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 - 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 - 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 - Balci, Kubilay A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A theoretical IR spectroscopic study based on DFT calculations for free mn-15S(2)O(3) maleonitrile-dithiacrown ether compound N2 - The theoretically possible stable conformers of free mn-15S2O3 maleonitrile-dithiacrown ether molecule were searched by means of a conformational study which consists of molecular dynamics and energy minimization calculations performed with MM2 force field and successive geometry optimization + frequency calculations performed first at B3LYP/3- 21G and then at B3LYP/6-31G(d) levels of theory. The obtained calculation results have clearly indicated that the free molecule in electronic ground state is very flexible and accordingly has many possible stable conformers of different conformational properties at room temperature; among them, the one having a macrocyclic ring structure in which all of the ether units oriented toward the center of the ring was determined the energetically most preferable conformer. In addition, the equilibrium geometrical parameters, vibrational normal modes and associated IR spectral data of the determined most stable three conformers of the molecule were calculated at B3LYP/6-31+G(d) and B3LYP/6-31++G(d,p) levels of theory. A successful assignment of the fundamental bands observed in the recorded experimental solid phase and solution phase IR spectra of the molecule was achieved in the light of the theoretical data obtained from these DFT calculations. To fit the calculated harmonic wavenumbers to the experimental ones, two different scaling procedures, referred to as "Scaled Quantum Mechanical Force Field (SQM FF) methodology" and "Scaling wavenumbers with empirical dual scale factors", were proceeded independently. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2008.08.027 SN - 0022-2860 ER - TY - JOUR A1 - Balci, Kubilay A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A comparative vibrational spectroscopic investigation of free mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers based on DFT calculations N2 - A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2005.10.048 SN - 0022-2860 ER - TY - JOUR A1 - Balci, Kubilay A1 - Yapar, G. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A conformational analysis and vibrational spectroscopic investigation on 1,2-bis(o-carboxyphenoxy) ethane molecule JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy)ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople-style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major contribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibrations to conformation, substitution and dimerization were discussed. KW - Glycol podands KW - Salicylic acid KW - IR and Raman spectra KW - SQM FF KW - Dual Scale Factors Y1 - 2012 U6 - https://doi.org/10.1016/j.vibspec.2011.11.011 SN - 0924-2031 VL - 58 IS - 1-2 SP - 27 EP - 43 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 - Baranac-Stojanovic, Marija A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from s and p bonds by the natural chemical shieldingnatural bond orbital (NCSNBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity. KW - anisotropic effects KW - aromaticity KW - B,N heterocycles KW - density functional calculations KW - NMR spectroscopy Y1 - 2012 U6 - https://doi.org/10.1002/cphc.201200732 SN - 1439-4235 VL - 13 IS - 17 SP - 3803 EP - 3811 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Is the conventional interpretation of the anisotropic effects of C=C double bonds and aromatic rings in NMR spectra in terms of the p-electron shielding/deshielding contributions correct? JF - Chemistry - a European journal N2 - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring. KW - ab initio calculations KW - anisotropic effects KW - NMR spectroscopy KW - nucleus-independent chemical shift KW - pi interactions Y1 - 2012 U6 - https://doi.org/10.1002/chem.201101882 SN - 0947-6539 VL - 18 IS - 1 SP - 370 EP - 376 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Baranac-Stojanovic, Marija A1 - Tatar, Jovanan A1 - Kleinpeter, Erich A1 - Markovic, Rade T1 - High-Yield Synthesis of Substituted and Unsubstituted Pyridinium Salts Containing a 4-Oxothiazolidine Moiety N2 - A new series of unsubstituted and substituted pyridinium salts bearing a 4-oxothiazolidinyl moiety has been prepared by an efficient rearrangement of 2-(1-bromoalkylidene)thiazolidin-4-ones. The process in based on three steps, namely carbon-bromine cleavage, bromine transfer, and substitution, each induced by pyridine or its derivatives, acting as base and reactant. Y1 - 2008 ER - TY - JOUR A1 - 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 - Bauer, Monika A1 - Hartmann, Lutz A1 - Kleinpeter, Erich A1 - Kuschel, Frank A1 - Pithart, Cornelia A1 - Weissflog, Wolfgang T1 - Chiral Dopants Derived from Ephedrine/Pseudoephedrine: Structure and Medium Effects on the Helical Twisting Power JF - Molecular crystals and liquid crystals N2 - Chiral dopants were obtained by acylation of enantiomerically pure ephedrine and pseudoephedrine with promesogenic carbonyl reagents. The products have been investigated with respect to their chiral transfer ability on nematic host matrices characterized by extreme differences of the dielectric anisotropy. It has been found that the medium dependence of the helicity induction nearly disappears at reduced temperatures. Based on variable temperature H-1 NMR studies on monoacylated homologues, the estimated coalescence temperatures and free activation enthalpies for the hindered rotation around C-N bonds could be correlated with the helical twisting power. Measurements by dielectric spectroscopy reveal the correlation between the molar mass of substituents linked to the chiral building block and the dynamic glass transition of corresponding chiral dopants. Furthermore, the effect of intramolecular and intermolecular hydrogen bonds has been studied by ATR-FTIR spectroscopy. KW - ephedrine/pseudoephedrine KW - Chiral dopants KW - ATR-FTIR KW - molecular structure KW - dielectric spectroscopy KW - H-1 NMR Y1 - 2015 U6 - https://doi.org/10.1080/15421406.2014.949592 SN - 1542-1406 SN - 1563-5287 VL - 608 IS - 1 SP - 14 EP - 24 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Beitz, Toralf A1 - Koetz, Joachim A1 - Wolf, Gunter A1 - Kleinpeter, Erich A1 - Friberg, Stig E. T1 - Poly(N-vinyl-2-pyrrolidone) and 1-octyl-2-pyrrolidinone modified ionic microemulsions Y1 - 2001 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 - Benassi, Rois A1 - Bertarini, C. A1 - Hilfert, Liane A1 - Kempter, Gerhard A1 - Kleinpeter, Erich A1 - Spindler, Jürgen A1 - Taddei, F. A1 - Thomas, Steffen T1 - Exocyclic push-pull conjugated compounds : Part 3 Y1 - 2000 ER - TY - JOUR A1 - Benassi, Rois A1 - Bertarini, C. A1 - Kleinpeter, Erich A1 - Taddei, F. T1 - Exocyclic push-pull conjugated compounds, Part 2 : the effect of donor and acceptor substituents on the rotational barrier of push-pull ethylenes Y1 - 2000 ER - TY - JOUR A1 - Benassi, Rois A1 - Bertarini, C. A1 - Kleinpeter, Erich A1 - Taddei, F. A1 - Thomas, Steffen T1 - Exocyclic push-pull conjugated compounds : Part 1 ; theoretical study of the effect of ring size on the structure, electronic properties and rotational barriers of cyclic analogoues of 1,1-diamino-2.2-dicyanoethylene Y1 - 2000 ER - TY - JOUR A1 - Benassi, Rois A1 - Bregulla, Antje A1 - Friedrich, Alwin A1 - Henning, Dietrich A1 - Heydenreich, Matthias A1 - Mickler, Wulfhard A1 - Kleinpeter, Erich A1 - Kempter, Gerhard A1 - Schilde, Uwe A1 - Taddei, F. T1 - NMR spectroscopic and theoretical structural study of 5-exo-methylene-substituted hydantoins Y1 - 1998 ER - TY - JOUR A1 - Benassi, Rois A1 - Bregulla, Antje A1 - Henning, Dietrich A1 - Heydenreich, Matthias A1 - Kempter, Gerhard A1 - Kleinpeter, Erich A1 - Taddei, F. T1 - NMR-spectroscopic and theoretical structural analysis of 5-benzyl subtituted hydantoins in solutions Y1 - 1999 ER - TY - JOUR A1 - Boehm, Stanislav A1 - Tomašciková, Jana A1 - Imrich, Ján A1 - Danihel, Ivan A1 - Kristian, Pavol A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Klika, Karel D. T1 - Computational study to assign structure, tautomerism, E/Z and s-cis/s-trans isomerism, pi-delocalization, partial aromaticity, and the ring size of 1,3-thiazolidin-4-ones and 1,3-thiazin-4-ones formed from thiosemicarbazides N2 - A set of structures encompassing 1-(9-acridinyl)thiosemicarbazide and its 2-methyl derivative together with their various tautomeric structures; the 5-membered ring 1,3-thiazolidin-4-one products resulting from the reaction of 1- (9-acridinyl)thiosemicarbazide and its 2-methyl derivative with dimethyl acetylenedicarboxylate (DMAD) together with the alternative 6-membered ring isomeric reaction products as well as other potential isomeric structures; and the 6- membered ring 1,3-thiazin-4-one product resulting from the reaction of 2-methyl-1-(9-acridinyl)thiosemicarbazide with methyl propiolate (MP) together with the alternative 5-membered ring isomeric reaction product were all extensively studied by molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory. The ring-chain tautomerism of the thiosemicarbazides, the regio- and stereoselectivity of the reactions, the adopted conformations and E/Z configurations of the products, the prototropic tautomerism of all the compounds, and the reasons for the predominance of the s-cis conformation of the Z configuration of the 1,3-thiazolidin-4-one product in particular were all extensively analyzed. Comparison of the modeled structures were also made to the 1,3-thiazolidin-4-one and 1,3-thiazin-4-one structures of the methyl derivative as well as 1-(9-acridinyl)thiosemicarbazide available from X-ray crystallographic analysis. Tactics utilizing spectroscopic methods {1R frequencies (nu) and NMR chemical shifts (delta), scalar coupling constants (J), and NOEs (eta)} in conjunction with molecular modeling calculations of the spectral parameters (frequency calculations (v) and NMR 6 using the GIAO method and J by calculation of the Fermi contact term) were evaluated in terms of proving 5- or 6-membered ring formation. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/01661280 U6 - https://doi.org/10.1016/j.theochem.2009.09.019 SN - 0166-1280 ER - TY - JOUR A1 - Böhm, Stanislav A1 - Tomaszciková, Jana A1 - Imrich, Ján A1 - Danihel, Ivan A1 - Kristian, Pavol A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Klika, Karel D. T1 - Computational study to assign structure, tautomerism, E/Z and s-cis/s-trans isomerism, pi-delocalization, partial aromaticity, and the ring size of 1,3-thiazolidin-4-ones and 1,3-thiazin-4-ones formed from thiosemicarbazides N2 - A set of structures encompassing 1-(9-acridinyl)thiosemicarbazide and its 2-methyl derivative together with their various tautomeric structures; the 5-membered ring 1,3-thiazolidin-4-one products resulting from the reaction of 1- (9-acridinyl)thiosemicarbazide and its 2-methyl derivative with dimethyl acetylenedicarboxylate (DMAD) together with the alternative 6-membered ring isomeric reaction products as well as other potential isomeric structures; and the 6- membered ring 1,3-thiazin-4-one product resulting from the reaction of 2-methyl-1-(9-acridinyl)thiosemicarbazide with methyl propiolate (MP) together with the alternative 5-membered ring isomeric reaction product were all extensively studied by molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory. The ring-chain tautomerism of the thiosemicarbazides, the regio- and stereoselectivity of the reactions, the adopted conformations and E/Z configurations of the products, the prototropic tautomerism of all the compounds, and the reasons for the predominance of the s-cis conformation of the Z configuration of the 1,3-thiazolidin-4-one product in particular were all extensively analyzed. Comparison of the modeled structures were also made to the 1,3-thiazolidin-4-one and 1,3-thiazin-4-one structures of the methyl derivative as well as 1-(9-acridinyl)thiosemicarbazide available from X-ray crystallographic analysis. Tactics utilizing spectroscopic methods {IR frequencies (;) and NMR chemical shifts (;), scalar coupling constants (J), and NOEs (;)} in conjunction with molecular modeling calculations of the spectral parameters {frequency calculations (;) and NMR ; using the GIAO method and J by calculation of the Fermi contact term} were evaluated in terms of proving 5- or 6-membered ring formation. Y1 - 2009 SN - 0166-1280 ER - TY - JOUR A1 - Csuetoertoeki, Renata A1 - Szatmari, Istvan A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Starke, Ines A1 - Fueloep, Ferenc A1 - Kleinpeter, Erich T1 - Novel piperidine-fused benzoxazino- and quinazolinonaphthoxazines-synthesis and conformational study JF - TETRAHEDRON N2 - The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl) methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzox-azinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, G(tct)(1) for 4 and G(tct)(1) for 7, were corroborated by spatial NOE information relating to the H-7a-H-10a-H-15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements. (C) 2012 Elsevier Ltd. All rights reserved. KW - Quinazolines KW - Naphthoxazines KW - DFT structural study KW - Conformational analysis KW - NMR spectroscopy Y1 - 2012 U6 - https://doi.org/10.1016/j.tet.2012.05.048 SN - 0040-4020 VL - 68 IS - 31 SP - 6284 EP - 6288 PB - PERGAMON-ELSEVIER SCIENCE LTD CY - OXFORD 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 - 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 - 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 - Dargatz, M. A1 - Kellner, K. A1 - Kleinpeter, Erich A1 - Pallas, M. T1 - Quantitative Bestimmung geringer Phosphatmengen in Trinatriumphosphonoformiat mittels 31P-NMR-Spektroskopie Y1 - 1994 ER - TY - JOUR A1 - de Araujo, Martha T. A1 - Chacon, Eluzir P. A1 - Carneiro, José W. de M. