Vol 66, No 6 (2017)

The review summarizes the data on the synthesis of O-hetarylhydroxylamine derivatives (mainly oximes) published since the 1960s.

The results of theoretical search for model transition states of the electrophilic substitution reaction in 2H-tetrazole (1) without the preliminary formation of N-protonated azolium salts are presented for two routes that were previously suggested by the authors and thermodynamically investigated: A, the attack of molecule 1 by the nucleophile (HO^–(aq)) to form the anion to which the electrophile H₃O⁺(aq)) is added and B, the attack of molecule 1 by the same electrophile followed by the addition of the same nucleophile to the specifically solvated protonated species formed in the preceding reaction step. The calculations were performed using the DFT/B3LYP/6-31G(d) method and the scanning procedure of the potential energy surface (PES). Both steps of route A turned out to be nearly barrierless, while in route B only its first step is barrierless and the second one is conjugated with passing an activation barrier of ∼45 kcal mol^–1 between non-interacting or weakly interacting reactants and electrophilic substitution products. Unlike the specifically solvated protonated species of 1H-tetrazole in an aqueous solution, a similar species of 2H-tetrazole does not form a prereaction complex with the attacking nucleophile (HO^–(aq)) and the five-membered ring is destroyed in fact in the nitrogen-containing reaction product formed after passing the activation barrier. The optimized structure of the transition state differs strongly from the nitrogen-containing structure of the reaction product with the destroyed ring, which was found by scanning of the PES.

The experimental results for the concerted molecular decomposition of alkyl iodides RI to olefin and HI were analyzed in terms of the intersecting parabolas model (IPM). The activation energies (E) and rate constants (k) of the earlier unstudied reactions of the concerted molecular decomposition of RI were calculated on the basis of the enthalpy of the reaction and IPM algorithms. The factors that influence on E of RI decay were established: the enthalpy of the reaction, the energy of stabilization of radical R*, the length and force constant of the C—I bond, and the size of the halogen atom. The values of E and k for the backward reactions of HI addition to olefins were estimated.

Colloidal dispersions of MoS₂ in DMF were obtained, and a procedure for the preparation of the fraction of particles with the size distribution 1.5 times narrower than that in the original dispersion was developed. It was shown that for the gradual centrifugation of dispersions with an increase in the acceleration from 126g to 2016g the average thickness of nanosheets decreased from 35 to 8 nm and the average lateral sizes decreased from 250 nm to a constant value of 160 nm. A linear dependence of the absorbance of the dispersions on the concentration of MoS₂ was established.

The thermal decomposition of the energetic component and chemical reactions occurring at elevated temperatures in a flameless combustion wave of systems based on hexogen (filled with iron(II) formate and polyisocyanurate binding agent) afford a mixture of iron oxides and iron nitride as nanosized particles. The purposeful change in the ratio of the indicated basis components can provide individual Fe₂O₃, Fe₃O₄, or FeO in the conversion products. Additives of anthracene and hydroquinone to the initial composition can result in the formation of predominantly iron carbide in the products, whereas mainly iron nitrides are formed upon the addition of guanidine nitrate or 5-aminotetrazole. The addition of aluminum hydride components to the initial mixture results in the reduction of iron to the zero-valence state in the form of iron—aluminum intermetallic compounds.

Hybrid compounds containing organic layers composed of tetrathiafulvalenes (BEDT-TTF, BETS, BEDO-TTF) and inorganic layers consisting of anions based on lead bromide were synthesized. The crystal structure of (BEDT-TTF)₆Pb₃Br₁₀(PhBr) was determined. The temperature dependences of electrical conductivity for the synthesized compounds were measured and the EPR spectra of these compounds were recorded. In the structure of (BEDT-TTF)₆Pb₃Br₁₀(PhBr), the organic conducting layers of BEDT-TTF molecules alternate with non-conducting layers composed of infinite chains of bromoplumbate anions [Pb₃Br₉]^3–, solvent molecules, and Br^– anions. The newly synthesized BEDT-TTF bromoplumbates have similar linewidths of EPR signals, which indicate that their conducting layers have similar structures. The BEDT-TTF bromoplumbates are semiconductors, while temperature-dependent electrical resistivity measurements show the metallic behavior for BEDO-TTF and BETS bromoplumbates.

Approaches that allow one to carry out quantitative analysis of real objects, solutions of nitric acid after contact with sorbents based on N,N,N′,N′-tetra-n-octyldiglycolamide (TODGA), by MALDI mass spectrometry are considered. The internal standard for the quantitative determination of the target component in real samples containing a high excess of inorganic salts is selected. It is found out that reproducible results can be obtained by the external standard method for a large sampling of experimental data, but the internal standard method can significantly improve the accuracy of quantitative analysis. The use of the internal standard makes it possible to eliminate an inaccuracy related to nonuniformity of sample preparation.

