TY - JOUR A1 - Thomas, Steffen A1 - Kleinpeter, Erich T1 - Zur Zuordnung der 13C-Chemischen Verschiebungen substituierter Naphthaline aus Ladungsdichten mit Hilfe eines neuronalen Netzes Y1 - 1995 ER - TY - JOUR A1 - Ströhl, D. A1 - Kleinpeter, Erich T1 - Zur Stereochemie acyclischer Verbindungen : III. Bestimmung der Vorzugskonformstion unterschiedlich substituirternY-Chlorpropylether Y1 - 1993 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Y-aromaticity - existing: yes or no? An answer given on the magnetic criterion (TSNMRS) JF - Tetrahedron N2 - The spatial magnetic properties (Through Space NMR Shieldings - TSNMRS) of a number of Y-shaped structures possessing 4n+2 pi-electrons (i.a. the trimethylenemethane ions TMM2+, TMM2-, the guanidinium cation, substituted and hetero analogues) have been computed, visualized as Isochemical Shielding Surfaces (ICSS) of various size and direction, were examined subject to present Y-aromaticity and the results compared with energetic and geometric criteria obtained already. (C) 2016 Elsevier Ltd. All rights reserved. KW - Y-aromaticity KW - pi-Electron delocalization KW - Theoretical calculations KW - ICSS KW - TSNMRS Y1 - 2016 U6 - https://doi.org/10.1016/j.tet.2016.02.020 SN - 0040-4020 VL - 72 SP - 1675 EP - 1685 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Klod, Sabrina A1 - Koch, Andreas T1 - Visualization of through space NMR shieldings of aromatic and anti-aromatic molecules and a simple means to compare and estimate aromaticity N2 - Through space NMR shieldings of aromatic (benzene, mono-substituted and annelated benzenes, ferrocene, [14]- and [18]-annulenes, phenylenes and tetra- to heptahelicene) and anti-aromatic molecules (cyclobutadiene and pentalene) were assessed by ab initio molecular-orbital calculations. Employing the nucleus-independent chemical shifts (NICS) concept, these through space NMR shieldings were visualized as iso-chemical-shielding surfaces (ICSSs) and can be applied quantitatively to determine the stereochemistry of proximal nuclei. In addition, the distances in Å at ICSS values of ±0.1 ppm in-plane and perpendicular-to-center of the aromatic ring system were employed as a simple means to compare and estimate qualitatively the aromaticity of the systems at hand. Y1 - 2007 UR - http://www.sciencedirect.com/science/journal/01661280 U6 - https://doi.org/10.1016/j.theochem.2007.02.049 SN - 0166-1280 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Visualization of homoaromaticity in cations, neutral molecules and anions by spatial magnetic properties (through space NMR shieldings) - an 1H/13C NMR chemical shift study N2 - Prototypes for homoaromaticity in cations, neutral molecules, and anions are theoretically studied at the MP2 level of theory. For the global minimum structures on the potential energy surface both 1H/13C chemical shifts and spatial magnetic properties as through space NMR shieldings (TSNMRS) were calculated by the GIAO perturbation method. The TSNMRS are visualized as iso-chemical-shielding surfaces (ICSS) of different sign and size. Coincident experimental and computed 1H/13C chemical shifts afforded the possibility to decide from the TSNMRSs at hand on both the existence and the size of homoaromaticity in the molecules studied. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2009.04.063 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Seidl, Peter R. T1 - Visualization and quantification of the anisotropic effect of C=C double bonds on 1H NMR spectra of highly congested hydrocarbons-indirect estimates of steric strain N2 - The anisotropic effect of the olefinic C=C double bond has been calculated by employing the NICS (nucleus independent chemical shift) concept and visualized as an anisotropic cone by a through space NMR shielding grid. Sign and size of this spatial effect on 1H chemical shifts of protons in norbornene, exo- and endo-2-methylnorbornenes, and in three highly congested tetracyclic norbornene analogs have been compared with the experimental 1H NMR spectra as far as published. 1H NMR spectra have also been calculated at the HF/6-31G* level of theory to get a full, comparable set of proton chemical shifts. Differences between ;(1H)/ppm and the calculated anisotropic effect of the C=C double bond are discussed in terms of the steric compression that occurs in the compounds studied. Y1 - 2008 UR - http://pubs.acs.org/doi/full/10.1021/jp801063t U6 - https://doi.org/10.1021/Jp801063t ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Szatmári, István A1 - Lázár, László A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Fulop, Ferenc T1 - Visualization and quantification of anisotropic effects on the 1H NMR spectra of 1,3-oxazino[4,3- alpha]isoquinolines - indirect estimates of steric compression N2 - The anisotropic effects of the phenyl, alpha- and beta-naphthyl moieties in four series of 1,3-oxazino[4,3- a]isoquinolines on the H-1 chemical shifts of the isoquinoline protons were calculated by employing the Nucleus Independent Chemical Shift (NICS) concept and Visualized as anisotropic cones by a through-space NMR shielding grid. The signs and extents of these spatial effects on the H-1 chemical shifts of the isoquinoline protons were compared with the experimental H-1 NMR spectra. The differences between the experimental delta (H-1)/ppm values and the calculated anisotropic effects of the aromatic moieties are discussed in terms of the steric compression that occurs in the Compounds studied. Y1 - 2009 U6 - https://doi.org/10.1016/j.tet.2009.07.038 SN - 0040-4020 ER - TY - GEN A1 - Kleinpeter, Erich A1 - Shainyan, Bagrat A. T1 - Very low-temperature dynamic Si-29 NMR study of the conformational equilibrium of (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane T2 - Magnetic resonance in chemistry Y1 - 2019 U6 - https://doi.org/10.1002/mrc.4870 SN - 0749-1581 SN - 1097-458X VL - 57 IS - 6 SP - 317 EP - 319 PB - Wiley CY - Hoboken 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 - Kirpichenko, Svetlana V. A1 - Shainyan, Bagrat A. A1 - Kleinpeter, Erich T1 - Unusual conformational preferences of 1,3-dimethyl-3-isopropoxy-3-silapiperidine JF - Journal of physical organic chemistry N2 - The conformational analysis of the first representative of the Si-alkoxy substituted six-membered Si,N-heterocycles, 1,3-dimethyl-3-isopropoxy-3-silapiperidine, was performed by low-temperature 1H and 13C NMR spectroscopy and DFT theoretical calculations. In contrast to the expectations from the conformational energies of methyl and alkoxy substituents, the Meaxi-PrOeq conformer was found to predominate in the conformational equilibrium in the ratio Meaxi-PrOeq : Meeqi-PrOax of ca. 2 : 1 as from the 1H and 13C NMR study. The thermodynamic parameters obtained by the complete line shape analysis showed that the main contribution to the barrier to ring inversion originates from the entropy term of the free energy of activation. KW - barrier to ring inversion KW - conformational equilibrium KW - DFT theoretical calculations KW - dynamic NMR KW - silapiperidines Y1 - 2012 U6 - https://doi.org/10.1002/poc.3028 SN - 0894-3230 VL - 25 IS - 12 SP - 1321 EP - 1327 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Szatmari, Istvan A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Fulop, Ferenc A1 - Kleinpeter, Erich T1 - Unexpected isomerization of new naphth[1,3]oxazino[2,3-a] isoquinolines in solution, studied by dynamic NMR and supported by theoretical DFT computations JF - Tetrahedron N2 - Through the reactions of 1-aminomethyl-2-naphthol and substituted 1-aminobenzyl-2-naphthols with 3,4-dihydroisoquinoline or 6,7-dimethoxy-3,4-dihydroisoquinoline under microwave conditions, naphth[1,2-e][1,3]oxazino[2,3-a]-isoquinoline derivatives were prepared in good yields. The latter reaction was extended by using 2-aminoarylmethyl-1-naphthols, leading to isomeric naphth-[2,1-e][1,3]oxazino[2,3-a] isoquinolines. Beside the detailed NMR spectroscopic and theoretical study of both stereochemistry and dynamic behaviour of these new conformational flexible heterocyclic ring systems an unexpected dynamic process between two diastereomers was observed in solution, studied by variable temperature H-1 NMR spectroscopy and the mechanism proved by theoretical DFT computations. KW - 3,4-Dihydroisoquinoline KW - Aminonaphthol KW - Dynamic NMR spectroscopy KW - DFT calculations KW - Conformational analysis Y1 - 2013 U6 - https://doi.org/10.1016/j.tet.2013.06.094 SN - 0040-4020 VL - 69 IS - 35 SP - 7455 EP - 7465 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Baier, Dieter A1 - Soyez, Konrad A1 - Streurs, Kerstin A1 - Kaiser, Jürgen A1 - Narodoslawski, Michael A1 - Kamm, Birgit A1 - Kromus, Stefan A1 - Kamm, Michael A1 - Zierke, Irene A1 - Koller, Matthias A1 - Hermann, Tim A1 - Schmeer, Ernst A1 - Thrän, Daniela A1 - Kleinpeter, Erich A1 - Starke, Ines A1 - Holzberger, Anja T1 - Umweltforschung für das Land Brandenburg BT - Projekt Ökotechnologie / Regenerative Energien JF - Brandenburgische Umwelt-Berichte : BUB ; Schriftenreihe der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Potsdam N2 - BAIER, D.; SOYEZ, K.: Dekontamination von Altholz ; BAIER, D. et al.: Untersuchungen zur Kompostierbarkeit von paraffinbeschichteten Verpackungsmaterialien ; KAISER, J.; SOYEZ, K.: Zum Wasser- und Wärmehaushalt des Intensivrotteprozesses der mechanisch-biologischen Abfallbehandlung ; KAMM, B. et al.: Green Biorefinery - European Network for the Implementation of Biorefineries (NIB) ; KAMM, B. et al.: Grüne Bioraffinerie Brandenburg ; KOLLER, M.; HERMANN, T.: Entscheidungshilfen für die ökologische Optimierung der Entsorgung häuslicher Restabfälle ; SCHMEER, E.: Solarthermie 2000 ; SCHMEER, E.: Forschungs- und Demonstrationsanlage zur Photovoltaik ; SOYEZ, K. et al.: Verbundvorhaben "Mechanisch-biologische Restabfallbehandlung" ; STARKE, I. et al.: Carbohydrates as raw material from a Green BioRefinery Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-3831 SN - 1434-2375 SN - 1611-9339 VL - 8 SP - 230 EP - 301 ER - TY - JOUR A1 - Wentrup, Curt A1 - Koch, Rainer A1 - Kleinpeter, Erich T1 - Twisted C=C Double Bonds with Very Low Rotational Barriers in Dioxanediones and Isoxazolones Determined by Low-Temperature Dynamic NMR Spectroscopy and Computational Chemistry JF - European journal of organic chemistry KW - NMR spectroscopy KW - Twisted double bonds KW - Push-pull effect KW - Density functional calculations Y1 - 2016 U6 - https://doi.org/10.1002/ejoc.201600931 SN - 1434-193X SN - 1099-0690 SP - 4985 EP - 4990 PB - Wiley-VCH CY - Weinheim 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 - Kleinpeter, Erich T1 - The structure of hydantoins in solution and in the solid state Y1 - 1996 ER - TY - JOUR A1 - Kleinpeter, Erich T1 - The Structure of hydantions in solution and in the solid state Y1 - 1997 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Ushakov, Igor A. A1 - Meshcheryakov, Vladimir I. A1 - Schilde, Uwe A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - The stereodynamics of 3,5-bis(trifluoromethylsulfonyl)-1,3,5-oxadiazinane