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Analysis of anisotropic effects in trinuclear metal carbonyl compounds by visualization of through-space NMR shielding N2 - Through-space NMR shieldings were calculated for trinuclear metal-carbonyl compounds [M-3(CO)(12)] (M = Fe, Ru, Os), employing the nucleus-independent chemical shift approach. The through-space shieldings were visualized as a contour plot of iso-chemical shielding surfaces, and were applied to quantify the overall anisotropic effect of the carbonyl groups, as well as to identify the influence of the transition metal on the scopes of the corresponding anisotropy cones. The shielding surfaces show that the anisotropic effect of the carbonyl groups at equatorial positions changes depending on the metal. This effect was associated with pi-backdonation from the metal to the carbonyl groups in that position, in agreement with geometric data as well as calculated NMR parameters. Therefore, visualization of the through-space NMR shieldings of trinuclear metal-carbonyl compounds of group 8 is able to reflect the distinct arrangements of the carbonyl groups in these organometallic compounds. Y1 - 2010 UR - http://www.springerlink.com/content/100529 U6 - https://doi.org/10.1007/s00894-010-0662-3 SN - 1610-2940 ER - TY - JOUR A1 - Drexler, Hans-Joachim A1 - Grotjahn, Manuela A1 - Kleinpeter, Erich A1 - Holdt, Hans-Jürgen T1 - A novel polymeric disilver(I) complex containing both macrocyclic- and linear-coordinate silver(I) centres : [Ag-2(mn-15S(2)O(3))](infinity)(ClO4)(2 infinity) (mn-15S(2)O(3) = maleonitrile-dithia[15]crown-5) Y1 - 1999 ER - TY - JOUR A1 - Drexler, Hans-Joachim A1 - Starke, Ines A1 - Grojahn, Manuela A1 - Reinke, H. A1 - Kleinpeter, Erich A1 - Holdt, Hans-Jürgen T1 - SbCl3, BiCl3 and Na+ Complexes of maleonitrile-dithiacrown ethers: synthesis, crystal structures and DEP-MS experiments Y1 - 1999 ER - TY - JOUR A1 - Dzambaski, Zdravko A1 - Markovic, Rade A1 - Kleinpeter, Erich A1 - Baranac-Stojanovic, Marija T1 - 2-Alkylidene-4-oxothiazolidine S-oxides - synthesis and stereochemistry JF - Tetrahedron N2 - A series of 5-unsubstituted and 5-substituted 2-alkylidene-4-oxothiazolidine-S-oxides were synthesized by the sulfur-oxidation with m-CPBA. The stereochemistry of 5-substituted sulfoxides was determined by means of NMR spectroscopy and DFT theoretical calculations. It was found that the thermodynamically less stable anti-isomer was initially formed in the course of the oxidation, but it underwent epimerization to the mixture enriched in the more stable syn-isomer, during the work-up process. The higher stability of syn-isomers is ascribed to the stronger hyperconjugative sigma(C-H)->sigma*(S-O) interaction versus the weaker sigma(C-C)->sigma*(S-O) delocalization in their anti-counterparts and to the existence of intramolecular 1,5-CH center dot center dot center dot C hydrogen bonds. KW - 2-Alkylidene-4-oxothiazolidine KW - Sulfoxide KW - Diastereoselectivity KW - Density functional calculations KW - CH center dot center dot center dot O hydrogen bonds Y1 - 2013 U6 - https://doi.org/10.1016/j.tet.2013.05.087 SN - 0040-4020 VL - 69 IS - 31 SP - 6436 EP - 6447 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Fechner, Mabya A1 - Kramer, Markus A1 - Kleinpeter, Erich A1 - Koetz, Joachim T1 - Polyampholyte-modified ionic microemulsions N2 - This paper is focused on the influence of added polyampholyte, namely poly(N,N;-diallyl-N,N;- dimethyl-alt-maleamic carboxylate) on the inverse micellar phase range of the pseudo-ternary system consisting of toluene-pentanol (1:1)/SDS/water in dependence on the pH value and the temperature. Investigations on phase behavior have revealed that a greater extension in direction to the water-rich corner can be found at pH 4 compared to pH 9. In order to understand changes in the microstructure, polymer-surfactant interactions in dependence on pH have been examined by means of diffusion-ordered spectroscopy, differential scanning calorimetry, as well as conductivity measurements. The results have proven that the present microemulsion consists of water-in-oil droplets, with the polyampholyte located more in the inner core of the water droplets at pH 9 rather than at the interphase of the surfactant film at pH 4. Y1 - 2009 UR - http://www.springerlink.com/content/101551 U6 - https://doi.org/10.1007/s00396-009-2074-4 SN - 0303-402X ER - TY - JOUR A1 - Fettke, Anja A1 - Kramer, Markus A1 - Kleinpeter, Erich T1 - Lectin-bound conformations and non-covalent interactions of glycomimetic analogs of thiochitobiose N2 - The bound conformations of five S-glycoside analogs of N,N'-diacetylchitobiose as well as their non- covalent interactions with two lectins, Phytolacca americana lectin (PAL) and wheat germ agglutinin (WGA), are reported. The conformations of the ligands were examined by trNOESY experiments and compared with the free, solution-state conformations and molecular modeling data obtained by force field calculations. In the case of S-aryl, S-glycosides with exclusively S-glycosidic linkages, similar free and lectin-bound conformations and non-covalent interactions were found, whereas they differed for mixed glycosides and for a thiazoline derivative. In addition, STD (saturation transfer difference) NMR magnetization transfer efficiencies at three different temperatures were determined and assessed with respect to the structural differences of these pseudosaccharides. The binding epitopes of each substrate with PAL and WGA were also determined. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2010.04.012 SN - 0040-4020 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 - Germer, Antje A1 - Klod, Sabrina A1 - Peter, Martin G. A1 - Kleinpeter, Erich T1 - NMR spectroscopic and theoretical study of the complexation of the inhibitor allosamidin in the binding pocket of the plant chitinase hevamine N2 - Based on NMR spectroscopic information about the allosamidin-hevamine complex, ab initio MO calcns. of the ring current effect of the arom. moieties of Trp255, Tyr183 and Tyr6 of hevamine were carried out to investigate the role of these amino acid residues in binding interactions with allosamidin in soln. In addn., the intermol. steric compression effect on the 13C chem. shifts of the allosamizoline carbon atoms and the hydrogen bonding to Glu127 was identified. It can be inferred that the binding forces are strongest in the allosamizoline moiety of allosamidin. 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 - 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 - 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 - Grotjahn, Manuela A1 - Drexler, Hans-Joachim A1 - Jäger, Norbert A1 - Kleinpeter, Erich A1 - Holdt, Hans-Jürgen T1 - Molecular dynamic and conformational study of an unsaturated 12-crown-S202 ether and its AgI complexes Y1 - 1997 ER - TY - JOUR A1 - Grotjahn, Manuela A1 - Jäger, Norbert A1 - Drexler, Hans-Joachim A1 - Holdt, Hans-Jürgen A1 - Kleinpeter, Erich T1 - Molecular modeling study of the PtCl2 complexes of unsaturated S2On+1- coronands: dynamic simulations and investigation of the ring interconversion Y1 - 1999 ER - TY - JOUR A1 - Grotjahn, Manuela A1 - Kleinpeter, Erich T1 - Conformational behaviour of N-tosyl-substituted diaza-crown ethers Y1 - 1999 ER - TY - JOUR A1 - Grotjahn, Manuela A1 - Lehmann, S. A1 - Aurich, Ines A1 - Holdt, Hans-Joachim A1 - Kleinpeter, Erich T1 - NMR spectroscopic and molecular modelling studies of the solution structure and complexational behaviour of some bis(benzocrown ether)s N2 - Structural information about the bis(benzo crown ether)s I-VI and their complexes with alkali metal cations was deduced from the 13C NMR chemical shifts, the salt-induced 1H and 13C chemical shifts and the vicinal 1H,1H coupling constants. Especially the isomerism with respect to the amide O=C - NH bonds and imine fragments were assigned by various useful NMR parameters ( C=O, 1JN,H, 1JC,H) and proved to be E,E-anti,anti. Furthermore, stereochemical information about preferred conformations about flexible bonds was obtained from 2D ROESY NMR experiments. The complex formation (2:1 complexes and sandwich-like 1:1 complexes, respectively) were determined also by 23Na NMR spectroscopy. The conformational study of the crown ethers was accompanied and corroborated by molecular dynamics and quantum chemical calculations. Y1 - 2001 ER - TY - JOUR A1 - Hansen, Poul Erik A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Ring current and anisotropy effects on OH chemical shifts in resonance-assisted intramolecular H-bonds JF - Tetrahedron letters N2 - Ring current effects on resonance-assisted and intramolecularly bridged hydrogen bond protons for 10-hydroxybenzo[h]quinoline 1 