Nikodem Kuźnik

Double bond migration in Sallyl systems catalysed by [RuClH(CO)(PPh3)3]

Abstract Reactions of S allyl systems (allyl sulphides of RSallyl type, where R=Et, allyl, Ph, Me 3 C, Ph 3 C, as well as of allyl phenyl sulphoxide, allyl phenyl sulphone, 2,5-dihydro-1,1-dioxothiophene) with [RuClH(CO)(PPh 3 ) 3 ] and other ruthenium compounds have been investigated. Double-bond migration was observed in the case of allyl trityl sulphide, allyl t -butyl sulphide and both sulphones, that is, where co-ordinating properties of sulphur were not too strong. High-yielded syntheses of ( E )- and ( Z )-RSCHCHCH 3 (R=Me 3 C, Z : E =96:4 and Ph 3 C, Z : E =92:8), ( E )PhS(O 2 )CHCHCH 3 and 2,3-dihydro-1,1-dioxothiophene from respective allyl systems are described. The binuclear Ru complex, formed in the model reaction of allyl phenyl sulphide with [RuClH(CO)(PPh 3 ) 3 ] has been isolated and its structure has been resolved. The mechanism of the reaction between S allyl systems and [RuClH(CO(PPh 3 ) 3 ] is proposed.

Synthesis of Selectively Protected Genistein Derivatives

Abstract Differential functionalization of the phenolic groups in Genistein by sequential silylation/acylation reactions, involving some unexpected regioselective O-silyl group replacement, is described.

Multiwalled carbon nanotube hybrids as MRI contrast agents

Summary Magnetic resonance imaging (MRI) is one of the most commonly used tomography techniques in medical diagnosis due to the non-invasive character, the high spatial resolution and the possibility of soft tissue imaging. Contrast agents, such as gadolinium complexes and superparamagnetic iron oxides, are administered to spotlight certain organs and their pathologies. Many new models have been proposed that reduce side effects and required doses of these already clinically approved contrast agents. These new candidates often possess additional functionalities, e.g., the possibility of bioactivation upon action of particular stimuli, thus serving as smart molecular probes, or the coupling with therapeutic agents and therefore combining both a diagnostic and therapeutic role. Nanomaterials have been found to be an excellent scaffold for contrast agents, among which carbon nanotubes offer vast possibilities. The morphology of multiwalled carbon nanotubes (MWCNTs), their magnetic and electronic properties, the possibility of different functionalization and the potential to penetrate cell membranes result in a unique and very attractive candidate for a new MRI contrast agent. In this review we describe the different issues connected with MWCNT hybrids designed for MRI contrast agents, i.e., their synthesis and magnetic and dispersion properties, as well as both in vitro and in vivo behavior, which is important for diagnostic purposes. An introduction to MRI contrast agent theory is elaborated here in order to point to the specific expectations regarding nanomaterials. Finally, we propose a promising, general model of MWCNTs as MRI contrast agent candidates based on the studies presented here and supported by appropriate theories.

Amalgamation of complex iron(III) ions and iron nanoclusters with MWCNTs as a route to potential T2 MRI contrast agents.

Iron-filled multiwall carbon nanotubes (Fe@MWCNTs) were functionalized toward a variety of potential magnetic resonance imaging contrast agents. Oxidized Fe@MWNCTs were covered with PEG5000 via direct esterification or using acyl chloride derivatives. Alternatively, the latter were functionalized with an aminophenol ligand (Fe@O-MWCNT-L). Moreover, pristine Fe@MWCNTs were functionalized with N-phenylaziridine groups (Fe@f-MWCNT) via [2+1] cycloaddition of nitrene. All of these chemically modified nanotubes served as a vehicle for anchoring Fe3+ ions. The new hybrids – Fe(III)/Fe@(f-/O-)MWCNTs – containing 6%–14% of the “tethered” Fe3+ions were studied in terms of the acceleration of relaxation of water protons in nuclear magnetic resonance. The highest transverse relaxivity r2=63.9±0.9 mL mg−1 s−1 was recorded for Fe(III)/Fe@O-MWCNT-L, while for Fe(III)/Fe@f-MWCNT, with r2=57.9±2.9 mL mg−1 s−1, the highest impact of the anchored Fe(III) ions was observed. The T1/T2 ratio of 30–100 found for all of the nanotube hybrids presented in this work is a very important factor for their potential application as T2 contrast agents. Increased stability of the hybrids was confirmed by ultraviolet–visible spectrophotometry.