and 1,3,5- tris(trifluoromethylsulfonyl)-1,3,5-triazinane- an experimental and theoretical study N2 - Multinuclear dynamic NMR spectroscopy of 3,5-bis(trifluoromethylsulfonyl)-1,3,5-oxadiazinane (3) revealed the existence of two conformers with differently oriented CF3 groups with respect to the ring, and two dynamic processes: ring inversion and restricted rotation about the N-S bond. Two transition states connecting the two conformers and corresponding to clockwise and counterclockwise rotations about the N-S bond were found; the calculated activation barriers of about 12 kcal/mol are in excellent agreement with those measured experimentally for the related molecule 1,3,5-tris(trifluoromethylsulfonyl)-1,3,5-triazinane (1). X-ray analysis proved the existence of the symmetric isomer of 3, which is the minor isomer in solutions but the only one in the crystal due to packing effects. The normal Perlin effect (JCHax < JCHeq)observed for 2(6)-CH2 in 3, whereas the reversed Perlin effect was found for the 4-CH2 group in 3 as well as for all CH2 groups in 1 both experimentally and theoretically. The latter effect in compounds 1, 3, and 1- (methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane (2) can be considered as a genuine reverse Perlin effect since larger values of 1JCH are observed for longer C-H bonds. Y1 - 2007 UR - http://www.sciencedirect.com/science/article/pii/S0040402007016389 U6 - https://doi.org/10.1016/j.tet.2007.09.041 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Ströhl, D. A1 - Peinze, S. A1 - Brandt, W. A1 - Schmidt, R. A1 - Neubert, K. T1 - The solution conformation of cyclic ß-casomorphine-5 analogues Y1 - 1996 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The multiple bond character of the carbon-boron bond in boron trapped N-heterocyclic carbenes (NHCs) and cyclic(alkyl)(amino) carbenes (CAACs) on the magnetic criterion JF - Tetrahedron N2 - Geometry, 11B, 13C chemical shifts and the spatial magnetic properties (Through-Space NMR Shieldings -TSNMRS) of both cations and anions of boron-trapped N-heterocyclic carbenes (NHCs) and cyclic (alkyl)(amino)carbenes (CAACs) and of the corresponding diborane/diborene/diboryne dis-carbene adducts have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept; the TSNMRS results are visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The ICSS of the TSNMRS (actually the anisotropy effects measurable in 1H NMR spectroscopy) are employed to qualify and quantify the present multiple bond character of the Carbene-Boron bond in the trapped NHCs and CAACs. Results are confirmed by bond length and 11B/13C chemical shift variations. Thus the partial multiple bond character of the Carbene-Boron bond cannot be expressed by the arrow of weak, much longer dative bonds and should be omitted as in other covalent lone pair-it or triel bonds. & COPY; 2023 Elsevier Ltd. All rights reserved. KW - NHCs KW - CAACs KW - Multiple NHC(CAAC)-Boron bonds KW - Through -space NMR KW - shieldings (TSNMRS) KW - NICS KW - Anisotropy effect KW - Ring current effect Y1 - 2023 U6 - https://doi.org/10.1016/j.tet.2023.133469 SN - 0040-4020 SN - 1464-5416 VL - 140 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Schulenburg, Anja A1 - Zug, Ines A1 - Hartmann, Horst T1 - The interplay of thio(seleno)amide/vinylogous thio(seleno)amide "Resonance" and the anisotropic effect of thiocarbonyl and selenocarbonyl functional groups N2 - [GRAPHICS] Amino-substituted thio(seleno)acrylamides 1-4 were synthesized and their H-1 and C-13 NMR spectra assigned. Both the NMR data and the results of theoretical calculations at the ab initio level of theory were employed to elucidate the adopted structures of the compounds in terms of E/Z isomerism and s-cis/s-trans configuration. In the case of the asymmetrically N(Me)Ph-substituted compounds, ab initio GIAO-calculated ring current effects of the N-phenyl group were applied to successfully determine the preferred conformer bias. The restricted rotations about the two C-N partial double bonds were studied by DNMR and the barriers to rotation (Delta G(c)(double dagger)) determined at the coalescence temperatures, and these were discussed with respect to the structural differences between the compounds. The barriers to rotation were also calculated at the ab initio level of theory where the best results (R-2 = 0.8746) were obtained only with inclusion of the solvent at the SCIPCMHF/6-31G* level of theory. The calculations also provided means of assessing structural influences which were not available due to inaccessible rotation barriers. By means of natural bond orbital (NBO) analysis of 1-4, the occupation numbers of nitrogen lone pairs and bonding/antibonding pi/pi* orbitals were shown to quantitatively describe thio(seleno)amide/vinylogous thio(seleno)amide "resonance". Finally, the thio(seleno)carbonyl anisotropic effect was quantitatively calculated by the GIRO method and visualized by isochemical shielding surfaces (ICSS). Only marginal differences between the two anisotropic effects were calculated and are therefore of questionable utility for previous and future applications with respect to stereochemical assignments Y1 - 2005 SN - 0022-3263 ER - TY - JOUR A1 - Scholl, S. A1 - Koch, Andreas A1 - Henning, Dietrich A1 - Kempter, Gerhard A1 - Kleinpeter, Erich T1 - The influence of structure and lipophilicity of hydantoin derivatives on anticonvulsant activity Y1 - 1999 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Seidl, Peter Rudolf T1 - The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis N2 - Carbon-13 NMR is widely used in the determination of the stereochemistry of organic compounds. Changes in chemical shifts caused by interactions of groups that are close in space normally result in shielding of the carbon and deshielding of the hydrogen nuclei that are involved. This is not always the case, however, and further work on the origin of these effects would be desirable. Early applications of theoretical methods to the study of NMR shielding parameters were not particularly successful, but in recent years, the calculation of NMR shielding parameters by theoretical methods has developed into a useful and popular tool for structural studies by NMR. A promising approach to the problem of distinguishing and evaluating stereochemical influences on carbon and hydrogen chemical shifts is provided by natural chemical shielding (NCS) analysis. This method allows a partitioning of theoretical NMR shieldings into magnetic contributions from bonds and lone pairs of the molecule using the natural bond orbital (NBO) method. In order to investigate the origins of steric effects, we employed the NCS analysis to axial/equatorial-Me-cyclohexane, norbornane and exo/endo-Me-norbornane, in addition to n-pentane in the anti, gauche and g(P) g(M) conformations. Our results indicate that distortions in molecular structure due to steric effects can result in bond stretching or compression or in angular distortions. Changes in bond lengths result in the predictable shielding or deshielding of the nuclei that are involved. Where the molecular framework may be distorted to alleviate strain, chemical shifts appear to reflect changes in angles. Copyright (C) 2004 John Wiley Sons, Ltd Y1 - 2004 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Seidl, Peter Rudolf T1 - The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis Y1 - 2005 SN - 0894-3230 ER - TY - JOUR A1 - Holdt, Hans-Jürgen A1 - Müller, Holger A1 - Potter, Matthias A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Starke, Ines A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich T1 - The first sandwich complex with an octa(thioether) coordination sphere : Bis(maleonitrile-tetrathia-12-crown- 4)silver(I) N2 - The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S(4)) and maleonitrile-tetrathia-13-crown- 4 (mn13S(4)) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1: 1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S(4))(2)]BF4 (3a), [Ag(mn13S(4))(2)]BF4 (4a) and [Ag-2(mn13S(4))(3)](PF6)(2) (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S(4))(2)](+) where each mn12S(4) ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S(4))(2)](+) is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mnl3S(4))(2)](+), exhibits a half-sandwich structure. One mn13S(4) ligand coordinates to Ag+ by all four S donor atoms and the other 13S(4) crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b-8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL](+) (L = mn12S(4), mn13S(4)). The C-13 NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (Delta G(double dagger)) for [Ag(mn12S(4))(2)](+) was determined to be 64 kJmol(-1). Y1 - 2006 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/27721/ U6 - https://doi.org/10.1002/ejic.200501109 SN - 1434-1948 ER - TY - JOUR A1 - Balci, K. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Collier, W. B. A1 - Stricker, M. C. A1 - Stover, D. D. A1 - Ritzhaupt, G. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - The effects of conformation and zwitterionic tautomerism on the structural and vibrational spectral data of anserine JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - In this study, the stable conformers of neutral anserine were searched by molecular dynamics simulations and energy minimization calculations using the MM2 force field. Thermochemical calculations at B3LYP/6-31G(d) level of theory followed these preliminary calculations. The results confirmed that neutral anserine has quite a flexible structure and many stable gauche and trans conformers at room temperature. Nevertheless, two are considerably more favourable in energy than the others and expected to dominate the gas-phase and matrix IR spectra of the molecule. The corresponding structural and vibrational spectral data for these two conformers of neutral anserine, whose relative stabilities were also examined by high-accuracy energy calculations carried out using G3MP2B3 method, and for the most stable conformer of anserine in zwitterion form were calculated at B3LYP/6-311++G(d,p) level of theory. The calculated harmonic force constants were refined using the Scaled Quantum Mechanical Force Field (SQM-FF) method and then used to produce the refined wavenumbers, potential energy distributions (PEDs) and IR and Raman intensities. These refined data together with the scaled harmonic wavenumbers obtained using another method, Dual Scale factors (DS), enabled us to correctly analyse the observed IR and Raman spectra of anserine and revealed the effects of conformation and zwitterionic tautomerism on its structural and vibrational spectral data. (C) 2016 Elsevier B.V. All rights reserved. KW - Anserine KW - Matrix IR spectrum KW - Tautomerism KW - SQM-FF KW - Dual scale factors Y1 - 2016 U6 - https://doi.org/10.1016/j.vibspec.2016.08.003 SN - 0924-2031 SN - 1873-3697 VL - 86 SP - 277 EP - 289 PB - Elsevier CY - Amsterdam 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 - Taddei, F. A1 - Kleinpeter, Erich T1 - The anomeric effect in substituted cyclohexanes : II. The role of hyperconjugative interactions and steric effect in 1,4-disubstituted cyclohexanes N2 - The conformational equilibria of the cis/trans isomers of some 1,4-di-substituted cyclohexanes (X = OH, OMe, Me, OCOCH3, OCOC(CH3)(3), OCOCCl3, OCOCF3) were calculated at several levels of theory; the best correlation between calculated and experimentally available Delta G(0)s refers to the MP2/6-311 +G*//MP2/6-311G* results. In addition, the hyperconjugative effect of the substituents was studied with the NBO options included in the GAUSSIAN-98 package; a number of interactions between filled NBOs and antibonding orbitals could be considered as most representative for delocalization along the molecules studied. The effect of the substituents on the molecular geometry of the substituted cyclohexanesas well as the partitioning of both hyperconjugative and steric substituent effects on the present conformational equilibria is critically evaluated. Our model [E. Kleinpeter, F. Taddei, J. Mol. Struct. (THEOCHEM) 683 (2004) 29] for interpreting the relative stability of conformers of substituted cyclohexanes could be further verified and its reliability assessed. