TY - JOUR A1 - Klinka, Karel D. A1 - Balentova, Eva A1 - Bernát, Juraj A1 - Imrich, Jan A1 - Vavrusova, Martina A1 - Kleinpeter, Erich A1 - Pihlaja, Kalevi A1 - Koch, Andreas T1 - Tautomerism, regioisomerism, and cyclization reactions of acridinyl thiosemicarbazides N2 - The regioselectivities of methyl- and phenylhydrazine with acridin-9-yl isothiocyanate (thus yielding thiosemicarbazides with acridine substituted on the urea-type side) were examined. Methythydrazine regioselectivity was high with the alpha-nitrogen atom overwhelmingly more nucleophilic than the beta-nitrogen atom; phenylhydrazine regioselectivity was poor but varied with the solvent and only in the case of ethanol was nucleophilic predominance of the alpha-nitrogen atom pronounced. Of note, whilst both phenyl thiosemicarbazides were present in solution only as spiro forms, the methyl product was present as an equilibrium mixture of open-chain and spiro thiosemicarbazides. Reactions on the NH2 blocked analogue of methyl acridin-9-ylthiosemicarbazide (1-isopropylidene-2- methylthiosemicarbazide) were also examined. Interestingly, present in the starting material itself was a structural motif of novelty wherein a triazolethione represented the major species of an equilibrium between cyclic and open-chain forms Y1 - 2006 UR - http://www3.interscience.wiley.com/journal/121521817/toc U6 - https://doi.org/10.1002/jhet.5570430317 SN - 0022-152X ER - TY - JOUR A1 - Schilde, Uwe A1 - Erk, Çakil A1 - Kleinpeter, Erich T1 - The crystal and molecular structures of sodium and barium complexes of dibenzo-24-crown-8 ether N2 - The sodium and barium isothiocyanate complexes of 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]- 1,4,7,10,13,16,19,22-octaoxacyclotetracosin (dibenzo-24-crown-8 ether = DB24C8) were synthesized and analyzed by X-ray diffraction. The sodium complex, [Na(DB24C8)(NCS)(H2O)] 1, crystallizes in the orthorhombic space group Fdd2 with 16 molecules in the unit cell. The coordination number of Na is 6 and the central ion is located in a distorted octahedric environment. Only four of the crown ether oxygen atoms are involved. The coordination polyhedron is completed by the isothiocanate anion and by a water molecule, which is stabilized by hydrogen bonds. The barium complex, [Ba(DB24C8)(NCS)(2)] 2, crystallizes in the trigonale space group P3(1)21 with 3 molecules in the unit cell. Crystallographic C-2 symmetry is observed for the complex. The coordination number of Ba is 10. Barium is coordinated with the eight oxygen atoms of the macrocyclic ligand and with two isothiocyanate anions. The absolute structure was estimated using the FLACK parameter Y1 - 2006 U6 - https://doi.org/10.1524/zkri.2006.221.3.231 ER - TY - JOUR A1 - Kamm, Birgit A1 - Kamm, Michael A1 - Schmidt, Matthias A1 - Starke, Ines A1 - Kleinpeter, Erich T1 - Chemical and biochemical generation of carbohydrates from lignocellulose-feedstock (Lupinus nootkatensis) : quantification of glucose N2 - Different chemical and enzymatic methods were applied for the hydrolysis of main stems from Lupinus nootkatensis (harvest November 2002). The whole process (all steps) is based on the lignocellulose-feedstock biorefinery regime. The acid hydrolysis of L. was performed with concentrated hydrochloric acid; advantages in this process are exothermic hydrolysis and the possibility of acid recovery. Enzymatic hydrolysis achieved high yields of fermentable carbohydrates (regarding to input cellulose) with high selectivity. However, this way requires the generation of cellulose from L. by chemical pulping. Monosaccharide derivatives thus obtained were identified by their GC retention times and the corresponding MS fragmentation. Hexamethyldisilazane was used as derivatization reagent to prepare the trimethylsilyl derivatives of the carbohydrates and of the degradations products of cellulose from the different fractions. The glucose content was quantified by GC peak integration with respect to an internal standard. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00456535 U6 - https://doi.org/10.1016/j.chemosphere.2005.03.073 SN - 0045-6535 ER - TY - JOUR A1 - Rasovic, Aleksandar A1 - Steel, Peter J. A1 - Kleinpeter, Erich A1 - Markovic, Rade T1 - Regioselective synthesis of 1,3-thiazines by sequential 4-oxothiazolidine to 1,2-dithiole to 1,3-thiazine transformations : role of intramolecular non-bonded S...O interactions N2 - A new synthetic approach to 2,3-dihydro-4H-1,3-thiazine derivatives based upon reductive rearrangement of 1,2- dithiole-3-ylidene thiones has been developed. In turn, the 1,2-dithiole derivatives were prepared by an efficient ring- opening-closing process of 2-alkylidene-4-oxothiazolidines, induced in the presence of Lawesson's reagent by intramolecular non-bonded 1,5-type S...O interactions in the 4-oxothiazolidine precursors. Y1 - 2007 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2006.12.075 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Rolla, Nadja A1 - Koch, Andreas A1 - Taddei, Fernando T1 - Hyperconjugation and the increasing bulk of OCOCX3 substituents in trans-1,4-disubstituted cyclohexanes destabilize the diequatorial conformer N2 - The trans diesters of 1,4-cyclohexanediol with a number of acetic acid analogues, CX3COOH, of varying steric hindrance and polarity (CX3 = Me, Et, iso-Pr, tert-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, CBr3) were synthesized, and the axial, axial/equatorial, equatorial conformational equilibria were studied by low-temperature H-1 NMR spectroscopy in CD2Cl2. The structures and relative energies of the axial, axial and equatorial, equatorial conformers were calculated at both the MP2/6-311G* and the MP2/6-311+G* levels of theory, and it was only by including diffuse functions that a good correlation of Delta G degrees(calcd) vs Delta G(exptl) could be obtained. Both the structures and the energy differences of the axial, axial and equatorial, equatorial conformers are discussed with respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions sigma(C-C)/sigma(C-H)->sigma*(C-O), together with a steric effect which also destabilizes the equatorial, equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference of the axial, axial conformers with respect to their equatorial, equatorial analogues was greater than expected from the conformational energies of the corresponding substituents in the monosubstituted cyclohexyl esters. The reason for this very interesting and unexpected result is also discussed Y1 - 2006 UR - http://pubs.acs.org/journal/joceah U6 - https://doi.org/10.1021/Jo0600858 SN - 4393-4399 ER - TY - JOUR A1 - Yoneda, Julliane Diniz A1 - Leal, Katia Zaccur A1 - Seidl, Peter Rudolf A1 - Azeredo, Rodrigo Bagueira de V. A1 - Kleinpeter, Erich T1 - Camphor : a good model for illustrating NMR techniques N2 - CAMPHOR: A GOOD MODEL FOR ILLUSTRATING NMR TECHNIQUES. The use of Nuclear Magnetic Resonance spectroscopy to establish the three-dimensional structures of molecules is an important component of modern Chemistry courses. The combination of techniques that can be used for this purpose is conveniently illustrated by their application to the camphor molecule. This paper presents applications of several techniques used in NMR spectral interpretation in an increasing order of complexity. The result of individual experiments is illustrated in order to familiarize the user with the way connectivity through bonds and through space is established from 1D/2D-NMR spectra and molecular stereochemistry is determined from different NMR experiments Y1 - 2007 ER - TY - JOUR A1 - Modarresi-Alam, Ali Reza A1 - Khamooshi, Ferydoon A1 - Rostamizadeh, Mohsen A1 - Keykha, Hossein A1 - Nasrollahzahdeh, Mahmoud A1 - Bijanzadeh, Hamid-Reza A1 - Kleinpeter, Erich T1 - Dynamic 1H NMR spectroscopic study of the restricted S-N rotation in aryl-N-(arylsulfonyl)-N- (triphenylphosphoranylidene)imidocarbamates N2 - Dynamic 1H NMR (500 MHz) investigation of aryl-N-(arylsulfonyl)-N-(triphenylphosphoranylidene)imidocarbamates in CDCl3, CD3COCD3, and CD3OD at the temperature range of 183-298 K is reported. The observed free energy barriers (almost 12 kcal mol;1) are attributed to conformational isomerization about the NùS bond and these barriers show very little solvent dependence. Y1 - 2007 ER - TY - JOUR A1 - Modarresi, Ali Reza A1 - Najafi, Parisa A1 - Rostamizadeh, Mohsen A1 - Keykha, Hossein A1 - Bijanzadeh, Hamid-Reza A1 - Kleinpeter, Erich T1 - Dynamic 1H NMR study of the barrier to