Improved Synthesis of 4,4′-Disubstituted-2,2′-Bipyridines

Ruthenium(II) tris(2,2′-bipyridine) complexes show interesting photochemical properties^1. Complexes containing substituents in the 4-and 4′-position of the 2,2′-bipyridine ligand have recently been used in systems which are aimed at the conversion and storage of solar energy^2,3. 2,2′-Bipyridine has a long history as a metal-chelating agent⁴. The use of 4,4′-disubstituted bipyridines as metal-chelating agents so far has been restricted probably because the reported syntheses of these compounds are rather laborious and the yields are low or moderate^5–8.     

Syntheses of 5′-O-glycosylnucleosides

A general synthetic approach to 2,3-unsaturated glycosides connecting with nucleosides involving Ferrier rearrangements of glycals is discussed. The new compounds were identified by NMR and MS (HRFAB⁺). The hydroxylation of the resulting 2,3-unsaturated glycosides was completed using OsO₄ to give 5′-O-glycosylnucleosides in good yield.     

Synthesis of 5,5′-Dialkyl-6,6′-dichloro-2, 2′-bipyridines

5,5′-Dialkyl-6,6′-dichloro-2,2′-bipyridines were synthesized starting from 3-substituted 2-chloro-6-iodopyridines using Pd-catalyzed coupling conditions. 6-Alkyl-3,5-dichloro-2H-1,4-oxazin-2-ones were excellent precursors for the synthesis of these functionalized 2-iodo-6-chloropyridines.     

Investigations of 2,3′-biquinolines 23. Synthesis of 1′-R-1′,4′-dihydro-2,3′-biquinolin-4′-ones by Claisen condensation

A method has been developed for the synthesis of 1′-R-1′,4′-dihydro-2,3′-biquinolin-4′-ones based on the interaction of quinaldine with N-alkyl-N-formylanthranilic acid methyl esters under the conditions of the Claisen condensation. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 409–410, March 2008.     

Synthesis of 5′-deoxy-5′-[18F]fluoro-adenosine by Radiofluorination of 5′-deoxy-5′-haloadenosine Derivatives

5-Deoxy-5-[¹⁸F]fluoro-adenosine was synthesised by nucleophilic radiofluorination reactions of 5-deoxy-5-haloadenosines. The homogeneous isotope exchange in 5-deoxy-5-fluoro-adenosine was also investigated. The conversion of these reactions was found to be rather low and depends on the strength of the halogen-carbon bond: 0.248% for chloride-, 0.488% for bromide- and 1.070% for iodide-derivative; there was no reaction observed in the case of fluoro-compound.     

Calorimetric study of 2′-methylacetophenone and 4′-methylacetophenone

Values of the condensed phase standard (p = 0.1 MPa) molar enthalpy of formation for 2′- and 4′-methylacetophenones were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The values of the standard molar enthalpy of vaporization, at T = 298.15 K, were measured by Calvet microcalorimetry. Combining these two values, the following enthalpies of formation in the gas phase, at T = 298.15 K, were then derived: 2′-methylacetophenone, –(115.7 ± 2.4) kJ · mol⁻¹, and 4′-methylacetophenone, –(122.6 ± 2.4) kJ · mol⁻¹. Substituent effects are discussed in terms of stability and compared with other similar compounds. The value of the standard molar enthalpy of formation for 3′-methylacetophenone was estimated from isomerization schemes.     

Resolution and determination of the absolute configuration of 3,3′4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxylic acid

(±)-3,3′4,4′-Tetramethyl-1,1′-diphosphaferrocene-2-carboxylic acid 1 was resolved via diastereomeric salts with brucine. The (R)-absolute configuration of (+)-1 was determined by X-ray crystallography.     

Synthesis of 2′-5′,3′-5′ linked triadenylates

2′-5′,3′-5′ Linked triadenylates have been synthesized by direct bisadenylylation of adenosine 2′ and 3′ hydroxyls with an adenosine 5′-phosphorochloridite followed by oxidation.     

The reductive cyclization of 8,8′-bisbromomethyl-1,1′-binaphthyl

Reductive cyclization of the title compound to the corresponding dinaphthocycloöctatriene is a facile process. The dinaphthocycloöctatriene does not undergo ring inversion on the NMR time scale, even at elevated temperatures.     

