Showing papers in "Russian Chemical Bulletin in 1995"
TL;DR: In this article, general formulas for calculating the Wiener index (W) and the hyper-Wiener index(R) in spiro-graphs containing three-to six-membered rings are proposed.
Abstract: General formulas for calculating the Wiener index (W)2 and the hyper-Wiener index (R)3 in spiro-graphs containing three- to six-membered rings are proposed. They are derived on the basis of Hosoya's formula4 and the Klein-Lukovitz-Gutman5 formula for evaluatingW andR, respectively, in cycle-containing graphs, by using the layer matrix of cardinality (LC).6 An extension of the Wiener number, theW* number of Gutman7 is also evaluated for these spiro-graphs.
112 citations
TL;DR: In this article, five cyclic depsipeptides with molecular masses of 1007, 1021, 1024, 1024 and 1035 were obtained from Bacillus pumilus KMM 150 associated with Australian marine sponge.
Abstract: Five cyclic depsipeptides with molecular masses of 1007, 1021, 1021, 1035, and 1035 were obtained fromBacillus pumilus KMM 150 associated with Australian marine spongeIrcinia sp. Their structures were assigned by mass spectrometric techniques (high-resolution fast atom bombardment and electron impact mass spectrometry), chemical modification, and extensive spectroscopic analysis, including several types of two-dimensional NMR.
42 citations
TL;DR: In this article, the influence of lignin origin on the yields of vanillin and syringaldehyde as well as the correlation between the rates of wood delignification and the aldehydes formation are discussed.
Abstract: The oxidation of a number of lignin species by molecular oxygen was studied. The selectivity of the process was found to be close to that of the oxidation with nitrobenzene. The influence of lignin origin on the yields of vanillin and syringaldehyde as well as the correlation between the rates of wood delignification and the aldehydes formation are discussed.
41 citations
TL;DR: In this paper, it has been proved by means of chemical analysis, X-ray powder, and IR spectral studies that the desolvation of zirconium and hafnium alkoxides is accompanied by the formation of amorphous oxocompounds M3O(OPri)10.
Abstract: The direct electrochemical synthesis of zirconium (1a) and hafnium (1b) alkoxides, M(OPri)4·PriOH, Zr(OBui)4·BuiOH (4a) and M(OR)4, where R=Et (2a,b), Bun (3a), Bus (5a), C2H4OMe (6a,b) has been carried out by anodic oxidation of metals in anhydrous alcohols in the presence of LiCl as a conductive additive to give quantitative yields. The solubility polytherms and dissociation pressure of1a,b have been investigated. It has been proved by means of chemical analysis, X-ray powder, and IR spectral studies that the desolvation of 1a,b and Sn(OPri)4·PriOH (1c) is accompanied by the formation of amorphous oxocompounds M3O(OPri)10. On the basis of1H NMR data it has been proved that the structure of the latter is analogous to that of known triangular cluster molecules M3(μ3-O)(μ3-OR)(μ-OR)3(OR)6, where M=Mo, W, U. Mass-spectral data and the determined physicochemical characteristics of1–5 permit to conclude that the samples of composition M(OR)4, where M=Zr, Hf, and2,3,5 contain tri- and tetranuclear oxocomplexes M3O(OR)10 and M4O(OR)14 respectively, along with Zr(OR)4 oligomers of different molecular complexity.
32 citations
TL;DR: The data on the synthesis, properties, and practical application of porphyrazines (tetraazaporphines), the nearest structural analogs of porphyrins and phthalocyanines, have been systematized as discussed by the authors.
Abstract: The data on the synthesis, properties, and practical application of porphyrazines (tetraazaporphines), the nearest structural analogs of porphyrins and phthalocyanines, have been systematized.
31 citations
TL;DR: In this paper, the methods for preparation and properties of dinitramide salts with ammonia, hydrazine, hydroxylamine, formamidine, their alkylated and aminated derivatives, etc.
Abstract: The methods for preparation and the properties of dinitramide salts with ammonia, hydrazine, hydroxylamine, formamidine, their alkylated and aminated derivatives,etc. are described.
24 citations
TL;DR: In this paper, van der Waals radii of elements were determined from the data of the structural inorganic chemistry: from intersitial distances in CdX2-and graphite-type structures, bond lengths in van derWaals molecules, molar volumes of A2-type substances, refractometry data, and from quantum chemical and correlation ratios.
Abstract: Van der Waals radii of elements were determined from the data of the structural inorganic chemistry: from intersitial distances in CdX2- and graphite-type structures, bond lengths in van der Waals molecules, molar volumes of A2-type substances, refractometry data, and from quantum chemical and correlation ratios. The recommended values of van der Waals radii of elements are tabulated.
