Synthesis of nitrogen- and oxygen-containing macrocycles--derivatives of lithocholic Acid

Palladium-catalyzed amination of 3,24-bis(3-bromophenoxy)cholane (4) with various polyamines and polyoxadiamines 5 taken in 1:1 ratio was used for the synthesis of the macrocycles 6, which contain steroidal and polyamine moieties and were obtained in 38-65 % yields. The same reaction with excess polyamine (2.2-3 equiv) provided bis(polyamino) derivatives of 3,24-diphenoxycholane 7 in excellent yields, whereas the diarylation of polyamines with two equivalents of 3,24-bis(3-bromophenoxy)cholane afforded their bis(steroidal) derivatives 8. Compounds 7 and 8 were employed in the syntheses of cyclodimers 9, which possess two steroidal and two polyamine fragments; the efficiency of two methods was compared.     

Electrolytic partial fluorination of organic compounds.71. Highly diastereoselective anodic fluorination of sulfides having oxygen-containing heterocyclic groups

Diastereoselective anodic fluorination of sulfides having various oxygen-containing heterocyclic substituents such as 2-furanyl, 1,3-dioxolanyl, 2,2-dimethyl-1,3-dioxolanyl, 2-spirocyclohexyl-1,3-dioxolanyl, 2-spiroadamantyl-1,3-dixolanyl, and 1,3-dioxolanonyl groups at the beta-position was comparatively studied. Among the oxygen-containing heterocyclic substituents, the 2-spirocyclohexyl-1,3-dioxolanyl group gave the best diastereoselectivity (80% de). The diastereoselectivity was also affected by supporting fluoride salts and solvents. Chemical fluorination using selectfluor resulted in much lower diastereoselectivity and extremely poor yield. The fluorinated products were readily converted into the corresponding fluorinated diol in good yields by acidic hydrolysis.     

15N and 17O NMR spectra of some nitrogen- and oxygen-containing polyfluoroaromatic compounds

The effect of substitution of hydrogen by fluorine on the ¹⁵N and ¹⁷O NMR chemical shifts in N-sulphinylarylamines, azoxy- benzenes, C,N-diarylnitrones and aromatic azomethines has been studied. Changes in nitrogen screening are controlled mainly by the radial factor <r^?3>_2p(N), which depends on the electron density on nitrogen, those in oxygen screening — by the two factors, the excitation energy ΔE^?1 and the radial factor <r^?3>_2p(0), which may operate in the same or opposite directions. The ¹⁵N and ¹⁷O NMR spectra of the above compounds did not show any specific effects of perfluorination.     

Microdetermination of nitro groups in organic compounds

Summary A simple procedure for microdetermination of nitro groups in organic compounds is described. It is based on reduction with palladium-on-carbon catalyst in acetic acid in a modified Roth apparatus.

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Zusammenfassung Ein einfaches Verfahren zur Mikrobestimmung von Nitrogruppen in organischen Verbindungen wurde beschrieben. Es beruht auf der Reduktion in Essigsäure mit Palladium-Kohle als Katalysator in einem modifizierten Apparat nachRoth.

     

Kinetic parameters of the cyclization and decyclization reactions of nitrogen- and oxygen-containing radicals

The intersecting parabolas model is used to analyze experimental data for the following radical cyclization and decyclization reactions: RCH=CH(CH₂)_nN·R₁ cyclo-[NR₁CH(CH₂)_n]C·HR,R(CH₂)₂OOCH₂C·HR cyclo-[RCHOCH₂] + RCH₂CH₂O·, cyclo-[(CH₂)_nOOCHC· HR] cyclo-[RCHOCH](CH₂)_nO·, cyclo-[(CH₂)_nOC·RO] RC(O)O(CH₂) _n–1C·H₂, and cyclo-[(CH₂)_nCHO·] CH(O)(CH₂) _n–1C·H₂. The activation energy of the thermally neutral reaction (E _e,0) is calculated for each class of reactions. E _e,0 depends on the electronegativity of the heteroatom Y of the reaction center C C...Y, the force constants of the reacting bonds, and the strain energy of the ring formed. For the cyclization and decyclization of six-membered rings, the empirical relationship between the elongation of the reacting bonds in the transition state (r _e) and the difference in electronegativity (EA) between the C and Y atoms (Y = C, N, O) has the form r _e ×10₁₁, m = 3.83 – 0.0198(EA, kJ/mol).Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 5–13.Original Russian Text Copyright © 2005 by Denisova, Denisov.     

Stereochemistry of vanadium in oxygen-containing compounds

Using Voronoi-Dirichlet (VD) polyhedra and the method of overlapping spheres, we analyze the coordination of 714 crystallographically different vanadium atoms in the structure of compounds containing VO _n polyhedra. Vanadium atoms are found to be bonded to 4, 5, 6, or 7 oxygen atoms. The effect of the valence state and coordination number of vanadium atoms on the main parameters of their VD polyhedra is considered. A unified linear dependence between the solid angles of VD polyhedron faces corresponding to V-O bonds and the respective interatomic distances varying in a range of 1.55 Å to 2.79 Å is stated to exist. It is shown that the parameters of VD polyhedra can be used to determine the valence state of vanadium atoms.     