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0166-1280 ER - TY - JOUR A1 - Taddei, F. A1 - Kleinpeter, Erich T1 - The anomeric effect in substituted cyclohexanes : I. The role of hyperconjugative interactions and steric effect in monosubstituted cyclohexanes N2 - The relative energy of conformers, DeltaE, of monosubstituted cyclohexanes with OR (R = Me, Et, i-Pr and t-Bu) and R substituents (R = Me, Et, i-Pr and t-Bu) was calculated with MO ab initio theory at RHF, MP2 and QCISD levels with the 6-311G* and 6-311 + G* basis sets. A selected group of delocalizing interactions were calculated with the natural bond orbital method in order to quantify the hyperconjugative contribution, DeltaE(hyp.), to the relative stability of conformers. From the calculated values of DeltaE and DeltaE(hyp.) an estimate of the differential steric effect, DeltaE(ster.), of substituents in cyclohexane was obtained. The values of DeltaE(hyp), and DeltaE(ster.) show that they have a similar magnitude for OR substituents, while for R substituents the values of are greater. The shift in the conformational equilibrium towards the axial conformer, the so-called anomeric effect, takes place when, within a series of substituents, hyperconjugative interactions and steric interactions balance in favour of the stability of this conformer. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0166-1280 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Lämmermann, Anica A1 - Kühn, Heiner T1 - The anisotropic effect of functional groups in H-1 NMR spectra is the molecular response property of spatial nucleus independent chemical shifts (NICS)-Conformational equilibria of exo/endo tetrahydrodicyclopentadiene derivatives N2 - The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the anisotropic effects of the functional groups in the H-1 NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS). Y1 - 2011 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Laemmermann, Anica A1 - Kühn, Heiner T1 - The anisotropic effect of functional groups in H-1 NMR spectra is the molecular response property of spatial nucleus independent chemical shifts (NICS)-Conformational equilibria of exo/endo tetrahydrodicyclopentadiene derivatives JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry N2 - The inversion of the flexible five-membered ring in tetrahydrodicyclopentadiene (TH-DCPD) derivatives remains fast on the NMR timescale even at 103 K. Since the intramolecular exchange process could not be sufficiently slowed for spectroscopic evaluation, the conformational equilibrium is thus inaccessible by dynamic NMR. Fortunately, the spatial magnetic properties of the aryl and carbonyl groups attached to the DCPD skeleton can be employed in order to evaluate the conformational state of the system. In this context, the anisotropic effects of the functional groups in the H-1 NMR spectra prove to be the molecular response property of spatial nucleus independent chemical shifts (NICS). Y1 - 2011 U6 - https://doi.org/10.1039/c0ob00356e SN - 1477-0520 VL - 9 IS - 4 SP - 1098 EP - 1111 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The anisotropic effect of functional groups in H-1 NMR spectra is the molecular response property of spatial NICS-the frozen conformational equilibria of 9-arylfluorenes JF - Tetrahedron N2 - Rotation about the single bond adjoining the aryl and fluorene moieties in 9-arylfluorenes can be frozen out on the NMR timescale if methyl groups are located at either one or both of the ortho positions of the aryl substituent. In the ground-state of these rotamers, the planes of the aryl and fluorene moieties are perpendicular to each other and the methyl substituents are consequently positioned either above the fluorene moiety or in-plane with it; thus, the methyl protons are either shielded or deshielded, respectively, due to the ring current effect of the fluorene moiety. This anisotropic effect on the H-1 chemical shifts of the methyl protons has been quantified on the basis of through-space NMR shieldings (TSNMRS) and subsequently Delta delta(calcd) compared with the experimentally observed chemical shift differences, Delta delta(exp). In this context, the experimental anisotropic effects of functional groups in the H-1 NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between Delta delta(calcd) and Delta delta(exp) were, for the first time, also quantified as arising from steric compression. KW - Through-space NMR shieldings (TSNMRS) KW - Spatial NICS KW - Anisotropic effect KW - Iso-chemical-shielding surfaces (ICSS) KW - 9-Arylfluorenes Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.06.005 SN - 0040-4020 VL - 67 IS - 32 SP - 5740 EP - 5743 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The anisotropic effect of functional groups in 1H NMR spectra is the molecular response property of spatial NICS-the frozen conformational equilibria of 9-arylfluorenes N2 - Rotation about the single bond adjoining the aryl and fluorene moieties in 9-arylfluorenes can be frozen out on the NMR timescale if methyl groups are located at either one or both of the ortho positions of the aryl substituent. In the ground-state of these rotamers, the planes of the aryl and fluorene moieties are perpendicular to each other and the methyl protons are either shielded or deshielded, respectively, due to the ringe current effect of the fluorene moiety. This anisotropic effect on the 1H chemical shifts of the methyl protons has been quantified on the basis of through- space NMR shieldings (TSNMRS) and subsequently _______ compared with the experimentally observed chemical shift differences _____. In this context, the experimental anisotropic effects of functional groups in the !H NMR have proven to quantitatively be the molecular response property of theoretical spatial nucleus independent chemical shieldings (NICS). Differences between _______ and _____ were, for the first time, also quantified as arising from steric compression. Y1 - 2011 UR - http://www.sciencedirect.com/science/article/pii/S0040402011008507 (13.9.13) SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - The 13 C chemical shift and the anisotropy effect of the carbene electron-deficient centre BT - simple means to characterize the electron distribution of carbenes JF - Magnetic resonance in chemistry N2 - Both the C-13 chemical shift and the calculated anisotropy effect (spatial magnetic properties) of the electron-deficient centre of stable, crystalline, and structurally characterized carbenes have been employed to unequivocally characterize potential resonance contributors to the present mesomerism (carbene, ylide, betaine, and zwitter ion) and to determine quantitatively the electron deficiency of the corresponding carbene carbon atom. Prior to that, both structures and C-13 chemical shifts were calculated and compared with the experimental delta(C-13)/ppm values and geometry parameters (as a quality criterion for obtained structures). KW - C-13 chemical shift KW - carbenes KW - zwitterions KW - carbene electron deficiency KW - nucleus-independent chemical shifts (NICS) KW - through space NMR shieldings KW - (TSNMRS) Y1 - 2019 U6 - https://doi.org/10.1002/mrc.4979 SN - 0749-1581 SN - 1097-458X VL - 58 IS - 3 SP - 280 EP - 292 PB - Wiley CY - Hoboken ER - 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 - Neuvonen, Kari A1 - Neuvonen, Helmi A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Taft equation in the light of NBO computations introduction of a novel polar computational substituent constant scale sigma(q)* for alkyl groups JF - Computational and theoretical chemistry N2 - The validity of the Taft equation: log(k(R)/k(CH3)) = rho*sigma* + delta E-S was studied with the aid of NBO computational results concerning cyclohexyl esters RCOOC6H11 [R = Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Isobutyl, sec-Butyl, tert-Butyl, Neopentyl, CH(CH2CH3)(2), CH(CH3)C(CH3)(3), C(CH3)(2)CH2CH3, C(CH3)(2)C(CH3)(3), CH(CH3)(Np), CH(iPr)(tBu), C(Me)(Et)(iPr), C(Et)(2)(tBu) or C(Et)(iPr)(tBu)]. It was proved that the sigma*(alkyl) value is a composite substitutent constant including the polar and steric contributions. A novel computational sigma(q)* substituent constant scale is presented based on the NBO atomic charges of the alpha-carbon and the computational total steric exchange energies E(ster) of the cyclohexyl esters specified above. The method used offers a useful way to calculate sigma*(alkyl) values for alkyl groups for which experimental Taft's polar sigma* parameters are not available. KW - NBO analysis KW - Taft equation KW - Polar substituent constant KW - Steric effect Y1 - 2012 U6 - https://doi.org/10.1016/j.comptc.2011.11.044 SN - 2210-271X VL - 981 IS - 2 SP - 52 EP - 58 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Neuvonen, Kari A1 - Neuvonen, Helmi A1 - Koch, Andreas T1 - Taft equation in the light of NBO computations : Introduction of a novel polar computational substituent constant scale for alkyl groups Y1 - 2012 SN - 2210-271X ER - TY - JOUR A1 - Griel, C. A1 - Ströhl, D. A1 - Jeschkeit, H. A1 - Kleinpeter, Erich T1 - Synthetische und NMR-spektroskopische Untersuchungen der Benzzyl-aminaddition an N-Maleyl- aminosäurederivaten Y1 - 1992 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Lazareva, Nataliya F. A1 - Shainyan, Bagrat A. A1 - Schilde, Uwe A1 - Chipania, Nina N. T1 - Synthesis, Molecular Structure, Conformational Analysis, and Chemical Properties of Silicon-Containing Derivatives of Quinolizidine Y1 - 2012 SN - 0022-3263 ER - TY - JOUR A1 - Lazareva, Nataliya F. A1 - Shainyan, Bagrat A. A1 - Schilde, Uwe A1 - Chipanina, Nina N. A1 - Oznobikhina, Larisa P. A1 - Albanov, Alexander I. A1 - Kleinpeter, Erich T1 - Synthesis, molecular structure, conformational analysis, and chemical properties of silicon-containing derivatives of quinolizidine JF - The