Browsing by Author "Jasiński, Radomir"

Now showing 1 - 9 of 9
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    A clean and simple method for deprotection of phosphines from borane complexes
    (Walter de Gruyter, 2017) Demchuk, Oleg M.; Jasiński, Radomir; Strzelecka, Dorota; Dziuba, Kamil; Kula, Karolina; Chrzanowski, Jacek; Krasowska, Dorota
    Simple, efficient, clean, and stereospecific protocols of protection of phosphorus atom with borane and deprotection from the borane complexes of the tertiary phosphines in mild conditions are reported. The proposed protection/deprotection reactions tolerate a range of functional groups and lead to pure products with excellent yield with no need for application of chromatographic or crystallisation purification procedures. For the first time mechanisms of the reactions of phosphine protection and deprotection have been studied based on experimental kinetic data as well as quantumchemical calculations, which allows designing reaction conditions suitable for a given substrate.
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    A General Phenomenon of Spontaneous Amplification of Optical Purity under Achiral Chromatographic Conditions
    (MDPI, 2019) Demchuk, Oleg M.; Pietrusiewicz, Kazimierz Michał; Borkowski, Mariusz; Strzelecka, Dorota; Kielar, Katarzyna; Kicińska, Wioleta; Karevych, Sergei; Jasiński, Radomir
    This work explores the behavior of chiral compound mixtures enriched in one of the enantiomers whilst a typical chromatography on the achiral stationary phase is employed. The influence of several factors, such as the eluent composition, ratio of the compound to the stationary phase, and the initial enatiomeric purity of the compound used on the distribution of the enantiomers in the collected chromatographic fraction, was studied. The obtained results indicate that the phenomenon of Self Disproportionation of Enantiomer (SDE) occurred in all cases, and some of the collected fractions got higher optical purities than the initial one. Thus, achiral column chromatography could be applied in some cases as the simplest approach for chiral purification. Based on the experimental results and DFT calculations, an alternative concept explaining the SDE phenomenon was proposed. Due to its generality and simplicity, SDE may also be responsible for the formation of the first chiral non-racemic compounds on the early Earth.
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    A Quantum-Chemical DFT Approach to Elucidation of the Chirality Transfer Mechanism of the Enantioselective Suzuki–Miyaura Cross-Coupling Reaction
    (Hindawi, 2017) Demchuk, Oleg M.; Jasiński, Radomir; Babyuk, Dmytro
    The DFT calculations of the simplified model of the asymmetric Suzuki–Miyaura coupling reaction were performed at the M062x/LANL2DZ theory level at first. It was found that enantioselective reactions mediated by the palladium complexes of chiral C,P-ligands follow a four-stage mechanism similar to that proposed previously as one of the most credible mechanisms. It should be underlined that the presence of substituents in the substrates and the chiral ligand at ortho positions determines the energies of possible diastereoisomeric transition states and intermediates in initial reaction steps. This suggests that, in practice, a sharp selection of theoretically possible paths of chirality transfer from the catalyst to the product should have a place and, therefore, the absolute configuration of the formed atropisomeric product is defined and can be predicted.
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    Green in water sonochemical synthesis of tetrazolopyrimidine derivatives by a novel core-shell magnetic nanostructure catalyst
    (Elsevier, 2018) Demchuk, Oleg M.; Maleki, Ali; Rahimi, Jamal; Wilczewska, Agnieszka Z.; Jasiński, Radomir
    A green approach for the one-pot four-component sonochemical synthesis of 5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylic esters from the reaction of 2-cyano-guanidine, sodium azide, various aromatic aldehydes and methyl or ethyl acetoacetate in the presence of a catalytic amount of Fe2O3@SiO2-(CH2)3NHC(O)(CH2)2PPh2 as a new hybrid organic–inorganic core–shell nanomagnetic catalyst is described. This is the first design, preparation, characterization and application of the present nanomaterial and also the first ultrasound irradiated synthesis of the biologically and pharmaceutically important heterocyclic compounds in water as a green solvent. This novel sonocatalysis/nanocatalysis protocol offers several advantages such as high yields, short reaction times, environmentally-friendly reaction media, easily isolation of the products, simple preparation, full characterization and recoverability of the nanocatalyst by an external magnet and reusing several times without significant loss of activity.
