Новий формат співробітництва (Договір про співробітництво між Національною академією наук України і Національною академією наук Киргизької Республіки)

A one-pot method has been developed for the oxidative cleavage of internal alkenes into aldehydes by using 0.5 mol % of the nonheme iron complex [Fe(OTf)2(mix-bpbp)] (bpbp=N,N′-bis(2-picolyl)-2,2′-bipyrrolidine) as catalyst and 1.5 equivalents of hydrogen peroxide and 1 equivalent of sodium periodate as oxidants. A mixture of diastereomers of the chiral bpbp ligand can be used, thereby omitting the need for resolution of its optically active components. The cleavage reaction can be performed in one pot within 20 h and under ambient conditions. Addition of water after the epoxidation, acidification and subsequent pH neutralization are crucial to perform the epoxidation, hydrolysis, and subsequent diol cleavage in one pot. High aldehyde yields can be obtained for the cleavage of internal aliphatic double bonds with cis and trans configuration (86–98 %) and unsaturated fatty acids and esters (69–96 %). Good aldehyde yields are obtained in reactions of trisubstituted and terminal alkenes (62–63 %). The products can be easily isolated by a simple extraction step with an organic solvent. The presented protocol involves a lower catalyst loading than conventional methods based on Ru or Os. Also, hydrogen peroxide can be used as the oxidant in this case, which is often disproportionated by second- and third-row metals. By using only mild oxidants, overoxidation of the aldehyde to the carboxylic acid is prevented

Проблеми ісламу України в їх науковому відтворенні

The Pd/TOMPP-catalysed (TOMPP = tris(2-methoxyphenyl)phosphine) telomerisation of 1,3-butadiene was studied under solvent- and base-free conditions with phenolic substrates that can be potentially derived from lignin. Large differences in catalytic activity were observed, with reactivity increasing in the order of phenol, p-cresol, guaiacol, creosol and syringol. This reactivity trend can be attributed to the substrates’ relative nucleophilicities, as induced by the donating effects of the p-methyl and o-methoxy substituents. The chosen reaction conditions, i.e. temperature, ligand/metal and butadiene/substrate ratios, strongly influenced both the conversion and selectivity of the reaction. Remarkably, the composition of the reaction medium, i.e. the butadiene/substrate ratio, exerted a strong influence on the linear/branched ratio. High conversions and selectivities to the linear products are obtained when excess butadiene is used. The linear telomer products could be readily converted from O-alkylated to Calkylated phenolics via the thermal Claisen rearrangement. High conversions and selectivities were observed after 2 hours at 200 1C. Branched o-octadienyl phenols were obtained in all cases except for the syringol telomer which gave the linear p-octadienyl product exclusively

Розробка мобільної технології ремонту низьковуглецевих стальних труб низького та високого тиску методом пайки низькотемпературними припоями

Розроблено технологію безвогневого ремонту дефектів конструкцій з низьковуглецевих сталей шляхом пайки низькотемпературними припоями. Розроблено та заявлено новий склад легкоплавкого припою на базі олова з домішками міді та вісмуту. Припій оптимально поєднує властивості рідкоплинності, корозійної стійкості, міцності та адгезійної міцності. Технологію пайки сталей низькотемпературними припоями із застосуванням високочастотного генератора електричного струму доведено до стану практичного застосування.Разработана технология безогневого ремонта дефектов конструкций из низкоуглеродистых сталей путем пайки низкотемпературными припоями. Разработан и заявлен новый состав легкоплавкого припоя на базе олова, с добавками меди и висмута. Припой оптимально объединяет свойства жидкотекучести, коррозионной стой кости, прочности и адгезионной прочности. Технологию пайки сталей низкотемпературными припоями с применением высокочастотного генератора электрического тока доведено до состояния практического применения.The technology of out fire defects repair in low carbon steel constructions by soldering with low- temperature solders is developed. The new fusible tin rich solder composition containing copper and bismuth additives is developed and declared. The solder has optimum properties of liquid stream, corrosion resistance, durability and adhesion strength. The low carbon steel soldering technology with application of high-frequency electric current generator is carried to practical application

Structural and Functional Models of Non-Heme Iron Enzymes : A Study of the 2-His-1-Carboxylate Facial Triad Structural Motif