22 citations
TL;DR: The structure of polynuclear PdII hydroxocomplexes (PHC) formed as a result of alkaline hydrolysis of Pd II chloride complexes was studied by EXAFS, SAXS, and TEM methods as discussed by the authors.
Abstract: The structure of polynuclear PdII hydroxocomplexes (PHC) formed as a result of alkaline hydrolysis of PdII chloride complexes was studied by EXAFS, SAXS, and TEM methods. It is established that in aqueous solutions a hydroxocomplex particle is a filament curled into a ball containing about 100 Pd atoms. The filament consists of planar coordination squares of PdO4 units linkedvia one or two oxygen bridges of different geometry. Aging of samples results in an increase in the number of single bridging ligands and a decrease in the diameter of particles. Interatomic distances around palladium atoms were determined.
22 citations
TL;DR: In this article, a simple route for the synthesis of 1,3-diketones by the reaction of acetylenic ketones with amines followed by hydrolysis of the resulting aminovinylketons is suggested.
Abstract: A simple route for the synthesis of 1,3-diketones by the reaction of acetylenic ketones with amines followed by hydrolysis of the resulting aminovinylketons is suggested.
21 citations
TL;DR: In this paper, the results of direct experimental determination of covalent bond lengths in molecular structures are presented, which made it possible to establish the values of normal Covalent radii.
Abstract: The results of direct experimental determination of covalent bond lengths in molecular structures are presented. This made it possible to establish the values of normal covalent radii. The recommended values of covalent radii for 56 elements are tabulated.
20 citations
TL;DR: In this article, the activation of terminal alkynes by metal complexes and reactivity patterns and selective preparations of unsaturated carbene, allenylidene, and cumulenylidsene derivatives of (arene)ruthenium complexes are reviewed.
Abstract: The author's studies aimed at activation of terminal alkynes by metal complexes and reactivity patterns and selective preparations of unsaturated carbene, allenylidene, and cumulenylidene derivatives of (arene)ruthenium complexes are reviewed.
TL;DR: The superacidic cyclization of aliphatic and partially cyclized C15-C25 terpenoid acids and their esters proceeds structure-selectively and stereospecifically, affording α-isomers of completely cyclized epimeric β,γ-unsaturated acids or esters; the configuration of their carboxylic or ester groups is predetermined by the configuration as mentioned in this paper.
Abstract: The superacidic cyclization of aliphatic and partially cyclized C15–C25 terpenoid acids and their esters proceeds structure-selectively and stereospecifically, affording α-isomers of completely cyclized epimeric β,γ-unsaturated acids or esters; the configuration of their carboxylic or ester groups is predetermined by the configuration of the double bond conjugated with the carboxyl or ester groups in the starting compounds.
TL;DR: In this article, the effects of salts present in the subphase on the properties of monolayers, i.e., molecular areas of proteins and Gibbs elasticities, were studied by the monolayer method.
Abstract: Effects of salts present in the subphase on the properties of monolayers,viz., molecular areas of proteins and Gibbs elasticities, were studied by the monolayer method.
TL;DR: In this paper, it has been shown that the introduction of a methoxy group into theortho-position of the phenyl fragment stabilizes the tetrazole tautomer more efficiently than introduction of this group in thepara-position.
Abstract: The intramolecular hydrogen bond between the phenolic hydroxyl and the pyrimidine nitrogen atom in the title compounds exerts a destabilizing effect on the tetrazole ring and shifts the azide-tetrazole equilibrium toward the azide form, especially in the case of tetrazolo[c]pyrimidine and -[c]quinazoline. It has been found that the introduction of a methoxy group into theortho-position of the phenyl fragment stabilizes the tetrazole tautomer more efficiently than introduction of this group into thepara-position.
TL;DR: In this paper, the first ansa bis(fluorenyl) complexes of zirconium and hafnium, (C13H8-C2H4-C 13Hs)MCl2 (M = Zr, Hf), have been prepared.
Abstract: Ansa metallocene dichloride complexes of titanium, zirconium, and hafnium can be activated by methyl aluminoxane (MAO) to give excellent catalysts for the homogeneous polymerization of ethylene and propylene. The symmetry of the corresponding metaliocene dichloride complexes is essential for the stereospecific polymerization of propylene (isotactic, syndiotactic or atactic). The application of fluorenyl groups instead of cyclopentadienyl groups greatly increases the activity of the catalysts. The first ansa bis(fluorenyl) complexes of zirconium and hafnium, (C13H8-C2H4-C13Hs)MCl2 (M = Zr, Hf), have been prepared. It was found that after the activation by MAO the zirconium derivative demonstrates a very high activity. Several model complexes are presented in order to discuss the mechanism of the polymerization.