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    New Insights into the Mechanism of Reduction of Tertiary Phosphine Oxides by Means of Phenylsilane
    (Wiley-Blackwell, 2015) Demchuk, Oleg M.; Jasiński, Radomir; Pietrusiewicz, Kazimierz Michał
    The mechanism of the reduction of phosphine oxides by PhSiH3 was established on the basis of kinetic measurements and Density Functional Theory (DFT) calculations. In particular, it has been proved that the model reaction between tri-n-butylphosphine oxide and phenylsilane occurs via a nonpolar mechanism. The data presented herein allow prediction and verification of the applicability of the new reduction reagents and conditions for industrially attractive processes.
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    New Rigid Polycyclic Bis(phosphane) for Asymmetric Catalysis
    (MDPI, 2019) Demchuk, Oleg M.; Pietrusiewicz, Kazimierz Michał; Szwaczko, Katarzyna; Mirosław, Barbara; Dybała, Izabela; Jasiński, Radomir
    A simple, highly efficient synthesis of a series of novel chiral non-racemic rigid tetracyclic phosphorus ligands, applicable in important chemical asymmetric transformations, was performed. In a tandem cross-coupling/C-H bond activation reaction, a well-recognised and readily available ligand (R,R)-NORPHOS was used as the starting material. The palladium complexes of new ligands were obtained and characterised on the example of a crystalline dichloropalladium complex of [(1R,2R,9S,10S,11R,12R)-4-phenyltetracyclo[8.2.1.02,9.03,8]trideca-3,5,7-triene-11,12-diyl]bis(diphenylphosphane). A notably high activity and stereoselectivity of the palladium catalysts based on the new ligands were confirmed in a model asymmetric allylic substitution reaction. Herein, we discuss the geometry of the palladium complexes formed and its impact on the efficiency of the catalysts. A comparison of their geometric features with other bis(phosphane) ligand complexes found in the Cambridge Structural Database and built density functional theory (DFT) commutated models is also presented and rationalised.
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    Novel functionalized β-nitrostyrenes: Promising candidates for new antibacterial drugs
    (Elsevier, 2019) Demchuk, Oleg M.; Boguszewska-Czubara, Anna; Kula, Karolina; Wnorowski, Artur; Biernasiuk, Anna; Popiołek, Łukasz; Miodowski, Dawid; Jasiński, Radomir
    The process of searching for new antibacterial agents is more and more challenging due to the increasing drug resistance, which has become a major concern in the field of infection management. Our study presents a synthesis and characterization by IR, UV, 1H NMR and 13C NMR spectra of a homogenous series of 1-EWG functionalized 2-aryl-1-nitroethenes which could prove good candidates for the replacement of traditional antibacterial drugs In vitro screening against a panel of the reference strains of bacteria and fungi and their cytotoxicity towards cultured human HepG2 and HaCaT cells was performed. Antimicrobial results indicated that four of the synthesized compounds exhibited a significant antimicrobial activity against all tested reference bacteria and fungi belonging to yeasts with a specific and strong activity towards B. subtilis ATCC 6633. Two of these compounds had no detectable cytotoxicity towards the cultured human cell lines, making them promising candidates for new antibacterial drugs.
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    Regio- and stereoselectivity of polar [2+3] cycloaddition reactions between (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone and selected (E)-2-substituted nitroethenes
    (Versita, 2014) Demchuk, Oleg M.; Jasiński, Radomir; Ziółkowska, Magda; Maziarka, Agata
    [2+3] Cycloaddition reactions of the highly reactive (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone with (E)-2-R-nitroethenes proceed under mild conditions and yield mixtures of stereoisomeric 2-methyl-3-(3,4,5-trimethoxyphenyl)-4-nitro-5-R-isoxazolidines. The effect of regiospecificity of the cycloadditions may be accounted for by the theory of electrophilicity indexes. Stereoselectivity, however, is determined by a compilation of steric and secondary orbital effects.
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    Regiospecific formation of the nitromethyl-substituted 3-phenyl-4,5-dihydroisoxazole via [3 + 2] cycloaddition
    (Springer Nature, 2018) Demchuk, Oleg M.; Mirosław, Barbara; Babyuk, Dmytro; Łapczuk-Krygier, Agnieszka; Kącka-Zych, Agnieszka; Jasiński, Radomir
    5-(Nitromethyl)-3-phenyl-4,5-dihydroisoxazole was obtained as a product of a high-yielding [3 + 2] cycloaddition reaction of in situ-generated benzonitrile N-oxide and 3-nitroprop-1-ene. For the first time, the regiochemistry of this reaction was unambiguously proven by X-ray structural analysis. The quantum-chemical calculation performed at the M06-2X/6-31G(d) (PCM) theoretical level affords a basis for explaining the course of reaction as well as the nature of transition states. Next, further DFT calculations together with spectral data shed light on structural aspects of the product.