Stabilization of even-electron ions in 4-amino-substituted cytosines. Appearance of the strong ortho effect between an aryl substituent and the pyrimidinyl ring

The mass fragmentation of 4-arylaminocytosine derivatives was investigated and it was found that the ortho effect is mainly responsible for the strong stabilization of even-electron ions formed during fragmentation. The ortho effect in this class of compounds completely eliminates other possible fragmentation patterns. This effect disappears when the aryl substituent is separated from the 4-amino group of the cytosine moiety by a methylene group.     

Acid-catalyzed cyclization of N-3-hydroxyalkyldithiocarbamates

A study was carried out on the reaction of N-3-hydroxyalkyldithiocarbamates with concentrated sulfuric acid, which may lead to the formation of alkyl derivatives of 2-methylthio-5,6-dihydro-4H-1,3-thiazines or 2-methylthio-2-thiazolines, depending on the structure of the hydroxyalkyl fragment.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 3, pp. 415–416, March, 1994.     

Thermal properties of N-substituted 4-vinylpyridinium ions and their polymers

4-Vinylpyridinium trifluoromethanesulfonate monomers substituted at nitrogen with H, O, CH₃, C₂H₅, C₆H₁₃, and C₁₂H₂₅ were synthesized and characterized spectroscopically. Thermal analyses (DSC and TGA) were carried out on all the compounds. The solid monomers (N? H, N? CH₃, N? C₆H₁₃, and N? C₁₂H₂₅) exhibited endothermic melting followed by exothermic polymerization and exothermic decomposition (>400°C). Liquid N? C₂H₅ monomer revealed only exothermic polymerization and decomposition. The N? O polymer underwent thermal decomposition below 300°C. The N–C₁₂H₂₅ homopolymer, prepared from monomer in the DSC or in bulk, displayed an unusual thermal transition at 250°C, which has been attributed to a polymer backbone reorientation leading to side-chain ordering of the dodecyl groups.     

Stabilization of methyl anions by first row substituents

A theoretical examination of the stabilization of simple carbanions, XCH₂^?, by substituents comprising elements of the Li-F period, reveals the particular effectiveness of the electropositive substituents, BH₂, BeH, and even Li, with vacant p-orbitals. The relative influence of pi and sigma stabilization or destabilization is assessed.     

Stabilization of methyl cations by second row substituents

With the exception of PH₂ ($\text{vs}$. NH₂) all second row substituents, Na, MgH, AlH₂, SiH₃, SH and Cl, stabilize methyl cations more effectively than their first row counterparts.     

Effects of the 3- and 4-methoxy and acetamide substituents and solvent environment on the electronic properties of N-substituted 1,8-naphthalimide derivatives

The photophysical properties of polar molecules in solution with an intramolecular charge-transfer effect in the excited state depend strongly on the polarity and proticity of the solvents. UV-visible spectra of 1,8-naphthalimide and some N-substituted derivatives in acetic acid, acetonitrile, dichloromethane, and p-dioxane were carried out. Several molecular cluster geometries formed with N-substituted 1,8-naphthalimide derivatives and a large set of random positioning of some solvent molecules in their environment were optimized by a semiempirical method. It provided a complete screening of possible solute-solvent configurations and resulted in a multiple minima hypersurface of the supramolecular systems. With such local minima energies, the main thermodynamic association functions were found. They also provided selected cluster geometries for calculations of vertical electronic transitions with a time-dependent density functional theory (TD-DFT), if the lowest energy structures were considered. Calculated vertical electronic transition energies at the TD-DFT level were compared with experimental data. The experimental absorption UV-visible spectra for the six compounds in the four solvents were performed in our laboratory. Moreover, X-ray photoelectron spectroscospy of the 1,8-naphthalimide was carried out in the ICP-CSIC laboratory. Thermodynamic function values show different association energies between each solvent and the molecules, in correlation with the possibility of hydrogen bond formation and the polarity and dielectric constant of the solvents. The 3- and 4-acetamide 1,8-naphthalimide derivatives have the highest conformer number and the most negative Gibbs free association energy values for a determined solvent. This indicates the importance of the entropic factors.     

Condensed thiolane 1,1-dioxide systems. 3. Two modes of cyclization of N-substituted trans-3-chloro-4-thioureidothiolane 1,1-dioxides

Reaction of trans-3-chloro-A-aminothiolane 1,1-dioxide hydrochloride with aryl isothiocyanates gives, according to the base involved, cis-perhydrothieno[3,4-d]imidazole-2-thione 5,5-dioxides or the hitherto undescribed cis-2-aryliminoperhydrothieno 3,4-d] thiazole 5,5-dioxides.For Part 2, see [1].Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1420–1423, October, 1988.     