and a number of related compounds were calculated and the through-space NMR shieldings (TSNMRS) obtained hereby visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. These calculations revealed that this through-space effect is comparably large (up to 2 ppm) dependent on the position of the intramolecularly bridged OH proton, and therefore, contribute considerably to the chemical shift of the latter making it questionable to use delta(OH)/ppm in the estimation of intramolecular hydrogen bond strength without taking this into account. Furthermore, the anisotropy effects of additional groups on the aromatic moiety (e.g. the carbonyl group in salicylaldehyde or in o-hydroxyacetophenone of ca. 0.6 ppm deshielding) should also be considered. These through-space effects need to be taken into account when using OH chemical shifts to estimate hydrogen bond strength. KW - RA-intramolecular hydrogen bond KW - Through-space NMR shieldings (TSNMRS) KW - Iso-chemical-shielding surfaces (ICSS) KW - Ring current effect KW - Anisotropy effect Y1 - 2018 U6 - https://doi.org/10.1016/j.tetlet.2018.05.006 SN - 0040-4039 VL - 59 IS - 23 SP - 2288 EP - 2292 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Haufe, G. A1 - Rolle, U. A1 - Kleinpeter, Erich A1 - Kivikoski, J. A1 - Rissanen, K. T1 - N-Heterocyclization in electrophilic haloamination reactions of 1,5-cyclooctadiene : formation of the granatanine and homotropane skeletons Y1 - 1993 ER - TY - JOUR A1 - Hausmann, J. A1 - Kass, S. A1 - Klod, Sabrina A1 - Kleinpeter, Erich A1 - Kersting, Berthold T1 - Binucleating aza-sulfonate and aza-sulfinate macrocycles : Synthesis and coordination chemistry N2 - The preparation and ligating properties of S-oxygenated derivatives of a macrobinucleating hexaazadithiophenolate macrocycle H2L1 of the Robson type towards nickel(II) and zinc(II) ions are reported. Nickel complexes of the hexaazadiphenylsulfonate ligand (L-2)(2-)[(L-2)Ni-2(II)(mu-L)](+)(L = m-Cl-OBz(-) (3), Cl- (4) and OAc- (6)] are readily obtained in high yields by oxidation of the respective [(L-1)Ni-2(II)(mu-L)](+) parent complexes [L = m- Cl-OBz- (2), Cl- (1), OAc- (5)] with meta-chloroperoxybenzoic acid or hydrogen peroxide. Decomposition of the sulfonate complexes gives the free macrocycle H2L2 which, upon treatment with Zn(OAc)(2)(.)2H(2)O, produces the diamagnetic zinc complex [(L-2)Z(2)(II)(OAc)](+) (8). A dinuclear Cu-II complex of the hexaazadisulfinate derivative (L-3')(2-), [(L-3)CU2II](2+) (9), is formed rather unexpectedly by air oxidation of (L-1)(2-) in the presence of Cu-I. The crystal- structure determinations of the perchlorate or tetraphenylborate salts of 2, 3, and 4 show that the new ligands support the formation of binuclear complexes with bowl-shaped, calixarene-like binding cavities. NMR spectroscopic studies of 8 show that the complexes retain their solid-state structures in solution. A crystal-structure determination of 9 reveals two five-coordinate Cu-II ions bridged by the two sulfinate functions of (L-3)(2-) Y1 - 2004 SN - 1434-1948 ER - TY - JOUR A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Zimmermann, Thomas T1 - Dynamic NMR study of the flexibility of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts Y1 - 1997 UR - http://www.springerlink.com/content/110258 U6 - https://doi.org/10.1007/s002160050205 SN - 0937-0633 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 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Kovacs, J. A1 - Toth, G. A1 - Kleinpeter, Erich T1 - Electronic influences on (3)J(C,H) coupling constants via -S-, -S(O)- and -SO2--: their determination, calculation and comparison of detection methods N2 - (3)J(C,H) coupling constants via a sulfur atom in two series of compounds, both including a sulfide, a sulfoxide and a sulfone, were detected experimentally and calculated by quantum mechanical methods. In the first series (1-3) the coupling between a hydrogen, bonded to an Sp(3) carbon, and an Sp(2) carbon is treated; the second series (4- 6) deals with the coupling between a hydrogen, bonded to an Sp3 carbon, and an Sp3 carbon. Different pulse sequences (broadband HMBC, SelJres, 1D HSQMBC, J-HMBC-2, selective J-resolved long-range experiment and IMPEACH-MBC) proved to be useful in determining the long-range (3)J(C,H) coupling constants. However, the dynamic behaviour of two of the compounds (4 and 6) led to weighted averages of the two coupling constants expected (concerning equatorial and axial positions of the corresponding hydrogens). DFT calculations proved to be useful to calculate not only the (3)J(C,H) coupling constants but also the different contributions of FC, PSO, DSO and SD terms; the calculation of the Fermi contact term (FC) was found to be sufficient for the correct estimation of (3)J(C,H) coupling constants. Copyright (C) 2004 John Wiley Sons, Ltd Y1 - 2004 SN - 0749-1581 ER - TY - JOUR A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Ristau, Thomas A1 - Knoll, Susanne A1 - Heinicke, Jochen A1 - Sieler, Joachim A1 - Niemitz, Matthias A1 - Mühlstädt, Manfred A1 - Kleinpeter, Erich T1 - Conformational analysis of sulfur-containing heterocycles ; part I: synthesis and structural determination of diastereomerically pure 4,6-bis(phenoxymethyl)-1,2,5-trithiepanes Y1 - 1998 ER - TY - JOUR A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Sarodnick, Gerhard A1 - Kleinpeter, Erich T1 - Quinoxalines XIV : Synthesis, H-1, C-13, N-15 NMR spectroscopic, and quantum chemical study of 1H-pyrazolo[3,4- b]quinoxalines (flavazoles) N2 - The synthesis of a series of 1H-pyrazolo[3,4-b]quinoxalines (flavazoles) by acylation, alkylation, halogenation, and aminomethylation of the parent compound is reported and their structure is investigated by H-1, C-13 and N-15 NMR spectroscopy. The restricted rotation about the partial C, N double bond of the N-acyl derivatives 7-10 is studied by dynamic NMR spectroscopy and the barriers to rotation are determined. In order to assign unequivocally the 15 N chemical shifts of N-4 and N-9, in case of 3-substituted flavazoles, exemplary the H-1, C-13, and N-15 NMR chemical shifts of 34, 35, and 39 are also theoretically calculated by quantum chemical methods [ab initio at different levels of theory (HF/6-3G* and B3LYP/6-31G*)]. (C) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0040-4020 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 - Wolf, G. A1 - Woller, Jochen A1 - Kleinpeter, Erich T1 - Restricted rotation of the amino group and ring inversion in highly substituted anilines. A dynamic NMR and computational study N2 - The reaction of cyclic ylidene malononitriles with acetylene (di)carboxylic acid esters led to the production of nine bicyclic systems incorporating highly substituted (5/6) anilines. The free energy of activation (DeltaG(#)) for the restricted rotation about the aniline-NH2 bond was experimentally measured in each case and a correlation was evident between the increase in steric strain in the ground state, the electron withdrawing capabilities of the ring substituents, and a reduction in the rotational barrier. For four of the compounds, the slow ring interconversion (chairreversible arrowchair) for the annelated saturated seven-membered ring that formed part of the bicyclic system was also evident. In these four compounds, both dynamic processes were also studied theoretically using ab initio methods whilst the ring interconversion was additionally studied using molecular dynamic simulations. The interconversion between the two stable chair forms was deemed to occur via a conformation series consisting of chairreversible arrowboatreversible arrowtwist-boatreversible arrowboatreversible arrowchair. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2004 SN - 0040-4020 ER - TY - JOUR A1 - Hilfert, Liane A1 - Sarodnick, Gerhard A1 - Kempter, Gerhard A1 - Kleinpeter, Erich T1 - 1H, 13C and 15 N NMR study and molecular modelling of 2,3- disubstituted quinoxalines with sterically hinderered aromatic and heteroaromatic substituents Y1 - 1998 ER - TY - JOUR A1 - Holdt, Hans-Jürgen A1 - Drexler, Hans-Joachim A1 - Starke, Ines A1 - Grotjahn, Manuela A1 - Kleinpeter, Erich T1 - Homologous series of the PdCl2 and PtCl2 complexes of maleonitrile-dithiacrown ethers : synthesis, crystal structures, NMR spectroscopy and mass spectrometry Y1 - 2001 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 - Holzberger, Anja A1 - Holdt, H. N. A1 - Kleinpeter, Erich T1 - NMR spectroscopic and molecular modelling study of the solution structure and the complexational behavior of maleonitrile tetrathia crown ethers with silver(I) N2 - The flexibility and complex formation of two maleonitrile tetrathia crown ethers were studied in solution using H-1 and C-13 NMR spectroscopy and molecular modelling. Both the stoichiometry and the stability of the complexes that these crown ethers form with Ag(I) were determined by NMR titration measurements. Spin-lattice relaxation time measurements provided information concerning the donor atoms involved in complex formation and also the intramolecular mobility of the free and complexed ligands. Molecular modelling was also used to gain further insight into the conformational space of the free ligands and their silver(I) complexes. Copyright (C) 2004 John Wiley Sons, Ltd Y1 - 2004 ER - TY - JOUR A1 - Holzberger, Anja A1 - Holdt, Hans-Jürgen A1 - Kleinpeter, Erich T1 - Conformational analysis of mixed oxathia crown ethers and their complexational ability towards Ag(I) and Pd(II) : an experimental solution NMR and theoretical molecular modelling study N2 - Both the conformation and flexibility of four mixed oxathia crown ethers and their Ag(I) and Pd(II) complexes were studied by H-1 NMR (delta, J, NOE, T-1), C-13 NMR, dynamic 1H NMR spectroscopy and molecular modelling. The stoichiometry and stability constants of the complexes were determined from corresponding Job's plots in the case of Ag(I) complexes as the interchange between free and complexed states was fast on the NMR timescale; interchange for the Pd(II) complexes was sufficiently slow such that distinct sub-spectra were observable for the free and complexed states. In all cases where complexation was observed, 1 : 1 complexes were formed. Global minima structures determined from the modelling studies were analysed with respect to the barriers to ring interconversion, the flexibility of the species in solution and the preferred complexation of Ag(I) and Pd(II) to the sulfur atoms of the crown ethers Y1 - 2004 SN - 1477-0520 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 - Kamm, Birgit A1 - Kamm, Michael A1 - Schmidt, Matthias A1 - Starke, Ines A1 - Kleinpeter, Erich T1 - Chemical and biochemical generation of carbohydrates from lignocellulose-feedstock (Lupinus nootkatensis) : quantification of glucose N2 - Different chemical and enzymatic methods were applied for the hydrolysis of main stems from Lupinus nootkatensis (harvest November 2002). The whole process (all steps) is based on the lignocellulose-feedstock biorefinery regime. The acid hydrolysis of L. was performed with concentrated hydrochloric acid; advantages in this process are exothermic hydrolysis and the possibility of acid recovery. Enzymatic hydrolysis achieved high yields of fermentable carbohydrates (regarding to input cellulose) with high selectivity. However, this way requires the generation of cellulose from L. by chemical pulping. Monosaccharide derivatives thus obtained were identified by their GC retention times and the corresponding MS fragmentation. Hexamethyldisilazane was used as derivatization reagent to prepare the trimethylsilyl derivatives of the carbohydrates and of the degradations products of cellulose from the different fractions. The glucose content was quantified by GC peak integration with respect to an internal standard. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00456535 U6 - https://doi.org/10.1016/j.chemosphere.2005.03.073 SN - 0045-6535 ER - TY - JOUR A1 - Kammer, Stefan A1 - Starke, Ines A1 - Pietrucha, Andreas A1 - Kelling, Alexandra A1 - Mickler, Wulfhard A1 - Schilde, Uwe A1 - Dosche, Carsten A1 - Kleinpeter, Erich A1 - Holdt, Hans-Jürgen T1 - 1,12-Diazaperylene and 2,11-dialkylated-1,12-diazaperylene iridium(III) complexes [Ir((CN)-N-boolean AND)(2)((NN)-N-boolean AND)]PF6: new supramolecular assemblies JF - Dalton transactions : a journal of inorganic chemistry, including bioinorganic, organometallic, and solid-state chemistry N2 - A series of new monocationic iridium(III) complexes [Ir((CN)-N-boolean AND)(2)((NN)-N-boolean AND)]PF6 with "large-surface" alpha,alpha'-diimin ligands (NN)-N-boolean AND (dap = 1,12-diazaperylene, dmedap = 2,11-dimethyl-1,12-diazaperylene, dipdap = 2,11-diisopropyl-1,12-diazaperylene) and different cyclometalating ligands (CN)-N-boolean AND (piq = 1-phenylisoquinoline, bzq = benzo[h]quinoline, ppz = 1-phenylpyrazole, thpy = 2-(2-thienyl)pyridine, ppy = 2-phenylpyridine, meppy = 2-(4-methylphenyl)pyridine, dfppy = 2-(2,4-difluorophenyl)pyridine) were synthesized. The solid structures of the complexes [Ir(piq)(2)(dap)]PF6, [Ir(bzq)(2)(dap)]PF6, [Ir(ppy)(2)(dipdap)]PF6, [Ir(piq)(2)(dmedap)]PF6, [Ir(ppy)(2)(dap)]PF6 and [Ir(ppz)(2)(dap)]PF6 are reported. In [Ir(piq)(2)(dap)]PF6, the dap ligand and one of the piq ligands of each cationic complex are involved in pi-pi stacking interactions forming supramolecular channels running along the crystallographic c axis. In the crystalline [Ir(bzq)(2)(dap)]PF6 pi-pi stacking interactions between the metal complexes lead to the formation of a 2D layer structure. In addition, CH-pi interactions were found in all compounds, which are what stabilizes the solid structure. In particular, a significant number of them were found in [Ir(piq)(2)(dap)]PF6 and [Ir(bzq)(2)(dap)]PF6. The crystal structures of [Ir(ppy)(2)(dipdap)]PF6 and [Ir(ppy)(2)(dmedap)]PF6 are also presented, being the first examples of bis-cyclometalated iridium(III) complexes with phenanthroline-type alpha,alpha'-diimin ligands bearing bulky alkyl groups in the neighbourhood of the N-donor atoms. These ligands implicate a distorted octahedral coordination geometry that in turn destabilized the Ir-N-N boolean AND N bonds. The new iridium (III) complexes are not luminescent. All compounds show an electrochemically irreversible anodic peak between 1.15 and 1.58 V, which is influenced by the different cyclometalated ligands. All of the new complexes show two reversible successive one-electron "large-surface" ligand-centred reductions around -0.70 V and -1.30 V. Electrospray ionisation mass spectrometry (ESI-MS) and collision induced decomposition (CID) measurements were used to investigate the stability of the new complexes. Thereby, the stability agreed well with the order of the Ir-N-N boolean AND N bond lengths. Y1 - 2012 U6 - https://doi.org/10.1039/c2dt30412k SN - 1477-9226 VL - 41 IS - 34 SP - 10219 EP - 10227 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kihampa, Charles A1 - Nkunya, Mayunga H. H. A1 - Joseph, Cosam C. A1 - Magesa, Stephen M. A1 - Hassanali, Ahmed A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich T1 - Antimosquito and antimicrobial clerodanoids and a chlorobenzoid from