A new class of bioactivable self-immolative N,O-ligands

A hexadentate ligand built on an amine-bis(phenol) skeleton with an aminal, self-immolative moiety is presented. Synthesis of the ligand is convenient and relatively high yielded. Moreover, it enables synthesis of many derivatives, both in the amino-phenol and aminal fragment (various heterocycles). Once the final hexadentate ligand is synthesized via the Katritzky reaction, it becomes prone to hydrolysis. Bioactivation by β-galactosidase cleaves the glycosylic bond and a spontaneous collapse of the aminal fragment occurs, thus leading to a pentadentate chelate. This bioactivation has been shown for pyrazole, 1,2,4-triazole and benzotriazole derivatives.

Coupling of C-nitro-NH-azoles with arylboronic acids. A route to N-aryl-C-nitroazoles

Summary A method for the synthesis of N-aryl-C-nitroazoles is presented. A coupling reaction between variously substituted arylboronic acids and 3(5)-nitro-1H-pyrazole catalyzed by copper salt has been carried out in methanol in the presence of sodium hydroxide to afford the desired N-aryl-C-nitroazoles in good yields. This synthetic route has also been successfully applied to obtain N-phenyl derivatives of 4-nitropyrazole, 2-nitroimidazole, 4(5)-nitroimidazole and 3-nitro-1,2,4-triazole.

Studies on the redox activity of iron N,O-complexes: Potential T1-contrast agents

Objectives: The goal of this study was to determine the redox activity of iron (ethylenebis[2-(o-hydroxyphenyl)glycine]) (EHPG) and (ethylenebis[2-(o-hydroxybenzyl)glycine]) (EHBG) (N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid) derivative complexes and of some N,O–salan complexes of iron. The hexadentate chelate (EHPG and EHBG) ligands varied in their substituents (polar OMe, NHAc, or lipophilic Ph), while the latter had different charge and lipophilicity. The low redox activity of these complexes is important in their potential applications as magnetic resonance imaging contrast agents. Methods: Redox activity was assessed in the entire Haber–Weiss cycle and separately in the Fenton reaction. The spin-trapping method with 5,5-dimethyl-1-pyrroline-N-oxide monitored in electron paramagnetic resonance was used. The standard Mn marker was applied as a reference for quantitative analysis. Additionally, ascorbate oxidation was analyzed with UV–Vis spectrophotometry. Results: Both the Haber–Weiss cycle and in particular the Fenton reaction showed low redox activity of the studied complexes, which did not exceed 30% of [Fe(EDTA)]− or FeCl3 activity. The N,O–salan complexes expressed even lower activity, i.e. 10–20% activity of [Fe(EDTA)]−. Discussion: For the EHPG and EHBG complexes, it is likely that hydrophobicity and the possibility of H-bond formation play a major role in the resulting redox effects. For this reason, chelates equipped with phenyl groups in the majority belong to less redox-active complexes. For N,O–salan complexes, activity is not correlated with the charge of the coordination sphere, but again, the highly hydrophobic character of the groups and the non-pendant substituents capable of H-bonding that are present in these ligands limit the affinity of hydrophilic species.

1,4-Bis[(1-methyl-1-phenylethyl)peroxymethyl]benzene.

The title compound, C(26)H(30)O(4), is one of the first alkyl bis-peroxides to be structurally characterized. The molecule lies on a centre of inversion and therefore the terminal phenyl rings are parallel. Although there are three aromatic rings in the molecule, the C-O-O-C torsion angle of 163.10 (10) degrees is close to the value found in Me(3)COOCMe(3).