Vol 68, No 7 (2019)

The review systematizes material by key types of reactions promoted by iron carbonyls. The reaction types are subdivided into several principal directions, focusing mainly on new examples where iron carbonyls are used in the synthetically valuable C—C bond formation processes.

Model supramolecular associates possessing nondirectional intermolecular interactions were investigated in order to demonstrate the opportunity of plotting of an atomic connectivity graph based on trajectories of Hessian eigenvector of electron density corresponding to the largest eigenvalue. Such trajectories are a reasonable alternative to the gradient bond paths in the case of proximity of the latter to the T-shaped form upon the presence of parallel surface of the zero-flux of electron density in the neighborhood of gradient-based trajectory.

MCM-41 type mesoporous silica particles were obtained using a template method in an alkaline medium and cetyltrimethylammonium bromide as a matrix. The structural and adsorption characteristics of the mesoporous material were studied by dynamic light scattering, scanning electron microscopy, low-temperature adsorption—desorption of nitrogen, IR spectroscopy, and simultaneous thermal analysis. It was shown that the obtained mesoporous material possesses high porosity with the specific pore volume in excess of 1 cm³ g⁻¹. It was established that the size of silica particles does not exceed 200 nm, which is a value acceptable for the penetration of drugs through cell membranes. The optimal compositions of aqueous dispersions of MCM-41 with minimal sedimentation processes were determined. A drug (indomethacin) was encapsulated into the silica pores using the precipitation method at various temperatures (40 and 60 °C), the quantitative parameters of loading efficiency were calculated. The infl uence of temperature on the encapsulation ability was demonstrated.

A bisdiamidophosphite ligand with stereogenic phosphorus atoms as a part of 1,3,2-diaza-phospholidine rings and a bisoxazoline backbone was synthesized and studied in the Pd-catalyzed asymmetric allylic substitution. The use of this ligand provided up to 93% ee in the alkylation of (E)-1,3-diphenylallyl acetate with dimethyl malonate and up to 77% ee in the amination with pyrrolidine at quantitative conversion of the starting substrate.

1-Alkynyl-1-chlorocyclopropanes undergo chlorine-lithium exchange on treatment with BuⁿLi in THF at -40—0 °C. Thus generated organolithium species react with carbon dioxide (dry ice) and acetone to give selectively hitherto unknown 1-alkynylcyclopropanecarboxylic acids and the corresponding alcohols in up to 74% yields. Similar reactions involving methyl chloroformate result in the mixtures of cyclopropylacetylenic and vinylidenecyclopropanic esters, while the use of aliphatic aldehydes as electrophiles provides secondary allenic alcohols in up to 64% yields.

Bifunctional C₂-symmetric organocatalysts derived from chiral 1,2-diaminoethanes and (S)-2-aminomethylpyrrolidine were fi rst used for promoting the asymmetric Michael addition of aliphatic aldehydes to nitroalkenes. The synthesized enantioenriched (up to 82% ee) products can be transformed into various biologically active γ-aminobutyric acid derivatives.

Two synthetic approaches were used for the synthesis of 3,6-di-tert-butylcatecholate derivatives of titanium(iv). These approaches are based on the exchange reaction between sodium catecholate and titanium(iv) chloride and the reaction of 3,6-di-tert-butylpyrocatechol with titanium tetrabutoxide. Depending on the reaction conditions, the former method allows the synthesis of the titanium monocatecholate complex 3,6-CatTiCl2(THF)₂ (3,6-Cat is doubly deprotonated 3,6-di-tert-butylpyrocatechol) or bimetallic sodium titanium catecholate derivatives. Using the latter method, it is possible to synthesize six-coordinate titanium(iv) bis-cate-cholate complexes in high yields after the introduction of neutral bidentate donor ligands (TMEDA, DME, 2,2′-bipyridyl) to the reaction mixture.

A novel chiral phosphoramidite ligand, (S_a)-2-[N-ethyl-N-(1-naphthylmethyl)amino]-dinaphtho[2,1-d:1´,2´-f][1,3,2]dioxaphosphepane, was obtained and tested in Ir-catalyzed asymmetric hydrogenation of a series of 4-R-1,3-dihydro-2H-1,5-benzodiazepin-2-ones, wherein up to 74% ee was achieved. The structure of the resulting compounds was determined based on one- and two-dimensional NMR (¹H, ¹³C, ³¹P, ¹H—¹H COSY, ¹H—¹H ROESY, ¹H—¹³C HSQC and ¹H—¹³C HMBC) spectroscopy data.

Differences in the kinetics and mechanism of the reaction of glutathione (GSH) with hydrogen peroxide (H₂O₂) in deionized water and in phosphate buffer systems with pH ≥ 7 frequently used in biochemical studies were revealed. The formation of GSH dimers and complexes with H₂O₂ in water plays a substantial role in the kinetics of the process, which is manifested as nonlinear dependences of the rate of GSH consumption (W_GSH) and the rate of radical formation (W_i) on the reagent concentrations. In phosphate buffer solutions (PBS), the oxidation of GSH by air oxygen is enhanced and the radical formation rate decreases sharply. An effect of NaCl and KCl in PBS on W_GSH and W_i was observed, unlike a sodium—potassium phosphate buffer mixture (PB). Under other equivalent conditions, W_GSH PBS is several times lower and W_i is higher than those in PB containing no chlorides. It was found that the rate of the thiol-ene reaction of unsaturated phenol resveratrol (RVT) with GSH initiated by the radicals formed in the presence of H₂O₂ in PBS is nearly three times lower than that in water, whereas in PB resveratrol is not consumed under the same conditions. However, in the reactions with peroxyl radicals formed upon the decomposition of 2,2′-azobis(2-methylpropionamidine) dihydrochloride the GSH consumption rate is the same in both phosphate buffer systems.

A simplifi ed procedure for the synthesis of Pd⁰/TiO₂ xerogel has been developed, which includes the following steps: hydrolysis of tetrabutoxytitanium from its mixture with a palladium salt in an acetic acid atmosphere, drying and calcining the material at 860 °C. Palladium in the calcined xerogel is present in the form of spherical particles, titanium dioxide — as rutile aggregates.

The possibility of XeO₃ photo-activation in KHCO₃ + K₂CO₃ solutions at room temperature to oxidize Am^III was studied.