Tessmannia species N2 - The clerodane diterpenoids trans-kolavenolic acid, 18-oxocleroda-3,13(E)-dien-15-oic acid, ent-(18- hydroxycarbonyl)-cleroda- 3,13(E)-dien-15-oate, 2-oxo-ent-cleroda-3,13(Z)-dien-15-oic acid and trans-2-oxo-ent-cleroda- 13(Z)-en-15-oic acid, and the chlorobenzenoid O-(3-hydroxy-4-hydroxycarbonyl-5-pentylphenyl)-3-chloro-4-methoxy-6-pentyl- 2-oxybenzoic acid were isolated from Tessmannia martiniana var pauloi and T. martiniana var matiniana. Structures were established based on interpretation of spectroscopic data. Some of the compounds exhibited significant antimosquito, antifungal and antibacterial activities. Y1 - 2010 UR - http://www.naturalproduct.us/ SN - 1934-578X ER - TY - JOUR A1 - Kihampa, Charles A1 - Nkunya, Mayunga H. H. A1 - Joseph, Cosam C. A1 - Magesa, Stephen M. A1 - Hassanali, Ahmed A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich T1 - Anti-mosquito and antimicrobial nor-halimanoids, isocoumarins and an anilinoid from Tessmannia densiflora N2 - The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, and 5- pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00319422 U6 - https://doi.org/10.1016/j.phytochem.2009.07.024 SN - 0031-9422 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 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich A1 - Shainyan, Bagrat A. T1 - Conformational analysis of 3,3-dimethyl-3-silathiane, 2,3,3-trimethyl-3-silathiane and 2-trimethylsilyl-3,3- dimethyl-3-silathianeùpreferred conformers, barriers to ring inversion and substituent effec N2 - The first conformational analysis of 3-silathiane and its C-substituted derivatives, namely, 3,3-dimethyl-3- silathiane 1, 2,3,3-trimethyl-3-silathiane 2, and 2-trimethylsilyl-3,3-dimethyl-3-silathiane 3 was performed by using dynamic NMR spectroscopy and B3LYP/6-311G(d,p) quantum chemical calculations. From coalescence temperatures, ring inversion barriers ;G; for 1 and 2 were estimated to be 6.3 and 6.8;kcal/mol, respectively. These values are considerably lower than that of thiacyclohexane (9.4;kcal/mol) but slightly higher than the one of 1,1- dimethylsilacyclohexane (5.5;kcal/mol). The conformational free energy for the methyl group in 2 (;;G°;=;0.35;kcal/mol) derived from low-temperature 13C NMR data is fairly consistent with the calculated value. For compound 2, theoretical calculations give ;E value close to zero for the equilibrium between the 2-Meax and 2-Meeq conformers. The calculated equatorial preference of the trimethylsilyl group in 3 is much more pronounced (;;G°;=;1.8;kcal/mol) and the predominance of the 3-SiMe3 eq conformer at room temperature was confirmed by the simulated 1H NMR and 2D NOESY spectra. The effect of the 2-substituent on the structural parameters of 2 and 3 is discussed. Y1 - 2010 SN - 0894-3230 ER - TY - JOUR A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich A1 - Ushakov, Igor A. A1 - Shainyan, Bagrat A. T1 - Conformational Analysis of 3-Methyl-3-Silathiane and 3-Fluoro-3-Methyl-3-Silathiane JF - Journal of physical organic chemistry N2 - The conformational equilibria of 3-methyl-3-silathiane 5, 3-fluoro-3-methyl-3-silathiane 6 and 1-fluoro-1-methyl-1- silacyclohexane 7 have been studied using low temperature C-13 NMR spectroscopy and theoretical calculations. The conformer ratio at 103 K was measured to be about 5(ax):5(eq) - 15:85, 6(ax):6(eq)-50:50 and 7(ax):7(eq)-25:75. The equatorial preference of the methyl group in 5 (0.35 kcal mol(-1)) is much less than in 3-methylthiane 9 (1.40 kcal mol(-1)) but somewhat greater than in 1-methyl-1-silacyclohexane 1 (0.23 kcal mol(-1)). Compounds 5-7 have low barriers to ring inversion: 5.65 (ax -> eq) and 6.0 kcal mol(-1) (eq -> ax) (5), 4.6 kcal mol(-1) (6), 5.1 kcal mol(-1) (Me-ax -> Me-eq), and 5.4 kcal mol(-1) (Me-eq -> Me-ax) (7). Steric effects cannot explain the observed conformational preferences, like equal population of the two conformers of 6, or different conformer ratio for 5 and 7. Actually, by employing the NBO analysis, in particular, considering the second order perturbation energies, vicinal stereoelectronic interactions between the Si-X and adjacent C-H, C-S, and C-C bonds proved responsible. KW - conformational analysis KW - low-temperature NMR spectroscopy KW - NBO analysis KW - quantum chemical calculations KW - 3-silathianes Y1 - 2011 U6 - https://doi.org/10.1002/poc.1758 SN - 0894-3230 VL - 24 IS - 4 SP - 320 EP - 326 PB - Wiley-Blackwell CY - Hoboken 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 - Kleinpeter, Erich T1 - Quantitative study and visualization of spherical 2(N + 1)2 homoaromaticity by through space NMR shieldings (TSNMRS) N2 - The through space NMR shielding (TSNMRS) values of adamantane, the 2(N + 1)2 spherical (4c, 2e) homoaromatic compounds 1,3-dehydro-5,7-adamantandiyl dication (C10H122+) and 1,3-dehydro-5,7-cubandiyl dication (C8H42+), and the (6c, 8e) homoaromatic compound 2,2;,4,4;,6,6;,8,8;,10,10;-dehydroadamantane tetracation (C10H44+) have been ab initio calculated, employing the NICS concept, and visualized as iso-chemical shielding surfaces (ICSSs). TSNMRS values can be successfully employed to study both the endohedral and exohedral aromaticity/ antiaromaticity of the compounds studied. Y1 - 2008 U6 - https://doi.org/10.1016/j.theochem.2007.11.029 ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Push-pull alkenes : structure and pi-electron distribution N2 - Push-pull alkenes are substituted alkenes with one or two electron-donating substituents on one end of C=C double bond and with one or two electron-accepting substituents at the other end. Allowance for pi-electron delocalization leads to the central C=C double bond becoming ever more polarized and with rising push-pull character, the pi-bond order of this double bond is reduced and, conversely, the corresponding pi-bond orders of the C-Don and C- Ace bonds are accordingly increased. This push-pull effect is of decisive influence on both the dynamic behavior and the chemical reactivity of this class of compounds and thus it is Of Considerable interest to both determine and to quantify the inherent push-pull effect. previously, the barriers to rotation about the C=C, C-Don and/or C-Acc partial double bonds (Delta G(not equal), as determined by dynamic NMR spectroscopy) or the C-13 chemical shift difference of the polarized C=C partial double bond (Delta delta(C=C)) were employed for this purpose, However, these parameters can have serious limitations, viz. the barriers can be immeasurable on the NMR timescale (either by being too high or too low-, heavily-biased conformers are present, etc.) or Delta delta(C=C) behaves in a non-additive manner with respect to the combination of the four substituents. Hence, a general parameter to quantify the push-pull effect is not yet available. Ab initio MO calculations on a collection of compounds, together with NBO analysis, provided valuable information on the structure, bond energies, electron occupancies and bonding/antibonding interactions. In addition to Delta G(C=C)(not equal) (either experimentally determined or theoretically calculated) and Delta delta(C=C), the bond length of the C=C partial double bond was also examined and it proved to be a reliable parameter to quantify the push-pull effect. Equally so, the quotient of the occupation numbers of the antibonding and bonding pi orbitals of the central C=C partial double bond ( pi*(C=C)/pi(C=C) ) could also be employed for this purpose Y1 - 2006 UR - http://www.shd.org.rs/JSCS/ U6 - https://doi.org/10.2298/Jsc0601001k ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Quantification