Tamara A. Vaganova

Selective mono-and diamination of polyfluorinated benzenes and pyridines with liquid ammonia

Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine, octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination. The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed.

Evidence for the transition from SN to ET mechanism in the reaction of arene radical anion with alkyl halide evoked by the introduction of an electron withdrawing substituent into radical anion

The interaction of potassium salts of benzonitrile and 1.4-dicyanobenzene radical anions with cyclopropylmethyl bromide provides benzylcyclopropane, in the first case, and 4-alkyl- benzonitriles together with 2-alkyl-1,4-dicyanobenzenes containing both cyclopropylmethyl and its isomeric 3-butenyl fragment, in the second case. These results provide evidence for the change of reaction mechanism from SN to ET.

Crystal associates of 18-crown-6 and polyfluoro(het)arylenediamines: structure, properties, and selectivity of formation

The new group of objects in crystal engineering, namely, 1 : 1 associates of polyfluoro(het)arylenediamines and 18-crown-6, being supramolecular 1D assemblies, is considered. Diamine isomerism is shown to serve as a design tool for control of the supramolecular architecture, and the nature of the aromatic framework and location and volume of substituents determine linear dimensions of the elementary unit in an assembly. A linear dependence of the enthalpy of melting of co-crystals on the length of the assembly unit is observed in the series of the meta-(het)arylenediamine and 18-crown-6 associates. The effect of selective co-crystallization of polyfluoroarylenediamines with crown ether is used in practice for the isolation of high-purity compounds from mixtures of products of the non-selective amination of basic polyfluoroarenes.

Reductive activation of arenes. VII. Alkylation of 9-cyanoanthracene two-electron reduction products in liquid ammonia.

Abstract The reactions of the 9-cyanoanthracene dianion generated by the action of two equivalents of potassium in liquid ammonia with primary alkyl iodides and bromides gave 9-cyano-9,10-dialkyl-9,10-dihydroanthracenes. The alkylation of the 9-cyano-9,10-dihydro-9-anthryl anion generated by the two-electron reduction of 9-cyanoanthracene in liquid ammonia in the presence of ammonium chloride gave 9-cyano-9-alkyl-9,10-dihydroanthracene. The results obtained by using cyclopropylmethyl bromide as model reagent suggest these reactions to proceed through SN mechanism. The spatial structure of 9,10-dihydroanthracene derivatives obtained is discussed.

Controlled self-assembly of π-stacked/H-bonded 1D crystal structures from polyfluorinated arylamines and 18-crown-6 (2:1). Associates vs co-formers fluorescence properties

Supramolecular 1D assemblies supported by N–H⋯Ocr and π-stacking interactions were designed and synthesized using polyfluorinated arylamines, differing in the nature of the aromatic ring (benzene, naphthalene, pyridine) and para-substituents (H, F, CN, CF3), and 18-crown-6 ether. Co-crystal structures and intermolecular interactions were studied in detail using X-ray analysis and compared with those in individual arylamine crystals. In the co-crystals, all relatively weak H-bonds N–H⋯X (X = F, Nhet, Ncyano) are replaced by the stronger bond N–H⋯Ocrown and π-stacking in pairs of the arylamine molecules is realized. Depending on the arylamine structure, a parallel displaced, rotated, or slipped stack geometry occurs. Using DSC, phase transitions in the co-crystals were determined and the thermal characteristics were found to be reproduced in the melting-crystallization cycles, which indicates the regeneration of the crystal structure. For a number of compounds, there are significant changes in the fluorescence characteristics, in terms of both intensity and wavelength, due to the formation of associates with 18-crown-6: aggregation-induced emission in the pentafluoroaniline associate, a large shift of λem in the 4-cyanotetrafluoroaniline associate, and aggregation-caused quenching in the 4-aminotetrafluoropyridine associate. Crystal structure analysis reveals that π-stacking interactions between arylamines play a key role in the modulation of the solid-state fluorescence properties. The revealed effect of fluorescence build-up/quenching shows these types of supramolecular associates to be promising solid-state chemosensors.

Structure of molecular cocrystals of 18-crown-6 and polyhalogeno- meta -phenylenediamines

A motif of the supramolecular architecture of соcrystals of 18-crown-6 and polychloropolyfluoro-1,3- phenylenediamines or partially fluorinated 1,3-phenylenediamines (1:1 stoichiometry) is infinite 1D ensembles of alternating components. The mutual coordination of molecules in the ensembles is due to the hydrogen bond between crown ether oxygen atoms and hydrogen atoms of polyfluoroarene amino groups. Parameters of the architecture of соcrystals are determined by the effect of the number and arrangement of substituents (chlorine and fluorine atoms) in the polyhalogenated aromatic ring.