Unexpected racemization behavior of 8,8′-dialkyl-1,1′-biisoquinoline

The racemization behavior of a series of atropisomeric 8,8′-dialkyl-1,1′-biisoquinolines, in which methyl, ethyl, and isopropyl groups are introduced for enhancing the transannular steric hindrance, is reported. Contrary to prior expectations, their configurational stability was inversely proportional to the steric size of the alkyl groups.     

Study of infrared spectrum of 3,3′-dichloroindanthrone

A complete calculation has been performed for the infrared spectrum of the molecule of 3,3-dichloroindanthrone, including vibration frequencies and intensities and the spectral curve. The satisfactory agreement that has been obtained between the calculated and experimental spectra has made it possible to interpret the spectrum in detail; to determine the characteristic spectral regions for manifestation of vibrations that pertain in form to such structural fragments of the molecule as the anthraquinone fragment, the nitrogen-containing ring, and the ring that embodies a hydrogen bond; and to obtain information on the sensitivity of vibrations to chlorination of indanthrone. The features that have been revealed have the character of a spectrum/structure correlation and can be used for analytical purposes.K. A. Timiryazev Agricultural Academy. Scientific-Research Institute of Physical Problems. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 190–196, January–February, 1993.     

Transformations of β-d-xylofuranosyl nucleosides. Synthesis of 3′-azido-3′-deoxythymidine

A modified synthesis of 3′-azido-3′-deoxythymidine starting fromD-xylose is proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2062–2063, October, 1998.     

Kinetic analysis of the mechanochemical syntheses of dialkyl 2,2′-bipyridyl-4,4′-dicarboxylate complexes of palladium

Kinetic models for the ‘molecular’ mechanochemical syntheses of α- and β-dialkyl 2,2′-bipyridyl-4,4′-dicarboxylate complexes of palladium (PdLⁿI₂, where n specifies the number of carbons in the alkyl chain of the ligand and α and β refer to the substitution of the alkyl chain) are explored. The Johnson–Mehl–Avrami–Yerofeev–Kolmogrov (JMAYK) model was determined to best fit the data obtained via ¹H NMR spectroscopic analysis of the reaction mixtures over time. A rate enhancement, and corresponding increase in the Avrami exponent, was observed when the complex formed was liquid crystalline at milling temperatures.     

Synthesis of 1′-substituted 4′,4′-dimethyl-6′-methoxy-4′H-spiro[cyclohexane-1,3′-isoquinolines]

The reaction of 1-(4-methoxyphenyl)-1-(1-methylcyclohexyl)ethanol with nitriles in concentrated sulfuric acid afforded 1′-substituted 6′-methoxy-4′,4′-dimethyl-4′H-spiro[cyclohexane-1,3′-isoquinolines] as a result of consecutive Wagner-Meerwein rearrangement and Ritter reaction.     

Piers′ Borane-Induced Tetramerization of Arylacetylenes

We herein report that the reaction of Piers′ borane, i. e. HB(C₆F₅)₂, with an excess of arylacetylenes at room temperature leads to tetramerization of the acetylene and the diastereoselective formation of boryl-substituted tetra-aryl-tetrahydropentalenes. The reaction mechanism was investigated by isotope labeling experiments and DFT computations. These investigations indicate that a series of 1,2-carboboration reactions form an octatetraene that undergoes an electrocyclization. Two skeletal rearrangements then presumably lead to the formation of the tetrahydropentalene core. Overall, this intricate and unprecedented transformation comprises five carbon-carbon bond formations in a single reaction.     

Incompatibility of acid-labile 2′ and 5′ protecting groups for solid-phase synthesis of oligoribonucleotides

Cleavage of 2−O-tetrahydropyranyl groups from ribonucleoside derivatives used in solid-phase oligoribonucleotide synthesis takes place to an unacceptable extent during treatment with protic acid to remove 5′-O-pixyl groups.     

Synthesis of N′-phosphinatodiazene N-oxides

We have developed a regiospecific method for synthesis of N-phosphinatodiazene N-oxides, a previously unknown type of azoxy compounds in which the diazene oxide fragment is directly connected with the phosphinate group. The method involves reaction of amidoesters of alkyl- and arylphosphonic acids with nitroso compounds in the presence of dibromoisocyanurate.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2648–2656, November, 1992.