Strain-Release Arylations for the Bis-Functionalization of Azetidines

The addition of nucleophilic organometallic species onto in situ generated azabicyclobutanes enables the selective formation of 3-arylated azetidine intermediates through strain-release. Single pot strategies were further developed for the N-arylation of resulting azetidines, employing either SNAr reactions or Buchwald-Hartwig couplings.

ENSURING THE STABILITY OF INTERNAL DUMPS ACCORDING TO THE RESULTS OF PHYSICAL AND MECHANICAL PARAMETERS OF SOILS

Purpose. The paper considers the issues of ensuring the stability of internal dumps consisting of soft rocks. This issue is relevant because the stability of quarry boards and dumps affects the safety of work in quarries. Methodology. When assessing the stability of slopes, the method of determining the minimum coefficient of stability, equal to the ratio of restraining forces to shear forces that arise in the slope array. Findings. The calculation and assessment of the stability of the slopes of the dumps are carried out on the example of Malyshevsky rutile-zircon-ilmenite deposit. The geological structure of the deposit overburden is represented by loess-like loams, red-brown clays, gray-green clays, fine-grained sands. To ensure the stability of internal dumps, the selective formation of dumps is proposed, which is presented in this paper in two ways. In the first variant, the dumping of Sarmatian gray-green clays into the lower part of the heap, which are weakly permeable and have low strength, is considered. In the second variant, a layer of Sarmatian sands is poured into the base of the dump. According to the normative value of the coefficient of stability margin, depending on the physical and mechanical properties of the rocks that make up the array, the optimal height and slope angle of the dump are determined. When assessing the stability of the slopes of the dump, the impact of groundwater and the possibility of location in the developed space of the tailings were also taken into account. Originality and Practical implications. Studies have shown that the most rational option is the formation of internal heaps with embedding in the base of the lower tier of the heap with a height of 40 m layer of Sarmatian sands; in the case of embedding in the lower part of the inner heaps of gray-green clays, it is advisable to form the lower tier of the heap with 2 sub-tiers up to 20 m high; the upper tier of the dump is recommended to be formed by one massif 26 m high. Besides, in the produced space of the quarry, the location of the tailings is possible in case of dumping Sarmatian sands into the base of the dump.

Conversion of carboxylic acids to amides under the action of tantalum(V) chloride

It was found that the reaction of aliphatic carboxylic acids with secondary amines under the action of tantalum (V) chloride leads to the selective formation of carboxamides. N,N-Diethyladamantane-1-carboxamide were synthesized with a yield of 73% as well.

Regioselective Enzymatic Synthesis of Kojic Acid Monoesters

Kojic acid is a fungal metabolite and one of the strongest tyrosinase inhibitors. Its esters are used as lipid-compatible skin whitening components in cosmetic formulations. In this study, lipase PS, lipase AK, Lipolyve AN and pig pancreatic lipase catalyzed the acetylation of kojic acid under selective formation of the same product, kojic 7-acetate. However, the enzymes differed in their regioselectivity when catalyzing the alcoholysis of kojic acid diacetate. While lipase PS and lipase AK produced mixtures of both monoacetate regioisomers (7-acetate and 5-acetate of kojic acid), the pancreatic lipase almost exclusively produced 5-acetate. The enzyme displayed the same regioselectivity in the palmitoylation of kojic acid and in the alcoholysis of kojic acid dipalmitate. Simple reaction engineering with PPL as a catalyst thus provides the complementary monoesters of kojic acid. Kojic 7-acetate, 5-acetate, 7-palmitate and 5-palmitate were prepared with yields after purification of 57.3%, 38.2%, 31.7% and 31.4%, respectively.

Electrogenerated BF3 From Tetrafluoroborate-Based Ionic Liquids: Theoretical And Experimental Studies Towards Selective Styrene Oxide Isomerization

The anodic oxidation of tetrafluoroborate anion yields the Lewis acid BF3. If this reaction is carried out in an imidazolium ionic liquid, a quite stable system containing BF3 is obtained, whose reactivity is similar to the one of BF3·Et2O, but less harmful. The two reagents’ stabilities were compared by computational analysis, strongly suggesting a higher stability for BF3/BMIm-BF4 system. The effect of substituents on the imidazolium ring and of the electrochemical configuration on BF3 reactivity were studied in a model reaction, styrene oxide isomerization. The experimental conditions were defined for the selective formation of phenylacetaldehyde or of 2-benzyl-4-phenyl-1,3-dioxolane. Moreover, the formation of N-heterocyclic carbene-BF3 adduct was confirmed when carrying out the electrolysis in an undivided cell. Electrogenerated BF3/BMIm-BF4 system demonstrated to be a valid alternative to commercial BF3·Et2O.

