Vol 65, No 7 (2016)

Chiral N-(tert-butyl)sulfinyl aldimines easily prepared from commercially available compounds have been used as starting materials for the following processes: (i) hydrogen transfer, (ii) addition of zincates, (iii) In-promoted allylation, and (iv) addition of zinc enolates. In all cases, the final desulfinylation to yield the expected chiral α-substituted primary amines was easily performed with hydrochloric acid in an organic solvent. This methodology has been successfully applied to the preparation of chiral natural products such as alkaloids and amino acids.

The review is focused on the synthesis of fluoroalkyl-containing heteroannulated pyrimidines via the reactions of alkyl 3-oxo-3-polyfluoroalkylpropionates and their ethoxymethylidene and 2-arylmethylidene derivatives with hetarylamines. Heteroannulation of polyfluoroalkyl-containing pyrimidines is also discussed.

The literature data on the synthesis and properties of oxo-functionalized acyclic and cyclic sulfides obtained by the catalytic multicomponent reactions of 1,3-dicarbonyl compounds with formaldehyde and S-nucleophiles are summarized. An approach to the multimolecular four-component heterocyclization of 1,3-dicarbonyl compounds with CH₂O and S- and N-nucleophiles in the synthesis of sulfanyl-substituted azaheterocycles is discussed.

Thermodynamic characteristics of electrophilic substitution reactions in 1-methyltetrazole and 1H-tetrazole via the elimination–addition scheme (HO^– anion and hydroxonium ion as model agents) were compared by analysis of the quantum chemical calculation results performed using the DFT/B3LYP/6-31G(d,p) method taking into account specific solvation effects. The possibility for both reactions to occur without the preceding formation of N-protonated azolium salts was shown. This possibility has earlier been demonstrated for 1H-tetrazole using the DFT/B3LYP/6-31G(d,p) and DFT/B3LYP/6-31G(2df,p) methods taking into account the solvation effects in an aqueous solution in terms of polarized continuum model when proton was chosen as a model electrophile.

Solutions of lithium and 1-ethyl-3-methylimidazolium tetrafluoroborates ([emim][BF₄]) in propylene carbonate (PC) were studied by the high-resolution NMR method on ¹H, ⁷Li, ¹¹B, ¹³C, and ¹⁹F nuclei. The degree of solvation of lithium ions was determined by measuring selfdiffusion coefficients by pulse-field-gradient spin echo NMR method on ¹H, ⁷Li, and ¹⁹F nuclei. The hydrodynamic radii of solvated Li⁺ cations were estimated by the Stokes–Einstein equation. The model structures of the solvation complexes of Li⁺ ion with propylene carbonate molecules and BF₄^– anion and their associates with ionic liquid components were calculated in terms of the density function theory. The calculated values of the chemical shifts were compared with the experimental data. PC molecules were predominantly bound to the Li⁺ cation, while LiBF₄–[emim][BF₄]–PC (1: 4: 4) electrolyte had a maximum conductivity of 9.5 mS cm^–1 at 24 °С compared to the compositions of a lower content of the solvent.

Heterometallic complexes Ln(L¹)₅Zn (Ln = Sc, Sm, Gd) were obtained by the reactions of silylamides Ln[N(SiMe)₂]₃ with 2-(benzoxazol-2-yl)phenol (HL¹) in the presence of diethylzinc. Similar reactions with 3-(benzothiazol-2-yl)-2-naphthol (HL²) led to the formation of complexes Ln(L²)₅Zn (Ln = Nd, Er, Gd, Yb). The introduction of the zinc-containing fragments provided a considerable increase of photo- and electroluminescence intensity of the scandium complex.

A reaction of octa-1,7and deca-1,9-dienes with an excess of bromofluorocarbene proceeds predominantly with the formation of a monoadduct, whereas the bis-adduct can be prepared by repeated cyclopropanation. The [1+2] cycloaddition of dichlorocarbene to the monoadduct of bromofluorocarbene with deca-1,9-diene gave a new bis(cyclopropane) containing gem-dichloro- and gem-bromofluorocyclopropane fragments in one molecule. The bis-adducts obtained were subjected to the heterocyclization with nitronium triflate: in the case of bis(gem-bromofluorocyclopropane) the reaction proceeded with retention of one dihalocyclopropane fragment and gave mononuclear pyrimidine N-oxide.