4-Arylamino-1,2-naphthoquinones isomerize into 2-arylamino-1,4-naphthoquinones upon refluxing in acetic acid. The isomerization follows two routes via intermediate 2-hydroxy-1,4-naphthoquinone and 2-arylamino-1,4-naphthoquinone 4-N-arylimines.

A general approach to the synthesis of new 3-acetyl-substituted pyrrolo[3,4-f]indole-5,7-diones, 3-[3-(dimethylamino)acryloyl]-1-methoxypyrrolo[3,4-f]indole-5,7-diones and similar indole-5,6-dicarbonitriles has been developed. Dimethylaminoacryloyl derivatives synthesized on their basis regioselectively reacted with hydrazine hydrochlorides and hydroxylamine with the formation of the corresponding 5-substituted azoles.

Heating the substituted pyridinium and isoquinolinium salts with E-1,2-di(alkylsulfonyl)-1,2-dichloroethenes in either chloroform or acetone in the presence of three-fold excess of Et₃N gave high yields of substituted 1,2-di(alkylsulfonyl)indolizines and 1,2-di(alkylsulfonyl) pyrrolo[2,1-a]isoquinolines, respectively. Effects of the structure of 3-substituted pyridinium ylides on the regioselectivity of their reaction with E-1,2-di(alkylsulfonyl)-1,2-dichloroethenes were revealed. It was shown that the presence of electron-releasing and electron-withdrawing substituents in the pyridinium ylide favors the formation of 8-substituted and 6-substituted 1,2-(dialkylsulfonyl)indolizines, respectively.

The catalytic hydrogenation of benzodiazepinones using metal complexes with phosphite and phosphoramidite ligands was carried out for the first time. The mixed-ligand catalytic systems containing a chiral phosphoramidite or phosphite in combination with an achiral phosphine were shown to exhibit a higher enantioselectivity compared to catalysts containing homocombinations of chiral ligands.

The key steps of the synthesis of two high energy compounds, namely, 4-(2,2,2-trinitroethyl)-2,6,8,10,12-pentanitrohexaazaisowurtzitane and 4,10-bis(2,2,2-trinitroethyl)-2,6,8,12-tetranitrohexaazaisowurtzitane, were optimized. Their enthalpy of formation, density, impact and friction sensitivity, and thermal stability were experimentally determined.

Polymerization of methyl methacrylate and styrene in the presence of manganese cyclopentadienylcarbonyl complexes containing π-alkene (methyl methacrylate), vinylidene, and allenylidene ligands was investigated. It was found that metal complex ligand environment plays a key role in the initiation of the polymerization and in the regulation of the molecular weight characteristics of synthesized polymers. In particular, the manganese complexes with cumulenylidene ligands are capable to initiate spontaneously polymerization of vinyl monomers. The process of polymerization proceeds to high conversions (over 90%), and the resulting polymers are characterized by high values of molecular weight and relatively broad molecular weight distribution.

New star-like polydimethylsiloxanes with a cis-tetraphenylcyclotetrasilsesquioxane fragment as the core (branching center) were synthesized and characterized. The thermophysical properties of the obtained polymers were studied by DSC and TGA. The epoxy resin surface modified with the obtained polymers was analyzed by XPS.

A novel cross-linked copolymer of 1-vinyl-1,2,4-triazole and N,N′-methylene-bis-acrylamide was synthesized via free radical copolymerization. Sorption capacity of the copolymer toward palladium chloride(ii) in acid aqueous solutions was investigated. Sorption properties and efficiency of the polymer as a sorbent were evaluated. Mechanism of the copolymer interaction with palladium complex was identified by methods of IR- and Raman spectroscopy and elemental analysis.

Ethyl α-nitro-β-trifluoromethyl acrylate was synthesized by nucleophile-catalyzed reaction of ethyl nitroacetate with excess trifluoroacetaldehyde methyl hemiacetal and subsequent dehydration of the intermediate alcohol with P₂O₅. The synthesized nitro olefin regioselectively reacts with the substituted indoles to give fluorinated 3-indolyl-2-nitrobutyrates, which were converted into the corresponding β-trifluoromethyl-substituted tryptophan analogs via the nitro group reduction followed by saponification of the ethoxycarbonyl group. In the step of synthesis of amino ester, the 2-methylindole derivative was resolved into diastereomers, which were transformed to the corresponding acids separately. It was found that the synthesized β-trifluoromethyltryptophans have plant-growth regulating activity apparently attributable to their metabolic transformations into substituted α-trifluoromethylindol-3-ylacetic acids.

New pyrido[2′,3′:3,4]pyrazolo[5,1-c][1,2,4]triazin-4(6H)-one derivatives were synthesized from accessible 1,2,4-triazine and pyrazolo[5,1-c][1,2,4]triazine derivatives. Specific features of the reactions were studied and spectral characteristics of the compounds are reported.