TL;DR: In this article, the synthesis of 2-aryloxy(arylthio)- and 2-alkoxy(alkylthio) 2-thio(oxo)-1,3,2-oxazaphosphorinanes and their N-substituted derivatives based on the reactions of the corresponding dichlorophosphates, dichlorothio-, and dithiophosphate with 3-aminopropan-1-ol or its substituted derivatives in the presence of Et3N or aqueous alkali under phase transfer catalysis conditions
Abstract: Methods for the synthesis of 2-aryloxy(arylthio)- and 2-alkoxy(alkylthio)-2-thio(oxo)-1,3,2-oxazaphosphorinanes and theirN-substituted derivatives based on the reactions of the corresponding dichlorophosphates, dichlorothio-, and dithiophosphates with 3-aminopropan-1-ol or its substituted derivatives in the presence of Et3N or aqueous alkali under phase transfer catalysis conditions, as well as by the reaction of the tetramethylammonium salt of 2-hydroxy-2-thio-1,3,2-oxazaphosphorinane with alkyl- and acyl halides, by that of 2-chloro-2-thio-1,3,2-oxazaphosphorinane with sodium thiolates, and by other methods, were developed. The compounds obtained exhibit high nematocide activity but low toxicity for mammals. Some active synergists for permethrine were found among these compounds.
TL;DR: In this paper, the interaction of 3,6-di-tert-butyl-ortho-benzoquinone (1) and 3,5-di-, tert-, butyl-,ortho-, orbenzo-quinone (2) with NH3 in water-alcohol medium and with (NH4)2CO3 in a solid phase has been studied.
Abstract: The interaction of 3,6-di-tert-butyl-ortho-benzoquinone (1) and 3,5-di-tert-butyl-ortho-benzoquinone (2) with NH3 in water—alcohol medium and with (NH4)2CO3 in a solid phase has been studied. Redox processes with participation of a nucleophile of the medium take place for1, while2 reacts with NH3 at the carbonyl group with transformation of the quinone imide. The mechanism of redox transformation of1 has been proposed.
TL;DR: In this article, the vibrational and electronic spectra of dinitramide salts MN(NO2)2 (M=K, Na, Li, NH4, Fe, Ag, Mn, Mg, Rb, C(NH2)3) have been studied.
Abstract: The vibrational and electronic spectra of dinitramide salts MN(NO2)2 (M=K, Na, Li, NH4, Fe, Ag, Mn, Mg, Rb, C(NH2)3) have been studied. The IR and Raman spectra of solutions and melts of the salts have been satisfactorily interpreted on the basis of the anion model withC2v symmetry. The complication of the spectra in the crystalline phase has been explained by restructurization of the anion that reduces its symmetry and makes the nitro groups nonequivalent.
TL;DR: In this paper, a mechanism that involves the consecutive formation of several active complexes of vanadium(v) responsible for the oxidation of substrates and for the formation of ozone is suggested.
Abstract: Reactions of H2O2 in trifluoroacetic acid catalyzed by vanadium(v) compounds were studied. The system under study exhibits unusual behavior: along with oxygen, large quantitaties (10–15 %) of ozone are found in the products of hydrogen peroxide decomposition; difficultly oxidizable compounds (alkanes, arenes, and perfluoroalkenes) are oxidized under mild conditions. The rates of the oxidation of individual substrates are commensurable. However, when two compounds are simultaneously present in the reaction mixture, cyclohexane stops the oxidation of all of the other substrates, arenes suppress the oxidation of perfluoroolefins, and perfluoro-1-octene stops the consumption of internal perfluoroolefins. The effect of the oxidizable substrates on the amount of ozone evolved was studied. Based on the kinetic data obtained, a mechanism that involves the consecutive formation of several active complexes of vanadium(v) responsible for the oxidation of substrates and for the formation of ozone is suggested. In terms of the scheme suggested, the inner-sphere oxidation of the peroxo ligand by the coordinated peroxotrifluoroacetic acid affords a complex incorporating O
3
2−
as a ligand. The latter acts as the precursor of the ozone. A mathematical model that adequately describes the experimental data is proposed.
TL;DR: The interaction of 2-cyanoacryloyl chloride with unsaturated 1,4-diols leads to bis(2-cyclano acrylates) with a double or triple C-C bond as discussed by the authors.
