Showing papers in "Russian Chemical Bulletin in 2002"
TL;DR: In this paper, the main reagents used in cycloaddition and reaction mechanisms are surveyed, as well as possible applications of cycloadducts are considered, covering the investigations of the last five years and the most important earlier studies.
Abstract: Investigations on mono-[2+1]-, -[2+2]-, -[2+3]-, -[2+4]-, and polycycloaddition to [60]fullerene are reviewed. The main reagents used in cycloaddition and the reaction mechanisms are surveyed. The possible applications of cycloadducts are considered. The review covers the investigations of the last five years as well as the most important earlier studies.
114 citations
TL;DR: In this paper, a comparative analysis of the possibilities and characteristic features of the application of polyhedral boron compounds, viz., the closo-decaborate anion [B10H10]2], the carba-closo-dodecaborate aion [CB11H12]2, carboranes C2B 10H12, and bis(dicarbollide) complexes [M(C2B9H11)2] (M = Fe, Co, or Ni), for cancer detection is presented.
Abstract: The paper presents a comparative analysis of the possibilities and characteristic features of the application of various polyhedral boron compounds, viz., the closo-decaborate anion [B10H10]2–, the closo-dodecaborate anion [B12H12]2–, the carba-closo-dodecaborate anion [CB11H12]–, carboranes C2B10H12, and the bis(dicarbollide) complexes [M(C2B9H11)2]– (M = Fe, Co, or Ni), in boron neutron capture therapy (BNCT) for cancer. The requirements on compounds used in BNCT are formulated and the advantages of the application of the closo-dodecaborate anion are considered. The data on the synthesis of various derivatives of the closo-dodecaborate anion, which either already found use in BNCT or are most promising in this field, are summarized. The possibilities of the application of agents derived from the closo-dodecaborate anion in medical diagnostics are discussed.
90 citations
TL;DR: In this paper, X-ray diffraction and adsorption data suggested an increase in the crystallite size and a decrease in the value of limiting adaption and specific area of magnetite.
Abstract: Superfine magnetite particles were obtained by chemical condensation. Their size can be varied by the magnetic field application and a change in the crystallization temperature. The X-ray diffraction and adsorption data suggested an increase in the crystallite size and a decrease in the value of limiting adsorption and specific area of magnetite with an increase in the temperature and magnetic field intensity. The nature of surfactants and solvents has a substantial effect on the adsorption process. The IR spectroscopic and equilibrium adsorption data showed that oleic acid has the highest affinity to the surface among the surfactants studied (stearic, oleic, and linoleic acids and sodium oleate). On going from carbon tetrachloride to hexane, the value of limiting adsorption of oleic acid decreases.
54 citations
TL;DR: In this paper, the mechanism of the rhodium catalyst deactivation was studied by the kinetic method and 31P NMR spectroscopy, and the methods for the stabilization of the catalyst were found.
Abstract: Formic acid was synthesized in a high yield at room temperature in the presence of the Wilkinson complex and an excess of PPh3. The catalytic properties of the rhodium complex depend strongly on the reaction conditions. The mechanism of the rhodium catalyst deactivation was studied by the kinetic method and 31P NMR spectroscopy. The methods for the stabilization of the rhodium catalyst were found.
44 citations
TL;DR: In this article, the molecular and crystal structure of 2-amino-3-cyano-6-hydroxy-4-phenyl-4H-benzo[f]chromene was established by X-ray diffraction analysis.
Abstract: Substituted 2-aminochromenes were synthesized by three-component condensation of aromatic aldehydes, derivatives of cyanoacetic acid, and phenols or naphthols. The molecular and crystal structure of 2-amino-3-cyano-6-hydroxy-4-phenyl-4H-benzo[f]chromene was established by X-ray diffraction analysis.
43 citations
TL;DR: In this paper, the crystal structures of the (Ph4P)3[Re6S8(CN)6], (Ph 4P)2(H) [Re6Se8 (CN) 6]·8H2O, and (Et4N) 2(H)[Re6Te 8(CN6]·2H 2O clusters were solved by X-ray diffraction analysis.