rotation about the C-N bond in primary carbamates and its solvent dependence N2 - The dynamic 1H NMR study of some primary carbamates in the solvents CDCl3 and CD3COCD3 between 183 and 298 K is reported. The free energies of activation, thus obtained (12.4 to 14.3 kcal mol-1), were attributed to the conformational isomerization about the N-C bond. These barriers to rotation show solvent dependence in contrast to the tertiary analogues and are lower in free energy by ca. 2-3 kcal mol-1. Y1 - 2007 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Stamboliyska, Bistra A. T1 - Quantification of the Push-Pull Character of Donor-Acceptor Triazenes N2 - The Push-pull character of two series of donor-acceptor triazenes has been quantified by C-13 and N-15 chemical shift differences of the partial N(1)=N(2) and N(3)=C(4) double bonds in the central linking C=N-N=N-C unit and by the quotient of the occupations of both the bonding pi and antibonding orbitals pi* of these partial double bonds. Excellent correlations of the two estimates, to quantify the push-pull effect, with the bond lengths strongly recommend the occupation quotients pi*/pi, the N-15 chemical shift differences Delta delta[N(l),N(2)], and the corresponding bond lengths as reasonable sensors for quantifying charge alternation along the C=N-N=N-C linking unit, for the donor- acceptor quality of the triazenes 1 and 2 and for the molecular hyperpolarizability beta(0) of these compounds. Within this context, certain Substances can be strongly recommended for NLO application. Y1 - 2008 UR - http://pubs.acs.org/doi/full/10.1021/jo8013758 U6 - https://doi.org/10.1021/Jo8013758 ER - TY - JOUR A1 - Klika, Karel D. A1 - Kramer, Markus A1 - Kleinpeter, Erich T1 - DFT computational studies of hydrogen bonding-based diastereomeric complexes : limitations and applications to enantiodifferentiation N2 - Molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory have been performed on diastereomeric complexes formed between chiral carboxylate anions and chiral urea receptors, a combination previously demonstrated to enable enantiodifferentiation by electrochemical sensing. The calculations correctly predicted the stability order of the enantiomers in acetonitrile solution when the distinction between the enantiomers was above the declared threshold reliability value of 1 kcal mol;1 for computations at this level of theory. Thus, the calculations can not only be applied to predict the likely success of undertakings using the analytical method, it can also, provided ;E is sufficient, potentially be used to determine the absolute configuration of chiral analytes with at least the racemate in hand. The previously successful enantiodifferentiations of various amino acids and alcohols using chiral ion mobility spectroscopy (CIMS) with (S)-2-butanol as the chiral selector were also evaluated by DFT calculations. The calculations again correctly predicted the stability order of the enantiomers when the calculated ;E was above the threshold value though cases not providing a value for ;E above the threshold value was problematic for this system. Attempts to address this shortcoming included an expanded conformational evaluation, a broader analytical approach, and an extended basis set. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/01661280 U6 - https://doi.org/10.1016/j.theochem.2009.08.003 SN - 0166-1280 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Ushakov, Igor A. A1 - Meshcheryakov, Vladimir I. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Variable temperature NMR and theoretical study of the stereodynamics of 5-trifluoromethylsulfonyl-1,3,5- dioxaazinane : Perlin effect subject to heteroatom substitution N2 - Multinuclear dynamic NMR spectroscopy of 5-trifluoromethylsulfonyl-1,3,5-dioxaazinane (4) revealed the existence of two close in energy chair conformers with differently oriented CF3 groups with respect to the ring. Of the two alternative routes for their interconversion, the ring inversion path with intermediate formation of the corresponding 2,5-twist-conformer is preferred, with the energy barrier of 11.2 kcal/mol in excellent agreement with the experimental value (11.7 kcal/mol). The Perlin effect is studied experimentally and