Bifunctional even-electron ions. II. Fragmentation behaviour of aliphatic ω-hydroxy and ω-methoxy methoxonium ions

Bifunctional methoxonium ions \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R} -\mathop {\rm C}\limits^ + ({\rm OCH}_3 ) - ({\rm CH}_2 )_{\rm n} - {\rm OH}({\rm b}) $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R} - \mathop {\rm C}\limits^ + ({\rm OCH}_3 ) - ({\rm CH}_2 )_{\rm n} - {\rm OCH}_3 ({\rm c}) $\end{document} (c) show as the main reactions those caused by functional group interaction, as has already been found for the analogous hydroxonium ions (g). Although there are similarities in the fragmentation behaviour of the isomeric ions b and g, their fragmentation pathways are different, proving b and g as distinct species. The dominant primary fragmentation for b and c is loss of CH₃OH. The hydrogen migrations prior to this reaction have been established by deuterium labelling. The findings on the fragmentation behaviour of the bifunctional methoxonium ions have been extended to the general behaviour of hydroxy and alkoxy substituted alkoxonium ions.     

Bacteriostatic activities of N-substituted tris-thioureas bearing amino acid and aniline substituents

A series of tri-substituted thiourea derivatives were synthesized by the reaction of 1,3,5-triacetylbenzoyl isothiocyanate with aminoacids and aniline derivatives. All thiourea derivatives were characterized by FT-IR, ¹H and ¹³C NMR spectroscopy. Antibacterial activities against wild-type Escherichia coli American Type Culture Collection 8739 were determined by use of the turbidimetric methodto evaluate the effect of varying amino groups on the synthesized thioureas. Tris-thiourea derivatives bearing ortho-chloroaryl substituents showed excellent antibacterial activity against E. coli with minimal inhibitory concentration (MIC) of 96 ppm. The optimum inhibition was dependent on the type of amines and the position of the halogen in aniline.     

The effect of substituents on the average internal energy of benzoyl ions generated from N-(substituted-phenyl)benzamides

The [56.5^*]/[105]⁺ ratios observed in the spectra of N-(nitrophenyl)benzamides are greater than those observed in the spectra of N-(methoxyphenyl)benzamides. These results differ from those observed in the spectra of monosubstituted benzophenones. An explanation, based on energy distribution and breakdown curves, is employed to rationalize these results, as well as other phenomena reported in the literature.     

Synthesis of N-substituted 3-hydroxy-2-methyl-4-pyridones and -pyridonimines

Carbohydrates with 1,4 glycosidic bonds like maltose, lactose, dextrin or starch react with primary amines as well as amino acids or proteins to give i.e. 3-hydroxy-2-methyl-4-pyridones 5 and 3-hydroxy-2-methyl-4-pyridonimines 7. A generally applicable synthesis of compounds of this type is described. The pyridones 5 and pyridonimines 7 are strongly complexing agents. Molybdenum-derivatives, for instance, are suitable as fairly stable oxidation catalysts.     

Reversible cyclization of N-(3-hydroxy-1-alkenyl)pyridinium salts to pyridooxazines

Partially hydrogenated pyrido[2,1-b][1,3]oxazine, cyclopenta[d]pyrido[2,1-b][1,3]oxazine and pyrido[1,2-a]-[3,1]benzoxazine ring systems were easily formed in the reaction of 3-hydroxy-2-(2-hydroxy-1,3-dioxo-2-indanyl)-2-alken-1-one derivatives with tosyl chloride and pyridine bases. A facile interconversion between pyridooxazines and the corresponding pyridinium salts was also realized.     

Bifunctional even-electron ions: 1—Fragmentation behaviour of ω-methoxy-, ω-hydroxy- and ω-chloro-oxonium ions

Bifunctional oxonium ions—generated from tertiary aliphatic alcohols containing an additional hydroxy, methoxy or chloro group at the end of an alkyl side-chain—do not markedly exhibit fragmentations typical of ordinary oxonium ions, but show as the main reactions those caused by functional group interaction, through-space interaction being the dominant factor. The main primary fragmentation is loss of the additional functional group X as HX, followed by loss of the side-chain originally separating the two functional groups, leading to carbonyl cations. This typical reaction sequence is initiated by proton migration from the oxonium moiety to the additional functional group. The reaction behaviour of the bifunctional ions is discussed. The lowest homologues show specific deviations from the general fragmentation behaviour.     

N-3-oxoalkylamides and-thioamides in synthesis of heterocyclic compounds. 3. Study of cyclization of N-3-oxoalkylthioamides into 5,6-dihydropyridine-2(1H)-thiones

5,6-Dihydropyridine-2(1H)-thiones containing a hydrogen atom, aryl, or alkyl substituent in position 3 were obtained by cyclization of fatty acid N-3-oxoalkylthioamides with bases.See [1] for Communication 2.Omsk State University, Omsk 644077. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 73–76. January, 1998.