Bromination of 8R-4-phenyl-2,3-dihydro-1H-1,5-benzodiazepinones-2

The influence of the nature of the substituents and the brominating agent on the direction of the bromination of 8R-4-phenyl-2,3-dihydro-1H-1,5-benzodiazepinones-2 containing various substituents in the annelated benzene ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1133–1135, August, 1984.     

Interaction of [acacRh(CO) n ]+ ions (n=0–2) with aromatic nitro compounds in the gas phase

Summary The mass-spectrometry method has been applied to a study of the interaction of [acacRh(CO)₂]⁺ with aromatic nitro compounds in the gas phase and the reactivity order of these compounds has been determined. The coordination mechanism has been found to depend upon the nature of the nitro compound and its ability to replace carbonyl ligands increases with increasing electron-donor ability of substituents. Specific reactions leading to dissociation of C–H, N–O, and O–H bonds are discussed.     

Oxidative Ammonolysis of Dialkylpyridines

The cluster approach was used to simulate the chemisorption of dialkylperidines on the surface of a vanadium oxide catalyst, involving active centers of various nature, and to assess the enthalpy of proton abstraction from the alkyl substituents. Under oxidative ammonolysis conditions, the order of the transformation of the substituents in unsymmetrical dialkylpyridines into the cyano group is determined by the enthalpy of their deprotonation.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 159–163.Original Russian Text Copyright © 2005 by Vorob’ev, Sembaev.     

Features of the mass spectra of lycoctonine bases with 7,8-methylenedioxy groups

The mass-spectral properties of 21 lycoctonine bases with 1-methyoxy-7,8-methyl-enedioxy groups have been studied and generalized. An influence of a methyl-enedioxy group of the nature of the substituents at C-6 and C-10, and of a ¹⁰⁽¹²⁾ bond on the fragmentation of the alkaloids and their derivatives has been found.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Abu Ali ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 389–397, May–June, 1987.     

Thermodynamic characteristics of sorption of heterocyclic compounds m capillary gas chromatography

Dependences of sorption energies of sulfur-, oxygen-, and nitrogen-containing heterocyclic compounds on the nature of heteroatoms, structure of substituents and their position in the ring were studied. The contributions of heteroatoms, functional and alkyl groups to the energy of dispersive interaction of position isomers with nonpolar stationary phases were determined for imidazoles, piperidines, morpholines, thiomorpholines, dioxalanes, oxathiolanes, dithiolanes, thiophenes, and furans. The nonequivalence of contributions of the same substituents to the sorption energy of each of the heterocyclic compounds, depending on the nature of the heteroatom and position of the substituent, was shown. The obtained values of contributions of heteroatoms and substituents can be used for apriori calculation of retention indices of position isomers of five- and six-membered heterocycles containing one or two heteroatoms in the ring.Translated from lzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2033–2038, August, 1996.     

A mass spectrometric study of some dihydropyranocoumarins

Summary The mass spectra of ten angular and linear dihydropyranocoumarins without substituents and with hydroxy and acyloxy substituents in position 3 of the dimethylchroman ring have been studied. Depending on the presence and nature of these substituents the mass spectra of the compounds considered have different relative intensities of the fragments with m/e 228, 213, 176, 175, 83, and 85, which permits mass spectrometry to be used in this group of compounds for structural-analytical purposes.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 398–401, July–August, 1971.     

Acyclic analogs of pyrimidine nucleosides. Synthesis of 1-(2-hydroxyethoxymethyl)- and 1-(4-hydroxybutyl)-5-amino derivatives of uracil

With the objective of discovering new antiviral agents based on acyclic analogs of pyrimidine nucleosides, we have synthesized 1-(2-hydroxyethoxymethyl)- and 1-(4-hydroxybutyl) derivatives of uracil having various aromatic and heterocyclic amino-containing substituents in the 5 position of the pyrimidine ring.Scientific-Research Institute of Pharmacology, Volgograd Medical Academy, Volgograd 400066, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 971–978, July, 1998.     