calculated theoretically for all CH2 groups and found to be subject to the nature of the adjacent heteroatoms O and N, respectively. Y1 - 2008 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Shainyan, Bagrat A. T1 - Cyclobutadiene dianion derivatives : Planar 4c,6e or three-dimensional 6c,6e aromaticity? N2 - The spatial magnetic properties (Through Space NMR Shieldings - TSNMRS) of two cyclobutadiene derivatives (2 and 5) and of a number of cyclobutadiene dianion derivatives (3, 4 and 6-8) have been calculated by the GIAO perturbation method employing the Nucleus-Independent Chemical Shift (NICS) concept of P. v. Ragué Schleyer, and visualized as Iso-Chemical-Shielding Surfaces (ICSS) of various size and direction. TSNMRS values can be successfully employed to quantify and visualize the (anti)aromaticity of the compounds studied and to discuss the influence of Li+ complexation to cyclobutadiene dianion (4a, 7 and 8) on planar 4c,6e or three-dimensional 6c,6e aromaticity. Y1 - 2008 U6 - https://doi.org/10.1016/j.theochem.2008.05.027 ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Tatar, Jovanan A1 - Kleinpeter, Erich A1 - Markovic, Rade T1 - High-Yield Synthesis of Substituted and Unsubstituted Pyridinium Salts Containing a 4-Oxothiazolidine Moiety N2 - A new series of unsubstituted and substituted pyridinium salts bearing a 4-oxothiazolidinyl moiety has been prepared by an efficient rearrangement of 2-(1-bromoalkylidene)thiazolidin-4-ones. The process in based on three steps, namely carbon-bromine cleavage, bromine transfer, and substitution, each induced by pyridine or its derivatives, acting as base and reactant. Y1 - 2008 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Ushakov, Igor A. A1 - Tolstikova, Ljudmila L. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - N-Trifyl substituted 1,4-diheterocyclohexanesùstereodynamics and the Perlin effect N2 - The stereodynamic behaviour of 1-(trifluoromethylsulfonyl)piperidine 1, 4-(trifluoromethylsulfonyl)morpholine 2, 1,4-bis(trifluoromethylsulfonyl)piperazine 3 and 4-(trifluoromethylsulfonyl)thiomorpholine 1,1-dioxide 4 was studied by low-temperature 1H, 13C and 19F NMR spectroscopies. In acetone solution, compounds 1, 2 and 4 were found to exist as mixtures of two conformers in the ratio of 4:1, 4:1 and 8:1, respectively, differing by orientation of the CF3 group with respect to the ring. Compound 3 exists as a mixture of three conformers in the ratio of 3:28:69 also differing by the orientation of the two CF3 groups. Unlike the previously studied N-trifyl substituted 1,3,5-triheterocyclohexanes, the preferred conformers of compound 1 and of 1,4-diheterocyclohexanes 2-4 are those with the CF3 group directed outward from the ring, which is caused by intramolecular interactions of the oxygen atoms of the CF3SO2N groups with the equatorial hydrogens in the ;-position. B3LYP/6-311+G(d,p) calculations of the energy, geometry and NMR parameters corroborate the experimental data. The calculated Perlin effects for all conformers of compounds 1-4 as well as those measured for the major conformers of compounds 3 and 4 were analyzed by the use of the NBO analysis. Y1 - 2008 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Trisannelated benzenes - Aromatic molecules or 1,3,5-cyclohexatriene derivatives subjected to magnetic properties N2 - The through space NMR shielding (TSNMRS) values of two tricyclobutabenzene (TCBB) derivatives 2, of the corresponding hexamethylene and hexaoxo TCBB derivatives 3, of [4n]annuleno[4n + 2]annulene 5 and of its tricyclobutadiene parent compound 4 have been ab initio calculated by the GIAO perturbation method employing the nucleus- independent chemical shift (NICS) concept of Paul von Ragué Schleyer, and visualized as iso-chemical shielding surfaces (ICSS). TSNMRS values can be successfully employed to quantify and visualize the aromaticity of the central, and in 5 also of the terminal benzene ring moieties. Y1 - 2008 U6 - https://doi.org/10.1016/j.theochem.2008.02.013 ER - TY - JOUR A1 - Starke, Ines A1 - Schuster, Ildikkó A1 - Fulop, Ferenc A1 - Kleinpeter, Erich T1 - Mass spectra of tetrahydroisoquinoline-fused 1,3,2-O,N,P- and 1,2,3-O,S,N-heterocycles: influence of ring size and fusion, of present