Abstract: The cluster anions [Re6X8(CN)6]34– (X = S, Se, or Te) containing 23 cluster valence electrons in the Re6 octahedron were synthesized and isolated as salts with organic cations. The crystal structures of the (Ph4P)3[Re6S8(CN)6], (Ph4P)2(H)[Re6Se8(CN)6]·8H2O, and (Et4N)2(H)[Re6Te8(CN)6]·2H2O clusters were solved by X-ray diffraction analysis. Removal of one electron has virtually no effect on the geometry and interatomic distances in the cluster anion but leads to a substantial change in the electronic spectrum and to an increase in stretching vibration frequencies νCN compared to those of the [Re6X8(CN)6]4– anions.
34 citations
TL;DR: The binuclear complex cation [Sm(H2O)4]2(Cuc)3}Br6·44H 2O (Cuc = C36H36N24O12) was established by X-ray diffraction analysis as mentioned in this paper.
Abstract: The supramolecular compound {[Sm(H2O)4]2(Cuc)3}Br6·44H2O (Cuc = C36H36N24O12) was synthesized. Its crystal and molecular structure was established by X-ray diffraction analysis. The binuclear complex cation {(Cuc)[Sm(H2O)4](Cuc)[Sm(H2O)4](Cuc)}6+ built from the alternating cucurbituril molecules (C36H36N24O12) and the [Sm(H2O)4]3+ aqua ions is a triple-decker nanosized (33 A) sandwich.
34 citations
TL;DR: In this paper, a joint FTIR spectroscopic study and ab initio quantum-chemical calculations (HF/3-21G and PBE/TZ2P methods) showed that thiocalix[4] arene molecules adopt the cone conformation in CCl4 solutions.
Abstract: The joint FTIR spectroscopic study and ab initio quantum-chemical calculations (HF/3-21G and PBE/TZ2P methods) showed that thiocalix[4] arene molecules adopt the cone conformation in CCl4 solutions The weakening of the cooperative intramolecular H bond in thiocalix[4]arenes compared to the corresponding calix[4]arenes can be due to the larger thiocalixarene macrocycle, bifurcated hydrogen bond in it, and electron density transfer from the bridging S atom to the benzene ring
32 citations
TL;DR: In this article, simple methods for the synthesis of previously unknown sulfur-containing pyridin-2-ones and 5,6,7,8-tetrahydroquinolines from cyanothioacetamide and anilinomethylidene derivatives of cyclic 1,3-dicarbonyl compounds were developed.
Abstract: Simple methods for the synthesis of previously unknown sulfur-containing pyridin-2-ones and 5,6,7,8-tetrahydroquinolines from cyanothioacetamide and anilinomethylidene derivatives of cyclic 1,3-dicarbonyl compounds were developed. Structures and chemical transformations of compounds obtained were studied.
31 citations
TL;DR: In this paper, the electroreduction of CO2 was studied in methanol in the presence of mono-and diphthalocyanine complexes and ph-thyanine films prepared by electrochemical anodic polymerization.
Abstract: The electroreduction of CO2 was studied in methanol in the presence of mono- and diphthalocyanine complexes and phthalocyanine films prepared by electrochemical anodic polymerization. Methyl formate is the main reaction product of the reaction catalyzed by the mono- and diphthalocyanine complexes of rare-earth metals. Copper 2,9,16,23-tetra-tert-butylphthalocyanine allows the transformation of CO2 into methane in ∼30% yield. In the presence of both electropolymerized and graphite electrode-supported copper 2,9,16,23-tetraaminophthalocyanine, CO and methyl formate are the main reaction products.
31 citations
TL;DR: The algorithm GArna was used to study the effects of nucleotide composition on characteristics of the secondary structure of random RNA sequences and the results were interpreted in terms of secondary structure influence on translation initiation and on the general scheme of expression regulation.
Abstract: A fast genetic algorithm GArna for mass calculations of RNA secondary structures through the Internet is proposed. The algorithm GArna was used to study the effects of nucleotide composition on characteristics of the secondary structure of random RNA sequences. A contextual characteristics for evaluation of the stability was proposed and the application of standard statistical tests for heterogeneous RNA samplings was justified. The structure-contextual characteristics by which the 5"-untranslated regions of high- and low-expression genes of dicot plants and mammals differ were found, and the results were interpreted in terms of secondary structure influence on translation initiation and on the general scheme of expression regulation. The application of the results obtained for the development of computer methods for RNA structural genomics, in particular, for RNA search in genome sequences, is discussed.