Role played by the organometallic fragment on the first hyperpolarizability of iron–acetylide complexes: A TD-DFT study

The static first hyperpolarizabilities (β) for a series of both substituted thiophene-acetylide ligands and the corresponding η⁵–monocyclopentadienyliron(II) complexes were determined by density functional theory (DFT) calculations. The effect on the hyperpolarizabilities by various donor and acceptor substituents in the thiophene-acetylide ligands was studied. The nature and role of the electronic excitation contributions to the first hyperpolarizability, using time-dependent DFT (TD-DFT) calculations, are rationalized in terms of the two-level model. Our calculations show that the organometallic fragment can form a very effective push-pull system in combination with electron-withdrawing substituents in the thiophene-acetylide moiety, leading to enhanced static first hyperpolarizabilities. Also, an improvement of the magnitude of β is expected if solvation effects are taken into account.     

Investigation of complexes of DNA with synthetic peptide fragments of the N-end of histone H2B

The nature of the interaction of high- and low-molecular-weight DNAs (6×10⁶ and 3×10⁵ daltons) with synthetic oligopeptides of the N-end of histone H2B having the sequences 1–21, 1–10, 1–13, 11–21, and 14–21, differing in molecular weight and amino acid composition, as a function of the amount of peptide component in the complex and the ionic strength of the solution has been studied by the methods of UV and CD spectroscopy and the spectrophotometric analysis of melting curves. It has been shown that of all the peptides studied only the 1–21 peptide possesses the capacity of condensing DNA. This capacity depends on the amount of peptide component in the complex, the molecular weight of the DNA, and the ionic strength of the solution. The interaction with peptides under all the conditions studied, without changing the conformational parameters of the DNA, stabilizes its secondary structure in relation to the action of the temperature, which depends on the number of lysine residues in the peptides.N. I. Nikitin Institute of Chemistry of the TadzhSSR Academy of Sciences, Dushanbe. Institute of Cytology of the USSR Academy of Sciences, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 708–713, September–October, 1987.     

Solvent and Substituent Effects on the Protonation of Anilines in Dioxane–Water Mixtures

Protonation constants of a number of mono-substituted anilines were determined potentiometrically in 0, 20, 30, 40, 50, and 60% (v/v) dioxane–water mixtures at (25.00 ± 0.0.02)°C at an ionic strength of 0.1 mol-dm^–3 in sodium perchlorate. The data from the potentiometric titrations were evaluated using the BEST computer program. The trends in the values of the protonation constants of anilines were explained in terms of the nature of substituent and the solute–solvent and solvent–solvent interactions. Furthermore, the effects of the substituents on the basicity of aniline, the additivies of these effects, and the applicability of the Hammett equation to the behavior of these substituents are discussed.     

A force-field model and steric reactivity factor estimation

Steric reactivity factor estimation is considered on the basis of the energies of various substrate and intermediate conformations within the framework of a forcefield model. The example of alkali hydrolysis of ethyl esters of substituted acetic and malonic acids is taken to examine the relationship between the steric reactivity indices, the steric constants of the substituents, and the rate constants. It is found that the main contribution to the steric component of the free energy of activation comes from the van der Waals interaction in these systems.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 3, pp. 366–370, May–June, 1986.     

Reactions involving isotopic exchange of heterocyclic compounds with D2O in the presence of transition metals (review)

The results of isotopic exchange with D₂O of various O-, N-, and S-containing heterocycles and some hydrocarbons on transition metals are discussed from the positions of the theory of -complex adsorption. The effect of various fragments of the molecules (the aromatic or alicyclic ring, electron-donor or electron-acceptor substituents, double bonds, and the number and nature of the heteroatoms) on the character of the substrate-catalyst interaction and on the reaction as a whole is examined on the basis of kinetic data from ¹H and ¹³C NMR spectroscopy and Chromatographic mass spectrometry. Isotopic exchange mechanisms are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1021, August, 1982.     

Reactions of organyltrifluoro- and diorganyldifluoro- silanes with 1,1,3,3-tetramethyldisiloxane

1,1,3,3-Tetramethyldisiloxane is decomposed by organyltrifluoro- and diorganyl- difluorosilanes already at 20C in the presence of catalysts with formation of hitherto unknown 1,1-dimethyl-3,3-diorganyl-3-fluoro- and 1,1-dimethyl-3-organyl-3,3-difluorodisiloxanes of general formula R_4–nSiF_n–1OSiH(CH₃)₂ (n=2–3) in yields of 50–70%. On storing these decomposition products easily disproportionate in various directions, in which their propensity to disproportionation is determined by the nature of the substituents at the silicon atoms and the number of fluorine atoms in the molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1162–1166, May, 1991.     