Abstract: The interaction of 2-cyanoacryloyl chloride with unsaturated 1,4-diols leads to bis(2-cyanoacrylates) with a double or triple C-C bond.
TL;DR: Highly efficient kinetic resolution of racemic secondary alkyl diazoacetates in intramolecular carbon-hydrogen insertion reactions has been achieved using chiral dirhodium(ii) carboxamidates.
Abstract: Highly efficient kinetic resolution of racemic secondary alkyl diazoacetates in intramolecular carbon-hydrogen insertion reactions has been achieved using chiral dirhodium(ii) carboxamidates. Products formed from catalytic diazo decomposition of racemic 2-octyl diazoacetate and, separately, its (2R)- and (2S)-enantiomeric forms, as well as bothcis- andtrans-2-methylcyclohexyl diazoacetates, have been systematically evaluated. Enantioselectivities up to 99 %ee have been obtained for γ-lactone formation. β-Lactone production has been observed and, although minor with cyclohexyl diazoacetates, is the major insertion pathway for diazo decomposition of 2-octyl diazoacetate.
TL;DR: In this article, the regio-and stereoselectivity of the reactions of carbanions, generated from alkanals, carboxylates of the type XYCHCOOEt (X = EtOOC, CN, Ac; Y = H, Br), or derivatives of 3-methyl-4-phosphono-2-butenoic acid using PTC techniques, with aldehydes of various types (alkanals, α,β-enals, cross-conjugated enedials, benzaldehydes,
Abstract: The regio- and stereoselectivity of the reactions of carbanions, generated from alkanals, carboxylates of the type XYCHCOOEt (X = EtOOC, CN, Ac; Y = H, Br), or derivatives of 3-methyl-4-phosphono-2-butenoic acid using PTC techniques, with aldehydes of various types (alkanals, α,β-enals, cross-conjugated enedials, benzaldehydes,etc.) are reviewed. The factors affecting the outcome of these reactions are discussed. The carbanion analogs, triphenylphosphorus ylides, are shown to attack selectively at one of the aldehyde groups of aromatic dialdehydes. The regularities found for the title reactions were used in the syntheses of some biologically active isoprenoids.
TL;DR: In this article, the structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores have been studied by the molecular dynamics approach, and the mechanism of the Cationic transport has been examined.
Abstract: The structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores has been studied by the molecular dynamics approach. The mechanism of the cationic transport has been examined. The dependence of the cationic transport coefficients on temperature and the number of water molecules has been investigated.
TL;DR: In this article, two methods for the generation of nitroformonitrile oxide (NFNO) were proposed, namely, by dehydration of dinitromethane and by nitration of 2-methyl-1-nitro-1propene.
Abstract: Two methods for the generation of nitroformonitrile oxide (NFNO) were proposed, namely, by dehydration of dinitromethane and by nitration of 2-methyl-1-nitro-1-propene. NFNO was identified as its cyclodimerization product, dinitrofuroxan.
TL;DR: In this article, the nature of the substituent in the ligand affects both the rate of the catalyzed peroxide decomposition and catalytic activity of the complexes studied in the alkane oxidation.
Abstract: Oxidation of alkanes (methane, ethane, hexane, and cyclohexane) by hydrogen peroxide andtert-butyl hydroperoxide in acetonitrile catalyzed by binuclear μ-oxo-bridged iron complexes [Fe2OL4(H2O)2](ClO4)4 and [Fe2OL2PhCOO)2(H2O)2](ClO4)2, where L = bpy, 4,4′-Me2bpy, 4,4′-(ClCH2)2bpy, phen, and 5-NO2phen, was studied. It was shown that the nature of the substituent in the ligand affects both the rate of the catalyzed peroxide decomposition and catalytic activity of the complexes studied in the alkane oxidation.
TL;DR: In this paper, the synthesis of MeS-substituted pyrido[2,3d]pyridin-5-one, pyrimido[4,5d]-pyrimidine, and 4-methylenepyrimido [4, 5d] pyrimidin2-2-one based on 5-acetyl-6-amino-4-methylthio-2 -phenylpyrimidine, which was prepared from the adduct of benzoyl isothiocyanate with acetyl
Abstract: Schemes for the synthesis of MeS-substituted pyrido[2,3-d]pyrimidin-5-one, pyrimido[4,5-d]pyrimidine, and 4-methylenepyrimido[4,5-d]pyrimidin-2-one based on 5-acetyl-6-amino-4-methylthio-2-phenylpyrimidine, which was prepared from the adduct of benzoyl isothiocyanate with acetylketeneN-benzoylaminal, were suggested.