TY  - JOUR
A1  - Lehmann, J.
A1  - Kleinpeter, Erich
T1  - 1H NMR Lanthanideinduced Shift (LIS) investigations of highly flexible molecules : a new approach
Y1  - 1993
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Shainyan, Bagrat A.
A1  - Schilde, Uwe
A1  - Chipanina, Nina N.
A1  - Oznobikhina, Larisa P.
A1  - Albanov, Alexander I.
A1  - Kleinpeter, Erich
T1  - Synthesis, molecular structure, conformational analysis, and chemical properties of silicon-containing derivatives of quinolizidine
JF  - The journal of organic chemistry
N2  - A silicon analog of quinolizidine 3,3,7,7-tetramethylhexahydro-1H-[1,4,2]oxazasilino[4,5-d][1,4,2]oxazasilin-9a-yl)methanol 3 was synthesized. X-ray diffraction analysis confirmed the trans configuration and low temperature NMR spectroscopy both the flexibility (barrier of interconversion 5.8 kcal mol(-1)) and the conformational equilibrium (chair-chair and chair-twist conformers) of the compound. The relative stability of the different isomers/conformers of 3 was calculated also at the MP2/6-311G(d,p) level of theory. Intra- and intermolecular hydrogen bonding in 3 and the appropriate equilibrium between free and self-associated molecules was studied in solvents of different polarity. Both the N-methyl quaternary ammonium salt and the O-trimethylsilyl derivative of 3 could be obtained and their structure determined.
Y1  - 2012
U6  - https://doi.org/10.1021/jo202658n
SN  - 0022-3263
VL  - 77
IS  - 5
SP  - 2382
EP  - 2388
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - 4-Alkyl-2,2,6,6-tetramethyl-1,4,2,6-oxaazadisilinanes : synthesis, structure, and conformational analysis
N2  - 4-Alkyl-2,2,6,6-tetramethyl-1,4,2,6-oxaazadisilinanes RN[CH2Si(Me)2]2O [R = Me (1), i-Pr (2)] were synthesized by two methods which provided good yields up to 84%. Low temperature NMR study of compounds (1) and (2) revealed a frozen ring inversion with the energy barriers of 8.5 and 7.7 kcal/mol at 163 and 143 K, respectively, which is substantially lower than that for their carbon analog, N-methylmorpholine. DFT calculations performed on the example of molecule (1) showed that N-Meax conformer to exist in the sofa conformation with the coplanar fragment C-Si-O-Si-C, and its N-Meeq conformer in a flattened chair conformation.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/4569
U6  - https://doi.org/10.1002/Poc.1605
SN  - 0894-3230
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Albanov, Alexander I.
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes: low temperature NMR study and quantum chemical calculations
Y1  - 2012
UR  - http://www.sciencedirect.com/science/article/pii/S0040402011018321
U6  - https://doi.org/10.1016/j.tet.2011.11.077
ER  - 
TY  - JOUR
A1  - Lazareva, Nataliya F.
A1  - Albanov, Alexander I.
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes low temperature NMR study and quantum chemical calculations
JF  - Tetrahedron
N2  - A number of N-substituted 2,2-dimethyl-1,4,2-oxazasilinanes 1 were synthesized and studied by variable temperature dynamic H-1 and C-13 NMR spectroscopy, room temperature N-15 NMR spectroscopy and theoretical calculations at the DFT and MP2 levels of theory. Both the preferred conformers were assigned and the barrier to the ring inversion of the saturated six-membered ring determined. From 1 the corresponding methyl iodide salts were produced, their structure studied by X-ray analysis and found to be in excellent agreement with the results of the theoretical calculations.