Stereochemistry of thorium in oxygen-containing compounds

Voronoi–Dirichlet (VD) polyhedra and the method of intersecting spheres have been used to perform analysis of coordination of 198 types of crystallographically different Th(IV) atoms in the crystal structures of oxygen-containing compounds characterized with R ≤ 0.05. The volumes of VD polyhedra have been determined for the thorium atoms forming ThO_n complexes in which the Th–O bond lengths (2.14–2.91 Å) are roughly independent of the CN (n), varying from 4 to 12. It has been found that the phase transition of thorianite ThO₂ at elevated pressure is accompanied by a considerable distortion of the thorium VD polyhedra because of the appearance of faces corresponding to Th–Th contacts in which the interatomic distances are shorter than in thorium metal. It has been demonstrated that the baric phase transitions in thorium metal and thorianite are accompanied by similar changes in characteristics of Th VD polyhedra, which are tentatively believed to be a result of appearance of bonding 5f interactions between thorium atoms.     

On oxygen-containing groups in chemically modified graphenes

Reduced graphenes (belonging to the class of chemically modified graphenes, CMG) are one of the most investigated and utilized materials in current research. Oxygen functionalities on the CMG surfaces have dramatic influences on material properties. Interestingly, these functionalities are rarely comprehensively characterized. Herein, the four most commonly used CMGs, mainly electrochemically reduced graphene oxide (ER-GO), thermally reduced graphene oxide (TR-GO), and the corresponding starting materials, that is, graphene oxide and graphite oxide, were comprehensively characterized by a wide variety of methods, such as high-resolution X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, UV/Vis spectroscopy, transmission electron microscopy (TEM), and voltammetry, to establish connections between the structures of these materials that carry different oxygen functionalities and their electrochemical behaviors. This was followed by the quantification of the negatively charged oxygen-containing groups (OCGs) by UV/Vis spectroscopy and of the electrochemically reducible OCGs by voltammetry. Lastly, a biofunctionalization with gold nanoparticle (AuNP)-modified DNA sequences was performed by the formation of covalent bonds with the carboxylic groups (-COOH) on the CMG surfaces. There was an evident predominance of functionalizable -COOH groups on the ER-GO surface, as confirmed by a higher amount of Au detected both with differential-pulse voltammetry and impedance spectroscopy, coupled with visualization by TEM. We exploited the DNA-Au bioconjugates as highly specific stains to localize and visualize the positions of carboxylic groups. Our findings are very important to clearly identify the presence, nature, and distribution of oxygen functionalities on different chemically modified graphenes.     

Chromatographic determination of alkoxyl groups in organic compounds

Conclusions A gas-chromatographic method was developed to determine the ethoxyl groups in organic compounds. The accuracy of the method is ±0.3%, and the analysis time is 25–30 min.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2090–2092, September, 1971.     

The microdetermination of C-methyl groups in organic compounds

Summary Existing standard procedures for the microdetermination of C-methyl groups in organic compounds have been discussed, and a modified micromethod, in which the oxidation of the sample and the distillation of the resulting acetic acid are carried out simultaneously, has been presented. New and useful information on the stability of acetic acid, when heated in presence of chromic-sulphuric acid mixture of varying strengths, for periods ranging between 15–90 minutes, and at temperatures varying between 130–300° C, has been given. A number of simple organic substances have been analysed for their C-methyl values by the different procedures, and the results have been recorded and discussed.

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Zusammenfassung Bekannte Verfahren für die Mikrobestimmung von C-Methylgruppen in organischen Verbindungen wurden diskutiert und eine modifizierte Mikromethode vorgeschlagen, bei der die Oxydation der Substanz und die Destillation der dabei entstehenden Essigsäure gleichzeitig durchgeführt werden. Neue und wertvolle Angaben über die Beständigkeit der Essigsäure gegenüber heißer Chromsäure-Schwefelsäure verschiedener Konzentration bei Einwirkungszeiten von 15 bis 90 Minuten und Temperaturen zwischen 130 und 300° werden gemacht. Eine Reihe einfacher organischer Substanzen wurden nach verschiedenen Verfahren auf ihren C-Methylgehalt untersucht: die Ergebnisse werden angeführt und diskutiert.

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Résumé On a discuté les procédés «standards» existant pour doser les groupes C-méthylés dans les composés organiques et l'on a présenté une microméthode modifiée dans laquelle l'on effectue simultanément l'oxydation de l'échantillon et la distillation de l'acide acétique résultant. On a donné une indication nouvelle et utile sur la stabilité de l'acide acétique chauffé en présence du mélange sulfochromique de forces différentes, pendant des durées allant de 15 à 90 minutes et à des températures comprises entre 130 et 300° C. On a analysé un certain nombre de substances organiques du point de vue de leurs teneurs en C-méthylés au moyen de différents procédés et l'on a rassemblé et discuté les résultats.

     

Photometric microdetermination of acetyl groups in organic compounds

A method for the microdetermination of acetyl groups is described which combines features of the known transesterification and the hydroxamate methods. All acetyl groups attached to oxygen or nitrogen are converted to methyl acetate which is distilled off and determined photometrically as the iron complex of the acethydroxamic acid. A slightly modified technique permits the selective determination of acetyl groups in the presence of formyl groups.