TL;DR: In this article, a one-pot synthesis of stable phosphorus ylides by the condensation of triphenylphosphine with dialkyl acetylenedicarboxylate and CH acids, such as penta-2,4-dione or diethyl propane-1,3-dioate, in the presence of β-cyclodextrin as a catalyst, without using toxic organic solvents was proposed.
Abstract: A convenient one-pot synthesis of stable phosphorus ylides by the condensation of triphenylphosphine with dialkyl acetylenedicarboxylate and CH acids, such as penta-2,4-dione or diethyl propane-1,3-dioate, in the presence of β-cyclodextrin as a catalyst (to increase the solubility of the reactants in water) without using toxic organic solvents was proposed. This methodology is of interest due to the use of water as a solvent, thus minimizing such factors as the cost, operational hazards, and environmental pollution.
TL;DR: In this article, the synthesis of chiral auxiliaries (S)-N-(2-benzoylphenyl)-1-(3,4-dichlorobenzyl)-pyrrolidine-2-carboxamide (1a), (S]-N-( 2-benzo-lphoenyl)- 1-(pentafluorobenzym)pyrroborbenzyl)-polyphenyl (PBP), and their application in the asymmetric synthesis of amino acids using NiII complexes of their Schiff"s bases with
Abstract: The synthesis of new chiral auxiliaries (S)-N-(2-benzoylphenyl)-1-(3,4-dichlorobenzyl)-pyrrolidine-2-carboxamide (1a), (S)-N-(2-benzoylphenyl)-1-(pentafluorobenzyl)pyrrolidine-2-carboxamide (1b), and (S)-N-(2-benzoylphenyl)-1-(4-isopropoxytetrafluorobenzyl)pyrrolidine-2-carboxamide (1c) and their application in the asymmetric synthesis of amino acids using NiII complexes of their Schiff"s bases with alanine and glycine are described. Compound 1a is particularly appropriate for highly stereoselective synthesis of α-methyl-α-amino acids with high enatiomeric purity (ee >95%).
TL;DR: In this article, the C-H bond dissociation energies were calculated on the basis of the parabolic model from the rate constants of free radical reactions for more than 160 oxygen-containing compounds.
Abstract: The C—H bond dissociation energies were calculated on the basis of the parabolic model from the rate constants of free radical reactions for more than 160 oxygen-containing compounds. The enthalpies of formation of free radicals formed from these compounds were calculated. The method was modified taking into account the influence of functional groups on the partial rate constant and for the case when the reference reaction in the reaction series belongs to another class of structurally similar reactions.
TL;DR: In this paper, the main approaches to increasing the NO concentration by introducing various types of exogenous nitric oxide donors into the organism and chemical and biological characteristics of these donors are considered.
Abstract: The review considers problems related to the formation, in the living organism, of nitric oxide, a versatile and vitally important regulator of cell metabolism. The pathways of formation of endogenous nitric oxide from L-arginine are discussed and the main approaches to increasing the NO concentration by introducing various types of exogenous nitric oxide donors into the organism and chemical and biological characteristics of these donors are considered. Primary attention is devoted to the known drugs that were shown to release NO under hydrolytic, oxidative, or reductive conditions. The solution of problems related to the elucidation of the mechanisms of drug action requires that the formation of nitric oxide be taken into account.
TL;DR: In this article, femtosecond laser photolysis was used to study the relaxation of photoexcited states in nanosized semiconductor particles of iron oxides, including nanocrystals of ferrihydrite 5Fe2O3·9H2O, contained in the protein shell of ferritine.
Abstract: Relaxation of photoexcited states in nanosized semiconductor particles of iron oxides was studied by femtosecond laser photolysis techniques: (1) in an aqueous colloidal solution of α-Fe2O3; (2) in Fe2O3 particles in the Nafion® cation-exchange polymeric membrane; (3) in an aqueous colloid of γ-Fe2O3; and (4) in nanocrystals of ferrihydrite 5Fe2O3·9H2O, which are contained in the protein shell of ferritine. The photoinduced excited states relax at the femtosecond and picosecond time scale. The spectra of photoinduced absorption of photoexcited states and the relaxation dynamics in the studied iron oxides weakly depend on the structure and surface environment of a nanoparticle.
TL;DR: In this article, a simple and convenient method for the synthesis of 1-substituted 3,3-dimethyl-3,4-dihydroisoquinolines was developed.