journal of organic chemistry N2 - A silicon analog of quinolizidine 3,3,7,7-tetramethylhexahydro-1H-[1,4,2]oxazasilino[4,5-d][1,4,2]oxazasilin-9a-yl)methanol 3 was synthesized. X-ray diffraction analysis confirmed the trans configuration and low temperature NMR spectroscopy both the flexibility (barrier of interconversion 5.8 kcal mol(-1)) and the conformational equilibrium (chair-chair and chair-twist conformers) of the compound. The relative stability of the different isomers/conformers of 3 was calculated also at the MP2/6-311G(d,p) level of theory. Intra- and intermolecular hydrogen bonding in 3 and the appropriate equilibrium between free and self-associated molecules was studied in solvents of different polarity. Both the N-methyl quaternary ammonium salt and the O-trimethylsilyl derivative of 3 could be obtained and their structure determined. Y1 - 2012 U6 - https://doi.org/10.1021/jo202658n SN - 0022-3263 VL - 77 IS - 5 SP - 2382 EP - 2388 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Suslova, Elena N. A1 - Tran Dinh Phien, A1 - Shlykov, Sergey A. A1 - Kleinpeter, Erich T1 - Synthesis, conformational preferences in gas and solution, and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations JF - Tetrahedron N2 - 1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature C-13 NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph-ax conformer (1-Ph-eq:1-Ph-ax ratio of 20:80%, Delta G degrees (317 K) = -0.87 kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C-ipso and C(1,5) carbon signals in C-13 NMR spectra at 103 K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2 = 1:1:3), which is still liquid at 100 K, the 1-Ph-eq conformer was found to be the preferred one [(1-Ph-eq: 1-Ph-ax = 77%: 23%, K = 77/23 = 2.8; -Delta G degrees = -RT In K (at 103 K) = 0.44 +/- 0.1 kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X = H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph-ax conformer in the gas phase and of the Ph-eq conformer in solution is confirmed. KW - 1-(Dimethylamino)-1-phenyl-1-silacyclohexane KW - Conformational analysis KW - Gas phase electron diffraction KW - Low-temperature d-NMR KW - DFT KW - MP2 KW - M062X/6-311G** calculations Y1 - 2018 U6 - https://doi.org/10.1016/j.tet.2018.06.023 SN - 0040-4020 VL - 74 IS - 32 SP - 4299 EP - 4307 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Virta, P. A1 - Koch, Andreas A1 - Roslund, M. U. A1 - Mattjus, P. A1 - Kleinpeter, Erich A1 - Kronberg, L. A1 - Sjoholm, R. A1 - Klika, Karel D. T1 - Synthesis, characterisation and theoretical calculations of 2,6-diaminopurine etheno derivatives N2 - Four derivatives of 2,6-diaminopurine (1) were synthesised and characterised. When 1 was reacted with chloroacetaldehyde, 5-aminoimidazo[2,1- i] purine (2), 9-aminoimidazo[2,1-b]purine (3), 9-aminoimidazo[1,2- a]purine (4) and diimidazo[2,1-b: 2', 1'-i]purine (5) were formed. The purified products (3 - 5) were fully characterised by MS, complete NMR assignments as well as fluorescence and UV spectroscopy. The purified, isolated yields of these products ( 3 - 5) varied from 2.5 to 30%. The relative stability of different tautomers was investigated by theoretical calculations. Fluorescence characteristics are also discussed and compared to the starting material 1 and a reference molecule 2-aminopurine Y1 - 2005 SN - 1477-0520 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Stojanovic, Milovan A1 - Markovic, Rade A1 - Baranac-Stojanovic, Marija T1 - Synthesis of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions N2 - Syntheses of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined and discussed. The formation of (5,6)-membered systems was feasible with all nucleophiles tried (O, S and N), while the closing of the five-membered ring was restricted to O- and S-nucleophiles. The closure of a four-membered ring failed. Instead, the bicyclic (5,6)-membered acetal derivative and the tricyclic system with an eight-membered central ring were obtained from the substrates containing O and S nucleophilic moieties, respectively. The reaction outcome and stereochemistry are rationalized using quantum chemical calculations at B3LYP/6-31G(d) level. The exclusive cis-stereoselectivity in the formation of (5,6)- and (5,5)-membered systems results from thermodynamic control, whereas the formation of the eight-membered ring was kinetically controlled. Y1 - 2012 SN - 1477-0520 ER - TY - JOUR A1 - Stojanovic, Milovan A1 - Markovic, Rade A1 - Kleinpeter, Erich A1 - Baranac-Stojanovic, Marija T1 - Synthesis of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions JF - Organic & biomolecular chemistry : an international journal of synthetic, physical and biomolecular organic chemistry N2 - Syntheses of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined and discussed. The formation of (5,6)-membered systems was feasible with all nucleophiles tried (O, S and N), while the closing of the five-membered ring was restricted to O- and S-nucleophiles. The closure of a four-membered ring failed. Instead, the bicyclic (5,6)-membered acetal derivative and the tricyclic system with an eight-membered central ring were obtained from the substrates containing O and S nucleophilic moieties, respectively. The reaction outcome and stereochemistry are rationalized using quantum chemical calculations at B3LYP/6-31G(d) level. The exclusive cis-stereoselectivity in the formation of (5,6)- and (5,5)-membered systems results from thermodynamic control, whereas the formation of the eight-membered ring was kinetically controlled. Y1 - 2012 U6 - https://doi.org/10.1039/c1ob06451g SN - 1477-0520 VL - 10 IS - 3 SP - 575 EP - 589 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Modarresi-Alam, Ali Reza A1 - Inaloo, Iman Dindarloo T1 - Synthesis of primary thiocarbamates by silica sulfuric acid as effective reagent under solid-state and solution conditions N2 - A simple and efficient method for the conversion of alcohols and phenols to primary O-thiocarbamates and S- thiocarbamates in the absence of solvent (solvent-free condition) using silica sulfuric acid (SiO2OSO3H) as a solid acid is described. The products are easily distinguished by IR, NMR and X-ray data. X-ray data of the compounds reveal a planar trigonal orientation of the NH2 nitrogen atom with the partial C,N double-bond character and the CS or CO groups in synperiplanar position with CarylO and CalkylS moieties, respectively. Moreover, the OCSNH2 group which is perpendicular to the plane of the benzene ring in 1c and the central thiocarbamate SCONH2 group in 2b are essentially planar. Y1 - 2012 SN - 0022-2860 ER - TY - JOUR A1 - Modarresi-Alam, Ali Reza A1 - Inaloo, Iman Dindarloo A1 - Kleinpeter, Erich T1 - Synthesis of primary thiocarbamates by silica sulfuric acid as effective reagent under solid-state and solution conditions JF - Journal of molecular structure N2 - A simple and efficient method for the conversion of alcohols and phenols to primary O-thiocarbamates and S-thiocarbamates in the absence of solvent (solvent-free condition) using silica sulfuric acid (equivalent to SiO2-OSO3H) as a solid acid is described. The products are easily distinguished by IR, NMR and X-ray data. X-ray data of the compounds reveal a planar trigonal orientation of the NH2 nitrogen atom with the partial C,N double-bond character and the C=S or C=O groups in synperiplanar position with C-aryl-O and C-alkyl-S moieties, respectively. Moreover, the -O-CS-NH2 group which is perpendicular to the plane of the benzene ring in 1c and the central thiocarbamate -S-CO-NH2 group in 2b are essentially planar. KW - Solvent-free KW - N-unsubstituted(primary)O-thiocarbamates KW - N-unsubstituted (primary)S-thiocarbamates KW - Isothiocyanic acid KW - Solid acid KW - Silica sulfuric acid Y1 - 2012 U6 - https://doi.org/10.1016/j.molstruc.2012.05.033 SN - 0022-2860 VL - 1024 IS - 9 SP - 156 EP - 162 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ryppa, C. A1 - Senge, Mathias O. A1 - Hatscher, S. S. A1 - Kleinpeter, Erich A1 - Wacker, Philipp A1 - Schilde, Uwe A1 - Wiehe, A. T1 - Synthesis of mono- and disubstituted porphyrins : A- and 5,10-A(2)-type systems N2 - General syntheses have been developed for meso-substituted porphyrins with one or two substituents in the 5,10- positions and no beta substituents. 5-Substituted porphyrins with only one meso substituent are easily prepared by an acid-catalyzed condensation of dipyrromethane, pyrrole-2-carbaldehyde. and an appropriate aldehyde using a "[2+1+1]" approach. Similarly, 5,10-disubstituted porphyrins are accessible by simple condensation of unsubstituted tripyrrane with pyrrole and various aldehydes using a "[3+1]" approach. The yields for these reactions are low to moderate and additional formation of either di- or mono-substituted porphyrins due to scrambling of the intermediates is observed. However, the reactions can be performed quite easily and the desired target compounds are easily removed due to large differences in solubility. A complementary and more selective synthesis involves the use of organolithium reagents for SNAr reactions. Reaction of in situ generated porphyrin (porphine) with 1.1-8 equivalents of RLi gave the monosubstituted porphyrins, while reaction with 3-6 equivalents of RLi gave the 5,10-disubstituted porphyrins in yields ranging from 43 to 90%. These hitherto almost inaccessible compounds complete the series of different homologues of A-, 5,15-A(2)-, 5,10-A(2)-, A(3)-, and A(4)-type porphyrin's and allow an investigation of the gradual influence of type, number, and regiochemical arrangement of substituents on the properties of meso-substituted porphyrins. They also present important starting materials for the synthesis of ABCD porphyrins and are potential synthons for supramolecular materials requiring specific substituent orientations Y1 - 2005 SN - 0947-6539 ER - TY - JOUR A1 - Kirpichenko, Svetlana A1 - Shainyan, Bagrat A. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Tran Dinh Phien, A1 - Albanov, Alexander T1 - Synthesis of 3-fluoro-3-methyl-3-silatetrahydropyran and its conformational preferences in gas and solution by GED, NMR and theoretical calculations JF - Tetrahedron N2 - The 3,3-disubstitued 3-silaheterocyclohexane with an electronegative substituent at silicon, 3-fluoro-3-methyl-3-silatetrahydropyran 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED) and low temperature C-13 and F-19 NMR spectroscopy. Quantum-chemical calculations were carried out both for the isolated species and Hcomplexes in gas and in polar medium. The predominance of the 1-FeqMeax conformer (1-F-eq:1-F-ax ratio of 65:35, Delta G degrees = 0.37 kcal/mol) determined from GED is close to the theoretically estimated conformational equilibrium, especially at the DFT level. In solution, low temperature NMR spectroscopy showed no decoalescence of the signals in C-13 (down to 95 K) and F-19 NMR spectra (down to 123 K). However, the calculated F-19 chemical shift of -173.6 ppm for the 1-FeqMeax conformer practically coincides with the experimentally observed value (-173 to -175 ppm) as distinct from that for the 1-FaxMeeq conformer (-188.8 ppm), suggesting compound 1 to be anancomeric in solution, in compliance with its theoretical and experimental preference in the gas phase. KW - 3-Fluoro-3-methyl-3-silatetrahydropyran KW - Conformational analysis KW - Gas phase electron diffraction KW - Low-temperature NMR KW - DFT KW - MP2 and CCSD(T) calculations Y1 - 2018 U6 - https://doi.org/10.1016/j.tet.2018.02.055 SN - 0040-4020 VL - 74 IS - 15 SP - 1859 EP - 1867 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Barta, Petra A1 - Szatmari, Istvan A1 - Fueloep, Ferenc A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Synthesis and stereochemistry of new naphth[1,3]oxazino[3,2-a] benzazepine and naphth[1,3]oxazino[3,2-e]thienopyridine derivatives JF - Tetrahedron N2 - Through the reactions of 1- or 2-naphthol and 4,5-dihydro-3H-benz[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine, new aminonaphthol derivatives were prepared. The syntheses were extended by using N-containing naphthol analogues such as 5-hydroxyisoquinoline and 6-hydroxyquinoline. The ring closures of the novel bifunctional compounds were also achieved, resulting in new naphth[2,1-e][1,3]oxazines, naphth[1,2-e][1,3]oxazines, isoquinolino[5,6-e][1,3]oxazines and quinolino[5,6-e][1,3]oxazines. H-1 NMR spectra of the target heterocycles 16, 20 and 21 were sufficiently resolved to indentify the present stereochemistry; therefore, beside computed structures, spatial experimental (dipolar coupling-NOE) and computed (ring current effect of the naphthyl moiety-TSNMRS) NMR studies were employed. The studied heterocycles exist exclusively as S(14b),R(N), R(14b),S(N), and S(16b)S(N) isomers, respectively. The flexible moieties of the studied compounds prefer. (C) 2016 Elsevier Ltd. All rights reserved. KW - Modified Mannich reaction KW - Thienopyridine KW - Benzazepine KW - NMR spectroscopy KW - Stereochemistry KW - Theoretical calculations Y1 - 2016 U6 - https://doi.org/10.1016/j.tet.2016.03.058 SN - 0040-4020 VL - 72 SP - 2402 EP - 2410 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Linker, Torsten T1 - Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer N2 - The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by 1H and 13C NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial/equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount. Y1 - 2012 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Linker, Torsten T1 - Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer JF - Tetrahedron N2 - The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by H-1 and C-13 NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial 'equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount. KW - 4-Substituted cyclohexanones KW - Conformational analysis KW - Dynamic NMR KW - Simulation of H-1 NMR spectra KW - Quantum chemical calculations KW - ALTONA equation Y1 - 2012 U6 - https://doi.org/10.1016/j.tet.2012.01.022 SN - 0040-4020 VL - 68 IS - 10 SP - 2363 EP - 2373 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Werner, Peter A1 - Linker, Torsten T1 - Synthesis and NMR spectroscopic conformational analysis of benzoic acid esters of mono- and 1,4-dihydroxycyclohexane, 4-hydroxycyclohexanone and the -ene analogue - The more polar the molecule the more stable the axial conformer JF - Tetrahedron N2 - para-Substituted benzoic acid esters of cyclohexanol, 1,4-dihydroxycyclohexane, 4-hydroxy-cyclohexanone and of the corresponding exo-methylene derivative were synthesized and the conformational equilibria of the cyclohexane skeleton studied by low temperature H-1 and C-13 NMR spectroscopy. The geometry optimized structures of the axial/equatorial chair conformers were computed at the DFT level of theory. Only one preferred conformation of the ester group was obtained for both the axial and the equatorial conformer, respectively. The content of the axial conformer increases with growing polarity of the 6-membered ring moiety; hereby, in addition, the effect of sp(2) hybridization/polarity of C(4)= O/C(4)= CH2 on the present conformational equilibria is critically evaluated. Another dynamic process could be studied, for the first time in this kind of compounds. (C) 2017 Elsevier Ltd. All rights reserved. KW - Conformational analysis KW - A-values of COOAr on cyclohexane KW - Benzoic acid esters KW - Dynamic NMR KW - DFT calculations Y1 - 2017 U6 - https://doi.org/10.1016/j.tet.2017.04.029 SN - 0040-4020 VL - 73 SP - 3801 EP - 3809 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Lammermann, Anica A1 - Kühn, Heiner T1 - Synthesis and NMR spectra of the syn and anti isomers of substituted cyclobutanes-evidence for steric and spatial hyperconjugative interactions N2 - The syn and anti isomers of cis,cis-tricyclo[5.3.0.0(2.6)]dec-3-ene derivatives have been synthesized and their (1)H and (13)C NMR spectra unequivocally analyzed. Both their structures and their (1)H and (13)C NMR chemical shifts were calculated by DFT, the latter two calculations employing the GIAO perturbation method. Additionally, calculated NMR shielding values were partitioned into Lewis and non-Lewis contributions from the bonds and lone pairs involved in the molecules by accompanying NBO and NCS analyses. The differences between the syn and anti isomers were evaluated with respect to steric and spatial hyperconjugation interactions. Y1 - 2011 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Laemmermann, Anica A1 - Kühn, Heiner T1 - Synthesis and NMR spectra of the syn and anti isomers of substituted cyclobutanes-evidence for steric and spatial hyperconjugative interactions JF - Tetrahedron N2 - The syn and anti isomers of cis,cis-tricyclo[5.3.0.0(2.6)]dec-3-ene derivatives have been synthesized and their (1)H and (13)C NMR spectra unequivocally analyzed. Both their structures and their (1)H and (13)C NMR chemical shifts were calculated by DFT, the latter two calculations employing the GIAO perturbation method. Additionally, calculated NMR shielding values were partitioned into Lewis and non-Lewis contributions from the bonds and lone pairs involved in the molecules by accompanying NBO and NCS analyses. The differences between the syn and anti isomers were evaluated with respect to steric and spatial hyperconjugation interactions. KW - Conformational analysis KW - cis,cis-Tricyclo[5.3.0.0(2,6)]dec-3-enes KW - NMR KW - DFT calculation KW - NBO/NCS analysis Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.02.012 SN - 0040-4020 VL - 67 IS - 14 SP - 2596 EP - 2604 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Lazareva, Nataliya F. A1 - Albanov, Alexander I. A1 - Shainyan, Bagrat A. A1 - Kleinpeter, Erich T1 - Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes: low temperature NMR study and quantum chemical calculations Y1 - 2012 UR - http://www.sciencedirect.com/science/article/pii/S0040402011018321 U6 - https://doi.org/10.1016/j.tet.2011.11.077 ER - TY - JOUR A1 - Lazareva, Nataliya F. A1 - Albanov, Alexander I. A1 - Shainyan, Bagrat A. A1 - Kleinpeter, Erich T1 - Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes low temperature NMR study and quantum chemical calculations JF - Tetrahedron N2 - A number of N-substituted 2,2-dimethyl-1,4,2-oxazasilinanes 1 were synthesized and studied by variable temperature dynamic H-1 and C-13 NMR spectroscopy, room temperature N-15 NMR spectroscopy and theoretical calculations at the DFT and MP2 levels of theory. Both the preferred conformers were assigned and the barrier to the ring inversion of the saturated six-membered ring determined. From 1 the corresponding methyl iodide salts were produced, their structure studied by X-ray analysis and found to be in excellent agreement with the results of the theoretical calculations. KW - 1,4,2-Oxazasilinanes KW - Conformational analysis KW - Dynamic NMR KW - X-ray analysis KW - Quantum chemical calculations Y1 - 2012 U6 - https://doi.org/10.1016/j.tet.2011.11.077 SN - 0040-4020 VL - 68 IS - 4 SP - 1097 EP - 1104 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich T1 - Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane low temperature dynamic NMR and computational study JF - Arkivoc : free online journal of organic chemistry N2 - 1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the PhaxMeeq and PheqMeax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined. KW - 1,3-Dimethyl-3-phenyl-1,3-azasilinane KW - conformational analysis KW - low temperature NMR spectroscopy KW - quantum chemical calculations Y1 - 2012 SN - 1551-7004 IS - 24 SP - 175 EP - 185 PB - ARKAT CY - Gainesville ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Schainyan, Bagrat A. A1 - Kirpichenko, Svetlane V. T1 - Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane : low temperature dynamic NMR and computational study N2 - 1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the PhaxMeeq and PheqMeax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined. Y1 - 2012 SN - 1551-7004 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Hartmann, Jürgen A1 - Schroth, W. A1 - Hofer, O. A1 - Kalchhauser, H. A1 - Wurz, G. T1 - Synthesis and conformational behaviour of Ditosyldiaza[2.2]orthometacyclophanes Y1 - 1992 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 - Thiele, Gabriela A1 - Rottmann, Antje A1 - Germer, Antje A1 - Kleinpeter, Erich A1 - Spindler, Klaus-Dieter A1 - Synstad, Bjoenar A1 - Eijsink, Vincent G. H. A1 - Peter, Martin G. T1 - Synthesis and conformational analysis of pseudosugar analogues of chitotriose N2 - In this article, the synthesis of analogs of N,N',N''-triacetylchitotriose in which the central sugar residue was replaced by a succinic acid is presented. Mol. modeling calcns. revealed that the pseudotrisaccharides exist in low energy extended conformations which show similar space filling as N,N',N''-triacetylchitotriose. Of the N,N',N''-triacetylchitotriose pseudosugar analogs tested as chitinase inhibitors, none showed any appreciable competition (numerical data not presented). The conformational anal. along with further synthetic efforts will hopefully lead to more efficient pseudosaccharides as chitinase inhibitors. Y1 - 2002 ER - TY - JOUR A1 - Csütörtöki, Renáta A1 - Szatmári, István A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives Y1 - 2011 SN - 0040-4020 ER - TY - JOUR A1 - Csuetoertoeki, Renata A1 - Szatmari, Istvan A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Fueloep, Ferenc T1 - Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives JF - Tetrahedron N2 - A new highly functionalized aminonaphthol derivative, 1-(amino(2-aminophenyl)methyl)-2-naphthol (4), was synthesized by the reaction of 2-naphthol, 2-nitrobenzaldehyde and tert-butyl carbamate or benzyl carbamate, followed by reduction and/or removal of the protecting group. The aminonaphthol derivative thus obtained was converted in ring-closure reactions with formaldehyde. benzaldehyde and/or phosgene to the corresponding naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives. The conformational analysis of some derivatives by NMR spectroscopy and accompanying molecular modelling are also reported. KW - Naphthoxazinoquinazolines KW - NMR KW - Conformational analysis KW - DFT calculations KW - Hammett-Brown plots Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.08.074 SN - 0040-4020 VL - 67 IS - 44 SP - 8564 EP - 8571 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Thóth, Diána A1 - Szatmári, István A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Synthesis and conformational analysis of naphthylnaphthoxazine derivatives N2 - Four new primary aminonaphthols (4, 5, 9 and 10) were synthesized from 1- or 2-naphthol and 1- or 2- naphthaldehyde via naphthoxazines in modified Mannich condensations. Simple ring-closure reactions of these aminonaphthols with paraformaldehyde, 4-nitrobenzaldehyde, phosgene or 4-chlorophenyl isothiocyanate led to new heterocyclic derivatives. In these transformations, either an sp2 or an sp3 carbon was inserted between the hydroxy and amino groups. The effects of substituents and the naphthyl ring on the conformation were investigated by means of NMR measurements, employing both dipolar and scalar couplings. The structures were confirmed by DFT quantum chemical calculations involving computed coupling constants, intramolecular distances between nuclei and the relative energies of the preferred conformers. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2009.04.015 SN - 0166-1280 ER - TY - JOUR A1 - Belasri, Khadija A1 - Topal, Leila A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Fulop, Ferenc A1 - Szatmari, Istvan T1 - Synthesis and conformational analysis of naphthoxazine-fused phenanthrene derivatives JF - Molecules N2 - The synthesis of new phenanthr[9,10-e][1,3]oxazines was achieved by the direct coupling of 9-phenanthrol with cyclic imines in the modified aza-Friedel-Crafts reaction followed by the ring closure of the resulting bifunctional aminophenanthrols with formaldehyde. Aminophenanthrol-type Mannich bases were synthesised and transformed to phenanthr[9,10-e][1,3]oxazines via [4 + 2] cycloaddition. Detailed NMR structural analyses of the new polyheterocycles as well as conformational studies including Density Functional Theory (DFT) modelling were performed. The relative stability of ortho-quinone methides (o-QMs) was calculated, the geometries obtained were compared with the experimentally determined NMR structures, and thereby, the regioselectivity of the reactions has been assigned. KW - modified Mannich reaction KW - cyclic imines KW - [4+2] cycloaddition KW - NMR KW - spectroscopy KW - conformational analysis KW - DFT calculations Y1 - 2020 U6 - https://doi.org/10.3390/molecules25112524 SN - 1420-3049 VL - 25 IS - 11 PB - MDPI CY - Basel ER - TY - JOUR A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Szatmári, István A1 - Fulop, Ferenc A1 - Kleinpeter, Erich T1 - Synthesis and conformational analysis of naphth[1,2-e][1,3]oxazino[4,3-a][1,3]isoquinoline and naphth[2,1- e][1,3]oxazino[4,3-a]isoquinoline derivatives N2 - Through the cyclization of 1-(;-hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinoline and 1-(;- hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinoline with formaldehyde, phosgene, p-nitrobenzaldehyde or p-chlorophenyl isothiocyanate, 8-substituted 10,11-dihydro-8H,15bH-naphth[1,2-e][1,3]oxazino[4,3-a]isoquinolines (3 and 4) and 10,11- dihydro-8H,15bH-naphth[2,1-e][1,3]oxazino[4,3-a]isoquinolines (15 and 16) were prepared. Conformational analysis of both the piperidine and the 1,3-oxazine moieties of these heterocycles by NMR spectroscopy and an accompanying theoretical study revealed that these two conformationally flexible six-membered ring moieties prefer twisted chair conformers. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040402008009150 U6 - https://doi.org/10.1016/j.tet.2008.05.025 ER - TY - JOUR A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Klod, Sabrina A1 - Szatmari, Istvan A1 - Fulop, Ferenc A1 - Kleinpeter, Erich T1 - Synthesis and conformational analysis of naphth[1', 2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine and naphth[1', 2':5,6][1,3]oxazino[3,4-c][1,3]benzoxazine derivatives JF - Tetrahedron N2 - A new functional group, the hydroxy group, was inserted into a Betti base by reaction with salicylaldehyde, and the naphthoxazine derivatives thus obtained were converted by ring-closure reactions with formaldehyde, acetaldehyde, propionaldehyde or phosgene to the corresponding naphth[1',2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine derivatives. Further, the conformational analysis of these polycyclic compounds by NMR spectroscopy and an accompanying molecular modelling are reported; especially, both quantitative anisotropic ring current effects of the aromatic moieties in these compounds and steric substituent effects were employed to determine the stereochemistry of the naphthoxazinobenzoxazine derivatives. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2006.09.037 SN - 0040-4020 VL - 62 IS - 48 SP - 11081 EP - 11089 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Fettke, Anja A1 - Peikow, Dirk A1 - Peter, Martin G. A1 - Kleinpeter, Erich T1 - Synthesis and conformational analysis of glycomimetic analogs of thiochitobiose N2 - The synthesis of six analogs of N,N;-diacetylchitobiose is reported, including a novel transglycosylation reaction for the preparation of S-aryl thioglycosides. The conformations of the compounds were studied by a combination of NMR spectroscopy and molecular modeling, using force field calculations. In the case of the S-aryl thioglycosides with exclusively S-glycosidic linkages, dihedral angles of the disaccharidic S-glycosidic bonds, ;; and ;; and of the S-arylglycoside bonds, ; and ;, were found to be similar, whereas they were different in mixed glycosides and in a thiazoline derivative. An adequate correlation between the calculated H,H-distances of the local minima and the measured NOE contacts was achieved by applying population-weighted averages over participating conformers based on weighted relative energies. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2009.03.067 SN - 0040-4020 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Chipanina, Nina N. A1 - Oznobikhina, Larisa P. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu. T1 - Synthesis and Conformational Analysis of 3-Methyl-3-silatetrahydropyran by GED, FTIR, NMR, and Theoretical Calculations: Comparative Analysis of 1-Hetero-3-methyl-3-silacyclohexanes JF - The journal of organic chemistry N2 - 3-Methyl-3-silatetrahydropyran 1 was synthesized and its molecular structure and conformational behavior was studied by gas-phase electron diffraction (GED), FTIR, low temperature H-1 and C-13 NMR spectroscopy, and by theoretical calculations (DFT, MP2). Two conformers; 1-ax and 1-eq; were located on the potential energy Surface. In the gas phase; a slight predominance of the axial conformer was determined, with the ratio 1-ax:1-eq = 54(9):46(9) (from GED) or 53:47 or 61;39 (from IR). In solution, LT NMR spectroscopy at 103 K gives the ratio 1-ax:1-eq = 35:65 (-Delta G(103)degrees = 0.13 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the corresponding solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of 3-methyl-3-silatettahydropyran in the gas phase and in solution. Comparative analysis of the effect of heteroatom in 1-hetero-3-methyl-3-silacyclohexanes on the structure, stereoelectronic interactions, and relative energies of the conformers is done. Y1 - 2015 U6 - https://doi.org/10.1021/acs.joc.5b02355 SN - 0022-3263 VL - 80 IS - 24 SP - 12492 EP - 12500 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich T1 - Synthesis and conformational analysis of 1,3-azasilinanes JF - Tetrahedron N2 - 1-Isopropyl-3-methyl-3-phenyl-1,3-azasilinane 1 and 1-isopropyl-3,3-dimethyl-1,3-azasilinane 2 were synthesized and a detailed analysis of their NMR spectra, conformational equilibria and ring inversion processes is presented. Low temperature H-1/C-13 NMR spectroscopy, iteration of the H-1 NMR spectra and quantum chemical calculations showed slight predominance of the PheqMeax over the PhaxMeeq conformer of 1 at low temperature. The barrier for the chair to chair interconversion of both compounds was measured to be 8.25 kcal/mol. KW - 1,3-Azasilinanes KW - Conformational analysis KW - Dynamic NMR spectroscopy KW - Quantum chemical calculations KW - Ring current effect Y1 - 2012 U6 - https://doi.org/10.1016/j.tet.2012.05.106 SN - 0040-4020 VL - 68 IS - 36 SP - 7494 EP - 7501 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Csütörtöki, Renáta A1 - Szatmári, István A1 - Koch, Andreas A1 - Fulop, Ferenc T1 - Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-ones N2 - The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A1, but also the rearranged chain form A2 as a new tautomer were detected in DMSO at room temperature. The quantity of A2 in the tautomeric mixture was changed with time. Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS. Y1 - 2012 ER - TY - JOUR A1 - Csütörtöki, Renata A1 - Szatmari, Istvan A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c] quinazolin-13-ones JF - Tetrahedron N2 - The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A(1), but also the rearranged chain form A(2) as a new tautomer were detected in DMSO at room temperature. The quantity of A(2) in the tautomeric mixture was changed with time. Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS. KW - Naphthoxazinoquinazolinones KW - Aminonaphthols KW - NMR spectroscopy KW - Conformational analysis KW - Theoretical calculations KW - Ring current effect Y1 - 2012 U6 - https://doi.org/10.1016/j.tet.2012.04.026 SN - 0040-4020 VL - 68 IS - 24 SP - 4600 EP - 4608 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Syntheses and conformational analyses of mono- and trans-1,4-dialkoxy substituted cyclohexanes : the steric substituent/skeleton interactions N2 - Mono- and trans-1,4-dialkoxy substituted cyclohexanes (alkyl=Me, Et, i-Pr, t-Bu) were prepared using the solvomercuration-demercuration (SM-DM) procedure. The axialaxial and axial,axialequatorial, equatorial conformational equilibria of the products were studied by low temperature 1H and 13C NMR spectroscopy in CD2Cl2. The structures and relative energies of the participating conformers were calculated at both the B3LYP (6-311G*//6-311+G*) and MP2 (6-311+G*//6-311G*) levels of theory. In the case of DFT, good correlations of ;Gocalcd versus ;Goexptl were obtained. Both the structures and the energy differences of the conformers have been discussed with respect to established models of conformational analysis, viz. steric and hyperconjugative interactions. In addition, 1JH,C coupling constants were considered with respect to the hyperconjugation present. Y1 - 2007 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2007.06.094 SN - 0040-4020 ER - TY - JOUR A1 - Arrieta, A. A1 - Beyer, L. A1 - Lehmann, J. A1 - Dargatz, M. A1 - Kleinpeter, Erich T1 - Synthese und 1H-NMR-spektroskopische Untersuchungen neuer Curcuminanaloga Y1 - 1992 