of the (Anti)Aromaticity of Fulvalenes Subjected to -Electron Cross-Delocalization N2 - Fulvalenes 3-12 were theoretically studied at the ab initio level of theory. For the global minima structures, the occupation of the bonding (pi)C=C orbital of the interring C=C double bond obtained by NBO analysis quantitatively proves pi-electron cross-delocalization resulting in, at least partially, 2- or 6pi-electron aromaticity and 8pi- electron antiaromaticity for appropriate moieties. The cross-conjugation was quantified by the corresponding occupation numbers and lengths of the interring C=C double bonds, while the aromaticity or antiaromaticity due to cross- delocalization of the pi-electrons was visualized and quantified by through-space NMR shielding surfaces. Y1 - 2008 UR - http://pubs.acs.org/doi/full/10.1021/jo701520j U6 - https://doi.org/10.1021/Jo701520j ER - TY - JOUR A1 - Kleinpeter, Erich T1 - The Structure of hydantions in solution and in the solid state Y1 - 1997 ER - TY - BOOK A1 - Kleinpeter, Erich T1 - NMR-Spektoskopie : Struktur, Dynamik und Chemie des Moleküls Y1 - 1992 PB - Barth CY - Leipzig ER - TY - JOUR A1 - Kleinpeter, Erich T1 - NMR-Spektroskopie Y1 - 1996 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 - Conformational analysis of saturated six-membered oxygen-containing heterocyclic rings Y1 - 1998 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 - Kleinpeter, Erich T1 - Conformational analysis of six-membered sulfur-containing heterocycles Y1 - 1995 ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Effect of the variation of ring size of cyclic NR2 substituents on the barrier to rotation in amides, thioamides and related compounds Y1 - 1995 ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Are lithium and sodium salts of N-(2-hydroxyphenyl)-salicylaldimine aromatic metalla-hetero[10]annulenes? An answer given by spatial magnetic properties (through space NMR shieldings-TSNMRS) N2 - The spatial magnetic properties (through space NMR shieldings-TSNMRS) of the enol tautomer of N-(2- hydroxyphenyl)-salicylaldimine, the lithium and sodium salts in comparison with cyclodecapentaene and pyrano[2,3- b]pyrrole were studied to answer this question. Y1 - 2012 SN - 1463-9076 ER - TY - JOUR A1 - Kleinpeter, Erich ED - Webb, GA T1 - Quantification and visualization of the anisotropy effect in NMR spectroscopy by through-space NMR shieldings JF - Annual reports on NMR spectroscopy JF - Annual Reports on NMR Spectroscopy N2 - The anisotropy effect of functional groups (respectively the ring-current effect of aryl moieties) in H-1 NMR spectra has been computed as spatial NICS (through-space NMR chemical shieldings) and visualized by iso-chemical-shielding surfaces of various size and low(high) field direction. Hereby, the anisotropy/ring-current effect, which proves to be the molecular response property of spatial NICS, can be quantified and can be readily employed for assignment purposes in proton NMR spectroscopy-characteristic examples of stereochemistry and position assignments (the latter in supramolecular structures) will be given. In addition, anisotropy/ring-current effects in H-1 NMR spectra can be quantitatively separated from the second dominant structural effect in proton NMR spectra, the steric compression effect, pointing into the reverse direction, and the ring-current effect, by far the strongest anisotropy effect, can be impressively employed to visualize and quantify (anti) aromaticity and to clear up standing physical-organic phenomena as are pseudo-, spherical, captodative, homo-and chelatoaromaticity, to characterize the pi-electronic structure of, for example, fulvenes, fulvalenes, annulenes or fullerenes and to differentiate aromatic and quinonoid structures. KW - Through-space NMR shielding (TSNMRS) KW - Anisotropy effect KW - Stereochemistry KW - Ring-current effect KW - Aromatic or quinonoid KW - Aromaticity KW - Chelatoaromaticity KW - Binding pocket position KW - Supramolecular compounds KW - Diastereomers assignment Y1 - 2014 SN - 978-0-12-800184-4 U6 - https://doi.org/10.1016/B978-0-12-800184-4.00003-5 SN - 0066-4103 VL - 82 SP - 115 EP - 166 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Kleinpeter, Erich T1 - Recent advances in studying tautomerism in solution and in solid state Y1 - 2000 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Balci, Kubilay A1 - Yapar, G. A1 - Akkaya, S. A1 - Akyuz, S. A1 - Koch, Andreas T1 - A conformational analysis and vibrational spectroscopic investigation on 1,2-bis(o-carboxyphenoxy) ethane molecule N2 - The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy) ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople- style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major c ntribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibratb20s to conformation, substitution and dimerization were discussed. Y1 - 2012 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 - Kleinpeter, Erich A1 - Boelke, Ute A1 - Kreicberga, Jana T1 - Quantification of the push-pull character of azo dyes and a basis for their evaluation as potential nonlinear optical materials N2 - The push-pull characters of a large series of donor-acceptor substituted azo dyesù71 structures in allùhave been quantified by the NN double bond lengths, dNN, the 15N NMR chemical shift differences, ;;15N, of the two nitrogen atoms and the quotient, ;*/;, of the occupations of the antibonding ;*, and bonding ; orbitals of this partial NN double bond. The excellent correlation of the occupation quotients with the bond lengths strongly infers that both ;*/; and dNN are excellent parameters for quantifying charge alternation in the push-pull chromophore and the molecular hyperpolarizability, ;0, of these compounds. By this approach, selected compounds can be appropriately considered as viable candidates for nonlinear optical (NLO) applications. Y1 - 2010 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Branac-Stojanovi, Marija A1 - Koch, Andreas T1 - Is the Conventional Interpretation of the Anisotropic Effects of CC Double Bonds and Aromatic Rings in NMR Spectra in Terms of the -Electron Shielding/Deshielding Contributions Correct? N2 - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10;Å away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C=C double bond or the aromatic ring should not be explained in terms of the conventionally accepted ;-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring. Y1 - 2012 SN - 1521-3765 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Bölke, Ute A1 - Frank, Andrea T1 - Polar substituent effect of the ester group on conformational equilibria of O-mono-substituted cyclohexanesùthe para-substituent effect in cyclohexyl benzoates N2 - Together with the nonsubstituted reference compound, para-methoxy- and para-nitro cyclohexyl benzoates have been synthesized and their conformational equilibria studied by low temperature NMR spectroscopy and theoretical DFT calculations. The free energy differences ;G° between axial and equatorial conformers were examined with respect to polar substituent influences on the conformational equilibrium of O-mono-substituted cyclohexane. