Doklady Chemistry最新文献

Redox processes in the H₂PtCl₆·6H₂O–1,1,3,3-tetramethyl-1,3-divinyldisiloxane system both in the presence of ethanol and trimethylchlorosilane, and in the absence thereof were studied by ¹Н, ¹³С, and ²⁹Si NMR spectroscopy and gas–liquid chromatography. It was found for the first time that Pt(IV) and Pt(II) chlorides catalyze the reactions of hydrochlorination of vinyl groups with their transformation into β-chloroethyl groups and the elimination of the latter to form ethylene and dimethylchlorosilanes. Based on the results obtained, it was assumed that Pt(0) is coordinated to the siloxane group. A method to produce a high-temperature hydrosilylation catalyst consisting of nanosized Pt(0) and trimethylsilylsilicate was proposed and successfully tested in practice for curing SIEL-type compounds.

An approach was developed for the synthesis of multitarget compounds based on a tacrine molecule conjugated with a vanillin moiety using alkylimine or alkylamine linkers with different alkyl chain lengths (C2–C4). The synthesized conjugates effectively inhibit cholinesterases, displace propidium from the peripheral anionic site of acetylcholinesterase, which implies potential antiaggregant properties, and exhibit high antioxidant activity.

The efficient synthetic approaches to new 2,2'-bipyridine ligands functionalized with a 3-thienyl moiety have been developed. These compounds are of interest as monomeric units for electropolymerization. The “1,2,4-triazine” methodology was used for the synthesis.

A method for preparing 1-tosyl-3H-naphtho[1,2,3-de]quinoline-2,7-diones by the reaction of N-(9,10-anthraquinon-1-yl)chloroacetamide with sodium p-toluenesulfinate has been developed. Nucleophilic substitution of the tosyl group by nitrogen and oxygen nucleophiles has been found to proceed under mild conditions. The corresponding 1-substituted 3H-naphtho[1,2,3-de]quinoline-2,7-diones have been obtained by the reaction of these compounds with amines, phenol, sodium hydroxide, and sodium azide.

A method for the synthesis of betulin vinyl ether using calcium carbide as a source of acetylene has been proposed. Optimal conditions for synthesis of betulin mono- and divinyl ether have been selected. It has been found that the addition of alkali metal fluorides in an excess of calcium carbide promotes the formation of a divinylated product. Two-dimensional NMR spectroscopy proves the formation of monovinyl ether at the primary alcohol group.

A new approach to the synthesis of 2,3-disubstituted 2,3-dihydrothiazolo[3,2-a]pyrimidines under microwave activation conditions has been developed. The method consists in the nucleophilic addition of methanol to 2-arylmethylidene derivatives of thiazolo[3,2-a]pyrimidine followed by intramolecular rearrangement to form 3,5-diaryl-2,3-dihydrothiazolo[3,2-a]pyrimidine-2,6-dicarboxylates.

[1,2,4]Triazolo[4,3-c]quinazolines bearing p-bromophenyl or 5-bromothiophen-2-yl moiety at position 5 have been synthesized by cyclocondensation of the corresponding 4-hydrazinoquinazolines with ortho esters in boiling ethanol or glacial acidic acid. The synthesized tricyclic derivatives represent valuable intermediates for design of fluorophores and biologically active compounds. The possibility of modifying 5-(4-bromophenyl) derivatives by cross-coupling reaction has been demonstrated.

The bromination reaction of oligoetherdiol derived from allyl glycidyl ether by two procedures has been studied. It has been shown that one procedure provides monohydroxy conpounds and compounds containing no OH groups along with completely brominated oligoetherdiol. Their formation has been supposed to proceed via cyclodehydrobromination reaction due to elimination of one or two hydrogen bromide molecules from oligoetherdiol to form dioxane and dioxepane cyclic fragments. Conditions for complete bromination of oligodiol with retention of OH group functionality have been determined.

A new method was developed to prepare nanoscale Ni/La₂O₃ composites—efficient catalysts of the partial oxidation of methane (POM) into syngas. The catalysts are formed in situ during POM from LaNiO₃ obtained by the thermal decomposition of heterometallic La–Ni nitrate complexes. The catalysts ensure an almost 100% yield of syngas and are resistant to carbon deposition.

The antiradical activity of polycyclic compounds with indole and isoindole moieties was evaluated in vitro using a number of assays. All tested compounds, except for 3,5-di(tert-butyl)-4-hydroxybenzenecarbaldehyde N-(2-oxo-1,2-dihydro-3H-indole-3-ylidene)hydrazone, demonstrated much lower activity towards DPPH, ABTS^•+, and NO^• radicals than the well-known antioxidant ionol. All compounds showed a high radical-scavenging capacity relative to the superoxide radical anion generated in the enzymatic (NBT assay) and non-enzymatic (epinephrine autoxidation) systems. The high antiradical activity of 3,5-di(tert-butyl)-4-hydroxybenzenecarbaldehyde N-(2-oxo-1,2-dihydro-3H-indol-3-ylidene) hydrazone is attributable to the presence of 2,6-di-tert-butylphenol, indoline, and azine moieties, which promote the formation of a stable intermediate.