Abstract: A simple and convenient method for the synthesis of 1-substituted 3,3-dimethyl-3,4-dihydroisoquinolines was developed. The method is based on the [2+2+2] cyclization of alkyl- or alkoxybenzenes with isobutyraldehyde and nitriles.
TL;DR: The results of studies of rhenium chalcogenide cluster complexes with the Re4Q4 cubane core, where Q = S, Se, or Te, are reviewed in this article.
Abstract: The results of studies of rhenium chalcogenide cluster complexes with the [Re4Q4] cubane core, where Q = S, Se, or Te, are reviewed. Different approaches to the synthesis of these compounds are surveyed and their properties and structures are considered. Substitution reactions in the cluster core and replacements of terminal ligands are discussed. The formation of polymers consisting of the tetranuclear rhenium chalcogenide cyanide clusters as structural building blocks is considered.
TL;DR: In this paper, the crystal and molecular structure of 4H2O were determined by X-ray diffraction analysis, and they were obtained under conditions of hydrothermal synthesis from solutions of uranyl(vi) nitrate and cucurbituril in the presence of rubidium chloride.
Abstract: Crystals of supramolecular compound {[(UO2)4O2Cl4(H2O)6](H2O⊂C36H36N24O12)}·4H2O were obtained under conditions of hydrothermal synthesis from solutions of uranyl(vi) nitrate and cucurbituril in the presence of rubidium chloride. The crystal and molecular structure were determined by X-ray diffraction analysis.
TL;DR: In the general case, the efficacy of the cooperative interaction at the X*pY/ZZ" junction does not correlate with the energy of formation of the corresponding unified XY/ZZ dinucleotide pair in the structure of native DNA.
Abstract: Continuous stacking hybridization of oligodeoxyribonucleotides with the stem of a preformed minihairpin structure of a DNA template was studied by thermal denaturation in solution. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°37) were determined for the formation of all 16 possible types of coaxial stackings (or cooperative interactions) 5"
X*pY
3"/5"
ZZ"3" (an asterisk stands for a nick) between the terminal complementary base pairs of two adjacent duplexes formed on a common DNA template. The maximum efficacy ΔG°37 of coaxial stacking (1 M NaCl, pH 7.4) was observed for the G*pC/GC interaction (–2.76 kcal mol–1), whereas the minimum efficacy was observed for the T*pA/TA interaction (–0.85 kcal mol–1). In the general case, the efficacy of the cooperative interaction at the X*pY/ZZ" junction does not correlate with the energy of formation of the corresponding unified XY/ZZ" dinucleotide pair in the structure of native DNA. The formation of a stack by the terminal oligonucleotide bases upon their continuous stacking hybridization makes the major and governing contribution to the energy of cooperative interaction.
TL;DR: In this article, the optimum molar ratios between the catalyst and reagents were determined, and the reaction conditions for the highly selective synthesis of esters, aldehydes, ketones, and lactones from alcohols were found.
Abstract: Primary alcohols and diols with various structures were subjected to transformations into esters, aldehydes, ketones, and lactones under the action of carbon tetrachloride in the presence of manganese compounds (MnCl2, MnO2, Mn(OAc)2, Mn(acac)3) and vanadium compounds (VCl5, V2O5, VO(acac)2) as catalysts. These transformation proceeded with the involvement of alkyl hypochlorites, which were generated in the course of oxidation of alcohols with carbon tetrachloride catalyzed by manganese or vanadium compounds. The optimum molar ratios between the catalyst and reagents were determined, and the reaction conditions for the highly selective synthesis of esters, aldehydes, ketones, and lactones from alcohols were found.
TL;DR: In this paper, the effect of substituent R on the specific features of the nucleophilic substitution reaction observed in 3-nitro-4-R-furazans with ammonia was considered.
Abstract: The reactions of 3-nitro-4-R-furazans with ammonia were studied. The effect of the substituent R on the specific features of the nucleophilic substitution reaction observed was considered. The nitro group attached to the furazan ring can act as both the leaving group and the activating group facilitating the displacement of the second substituent (for example, OR" or N(NO2)R").
TL;DR: In this article, the relative stabilities of the starting and final propyne structures and corresponding allenes as well as the structure of intermediate carbanions were considered using the ab initio approach.
