Russian Chemical Bulletin最新文献

The rate constants of the reactions of β-alanyl-β-alanine with 2,4-dinitro- and 2,4,6-trinitrophenyl benzoates in a water—1,4-dioxane system under polythermal conditions were determined in the present kinetic study. The rate constants vary in a range of 0.7–30.58 L mol⁻¹ s⁻¹. The found activation parameters of dipeptide N-acylation are comparable (within the determination error) with the kinetic characteristics of the reactions of the same family. A twofold increase in the water content in the water—1,4-dioxane solvent results in a 2–2.5 times increase in the average value of the rate constant. A comparison of the kinetic parameters of the reactions under study with the earlier obtained results for reactions involving other dipeptides revealed the following order of the reactivity of dipeptides: β-Ala-β-Ala > Gly-Gly > Ala-Val > Gly-Leu > Tyr-Pro. This sequence is consistent with the order of decreasing basicity of these dipeptides and indicates a substantial influence of the basicity on the reactivity of dipeptides. Based on the results of quantum chemical calculations of the potential energy surfaces of the model reaction of β-alanyl-β-alanine with phenyl acetate in the gas phase and under the conditions of hydration of the amino group of dipeptide by a water molecule, a conclusion can be made that the bimolecular concerted nucleophilic substitution on the carbonyl reaction center is possible.

An effect of the substituents in pyridinium ylides on oxidative 1,3-dipolar cycloaddition to nitrostilbenes, the scope and limitations of this transformation were studied. This reaction depending of the nature of the substituents gave either 1,2-diarylindolizines or 3,4-diarylisoxazoline N-oxides.

A series of dispiro-fused imidazothiazolotriazine-pyrrolidine-oxindoles with two ester groups in the pyrrolidine ring was synthesized by the [3+2] cycloaddition of azomethine ylides to dipolarophiles, functionalized imidazothiazolotriazines bearing tetrasubstituted double bonds. The treatment of the synthesized compounds with bases resulted in the selective hydrolysis of one of the two ester groups thus providing possibility for the target modification of the compound functionality and synthesis of the corresponding carboxylic acids and then amides in good yields.

Reaction of readily available 1-aryl-1-chlorocyclopropanes with alcohols in the KOH—DMSO system at 80–100 °C affords corresponding 1-alkoxy-2-arylcyclopropanes in up to 92% yield. The procedure is simple to implement, provides high stereoselectivity, and in most cases allows one to obtain products with trans-arrangement of the alkoxy group and aryl fragment. The results obtained suggest that isomerization of 1-alkoxy-2-arylcyclopropanes can occur under the strongly basic conditions used due to inversion of the configuration of the cyclopropane carbon atom located at the aromatic substituent.

The regioselectivity of the cyclization of 7-[(E)-2-(dimethylamino)vinyl]pyrazolo-[1,5-a]pyrimidine-6-carbonitriles was studied in the reactions with hydrazine hydrate. Depending on the conditions, the reaction in acetic acid or DMF affords either linear 6-(1H-pyrazol-5-yl)pyrazolo[1,5-a]pyrimidin-7-amines via the ANRORC rearrangement or fused 6-iminopyrazolo[1,5-a]pyrido[3,4-e]pyrimidin-7(6H)-amines. The preliminary in vitro screening of the antibacterial activity of the synthesized compounds was performed against E. coli and S. aureus.

Inorganic nano- and microparticles offer great opportunities for use as microfertilizers and carriers of both high- and low-molecular-weight compounds. This review examines the principal types of inorganic nano- and microparticles, namely, metal and metal oxide nanoparticles, particles based on silicon compounds and insoluble calcium salts, as well as the methods for their preparation and their potential applications in plant growing.

Composites based on physically cross-linked polyvinyl alcohol (PVA) alcogels containing electrically conductive polypyrrole (PPy) were obtained. For the first time, polyvinyl alcohol gels (antifreeze-PVA) were formed by gelation of a PVA solution in aqueous ethanol under conditions that prevented freezing of the gel-like composition. During gelation, oxidative polymerization of pyrrole took place. It was shown that addition of ethanol into the system increases the PPy content in anti-freezing PVA gel compared to PVA cryogel (cryo-PVA). The resulting dried composites were characterized by scanning electron microscopy, energy dispersive X-ray microanalysis, and IR spectroscopy. The conductivity of antifreeze-PVA—PPy composites was an order of magnitude higher than that of cryo-PVA—PPy; with the increase in the PPy content, the current–voltage characteristics acquired a non-Ohmic nature.

Environmentally friendly processes for recycling synthetic polymers have recently gained popularity, and living organisms and their enzymes are playing a key role in these processes. Herein we evaluated the degradation of a polyethylene terephthalate matrix by various ascomycete species. Within 30 days, polyethylene terephthalate was the only source of carbon for Lecanicillum aphanocladii, Fusarium oxysporum, Talaromyces sayulitensis, and Trichoderma harzianum. All the considered micromycetes were capable of utilizing polyethylene terephthalate, but the greatest weight loss (22%) was observed upon growing Fusarium oxysporum. DSC analysis revealed an increase in melting points by 2.5 °C and in the glass transition temperatures by 1–3 °C for all the treated samples of polyethylene terephthalate. Changes in chemical structure were estimated using IR spectroscopy, demonstrating various effects of the ascomycetes on the degradation of polymer matrix.

To assess the factors influencing the catalytic action of the Pluronic F127 and Synperonic F68 triblock copolymers in the alkaline hydrolysis of O-alkyl-O-p-nitrophenyl chloromethyl phosphonates, the self-organization in polymer solutions was studied. The critical micelle concentration and size of the aggregates were determined. The kinetic dependencies of the reaction in micellar solutions of the polymers were obtained under pseudo-first-order conditions and analyzed within the framework of a pseudophase model of micellar catalysis. In the system based on Pluronic F127, hydrolysis is inhibited by up to 6.5 times. In the case of Synperonic F68, the micellar effect is temperature-dependent: at 25 °C, the reaction rate remains unchanged, while at 40 °C, a slight inhibition to 1.5 times is observed. This difference is likely attributed to the distinction in the aggregation behavior of the polymers under these conditions.

Uracil-1-acetic acid hydrazides were synthesized according to the standard procedures. The derivatives of this series containing 5-positioned chlorine, bromine, and iodine atoms are new compounds.