Doklady Chemistry最新文献

In the palladium-catalyzed cross-coupling of potassium pentafluorophenyltrifluoroborate with aryl chlorides in the presence of the precursor of SIMes carbene, the yields of pentafluorobiphenyls decrease, whereas the yield of 2,3,4,5,6-pentafluoro-4'-methylbiphenyl from 4-bromotoluene under the same conditions increases. An explanation for this phenomenon and for the intensification of the side hydrodeboration reaction of the initial borate has been proposed.

The activating effect of AlCl₃ in the amount of 10 mol % in the homocoupling of alkyl-, phenyl-, and silyl-substituted acetylenes with the Mg–Cp₂ZrCl₂ reagent system was found for the first time. The unique nature of this activation is indicated by the fact that in the presence of 10 mol % of Lewis acids BF₃⋅Et₂O, Me₃SiCl, InCl₃, and SnCl₄, the reaction with 5-decyne does not occur even after 5 h, while in the presence of AlCl₃, homocoupling products are selectively formed in high yields within 10 min at room temperature.

A five-stage method for the synthesis of Y-shaped push–pull fluorophores based on 2-(4'-methoxyphenyl)-1,2,3-triazole was proposed. The resulting molecules exhibited emission in the range from 350 to 450 nm with high quantum yields (QY) of 90–99% in solvents of various polarity. The products proved to be applicable as chemosensors for both aromatic and aliphatic nitro analytes in concentrations down to 300 ppb.

The course towards active development of the Arctic zone of the Russian Federation by fuel-and-energy companies involves the development of new methods and approaches to the storage and transportation of natural gas to reduce the negative impact on the ecosystems of cold regions while maintaining the economic feasibility of their use. This work proposes a method for optimizing the technology for transporting and storing natural gas in the form of gas hydrates using soy lecithin as a promoting additive. Experimental methods showed that the addition of soy lecithin to a concentration of 0.5 wt % is on a par with the most efficient promoter of hydrate formation—the surfactant sodium dodecyl sulfate at a concentration of 0.1 wt %. However, a comparison of environmental characteristics demonstrates a clear advantage of soy lecithin. In addition, it was demonstrated that the synthesis of methane hydrate from ground frozen solutions of soy lecithin is at least three times faster than that from liquid solutions.

Methylation and amination reactions of 4Н-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole salts (K⁺, Ag⁺, Et₃NH⁺, DBUH⁺) have been studied for the first time. It has been shown that the reaction of these salts with MeI results in two methylation products: K and Et₃N salts produce 4- and 5-isomers in equal amounts, while Ag and DBU salts form mainly 4-isomer. It has been found that the main amination product of K and DBU salts of 4Н-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole with O-(p-tolylsulfonyl)hydroxylamine is 4-azido-3-amino-1,2,5-oxadiazole. A mechanism of its formation via rearrangement of 5-amino-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole has been proposed.

A new method has been developed for the synthesis of 5,5-disubstituted N-methyl-1,3-oxazinanes as a mixture of diastereomers at the 5-position containing monoterpene and branched alkyl substituents in the 5-position. 1,3-Oxazinanes were obtained for the first time by reacting 2,2-substituted 3-aminopropan-1-ols with formaldehyde and sodium borohydride in one stage.

The effect of carbon supports and preparation methods of Pd/C catalysts on leaching of palladium-containing species to the solution upon interaction of a catalyst with a solvent was considered. The leaching of palladium from the support surface into pure solvents was studied by high resolution mass spectrometry. It has been shown that the type of leached palladium species formed in the solution depends not only on the solvent, but also on the method of catalyst deposition on the support and the support nature. It has been found that the use of phosphorus-doped carbon (PC) as a support also results in palladium leaching into solution. In addition, the activity of the catalysts supported on graphite and PC decreased to the same degree both in the Suzuki–Miyaura and Mizoroki–Heck reactions.

An analysis of literature data on the set of reactions for the production of macromolecules with a high content of phosphorus and sulfur has been carried out, and basic approaches that allow the introduction of these elements into the composition of polymers and polymeric materials have been considered in compliance with the fundamental principles of green chemistry. Methods for synthesis of functional polymers under mild conditions that require minimal energy input from external sources, which can become new growth points for green industrial technologies, are considered. Particular attention focuses on the synthesis of polyphosphazenes and polyphosphoesters for biomedical purposes, as well as on the inverse vulcanization reaction to give polymers used in sorption wastewater treatment, the creation of current sources, and IR optics.

New dialkyldithio derivatives of 2,6-dimethylphenol have been synthesized and characterized. The multifunctional properties have been studied for the first time for these compounds as additives to lubricating oils in friction and wear processes under boundary friction conditions, as inhibitors of high-temperature oxidation of hydrocarbons, and as protectors of metal surfaces. It was determined that even a 0.5 wt % concentration of the synthesized additives in lubricating oils contain more than doubles anti-wear properties. It was shown that the additives exhibit a complex antioxidant effect and high efficiency at all stages of the oxidation process, and even at ultralow concentrations (0.005 wt %), their ability to resist oxidation exceeds widely used analogues. The new additives are of significant interest to modern lubricant science and can be used in motor oil formulations and other lubricants.

Controlled radical polymerization of lauryl methacrylate in polyalphaolefin base oil has been performed for the first time in the presence of 2-cyano-2-propyl dodecyl trithiocarbonate. It has been shown that polymerization proceeds to high monomer conversions and leads to the formation of a polymer with a narrow molecular weight distribution. At the same time, the reaction mixtures retain their transparency after polymerization is completed. The synthesized polymers have a thickening ability, which naturally increases with an increase in their number-average molecular weight.