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Hejda M.,University of Pardubice | Lycka A.,Research Institute for Organic Syntheses | Jambor R.,University of Pardubice | Ruzicka A.,University of Pardubice | Dostal L.,University of Pardubice
Dalton Transactions | Year: 2014

A set of 1H-2,1-benzazaboroles as B-N analogues of 1H-indene and a set of 1H-pyrrolo[1,2-c][1,3,2]diazaborolidines as B-N analogues of 1H-pyrrolizine were prepared via nucleophilic addition of selected alkyl(aryl)lithiums (MeLi, tBuLi or PhLi) to, via N→B intramolecular interactions, the activated imino CN functionality in the structure of C,N- or N,N-chelated chloroboranes. All compounds were characterized by elemental analysis and 1H, 11B, 13C and 15N NMR spectroscopy, and molecular structures of isolated compounds were on several occasions established by means of single-crystal X-ray diffraction analysis. The presence of three adjacently bonded substituents and their systematic alternation on five-membered C3BN (1H-2,1-benzazaboroles) or C2BN2 (1H-pyrrolo[1,2-c][1,3,2]diazaborolidines) rings allowed us to follow both the influence of the steric repulsion and limitations for the formation of respective annulated heterocyclic systems. This journal is © the Partner Organisations 2014. Source


Hejda M.,University of Pardubice | Jambor R.,University of Pardubice | Ruzicka A.,University of Pardubice | Lycka A.,Research Institute for Organic Syntheses | Dostal L.,University of Pardubice
Dalton Transactions | Year: 2014

Reduction of C,N-chelated chloroborane [2-(CH=NtBu)C6H 4]BPhCl (1) with the potassium metal afforded (3,3′)-bis(1-Ph- 2-tBu-1H-2,1-benzazaborole) (2). Compound 2 is formed via C-C reductive coupling reaction. Subsequent reduction of 2 with two equivalents of the potassium metal produced orange crystals of 1Ph-2tBu-1H-2,1-benzazaborolyl (Bab) potassium salt K(THF)(Bab) (3). Compound 3 is able to react with simple electrophiles (MeI or Me3SiCl) resulting in the formation of substituted 1H-2,1-benzazaboroles. © the Partner Organisations 2014. Source


Hejda M.,University of Pardubice | Lycka A.,Research Institute for Organic Syntheses | Jambor R.,University of Pardubice | Ruzicka A.,University of Pardubice | Dostal L.,University of Pardubice
Dalton Transactions | Year: 2013

A set of C,N-intramolecularly coordinated boranes containing various C,N-chelating ligands L1-3 (where L1 = [o-(CHNtBu)C 6H4], L2 = [o-(CHN-2,6-iPr2C 6H3)C6H4], L3 = [o-(CH2NMe2)C6H4]); L 1-3BCl2 (for 1 L = L1, for 2 L = L2, for 5 L = L3), L1BPhCl (3) and L1BCy 2 (4) (where Cy = cyclohexyl) were synthesized and fully characterized by multinuclear NMR spectroscopy and in cases of 1 and 3-5 by the single crystal X-ray diffraction analysis. The reaction of 1-3 with the anilides ArNHLi (Ar = 2,6-Me2C6H3 or 2,6-iPr 2C6H3) proceeded via unexpected addition of anilide across the CN bond yielding 1,2,3-trisubstituted 1H-2,1-benzazaboroles 6-11, whose structures were unambiguously established by single crystal X-ray diffraction analysis (except for 11) and multinuclear NMR spectroscopy. In contrast, compounds 4 and 5 were inert towards ArNHLi. The investigation dealing with the reaction mechanism between the parent boranes 1-3 and ArNHLi revealed that amidolithiation of the CN double bond involved in the ligand backbones is the crucial step of the whole reaction. The CN double bond in 1-3 is activated by its coordination to the ortho bonded Lewis acidic boron center, which was also proven by the fact that the non-substituted ligand L1H did not react with ArNHLi under the same reaction conditions in an analogous reaction. © 2013 The Royal Society of Chemistry. Source


Svoboda T.,University of Pardubice | Jambor R.,University of Pardubice | Ruzicka A.,University of Pardubice | Jirasko R.,University of Pardubice | And 3 more authors.
Organometallics | Year: 2012

Organoantimony(III) and organobismuth(III) oxides (LMO) 2 (where L is the NCN-chelating ligand C 6H 3-2,6-(CH 2NMe 2) 2 and M = Sb (1), Bi (2)) reacted smoothly with arsenic oxides As 2O 5 and As 2O 3 to form the molecular oxides [(LM) 3(AsO 4) 2] and [(LM) 2(As 2O 5)] (where M = Sb (3, 5), Bi (4, 6)). All compounds were characterized by electrospray ionization (ESI) mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and, in the case of 5 and 6, single-crystal X-ray diffraction (XRD) analyses. Compound 3 formed two conformational isomers in a benzene or chloroform solution, as confirmed by 1H and 13C NMR spectroscopy. As in the case of 3, 5 also formed conformational isomers in a benzene solution, whereas the bismuth analogue 6 was unstable in solution. The stabilities of the three possible conformers of 5 were studied by density functional theory (DFT) calculations. © 2012 American Chemical Society. Source


Cifkova E.,University of Pardubice | Holcapek M.,University of Pardubice | Lisa M.,University of Pardubice | Ovcacikova M.,University of Pardubice | And 4 more authors.
Analytical Chemistry | Year: 2012

The identification and quantitation of a wide range of lipids in complex biological samples is an essential requirement for the lipidomic studies. High-performance liquid chromatography-mass spectrometry (HPLC/MS) has the highest potential to obtain detailed information on the whole lipidome, but the reliable quantitation of multiple lipid classes is still a challenging task. In this work, we describe a new method for the nontargeted quantitation of polar lipid classes separated by hydrophilic interaction liquid chromatography (HILIC) followed by positive-ion electrospray ionization mass spectrometry (ESI-MS) using a single internal lipid standard to which all class specific response factors (RFs) are related to. The developed method enables the nontargeted quantitation of lipid classes and molecules inside these classes in contrast to the conventional targeted quantitation, which is based on predefined selected reaction monitoring (SRM) transitions for selected lipids only. In the nontargeted quantitation method described here, concentrations of lipid classes are obtained by the peak integration in HILIC chromatograms multiplied by their RFs related to the single internal standard (i.e., sphingosyl PE, d17:1/12:0) used as common reference for all polar lipid classes. The accuracy, reproducibility and robustness of the method have been checked by various means: (1) the comparison with conventional lipidomic quantitation using SRM scans on a triple quadrupole (QqQ) mass analyzer, (2) 31P nuclear magnetic resonance (NMR) quantitation of the total lipid extract, (3) method robustness test using subsequent measurements by three different persons, (4) method transfer to different HPLC/MS systems using different chromatographic conditions, and (5) comparison with previously published results for identical samples, especially human reference plasma from the National Institute of Standards and Technology (NIST human plasma). Results on human plasma, egg yolk and porcine liver extracts are presented and discussed. © 2012 American Chemical Society. Source

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