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Boelke, Ute A1 - Koch, Andreas T1 - Subtle Trade-off Existing between (Anti)Aromaticity, Push-Pull Interaction, Keto-Enol Tautomerism, and Steric Hindrance When Defining the Electronic Properties of Conjugated Structures Y1 - 2010 SN - 1089-5639 ER - TY - JOUR A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Study of the tautomerism by experimentally and theoretically estimated 13C and 15N chemical shifts Y1 - 1997 ER - TY - JOUR A1 - Szatmari, Istvan A1 - Toth, Diana A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich A1 - Fulop, Ferenc T1 - Study of the substituent-influenced anomeric effect in the ring-chain tautomerism of 1-alkyl-3-aryl-naphth[1,2- e][1,3]oxazines N2 - The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values. Y1 - 2006 UR - http://onlinelibrary.wiley.com/doi/10.1002/ejoc.200600563/pdf U6 - https://doi.org/10.1002/ejoc.200600563 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Heydenreich, Matthias A1 - Chatterjee, S. K. A1 - Rudorf, Wolf-Dieter T1 - Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy, IV : the conformation and dynamic behaviour of substituted N-Phenyl-2,3-dihydro-4(1H)-pyridones Y1 - 1995 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Chatterjee, S. K. A1 - Rudorf, Wolf-Dieter T1 - Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy, III : the conformation of 3,4-Dihydro-4-oxo-2H-thiins Y1 - 1994 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Chatterjee, S. K. A1 - Rudorf, Wolf-Dieter T1 - Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy Y1 - 1994 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Thomas, Steffen A1 - Uhlig, G. A1 - Rudorf, Wolf-Dieter T1 - Study of the distribution of pi-Electrons in Push-Pull Alkenes by 1H an 13C NMR spectroscopy Y1 - 1993 ER - TY - JOUR A1 - Rasovic, Aleksandar A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Markovic, Rade T1 - Studies of the regioselective ring-opening closing mode of functionally different thiazolidine type enaminones - en route to the synthesis of trithiaazapentalene derivatives JF - Tetrahedron N2 - Trithiaazapentalene derivatives were prepared by the reaction of 2-alkylidene-4-oxothiazolidines with Lawesson's reagent. They are classified as two structurally different trithiaazapentalene compounds that have different contributions of monocyclic 1,2-dithiole and 1,2,4-dithiazole structures and degrees of aromaticity of the bicyclic trithiaazapentalene system. The electron-donating ability of substituents at the C(5) position of the trithiaazapentalene system is recognized as the main cause for changes in pi-Celectron distribution. This is the first complete study of substituent effects on the structure of trithiapentalenes. (C) 2013 Elsevier Ltd. All rights reserved. KW - Trithiapentalene KW - 1,2-Dithiole KW - 1,2,4-Dithiazole KW - 4-Oxothiazolidine KW - Rearrangement to trithiaazapentalene KW - Push-pull character Y1 - 2013 U6 - https://doi.org/10.1016/j.tet.2013.10.088 SN - 0040-4020 VL - 69 IS - 51 SP - 10849 EP - 10857 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Holzberger, Anja T1 - Structure, intramolecular flexibility, and complexation of aza crown ethers to anions H2PO4- and HSO4- in nonprotic solvents JF - Tetrahedron N2 - Both the structure and intramolecular flexibility of a series of aza crown ethers were studied by experimental NMR and theoretical molecular modeling. The stoichiometries of complexation to the anions H2PO4- and resulting complex stabilities were determined by experimental NMR (1H, 31P) titration and, in addition, the structure and mobility changes of the aza crown ethers upon complexation were also examined. Y1 - 2006 UR - https://www.sciencedirect.com/science/article/abs/pii/S0040402006012130 U6 - https://doi.org/10.1016/j.tet.2006.07.074 SN - 0040-4020 VL - 62 IS - 43 SP - 10237 EP - 10247 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Klaumuenzer, Ute A1 - Markovic, Rade A1 - Kleinpeter, Erich T1 - Structure, configuration, conformation and quantification of the push pull-effect of 2-alkylidene-4- thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives N2 - Structures of a series of push-pull 2-alkylidene-4-thiazolidinones and 2-alkylidene-4,5-fused bicyclic thiazolidine derivatives were optimized at the B3LYP/6-31G(d) level of theory in the gas phase and discussed with respect to configurational and conformational stability. Employing the GIAO method, C-13 NMR chemical shifts of the C-2, C-2', C-4 and C-5 atoms were calculated at the same level of theory in the gas phase and with inclusion of solvent, and compared with experimental data. Push-pull effect of all compounds was quantified by means of the quotient pi*/pi, length of the partial double bond, C-13 NMR chemical shift difference (Delta delta(C=C)) and H-1 NMR chemical shifts of olefinic protons. The effect of bromine on donating and accepting ability of other substituents of the push- pull C=C double bond is discussed, too. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2010.09.040 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Shlykov, Sergei A. T1 - Structure and Conformational Properties of 1,3,3-Trimethyl-1,3-Azasilinane : Gas Electron Diffraction, Dynamic NMR, and Theoretical Study. Y1 - 2012 SN - 1089-5639 ER - TY - JOUR A1 - Klinka, Karel D. A1 - Balentova, Eva A1 - Bernát, Juraj A1 - Imrich, Ján A1 - Vavrusová, Martina A1 - Pihlaja, Kalevi A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - Structural revision of products resulting from the reaction of methylhydrazine with acridin-9-yl isothiocyanate due to unexpected acridinyl migration And further reactions N2 - The reaction of methyl acridin-9-ylthiosemicarbazide under basic conditions with methyl bromoacetate resulted in a 1,3-thiazolin-4-one structure as provided by X-ray crystallography. The structure forced a re-evaluation of the reactant methyl acridin-9-ylthiosemicarbazide, originally thought to be 2-methyl 4-acridin-9-ylthiosemicarbazide based on synthetic expectations, but which when examined by X-ray crystallography was found to be in fact the isomeric 2- methyl 1-acridin-9-ylthiosemicarbazide resulting from rearrangement via a spiro form which it is in equilibrium with in solution. The product resulting from reaction with methyl iodide was also studied and the previously reported semicarbazide produced by reaction with MNO was re-examined. In both cases, the 1,2 isomer rather than the 2,4 isomer was found to be present based on the sign of the 3JCH3,N11 coupling. Full characterization of the compounds was rendered by 1H, 13C, and 15N solution-state NMR, and in the solid state, by both 13C and 15N NMR. Y1 - 2006 UR - http://arkat-usa.org/home.aspx?VIEW=BROWSE&MENU=ARKIVOC SN - 1551-7004 ER - TY - JOUR A1 - Wacker, Philipp A1 - Kleinpeter, Erich T1 - Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions N2 - Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus csol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation. Y1 - 2007 UR - http://www.springerlink.com/content/a584066q18q02857/ U6 - https://doi.org/10.1007/s10847-007-9332-1 ER - TY - JOUR A1 - Szatmari, Istvan A1 - Martinek, T. A. A1 - Lazar, L. A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Neuvonen, Kari A1 - Fulop, Ferenc T1 - Stereoelectronic effects in ring-chain tautomerism of 1,3-diarylnaphth[1,2-e][1,3]oxazines and 3-alkyl-1- arylnaphth[1,2-e][1,3]oxazines N2 - The disubstitution effects of X and Y in 1-(Y-phenyl)-3-(X-phenyl)-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines on the ring-chain tautomerism, the delocalization of the nitrogen lone pair (anomeric effect), and the C-13 NMR chemical shifts were analyzed by using multiple linear regression analysis. Study of the three-component equilibrium B reversible arrow A reversible arrow C revealed that the chain reversible arrow trans (A reversible arrow B) equilibrium constants are significantly influenced by the inductive effect (sigma(F)) of substituent Y on the 1-phenyl ring. In contrast, no significant substituent dependence on Y was observed for the chain reversible arrow cis (A reversible arrow C) equilibrium. There was an analogous dependence for the epimerization (C reversible arrow B) constants of 1-(Y-phenyl)-3- alkyl-2,3-dihydro-1H-naphth[1,2-e] [1,3]oxazines. With these model compounds, significant overlapping energies of the nitrogen lone pair was observed by NBO analysis in the trans forms B (to sigma*(C1-C1'), sigma*(C1-C10b), and sigma*(C3-O4)) and in the cis forms C (to sigma*(C1-H), sigma*(C1-C10b), and sigma*(C3-O4)). The effects of disubstitution revealed some characteristic differences between the cis and trans isomers. However, the results do not suggest that the anomeric effect predominates in the preponderance of the trans over the cis isomer. When the C-13 chemical shift changes induced Y by substituents X and Y (SCS) were subjected to multiple linear regression analysis, negative rho(F)(Y) and rho(F)(X) values were observed at C-1 and C-3 for both the cis and trans isomers. In contrast, the positive rho(R)(Y) values at C-1 and the negative rho(R)(X) values at C-3 observed indicated the contribution of resonance structures f (rho(R) > 0) and g (rho(R) < 0), respectively. The classical double bond-no-bond resonance structures proved useful in explaining the substituent sensitivities of the donation energies and the behavior of the SCS values Y1 - 2004 SN - 0022-3263 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Ushakov, Igor A. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Stereodynamics of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane: Experimental and theoretical analysis N2 - Dynamic NMR of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane reveals the existence of three conformers and two dynamic processes: ring inversion and rotation about the N-S bond, both processes having Delta G(double dagger) = 13.5 kcal/mol. An unprecedented large reverse Perlin effect (J(CHax) > J(CHeq)) was found experimentally and calculated theoretically. Y1 - 2006 UR - http://pubs.acs.org/doi/full/10.1021/jo061112x U6 - https://doi.org/10.1021/Jo061112x ER - TY - JOUR A1 - Markovic, Rade A1 - Baranac-Stojanovic, Marija A1 - Steel, Peter J. A1 - Kleinpeter, Erich T1 - Stereocontrolled synthesis of new tetrahydrofuro[2,3-d]thiazole derivatives via activated vinylogous iminium ions N2 - Heterocyclization of (Z)-5-(2-hydroxyethyl)-3-methyl-4-oxothiazolidines, bearing electron-withdrawing groups conjugated to an exocyclic double bond at C(2)-position, afforded under reductive conditions, cis-tetrahydroftiro[2,3- d]thiazole derivatives. The reactions of these functionalized push-pull beta-enamines occur in a stereocontrolled fashion via activated vinylogous N-methyliminium ions, which are trapped by an internal hydroxyethyl group Y1 - 2005 SN - 0385-5414 ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich T1 - Stereochemistry of 3-isopropoxy-3-methyl-1,3-oxasilinane-the first 3-silatetrahydropyran with an exo-cyclic RO-Si bond JF - Tetrahedron N2 - Molecular structure and conformational behavior of 3-isopropoxy-3-methyl-3-oxasilinane is studied by low temperature C-13 NMR spectroscopy and theoretical calculations (DFT, MP2). Two conformers, 1-ROax and 1-ROeq, were found experimentally and located on the potential energy surface. LT C-13 NMR spectroscopy gives almost equal population of the two conformers at 98 K with Delta G(98K)degrees=0.02 kcal/mol in favor of 1-ROax and Delta G(98K)(#)=4.5 kcal/mol. The corresponding DFT calculated values (Delta G(98K)degrees=0.03 kcal/mol, Delta G(98K)(#)=5.1 kcal/mol) are in excellent agreement with the experiment. Detailed DFT and MP2 calculations of the solvent effect on the conformational equilibrium were performed and highlighted the leveling out of the two conformers when transferred from gas to solution. (C) 2015 Published by Elsevier Ltd. KW - 1,3-Oxasilinanes KW - Conformational equilibrium KW - Barrier to ring inversion KW - Solvent effects KW - Assignment of stereochemistry Y1 - 2015 U6 - https://doi.org/10.1016/j.tet.2015.07.047 SN - 0040-4020 VL - 71 IS - 38 SP - 6720 EP - 6726 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Stohß, S. A1 - Schroth, W. T1 - Stereochemistry and complexational behaviour of dibenzo-crown ethers Y1 - 1992 ER - TY - JOUR A1 - Kramer, Markus A1 - Kleinpeter, Erich T1 - STD-DOSY : a new NMR method to analyze multi-component enzyme/substrate systems N2 - A new approach to analyze multi-component Saturation Transfer Difference (STD) NMR spectra by combining the STD and the DOSY experiment is proposed. The resulting pulse sequence was successfully used to simplify an exemplary multi- component protein/substrate system by means of standard DOSY processing methods. Furthermore, the same experiment could be applied to calculate the ratio of saturated substrate molecules and its saturation rate in the case of competitive interactions. This ratio depends on the strength of this interaction between the substrates and the protein, so that this kind of information could be extracted from the results of our experiment. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/10907807 U6 - https://doi.org/10.1016/j.jmr.2009.11.007 SN - 1090-7807 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Stable Carbenes or Betaines? JF - European journal of organic chemistry N2 - The anisotropy effect in H-1 NMR spectroscopy can be readily employed to indicate the position of carbene/betaine mesomeric equilibria. NR2 substituted carbene/betaines tend to adopt betaine structures, whereas in the absence of NR2 substituents, the betaine structures cannot stabilise the structure through both -donation effects of the NMe2 groups and the electronegativity of the nitrogen atoms, and the corresponding carbene-like structures are preferred. These conclusions are supported by calculated bond orders and (C-13)/ppm values. The spatial magnetic properties of isonitriles and carbon monoxide, which can be counted as stable carbenes or, at least, as carbene-analogues, also exist as stable betaine structures, which is again supported by structural and magnetic properties. KW - Carbenes KW - Betaines KW - Mesomerism KW - Through-space NMR shieldings (TSNMRS) KW - NMR spectroscopy KW - Conformation analysis Y1 - 2018 U6 - https://doi.org/10.1002/ejoc.201800462 SN - 1434-193X SN - 1099-0690 VL - 2018 IS - 24 SP - 3114 EP - 3121 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Starke, Ines A1 - Kammer, Stefan A1 - Holdt, Hans-Jürgen A1 - Kleinpeter, Erich T1 - Stability of disubstituted copper complexes in the gas phase analyzed by electrospray ionization mass spectrometry N2 - A series of nitrogen ligand (L)/copper complexes of the type [(CuL)-L-I](+), [(CuL)-L-II(X)](+) and [(CuL2)-L- I](+) (X = Cl-, BF4-, acac(-), CH3COO- and SO3CF3-) was studied in the gas phase by electrospray ionization mass spectrometry. The following ligands (L) were employed: 1,12-diazaperylene (dap), 1,1'-bisiso-quinoline (bis), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,11-disubstituted 1,12-diazaperylenes (dap), 3,3'- disubstituted 1,1'-bisisoquinoline (bis), 5,8-dimethoxy-substituted diazaperylene (meodap), 6,6'-dimethoxy- substituted bisisoquinoline (meobis) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Collision-induced decomposition measurements were applied to evaluate the relative stabilities of the different copper complexes. The influence of the spatial arrangement of the ligands, of the type of substituents and of the counter ion of the copper salts employed for the complexation was examined. Correlations were found between the binding constants of the [ML2](+) complexes in solution and the relative stabilities of the analogous complexes in the gas phase. Furthermore, complexation with the ligands 2,11-dialkylated 1,12-diazaperylenes [alkyl = ethyl (dedap) and isopropyl (dipdap)] was studied in the solvents CH3OH and CH3CN. Y1 - 2010 UR - http://www3.interscience.wiley.com/cgi-bin/jhome/4849 U6 - https://doi.org/10.1002/Rcm.4519 SN - 0951-4198 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Spatial magnetic properties subject to lone pair and pi electron delocalization in benzenoid and quinoid structures are quinoid tautomers really nonaromatic? JF - Arkivoc : free online journal of organic chemistry N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzenoid and quinoid tautomeric structures such as benzodifurantrione and phenazine-type molecules have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Rague Schleyer and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to quantify and visualize the partial aromaticity of the studied compounds. In the case of the surprisingly more stable quinoid tautomers, the aromaticity-synonymous with stability due to the conjugation of p electrons and lone pairs-was not found to be particularly reduced. KW - Through-space NMR shieldings (TSNMRS) KW - GIAO KW - NICS KW - benzenoid structures KW - quinoid structures KW - aromaticity Y1 - 2012 SN - 1551-7004 SP - 94 EP - 108 PB - ARKAT CY - Gainesville ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Spatial magnetic properties subject to lone pair and pi electron delocalization in benzenoid and quinoid structures : are quinoid tautomers really nonaromatic? N2 - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzenoid and quinoid tautomeric structures such as benzodifurantrione and phenazine-type molecules have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Rague Schleyer and visualized as iso- chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to quantify and visualize the partial aromaticity of the studied compounds. In the case of the surprisingly more stable quinoid tautomers, the aromaticity-synonymous with stability due to the conjugation of p electrons and lone pairs-was not found to be particularly reduced. Y1 - 2012 SN - 1551-7004 ER - TY - JOUR A1 - Germer, Antje A1 - Peter, Martin G. A1 - Kleinpeter, Erich T1 - Solution-state conformational study of the hevamine inhibitor allosamidin and six potential inhibitor analogues by NMR spectroscopy and molecular modeling N2 - The soln.-state conformations of the hevamine inhibitor allosamidin and six potential inhibitor analogs were studied by various NMR spectroscopic techniques and mol. modeling using force field calcns. Detn. solely of the global energy min. conformation was found to be insufficient for consensus with the NMR results, and agreement between the NMR exptl. data and the theor. calcns. was only reached by assessing the structures as population-weighted av. conformers on the basis of Boltzmann distributions derived from the calcd. relative energies. The conformations of the glycosidic linkages in the compds. were found to be similar when the sugar residues were the same, but differences were markedly evident otherwise and also for the various heterocyclic group linkages. The binding of the compds. to hevamine, which may also complex to chitinases in general, was assessed using HMQC, transfer-NOESY, and both 1-D and 2-D satn. transfer difference NMR expts. Under the conditions employed, only allosamidin was implicated to be bound to hevamine, and then only by HMQC with the dipolar coupling-based expts. failing to substantiate the formation of the complex. However, the results are consistent with the biochem. activities of the compds. whereby only allosamidin has been shown to act as a competitive inhibitor. Y1 - 2002 ER - TY - JOUR A1 - Germer, Antje A1 - Mugge, Clemens A1 - Peter, Martin G. A1 - Rottmann, Antje A1 - Kleinpeter, Erich T1 - Solution- and bound-state conformational study of N,N',N''-triacetyl chitotriose and other analogous potential inhibitors of hevamine: Application of trNOESY and STD NMR spectroscopy N2 - The soln.-state conformations of N,N',N''-triacetyl chitotriose (1) and other potential chitinase inhibitors 2-4 were studied using a combination of NMR spectroscopy (NOESY) and mol. mechanics calcns. Detn. solely of the global energy min. conformation was found to be insufficient for an agreement with the NMR results. An appropriate consistency between the NMR exptl. data and theor. calcns. was only reached by assessing the structures as population-weighted av. conformers based on Boltzmann distributions derived from the calcd. relative energies. Analogies, but also particular differences, between the synthetic compds. 2-4 and the naturally-occurring N,N',N''-triacetyl chitotriose were found. Furthermore, the conformation of compds. 1 and 2 when bound to hevamine was also studied using transferred NOESY expts. and the binding process was found to impart a level of conformational restriction on the ligands. The preferred conformation as detd. for 1 in the bound state to hevamine belonged to one of the conformational families found for the compd. when free in soln., although full characterization of the bound-state conformations was impeded due to severe signal overlap. Satn. transfer difference NMR expts. were also employed to analyze the binding epitopes of the bound compds. We thus detd. that it is mainly the acetyl amido groups of the trisaccharide and the heterocyclic moiety which are in close contact with hevamine. Y1 - 2003 ER - TY - JOUR A1 - Holzberger, Anja A1 - Kleinpeter, Erich T1 - Solution structure of the palladium(II) complex of 1,4,7,10-tetrathiacyclododec-2-ene-2,3-dicarbonitrile N2 - The solution structure of the Pd(II) complex of mn-12-S-4 was studied in detail by NMR spectroscopy. The stoichiometry of the complex was determined by H-1 NMR titration experiments. (3)J(H,H) coupling constants were extracted from the 2D J-resolved NMR spectrum of the complex providing information concerning the S-C-C-S torsional angles. Further conclusions about the conformation of [Pd(mn-12-S-4)](BF4)(2) were drawn from experimental NOES. The results of the NMR study were corroborated by molecular modelling. Copyright (C) 2004 John Wiley Sons, Ltd Y1 - 2004 SN - 0749-1581 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Ströhl, D. A1 - Peinze, S. T1 - Solution conformation of tripeptides by NMR spectroscopy and force field calculations Y1 - 1995 ER -