that arise in the Hartree-Fock-Roothaan approximation, which plays a significant role for the study of electronic structure and electron-nuclei interaction properties of atoms, molecules and solids. The algorithm described in the present work is valid for the arbitrary values of quantum numbers, screening constants and internuclear distances. The calculation results are in good agreement with those obtained using the alternative evaluation procedure.     

Benzimidazoles and related heterocycles

3-Aryl-1’H-spiro[2-pyrazoline-5,2’-quinoxalin]-3’(4’H)-ones, easily available by the reaction of 3-(2-aryl-2-oxoethylidene)-3,4-dihydroquinoxalin-2(1H)-ones with hydrazine hydrate (and phenylhydrazine), in boiling acetic acid undergo new acid-catalyzed rearrangement with the contraction of pyrazine ring of the quinoxaline system to form 2-(pyrazol-3-yl)benzimidazoles. Possible mechanisms of this rearrangement are considered.