heteroatoms, substituent effects and of the stereochemistry on fra N2 - The electron ionization (EI) mass spectra of a variety of stereoisomeric tricyclic 1,3,2-oxazaphosphino[4,3- a]isoquinolines (1-4), 1,2,3-oxathiazino[4,3-a]isoquinoline-4-oxides (5-7) and the -4,4-dioxides (8-10) of oxazaphospholo- and oxathiazolo[4,3-a]- (11, 12, 15 and 16) and -[3,4-b]isoquinolines (13, 14 and 17) were recorded. Ring size and fusion, the different heteroatoms (P and S) and substituents on the ring systems strongly influence the mass spectra. In addition, mass spectra of the stereoisomers of compounds 1, 2 and 13, 14 revealed stereochemically relevant differences which are not observed for the other pairs of isomers. Copyright © 2008 John Wiley & Sons, Ltd. Y1 - 2008 ER - TY - JOUR A1 - Schuster, Ildikó A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Forró, Enikö A1 - Lázár, László A1 - Sillanpää, Reijo A1 - Fulop, Ferenc T1 - Synthesis and Conformational Analysis of Tetrahydroisoquinoline-Fused 1,3,2-Oxazaphospholidines and 1,2,3- Oxathiazolidines N2 - The cyclizations of tetrahydroisoquinoline 1,2-amino alcohols with phenylphosphonic dichloride, bis(2- chloroethyl)phosphoramidic dichloride, thionyl chloride and sulfuryl chloride were utilized to synthesize 1,5,6,10b- tetrahydro-1,3,2-oxazaphospholo[4,3-a]isoquinolines (2, 3), 1,5,10,10a-tetrahydro-1,3,2-oxazaphospholo[3,4- b]isoquinolines (8, 9), 1,5,6,10b-tetrahydro-1,2,3-oxathiazolo[4,3-a]isoquinolines (4-6) anda 1,5,10,10a-tetrahydro- 1,2,3-oxathiazolo[3,4-b]isoquinoline (11), which are the first representatives of these ring systems. NMR spectroscopic analysis revealed the existence of conformational equilibria that are fast on the NMR timescale. Theoretical DFT calculations pointed to the participation of generally two preferred conformers in the conformational equilibria; the positions of the equilibria were indicated by the experimental NMR spectroscopic parameters, and they are in good agreement with the theoretically calculated energy differences of the participating conformers. For two compounds, which could be not isolated (10, 12), both the preferred conformers and the stereochemistry could be concluded from the DFT calculation results. Y1 - 2008 ER - TY - JOUR A1 - Starke, Ines A1 - Kammer, Stefan A1 - Grunwald, Nicolas A1 - Schilde, Uwe A1 - Holdt, Hans-Jürgen A1 - Kleinpeter, Erich T1 - Complexation of diazaperylene and bisisoquinoline with transition metal ions in the gas phase studied by electrospray ionization mass spectrometry N2 - The complex formation of the ligands 1,12-diazaperylene (dap), 1,1-bisisoquinoline (bis), 2,2-bipyridine (bpy) and 1,10-phenanthroline (phen) with transition metal ions (M = Fe, Co, Ni, Cu, Zn, Ru, Os, Re, Pd, Pt, Ag and Cd) in the gas phase has been studied by electrospray ionization mass spectrometry. With the exception of Ru, Os, Fe, Ni and Cu, singly charged complexes [MLn]+ (n = 1,2) were observed. The complexes of dap and bis with Ru, Os, Fe and Ni ions, and the mixed ligand complexes with bpy and phen, are preferably of the doubly charged type [ML3]2+. In addition, collision- induced dissociation (CID) measurements were employed to evaluate the relative stabilities of these complexes. The CID experiments of mixed-ligand complexes which contain both dap and phen or dap and bpy exhibit preferential elimination of bpy, indicating that bpy is a weaker ligand than phen and dap. Y1 - 2008 ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Quantitative study and visualization of spherical 2(N + 1)2 homoaromaticity by through space NMR shieldings (TSNMRS) N2 - The through space NMR shielding (TSNMRS) values of adamantane, the 2(N + 1)2 spherical (4c, 2e) homoaromatic compounds 1,3-dehydro-5,7-adamantandiyl dication (C10H122+) and 1,3-dehydro-5,7-cubandiyl dication (C8H42+), and the (6c, 8e) homoaromatic compound 2,2;,4,4;,6,6;,8,8;,10,10;-dehydroadamantane tetracation (C10H44+) have been ab initio calculated, employing the NICS concept, and visualized as iso-chemical shielding surfaces (ICSSs). TSNMRS values can be successfully employed to study both the endohedral and exohedral aromaticity/ antiaromaticity of the compounds studied. Y1 - 2008 U6 - https://doi.org/10.1016/j.theochem.2007.11.029 ER -