The structural and functional modeling of a specific group of non-heme iron enzymes by the synthesis of small synthetic analogues is the topic of this thesis. The group of non-heme iron enzymes with the 2-His-1-carboxylate facial triad has recently been established as a common platform for the activation of dioxygen in Nature. The oxidative transformations catalyzed by these enzymes are very diverse and many of them are unprecedented in synthetic organic chemistry. This makes this group of enzymes an attractive target for synthetic modeling studies. A new family of biomimetic N,N,O ligands that accurate model this facial triad has been developed. Structurally characterized copper complexes showed the potential of the new ligands as mimics of the facial triad. Mononuclear iron complexes of these ligands were also synthesized and in this way accurate models of the active sites of these enzymes were obtained. For instance, model complexes of the enzyme-substrate complexes of extradiol cleaving catechol dioxygenases were built and the reactivity of these complexes showed that the compounds were able to mimic the enzymes both in structure and function. Very accurate models of the closely related intradiol cleaving catechol dioxygenases were also synthesized with a slightly modified ligand system. These studies provided further insight into the factors governing the respective selectivities of these interesting enzymes. Furthermore, the reactivity of several non-heme iron complexes as oxidation catalysts was explored. Non-heme iron model complexes of the 2-His-1-carboxylate facial triad structural motif proved to be interesting oxidation catalysts and displayed both epoxidation as well as cis-dihydroxylation activity. Other catalysts showed promising reactivities in the oxidation of alkanes and alkenes. All complexes were characterized by variety of techniques including UV-Vis, IR, EPR spectroscopy, magnetic and mass spectrometric measurements, and X-ray crystal structure determinations. In the last part of the thesis, the focus is shifted to the exploration of the coordination of the new ligands with the transitions metals zinc and copper. The obtained results show that the ligands are quite versatile and interesting reactivities were discovered. The zinc complexes for instance mediate the conversion of pyruvate, an important metabolic junction, to oxalate. The copper complexes converted tetrachlorocatechol, a persistent organic pollutant, to chloranilic acid via an oxidative double dehalogenation. Both of these discovered reactivities are unprecedented

New trends for metal complexes with anticancer activity

Medicinal inorganic chemistry can exploit the unique properties of metal ions for the design of new drugs. This has, for instance, led to the clinical application of chemotherapeutic agents for cancer treatment, such as cisplatin. The use of cisplatin is, however, severely limited by its toxic side-effects. This has spurred chemists to employ different strategies in the development of new metal-based anticancer agents with different mechanisms of action. Recent trends in the field are discussed in this review. These include the more selective delivery and/or activation of cisplatin-related prodrugs and the discovery of new non-covalent interactions with the classical target, DNA. The use of the metal as scaffold rather than reactive centre and the departure from the cisplatin paradigm of activity towards a more targeted, cancer cell-specific approach, a major trend, are discussed as well. All this, together with the observation that some of the new drugs are organometallic complexes, illustrates that exciting times lie ahead for those interested in ‘metals in medicine

Chemocatalytic Conversion of Ethanol into Butadiene and Other Bulk Chemicals

The development of new and improved processes for the synthesis of bio-based chemicals is one of the scientific challenges of our time. These new discoveries are not only important from an environmental point of view, but also represent an important economic opportunity, provided that the developed processes are selective and efficient. Bioethanol is currently produced from renewable resources in large amounts and, in addition to its use as biofuel, holds considerable promise as a building block for the chemical industry. Indeed, further improvements in production, both in terms of efficiency and feedstock selection, will guarantee availability at competitive prices. The conversion of bioethanol into commodity chemicals, in particular direct ‘drop-in’ replacements is, therefore, becoming increasingly attractive, provided that the appropriate (catalytic) technology is in place. The production of green and renewable 1,3-butadiene is a clear example of this approach. The Lebedev process for the one-step catalytic conversion of ethanol to butadiene has been known since the 1930s and has been applied on an industrial scale to produce synthetic rubber. Later, the availability of low-cost oil made it more convenient to obtain butadiene from petrochemical sources. The desire to produce bulk chemicals in a sustainable way and the availability of low-cost bioethanol in large volumes has, however, resulted in a renaissance of this old butadiene production process. This paper reviews the catalytic aspects associated with the synthesis of butadiene via the Lebedev process, as well as the production of other, mechanistically related bulk chemicals that can be obtained from (bio)ethanol

Liquid-phase reforming and hydrodeoxygenation as a two-step route to aromatics from lignin