A series of cross-conjugated dienones was synthesized to study the dependence of physicochemical characteristics on the nature of substituents in the aromatic groups of symmetric cyclopentanone dibenzylidene derivatives. The structure of compounds was established by electronic, IR, and NMR spectroscopy and X-ray diffraction study. All the compounds obtained possess the E,E-geometry. In the crystalline state, the arrangement of the dienone molecules is unfavorable for the intermolecular [2+2] photocycloaddition to take place. The low-temperature phases transition for unsubstituted diphenyl derivative of cyclopentanone was detected using variable-temperature X-ray diffraction and differential scanning calorimetry. Oxidation and reduction potentials of the dienones were measured by cyclic voltammetry. Their dependence on the nature and placement of substituents in the benzene rings was demonstrated. A linear correlation (R = 0.9343) between the difference of electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum was found, that allows us to recommend the use of the data obtained in the correlation analysis of other compounds of this class.

Thermolysis of the melt of octakis(O-thiocarbamoyl)tetra(C-phenethyl)resorcinarene in a microwave reactor afforded a cavitand, the upper rim of which was formed due to the formation of disulfide bridges between the neighboring benzene rings of the resorcinarene framework. The reaction of 2,2’-bis(carbamoylthio)-1,1’-methylenedinaphthalene with LiAlH₄ gave a tricyclic derivative, in which the naphthalene rings were bound by methylene and disulfide bridges. The structure of 2,2’-dithiinedinaphthylmethane was confirmed by single crystal X-ray diffraction analysis of this compound.

1,3-Dipolar cycloaddition reactions of nitrones of general formula R²CH=N(O)R¹, where R¹ = Me, Bu^t, Ph, R² = Ph, Cp[Mn(CO)₃] with styrene and vinyl-η⁵-(cyclopentadienyl) manganese tricarbonyl were studied. The products of these reactions, i.e., isoxazolidines, were isolated, purified, and identified. A high selectivity of the cycloaddition reactions involving both dipoles and dipolarophiles containing cyclopentadienylmanganese tricarbonyl group was demonstrated.

New sterically hindered catecholaldimines derived from hydrazine were synthesized in high yields. Two procedures for the synthesis of sterically hindered catecholaldimines were developed: by the reaction of 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde with hydrazines (hydrazine hydrate, phenyl-, 1,1-diphenyl-, and (diphenylmethylene)hydrazines, acetyl and benzoyl hydrazides) or by the reaction of 3,5-di-tert-butyl-6-(hydrazonomethyl)catechol with a carbonyl compound (the reaction with 4-N,N-dimethylaminobenzaldehyde). The X-ray diffraction analysis and IR, UV, and NMR spectroscopic studies showed that these compounds exist in the catecholic form both in solution and the crystalline state.

Amination of 3,6-dichloropyridazine, chloropyrazine, 2,3and 2,6-dichloropyrazines, 2-chloroquinoxaline, 1-chloroand 1,3-dichloroisoquinolines with various adamantane-containing amines characterized by different steric hindrances at the amino group was studied. The yields of the amination products depended on the structure of starting compounds. In the reactions of all the dichloroheteroarenes, selective substitution of only one chlorine atom took place, with the best yields being observed for 2,6-dichloropyrazine. In the reaction of 1,3-dichloroisoquinoline, the chlorine atom at position 1 was selectively substituted in up to 90% yield.

A number of new functional derivatives of pyrido[2,1-c][1,2,4]benzothiadiazine 5,5-dioxide was obtained based on the reactions of 2-halobenzenesulfonyl chlorides with 2-aminopyridine derivatives. A quantitative criterion for the evaluation of a possibility for the reaction to proceed under noncatalytic conditions depending on the type of halogen and substituents in the starting compounds was suggested.

Aza-Michael reaction of (E)-4-(diphenylphosphoryl)but-3-en-2-one (1) with a number of mono-and bicyclic nitrogen heterocycles proceeds regioselectively in the absence of catalysts with the formation of corresponding β-azahetaryl β-diphenylphosphoryl ketones; in the case of imidazole, the presence of chiral organic catalysts allows one to increase the yields of the adducts and to obtain them in enantiomerically enriched form.

Reactivity of 5-diazoimidazoles and 5-diazopyrazoles in the reactions with alkyland aryl isocyanates was studied. A number of new imidazo-and pyrazolo[5,1-d][1,2,3,5]tetrazin-4 ones were synthesized, which are analogs of temozolomide. It was shown that diazoazoles do not react with isothiocyanates under similar conditions.

An ability of n-alkyl and 1-adamantylmethyl perchlorates to be converted to the corresponding N-alkylacetamides upon treatment with acetonitrile was demonstrated. This reaction is an example of Ritter-type reaction, which proceeds under exclusively mild conditions and requires no catalysis or special activation of reagents. N-Alkylacetamides were formed in quantitative yields in analytically pure form.

The prospects of the action of different types of chelating agents capable of binding to zinc, and salicylate ion comprising compounds on leukemic cells are reviewed. Survival rates and therapeutic indexes were compared.