Conductance study of the thermodynamics of ammonium ion complexes with several crown ethers in acetonitrile solution

A conductance study concerning the interaction between ammonium ion and several crown ethers in acetonitrile solution has been carried out at different temperatures. The stability constants of the resulting 11 complexes at various temperatures were determined from the molar conductance-mole ratio data and found to vary in the order DC18C6>18C6>DB30C10>DB21C7>DB24C8>DB18C6>15C5>B15C5. The enthalpy and entropy of complexation were determined from the temperature dependence of the formation constants. The influence on the thermodynamic data of different parameters such as cavity size and dimensionality of crown ethers, nature of substituents in the polyether ring, conformations of the free and complexed ligands, solvent-ligand interaction and number of N–H bonds available for hydrogen bonding are discussed.     

Hetarylethylene derivatives of 2,5-diphenyloxazole

A number of new effective luminophores were synthesized by PO olefination from 2-(4-bromomethylphenyl)-5-phenyloxazole and various heterocyclic aldehydes containing a furan ring. All of the compounds obtained have intense fluorescence in toluene and, depending on the nature of the substituents, the color of the luminescence changes from blue to green. It is shown that chloro, bromo, and methyl substituents have little effect on the spectral-luminescence properties of the compounds obtained, whereas a nitro group causes a decrease in the fluorescence quantum yield.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1616–1618, December, 1977.     

Anodic Oxidation of Hypophosphite on a Nickel–Phosphorus Electrode in the Presence of Some Organic Compounds

The effects some sulfur-, nitrogen-, or oxygen-containing organic compounds exert on the hypophosphite oxidation are compared. Catalytic and inhibiting effects of additives, which depend on their nature and occur in different concentration intervals, are discovered and examined. The inhibiting effect, exerted by all substances studied, is accompanied by a shift of steady-state potential in the positive direction and is determined by the adsorbability of substances, which is a function of the nature and number of heteroatoms and substituents. The best inhibiting properties are intrinsic to an additive with an –S–S– fragment and NH₂ groups. Catalytic influence, which is typical only for sulfur-containing compounds at low concentrations, is accompanied by a shift of steady-state potential in the negative direction and may be related to a surface modification and a change in the metal–hydrogen bond energy.     

Negative- and positive-ion mass spectra of aryl glycoside acetates

The low specificity of the electron-impact positive-ion mass spectrum in relation to the structure of an aromatic aglycone has been shown. The glycosidic moiety is determined unambiguously from the pattern of the mass spectrum. The dissociative electron-capture mass spectra are sensitive to the nature of the substituents of the aromatic nucleus of the aglycone. The influence of the aglycone is most pronounced in cases with substituents having high electron affinities.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok, Institute of Biochemistry, Academy of Sciences of the Armenian SSR, Erevan, Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 623–628, September–October, 1984.     

13C NMR spectra and structure of bungeidiol and its transformation products

The results are given of a study of the¹³C NMR spectra of the new terpenoid coumarin bungeidiol (I) and of the products of its transformation (II) and (III) and some model compounds (IV–VII). On the basis of the results obtained from these¹³C NMR spectra and with the use of additive contributions depending on the nature and positions of various substituents (hydroxy and methoxy groups) in the aromatic ring, the structure (I) has been confirmed and a complete assignment of the signals of all the carbon atoms both in the coumarin ring and in the aliphatic part of the molecule of (I) has been made.Institute of Toxicology, Ministry of Health of the USSR, Leningrad. Translated from Khimiya Prirodynkh Soedinenii, No. 3, pp. 294–301, May–June, 1982.     

Tautomerism in 1-phenyl-3-carbomethoxyphosphorinan-4-one and its derivatives

Conclusions The possibility is discussed of using tautomerism to determine the conformational free energies of ring substituents, and the free energy of steric interaction of the substituents in the individual stereoisomers of 1-phenyl-3-carbomethoxyphosphorinan-4-one and its derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1533–1540, July, 1978.     

Mono- and Binuclear Copper(II) Metal Chelates with 3,5-Di(tert-butyl)salicylaldehyde Acylhydrazones

Some new mono- and binuclear complexes of copper(II) acetate, nitrate, and perchlorate with acylhydrazones of substituted salicylaldehyde derivatives containing bulky tert-butyl substituents are synthesized. The structure and properties of the complexes isolated are shown to be determined by both the structural features of the ligand systems and by the nature of the acido ligands. The exchange parameters 2J ranging from –108 to –125 cm^–1 are calculated for the binuclear copper(II) metal chelates.