Vol 65, No 9 (2016)

The review is devoted to analysis of the modern data concerning microwave-assisted synthesis of metal-organic frameworks (MOFs). The prospects for the microwave activation of the reaction mixture as an effective method of MOF formation with tuned crystallite size are considered. Other aspects of this approach including impact of various factors (reaction mixture composition, microwave synthesis parameters) on the texture properties and morphology of MOFs are discussed. Comparative studies concerning the influence of preparation methods in the microwave fields and other procedures of MOF fabrication on the physicochemical properties of the samples are considered. Advantages of microwave synthesis from green chemistry point are outlined.

The review is focused on the application of β-formyl-β-nitroenamines, one of the push—pull alkenes, having the biased electron density as well as an electrophilic formyl group and a nucleophilic amino group in the organic synthesis. Due to the multi-functionality, β-formyl-β-nitroenamines exhibit versatile reactivity to facilitate the synthesis of polyfunctionalized compounds possessing push—pull property. Nitroenamines serve as a synthetic equivalent of unstable nitromalonaldehyde to afford nitropyrazoles, nitropyrimidines, nitrodiazepines, and nitrophenoles upon treatment with dinucleophiles such as hydrazines, amidines, 1,2-diamines, and ketones, respectively. When active methylene compounds allowed reacting with the nitroenamines, polyfunctionalized pyridones and 2-amino-5-nitropyridines are obtained. In addition, nitroenamines undergo [4+2] self-condensation to afford 3,5-dinitropyridinium ion, which is easily trapped by benzene derivatives leading to 4-arylated 1,4-dihydropyridines.

Theoretical and experimental data related to the chemistry of polyfluorinated 4H-chromen-4-ones were summarized and analyzed. The synthesis of the substances under investigation was reviewed. The aspects of reactivity, the routes for the functionalization of polyfluorinated 4H-chromen-4-ones and the formation of the novel heterocyclic systems on their basis are considered.

The review systematizes the data on the reactions of 1,2,4-triazines proceeding with a triazine ring contraction to the imidazole one. Imidazole derivatives are obtained upon treatment of 1,2,4-triazines of different saturation degree with reducing agents, oxidants, acids, as well as with the agents initiating tandem reactions, the last step of which is a triazine ring contraction, for example, nitrosating and aminating agents, organometallic compounds and aromatic aldehydes.

A new radical cation salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with iron(III) bis(1,2-dicarbollide) 8,8´-dichloro derivatives, that is (BEDT-TTF)₂[8,8´-Cl₂-3,3´-Fe-(1,2-C₂B₉H₁₀)₂], was synthesized. Its electroconducting and magnetic characteristics were studied, molecular and crystal structures were determined. The electroconductivity of crystals at room temperature was σ₂₉₃ ~5 Ω^–1 cm^–1, which is close to the corresponding value for the salt of cobalt bis(1,2-dicarbollide) dichloro derivative and is considerably higher than the electroconductivity of a similar salt of unsubstituted iron bis(1,2-dicarbollide). The measurements of magnetic susceptibility at 2—300 K showed that this salt is paramagnetic.

Approaches to the synthesis of complexones, succinic acid derivatives, from maleic acid and amino derivatives were considered. Acid-base properties of these complexones were studied.

An effect of boric acid additives on oxidation of 2,4,6-trinitrotoluene (TNT) to 2,4,6-trinitrobenzoic acid (TNBA) with chromic anhydride in concentrated (96—100%) H₂SO₄ has been studied. In the presence of tetrahydrosulfatoboric acid HB(HSO₄)₄ formed in situ (up to 5 mol.%) or added as a preliminary prepared solution (up to 1 mol. %), TNT is selectively oxidized to TNBA in the yields up to 95—99%. The mechanism including formation of TNT dication as a key step of its oxidation at the methyl group has been suggested.

Cyclization of pure enantiomers of 1-{2-[hydroxy(diaryl)methyl]phenyl}ethanol proceeds stereoselectively and affords 1,3-disubstituted 1,3-dihydroisobenzofurans (phthalans) in moderate-to-high enantiomeric (81.7% ee) or diastereomeric (72% de) purity.

A synthesis of hitherto unknown bicyclic nitroso acetals possessing two annulated six-membered rings is accomplished. The synthesis comprises formal [3+3] cycloaddition of six-membered cyclic nitronates with donor-acceptor cyclopropanes. Some chemical transformations and conformational preferability of the obtained nitroso acetals are discussed.

Methods for the preparation of stable 1,4,6,10-tetraazaadamantane quaternary derivatives were developed based on quaternization of a tertiary nitrogen atom in tris(β-oximinoalkyl)amines or isomeric 4,6,10-trihydroxy-1,4,6,10-tetraazaadamantanes. This process constitutes a convenient approach to the introduction of a hydrophilic 1,4,6,10-tetraazaadamantane moiety into lipophilic molecules in order to increase their solubility in water. 4,6,10-Trihydroxy-1,4,6,10-tetraazaadamantane N-oxide was synthesized by the oxidation of the tertiary nitrogen atom in the tris-oxime and subsequent intramolecular cyclotrimerization of the oximino groups. Quantum chemical calculations showed that the quaternization of the annular nitrogen atom led to a considerable stabilization of tetraazaadamantane framework as compared to the open-chain form of tris-oxime.

The structures and energies of 1,2,7-thiadiazepane 1,1-dioxide and the axial and equatorial conformers of 1,2,7-thiadiazepane 1-oxide were calculated using the hybrid density functional B3LYP with the cc-pVDZ basis set. The results obtained explain the lower stabilities of equatorial conformers compared to the axial analogs and the lower stabilities of sulfones compared to sulfoxides.

Adamantyl-containing 1,3-disubstituted ureas, bisureas, and biscarbamates containing different spacers between the ureylene or the carbamate groups and the adamantyl radical were synthesized. Their inhibitory activity against soluble epoxide hydrolases of mammals and humans (sEH, E.C. 3.3.2.10) was studied. The compounds were found to possess high inhibitory activity on the level of 0.8—2.7 nmol L^–1. A relationship between the inhibitor structure and its activity was established.

Diazotization of aminopyridines upon treatment with NaNO₂ and H₃PO₄ in acetonitrile led to the formation of N-pyridinylacetamides. This reaction constitutes a convenient and general preparative method for the synthesis of 2-, 3-, and 4-N-pyridinylacetamides under mild conditions in good yields. The in situ oxidation of the thus obtained N-pyridinylacetamides with hydrogen peroxide gave good yields of pyridinylacetamide N-oxides.