New derivatives of coumarin: 2-(N-R-imino)-2H-1-benzopyrans

Methods of synthesizing previously unknown derivatives of coumarin — 2-(N-R-imino)-2H-1-benzopyrans, where R = Alk, Ar — are proposed. Possibilities of alternative synthetic schemes are discussed, and hypotheses concerning probable mechanisms of the reactions are formulated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 760–766, June, 1994. Original article submitted May 23, 1994.     

Fractal character of effective Hall properties of a three-dimensional disordered composite

The dependencies of the effective Hall properties on a scale, obtained by means of an iterative averaging method, manifest their fractal character. The influence of an intensity of the Hall effect on the fractal character of the Hall properties was considered. Scale ranges and dimensional characteristics of the effective Hall properties behavior were calculated and discussed.     

Direct observation of charge-carrier capture in an array of self-assembled InAs/GaAs quantum dots

In this work, charge-carrier capture by an array of self-assembled InAs/GaAs quantum dots was directly observed for the first time by capacitance recharge. It is proposed to process the obtained transient-capture data by a similar method to that used for emission, by the box-car method. The capture activation energies are determined and compared with the emission activation energies.     

A structural investigation of a D-glucan fromYersinia pseudotuberculosis of serotype VI

It has been established that an -D-glucan isolated fromYersinia pseudotuberculosis, serotype VI, is branched and contains -14- and -16-bound D-glucopy-ranose residues in the main chain and the side chains, respectively.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostock. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 151–154, March–April, 1981.     

Methods for the construction of [1,2]isoindolo-condensed benzazepines, benzazocines, quinolines, and isoquinolines. 2. Isoindoloquinolines, isoindoloisoquinolines. (Review)

Data for 1966–2004 on methods for the construction of tetracyclic systems in which an isoindole ring is condensed with quinoline and isoquinoline fragments on the [1,2] side are reviewed. Methods and conditions for the synthesis of isoindoloquinolines and isoindoloisoquinolines are examined. Examples of the synthesis of physiologically active natural alkaloids possessing the structure of these condensed isoindoles are presented. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1123–1157, August, 2006.     

Product structure in the reaction of dimethyl acetylenedicarboxylate with 2-furyl-1,2,3,4-tetrahydroquinolines

Dimethyl acetylenedicarboxylate reacts with 4-substituted and 3,4-fused 2-furyl-1,2,3,4-tetrahydroquinoline derivatives at the furan fragment according to the [4 + 2]-cycloaddition pattern. The reaction is not stereoselective, and it yields two diastereoisomeric 7-oxabicyclo[2.2.1]hepta-2,5-dienes whose structure was determined by X-ray analysis and NMR spectroscopy.     

Intramolecular Diels—Alder reaction of 4-(N-furfuryl)aminobut-1-enes. New approach to the synthesis of 6,8a-epoxyoctahydroisoquinoline (3-aza-11-oxatricyclo[6.2.1.01,6]undec-9-ene) derivatives

The intramolecular Diels—Alder reaction of readily accessible 4-substituted 4-(N-furfuryl)aminobut-1-enes was studied and a new one-step method was developed for the synthesis of 6,8a-epoxy-1,2,3,4,4a,5,6,8a-octahydroisoquinoline (3-aza-11-oxatricyclo[6.2.1.0^1,6]undec-9-ene) derivatives. The [4+2]-cycloaddition proceeds stereoselectively to form exo-adducts. The influence of substituents at the nitrogen atom in 4-(N-furfuryl)aminobut-1-enes on the cycloaddition pathway was examined.     

Molecular structure of potassium [N,N′-bis(salicylideneamino)nitroguanidonate-N,N′,-O,O′]nickel(ii), the product of condensation of (salicylideneamino)nitroguanidine with salicylaldehyde on a Ni2+ ion template

The crystal structure of the product of the condensation of (salicylideneamino)nitroguanidine with salicylaldehyde on a Ni²⁺ ion template, K[Ni(C₁₅H₁₀N₅O₄)] · DMF, has been studied. It was established that a planar Ni complex, consisting of isolated [NiL]^– anions and solvated [K⁺ · DMF] cations, is formed. The negative charge of the anion is localized mainly on the O atoms of the nitro group. The nitroguanidine fragment of the ligand occurs in the tautomeric form, which was not reported previously.Deceased in 1995Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2273–2277, September, 1996.     

Electronic structure and Chemical bonding in Sr4Nb17O26

The electronic structure of oxoniobate Sr₄Nb₁₇O₂₆ is studied by the linear muffintin orbital (LMTO) method. It is shown that the highenergy conduction band consists of the Nb4d states and the hybridized valence band is formed by the Nb4d and O2p states. The band structure of this compound is characterized by superposition of the bands of the 2p states of perovskite oxygen atoms and the 4d states of monoxide niobium atoms. The degree of oxidation of the perovskite and monoxide niobium atoms is +5 and +2.56, respectively. Chemical bonding is analyzed using the electron localization function and model Hückel calculations. The niobiumoxygen bond is shown to be the strongest. The Fermi level is localized in the vicinity of the bottom of the niobium antibonding state band, which explains the existence of Sr_4−xNb₁₇O₂₆ in the homogeneity region corresponding to 0 < x < 0.3. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 5, pp. 771–780, September–October, 1998. This work was supported by RFFR grant No. 96-03-32015a.