A two-step approach to the conversion of organosolv, kraft and sugarcane bagasse lignin to monoaromatic compounds of low oxygen content is presented. The first step consists of lignin depolymerization in a liquid phase reforming (LPR) reaction over a 1 wt% Pt/γ-Al2O3 catalyst at 225 °C in alkaline ethanol– water. The first LPR step resulted in a decrease in lignin molecular weight of 32%, 57% and 27% for organosolv, kraft and bagasse lignin, respectively. GC analysis of the depolymerized lignin reaction mixture furthermore showed the formation of alkylated phenol, guaiacol and syringol-type products in 11%, 9% and 5% yields from organosolv, kraft and bagasse lignin, respectively. The lignin-oil that was isolated by extraction of the ethanol–water solution was subjected to a subsequent hydrodeoxygenation (HDO) reaction in the second conversion step. HDO of the lignin-oil was performed in dodecane at 300 °C under 50 bar hydrogen pressure over CoMo/Al2O3 and Mo2C/CNF catalysts. GC analysis of the product mixture obtained after the two-step LPR–HDO process revealed the formation of, amongst others, benzene, toluene, xylenes and ethylmethylbenzenes. Of the total observed monomeric products (9%), 25% consisted of these oxygen-free products. Notably, such products cannot be obtained by direct HDO of lignin. HDO of the lignin-oil at 350 °C resulted in the conversion of all tris-oxygenated products, with 57% of the observed monomeric products now identified as mono-oxygenated phenolics

Chemocatalytic Conversion of Ethanol into Butadiene and Other Bulk Chemicals

The development of new and improved processes for the synthesis of bio-based chemicals is one of the scientific challenges of our time. These new discoveries are not only important from an environmental point of view, but also represent an important economic opportunity, provided that the developed processes are selective and efficient. Bioethanol is currently produced from renewable resources in large amounts and, in addition to its use as biofuel, holds considerable promise as a building block for the chemical industry. Indeed, further improvements in production, both in terms of efficiency and feedstock selection, will guarantee availability at competitive prices. The conversion of bioethanol into commodity chemicals, in particular direct ‘drop-in’ replacements is, therefore, becoming increasingly attractive, provided that the appropriate (catalytic) technology is in place. The production of green and renewable 1,3-butadiene is a clear example of this approach. The Lebedev process for the one-step catalytic conversion of ethanol to butadiene has been known since the 1930s and has been applied on an industrial scale to produce synthetic rubber. Later, the availability of low-cost oil made it more convenient to obtain butadiene from petrochemical sources. The desire to produce bulk chemicals in a sustainable way and the availability of low-cost bioethanol in large volumes has, however, resulted in a renaissance of this old butadiene production process. This paper reviews the catalytic aspects associated with the synthesis of butadiene via the Lebedev process, as well as the production of other, mechanistically related bulk chemicals that can be obtained from (bio)ethanol

Influence of Levulinic Acid Hydrogenation on Aluminum Coordination in Zeolite-Supported Ruthenium Catalysts: A(27)Al 3QMAS Nuclear Magnetic Resonance Study

Contains fulltext : 184180.pdf (publisher's version ) (Open Access

In situ spectroscopic investigation of the cobalt-catalyzed oxidation of lignin model compounds in ionic liquids

The cobalt-catalyzed oxidation of lignin and lignin model compounds using molecular oxygen in ionic liquids proceeds readily under mild conditions, but mechanistic insight and evidence for the species involved in the catalytic cycle is lacking. In this study, a spectroscopic investigation of the complexes involved during this process was conducted using in situ ATR-IR, Raman, and UV-Vis spectroscopy. A plausible mechanism was proposed that explains the role of the ionic liquid and the other reaction conditions necessary to achieve high catalytic activity. Direct spectroscopic evidence for the species involved in the catalytic cycle was obtained. In addition, substrate consumption and product formation during the oxidation of several lignin model compounds, such as veratryl alcohol, cinnamyl alcohol, and a model compound with a β-O-4 linkage, was directly monitored. The reaction proceeds via the coordination of alcohol-containing substrates to the Co followed by formation of a Co-superoxo species. The presence of hydroxide is necessary for coordination of the alcohol to occur. Hydrogen peroxide that forms as a reaction by-product underwent rapid disproportionation to yield water and molecular oxygen. Involvement of the various intermediates was further confirmed by 18O2 labeling studies. The properties of the ionic liquid greatly influence the catalytic activity both by stabilizing reactive intermediates and by favoring the coordination of the substrate to the cobalt over the direct oxidation of the cobalt without substrate