Abstract: Acetylene—allene rearrangement in propargyl systems XCH2CH≡CH (X = H, Me, NMe2, OMe, F, and SMe) was studied using the ab initio approach. The relative stabilities of the starting and final propyne structures and the corresponding allenes as well as the structure of intermediate carbanions were considered. n� π�Conjugation was shown to dominate in allene stabilization while the inductive effect of heteroatomic substituents makes at least compa� rable contribution to stabilization (or destabilization) of the propynyl structure. In particular, relative instability of 1�methoxypropyne can be rationalized by high electronegativity of O atom, which leads to dramatic decrease in the total electron density in the region of the neighboring C≡C triple bond. The influence of substituents on the mobility of the migrating proton was considered for the gas phase and with solvation effects included. Calculations involving electron correlation at the MP2 level of theory were shown to be insufficient for correct reproduction of the energy differences between the corresponding propynes and allene structures. The results of MP4 calculations with inclusion of ZPE correction are in good agreement with the available experimental data.
TL;DR: In this article, four triterpene glycosides were isolated from the roots of Pulsatilla chinensis (Bunge) Regel (Ranunculaceae).
Abstract: Four triterpene glycosides were isolated from the roots of Pulsatilla chinensis (Bunge) Regel (Ranunculaceae). Two new glycosides, chinensiosides A (1a) and B (2), were identified as 3-O-[α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl]-28-O-[α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-3β,23-dihydroxylup-20(29)-en-28-oic acid and 3-O-{α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→4)]-α-L-arabinopyranosyl}-28-O-[α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-3β,23-dihydroxylup-20(29)-en-28-oic acid. The other two glycosides were identified as previously known hederasaponin C (3) from Hedera helix and glycoside III (4) from Pulsatilla cernua.
TL;DR: In this article, copolymerization of carbon dioxide with propylene oxide in the presence of zinc adipate was studied, and the effects of the temperature, nature of the solvent, and catalyst concentration on the molecular weight, molecular-weight distribution, and yields of the copolymers and propylene carbonate were examined.
Abstract: Copolymerization of carbon dioxide with propylene oxide in the presence of zinc adipate was studied. The effects of the temperature, nature of the solvent, and catalyst concentration on the molecular weight, molecular-weight distribution, and yields of the copolymer and propylene carbonate were examined. The structure of the polymer obtained was studied by 13N and 1I NMR spectroscopy.
TL;DR: In this paper, the authors calculated the heat of the addition of H atom and Me· radical to carbon atoms of a capped (10,10)-nanotube by the molecular dynamics method with Brenner's potential.
Abstract: The heats of addition of H atom and Me· radical to carbon atoms of a capped (10,10)-nanotube were calculated by the molecular dynamics (MD) method with Brenner"s potential. According to calculations, the reaction heats linearly depend on the pyramidalization angle, which is a quantitative measure of the local curvature and strain in the planar carbon sheet in the vicinity of the reaction center. Depending on the pyramidalization angle (0—20°), the change in the reaction energy can reach 1 eV. Comparison of the results obtained for a model reaction CH3
· + H· → CH4 using the ab initio approach and MD simulations with Brenner"s potential shows that this potential can be used in studies of the effect of pyramidalization of the carbon center on its reactivity.
TL;DR: In this paper, approaches to the synthesis of 3-aminothiophene-2,4-dicarboxylic acid derivatives and their conversion into thieno[3,4d]pyrimidines were presented.
Abstract: Approaches to the synthesis of 3-aminothiophene-2,4-dicarboxylic acid derivatives and to their conversions into thieno[3,4-d]pyrimidines, thieno[3,4-d]-1,2,3-triazines, and thieno[3,2-d]pyrimidines are developed.
TL;DR: In this article, the key approaches to the generation of reaction networks for the synthesis of products from CO and H2 are considered and the selection rules for the elementary steps on the surface of heterogeneous catalysts are formulated.
Abstract: The key approaches to the generation of reaction networks for the synthesis of products from CO and H2 are considered. The selection rules for the elementary steps on the surface of heterogeneous catalysts are formulated. Data on the surface compounds and steps related to reactions of CO and H2 are analyzed and a set of transforms (models of elementary steps) for generation of the reaction network are selected. Eight variants of generation of reaction networks for the formation of C1 products with different sets of transforms (12 to 31) were tested in computer experiments, and eight reaction networks comprising 34 substances and 132 to 1647 elementary steps were obtained. The pathways to CO2, CH4, and CH3OH and pairs of compounds CH4, CO2 and CH4, HCOOH obtained from the reaction network (220 elementary steps) are compared with the published schemes.