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040402008013082 U6 - https://doi.org/10.1016/j.tet.2008.07.024 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Csütörtöki, Renáta A1 - Szatmári, István A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Starke, Ines A1 - Fulop, Ferenc T1 - Novel piperidine-fused benzoxazino- and quinazolinonaphthoxazines-synthesis and conformational study N2 - The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl)methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzoxazinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, Gtct1 for 4 and Gtct1 for 7, were corroborated by spatial NOE information relating to the H7a-H10a-H15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements. Y1 - 2012 SN - 0040-4020 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 - Kleinpeter, Erich A1 - Dargatz, M. T1 - Eine 2D-INEPT-Variante zur Detektierung wenig empfindlicher Kerne Y1 - 1992 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Fettke, Anja T1 - Quantification of the (anti)aromaticity of fulvenes subject to ring size N2 - Tria-, penta-, hepta- and nonafulvenes (1-4) have been studied theoretically at the MP2 ab initio level of theory. For the global minimum structures, the occupation of the bonding ;C=C orbital of the exocyclic C=C double bond, obtained by NBO analysis, quantitatively proves ;-electron delocalization which can reveal partial 2-, 6- and 10-;-electron aromaticity, and 4-, 8- and 12-;-electron antiaromaticity of the ring moieties. Beside the corresponding occupation number, this conjugation was quantified by the length of the exocyclic C=C double bond whilst the (anti)aromaticity of the ring moieties of 1-4 was visualized and quantified by through space NMR shielding surfaces (TSNMRS). Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0040403908003766 U6 - https://doi.org/10.1016/j.tetlet.2008.02.137 SN - 0040-4039 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Frank, Andrea T1 - Quantification of the push-pull effect in substituted alkynes : evaluation of +/- I/+/- M substituent effects in terms of C C bond length variation N2 - C-13 chemical shifts of alkynes, published to date, were computed at the DFT (B3LYP/6-311G*) level of theory and compared with the experimental delta values, and the agreement was employed as a measure of quality for the underlying structures. For the corresponding global minima structures, thus obtained, the occupation quotients of antibonding pi* and bonding pi orbitals (pi*(C C)/pi(C C)) and the bond lengths (d(C C)) of the central C C triple bond were computed and correlated to each other. The linear dependence obtained for the two push-pull parameters d(C C) and pi*(C C)/pi(C C) quantifies changes in the push-pull effect of substituents while deviations from the best line of fit indicate and ascertain quantitatively to what extend the inductive (+/-l) substituent effect changes with respect to the bond length of the C C triple bond. Y1 - 2009 UR - http://pubs.acs.org/journal/jpcafh U6 - https://doi.org/10.1021/Jp9024359 SN - 1089-5639 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Frank, Andrea T1 - Distinction of Push,pull effect and steric hindrance in disubstituted alkynes N2 - The push,pull effect in two series of disubstituted alkynes was studied at the DFT level [B3LYP/6-311G(d)] by application of the 13C chemical shift differences (GIAO) between the alkyne carbon atoms (Delta delta (C C)), the charge difference between these carbons (Delta q(C C)), the occupation quotient (NBO) of anti-bonding pi*, and bonding pi orbitals (pi*(C C)/pi(C C)) and the bond length (d(C C)) of the C C triple bond. The linear dependence of d(C C) versus pi*(C C)/pi(C C) quantifies changes in the push,pull effect while deviations from the latter correlation indicate and ascertain quantitatively to what extent steric hindrance restricts the strain-less conjugation of the C C triple bond pi- orbitals in the disubstituted alkynes. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00404020 U6 - https://doi.org/10.1016/j.tet.2009.03.075 SN - 0040-4020 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Grotjahn, Manuela A1 - Klinka, Karel D. A1 - Drexler, Hans-Joachim A1 - Holdt, Hans-Jürgen T1 - Conformational and complexational study of some maleonitrile mixed oxadithia crown ethers by NMR spectroscopy and molecular modelling N2 - The macrocyclic ring interconversion of four maleonitrile mixed oxadithia crown ethers of variable ring size, mn-12-S2O2, mn-15-S2O3, mn-18-S2O4 and fn-12-S2O2, were studied by 1H and 13C NMR spectroscopy and by molecular modelling. The barriers to ring interconversion were estimated using variable temperature NMR spectroscopy and from the calculated activation energies, together with the spin-lattice relaxation times of the CH2 carbon atoms, conclusions were drawn regarding the intramolecular flexibility of the crown ethers in both the free state as well as the complexed state incorporating either AgI, BiIII, SbIII, PdII or PtII metal cations. Furthermore, both the stoichiometry of the complexes and the coordination sites of the crown ethers to the various cations were also clearly implicated. Molecular modelling was also utilised to ascertain the preferred conformers of the four compounds and their corresponding complexes, the results of which corroborated the experimental NMR results to a high degree. Y1 - 2001 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 - 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 - Heydenreich, Matthias A1 - Kalder, L. A1 - Koch, Andreas A1 - Henning, Dietrich A1 - Kempter, Gerhard T1 - NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution Y1 - 1997 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Kalder, L. A1 - Koch, Andreas A1 - Henning, Dietrich A1 - Kempter, Gerhard A1 - Benassi, Rois A1 - Taddei, F. T1 - NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution Y1 - 1997 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Krtitschka, Angela A1 - Krüger, Tobias A1 - Linker, Torsten T1 - NMR spectroscopic conformational analysis of 4-methylene-cyclohexyl pivalateThe effect of sp(2) hybridization JF - Magnetic resonance in chemistry N2 - The conformational equilibrium of the axial/equatorial conformers of 4-methylene-cyclohexyl pivalate is studied by dynamic NMR spectroscopy in a methylene chloride/freon mixture. At 153K, the ring interconversion gets slow on the nuclear magnetic resonance timescale, the conformational equilibrium (-G degrees) can be examined, and the barrier to ring interconversion (G(#)) can be determined. The structural influence of sp(2) hybridization on both G degrees and G(#) of the cyclohexyl moiety can be quantified. KW - 4-methylene-cyclohexyl pivalate KW - conformational analysis KW - dynamic NMR spectroscopy KW - exo-methylene conformational effect at cyclohexane KW - quantum chemical calculations Y1 - 2017 U6 - https://doi.org/10.1002/mrc.4630 SN - 0749-1581 SN - 1097-458X VL - 55 SP - 1073 EP - 1078 PB - Wiley CY - Hoboken 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 - Heydenreich, Matthias A1 - Shainyan, Bagrat A. T1 - At the experimental limit of the NMR conformational analysis BT - Si-29 and C-13 NMR study of the conformational equilibrium of 1-phenyl-1-tert-butylsilacyclohexane JF - Organic letters N2 - The low temperature (95 K) NMR study of 1-Ph-1-t-Bu-silacyclohexane (1) showed the conformational equilibrium to be extremely one-sided toward thePh(ax),t-Bueq conformer. The barrier to interconversion has been measured (4.2-4.6 kcal/mol) and the conformational equilibrium [Delta nu = 1990.64 ppm (Si-29), 618.9 ppm (C-13), 1-Ph-ax:1-Pheq = (95.6-96.6%):(3.4-4.4%), K = 25 +/- 3, Delta G degrees = -RT ln K = 0.58-0.63 kcal/mol] analyzed. The assignment and quantification of the NMR signals is supported by MP2 and DFT calculations. Y1 - 2021 U6 - https://doi.org/10.1021/acs.orglett.0c03878 SN - 1523-7060 SN - 1523-7052 VL - 23 IS - 2 SP - 405 EP - 409 PB - American Chemical Society CY - Washington ER -