PROPELLANS – PERSPECTIVE FRAME COMPOUNDS FOR THE CREATION OF HIGH-ENERGY SUBSTANCES

Важной задачей современной органической химии является открытие новых, ранее не известных науке веществ, которые могли бы расширить область наших знаний и пополнить номенклатуру высокоэнергетических или биологически активных продуктов. 3,7,10-Триоксо-2,4,6,8,9,11-гексааза[3.3.3|пропеллан и его нитропроизводные являются новейшими продуктами класса гетероциклов, их азотсодержащая полициклическая структура предполагает наличие интересных и полезных свойств, что обусловливает проявленный интерес к данной работе. Химия 3,7,10-триоксо-2,4,6,8,9,11-гексааза[3.3.3|пропеллана малоизучена и представлена лишь двумя алкилпроизводными и теоретическими расчетами энергетических характеристик нитропроизводных. В статье преставлены результаты исследования нитрования 3,7,10-триоксо-2,4,6,8,9,11-гексааза[3.3.3]пропеллана (THAP) концентрированнойазотной кислотой. Установлено, что в процессе нитрования наблюдается протекание двух конкурирующих реакций – лактам-лактимной перегруппировки и нитрования. Было показано, что продукты реакции сильно зависят от температуры реакционной массы. Установлено, что температуре -40 ºС протекает образование лактимной формы ТНАР, тогда как при постепенном увеличении температуры сначала образуется мононитропроизводное пропеллана, а при температуре 40 ºС идёт селективное образование 3,7,10-триоксо-2,6-динитро-2,4,6,8,9,11-гексааза[3.3.3]пропеллана с выходом 30%. An important task of modern organic chemistry is the discovery of new substances previously unknown to science, which could expand the area of our knowledge and replenish the range of high-energy or biologically active products. 3,7,10-Trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane and its nitro derivatives are the newest products of the class of heterocycles; interest in this work. The chemistry of 3,7,10-trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane is poorly understood and is represented by only two alkyl derivatives and theoretical calculations of the energy characteristics of nitro derivatives. The article presents the results of a study of the nitration of 3,7,10-trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane (THAP) with concentrated nitric acid. It was found that in the process of nitration, there are two competing reactions - lactam-lactam rearrangement and nitration. It was shown that the reaction products strongly depend on the temperature of the reaction mixture. It was found that at a temperature of -40 ºС the formation of the lactimic form of THAP proceeds, whereas with a gradual increase in temperature, a mononitro derivative of propellane is first formed, and at a temperature of 40 ºС, the selective formation of 3,7,10-trioxo-2,6-dinitro-2,4,6,8,9,11-hexaaza[3.3.3]propellane in 30% yield.

Selective preparation of furfural via the pyrolysis of cellulose catalyzed with nitrided HZSM-5

Furfural is a high-value compound that can be prepared by catalytic pyrolysis of biomass. In order to improve the selectivity of furfural in the process of cellulose catalytic pyrolysis, the ammonia-modified HZSM-5 (N-HZSM-5) was used as the catalyst for experimental research on a horizontal fixed bed. The effects of different nitriding temperatures and times on N-HZSM-5, and the effects of different catalyst to cellulose (CA to CL) ratios on furfural selectivity were evaluated. The results showed that N-HZSM-5 can effectively improve the selectivity for furfural. At the optimal conditions (nitriding temperature: 800 °C, nitriding time: 6 h, CA to CL ratio: 4), the selectivity of furfural was up to 24%, which was much higher than those of noncatalytic pyrolysis (1.2%) and HZSM-5 catalytic pyrolysis (3.6%). In order to better evaluate the performance of the catalyst, a series of characterizations were carried out on the N-HZSM-5. The results showed that compared with HZSM-5, N-HZSM-5 had an increased pore size, it was less acidic, and it had more uniform surface acidity. It was conducive to the selective formation of furfural. Therefore, the ammonia-modification can effectively control the structure and acidity of HZSM-5, and N-HZSM-5 exhibits a non-negligible potential in catalyzing the pyrolysis of cellulose for furfural.