KW  - 1,4,2-Oxazasilinanes
KW  - Conformational analysis
KW  - Dynamic NMR
KW  - X-ray analysis
KW  - Quantum chemical calculations
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2011.11.077
SN  - 0040-4020
VL  - 68
IS  - 4
SP  - 1097
EP  - 1104
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - STD-DOSY : a new NMR method to analyze multi-component enzyme/substrate systems
N2  - A new approach to analyze multi-component Saturation Transfer Difference (STD) NMR spectra by combining the STD and the DOSY experiment is proposed. The resulting pulse sequence was successfully used to simplify an exemplary multi- component protein/substrate system by means of standard DOSY processing methods. Furthermore, the same experiment could be applied to calculate the ratio of saturated substrate molecules and its saturation rate in the case of competitive interactions. This ratio depends on the strength of this interaction between the substrates and the protein, so that this kind of information could be extracted from the results of our experiment.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/10907807
U6  - https://doi.org/10.1016/j.jmr.2009.11.007
SN  - 1090-7807
ER  - 
TY  - JOUR
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings
Y1  - 2013
SN  - 1090-7807
ER  - 
TY  - JOUR
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings
JF  - Journal of magnetic resonance
N2  - The conformational analyses of six non-rigid N-acetyl glucosamine (NAG) derivatives employing residual dipolar couplings (RDCs) and NOEs together with molecular dynamics (MD) simulations are presented. Due to internal dynamics we had to consider different conformer ratios existing in solution. The good quality of the correlation between theoretically and experimentally obtained RDCs show the correctness of the calculated conformers even if the ratios derived from the MD simulations do not exactly meet the experimental data. If possible, the results were compared to former published data and commented.
KW  - NMR
KW  - Residual dipolar couplings
KW  - Molecular dynamics
KW  - N-acetyl glucosamine derivatives
KW  - Carbohydrates
Y1  - 2011
U6  - https://doi.org/10.1016/j.jmr.2011.06.029
SN  - 1090-7807
VL  - 212
IS  - 1
SP  - 174
EP  - 185
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - GEN
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings (vol 212, pg 174, 2011)
T2  - Journal of magnetic resonance
Y1  - 2011
U6  - https://doi.org/10.1016/j.jmr.2011.09.017
SN  - 1090-7807
VL  - 213
IS  - 1
SP  - 210
EP  - 211
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Kovacs, J.
A1  - Toth, G.
A1  - Kleinpeter, Erich
A1  - Schilde, Uwe
T1  - Crystal structure of trans, cis-(ñ)-3ï-4-fluorophenyl)-2-phenylspiro[2H-1-benzothiopyran-34H,2ï-oxiran]-4-one 1- oxide, C22H15FO3S
Y1  - 2003
UR  - ftp://ftp.oldenbourg.de/pub/download/frei/ncs/218-2/1267-1023.pdf
SN  - 1433-7266
ER  - 
TY  - JOUR
A1  - Kolocouris, Antonios
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
A1  - Stylianakis, Ioannis
T1  - 2-Substituted and 2,2-disubstituted adamantane derivatives as models for studying substituent chemical shifts and C-H-ax center dot center dot center dot Y-ax cyclohexane contacts-results from experimental and theoretical NMR spectroscopic chemical shifts and DFT structures
JF  - Tetrahedron
N2  - The complete H-1 and C-13 NMR chemical shifts assignment for various 2-substituted and 2,2-disubstituted adamantane derivatives 1-38 in CDCl3 solution was realized on the basis of NMR experiments combined with chemical structure information and DFT-GIAO (B3LYP/6-31+G(d,p)-GIAO) calculations of chemical shifts in solution. Substituent-induced C-13 NMR chemical shifts (SCS) are discussed. C-H-ax center dot center dot center dot Y-ax contacts are a textbook prototype of steric hindrance in organic chemistry. The nature of these contacts will be further investigated in this work on basis of new adamantane derivatives, which are substituted at C-2 to provide models for 1,4-C-H-ax center dot center dot center dot Y-ax and 1,5-C-H-ax center dot center dot center dot Y-ax contacts. The B3LYP/6-31+G(d,p) calculations predicted the presence of NBO hyperconjugative attractive interactions between C-H-ax and Y-ax groups along C-H-ax center dot center dot center dot Y-ax contacts. The H-1 NMR signal separation, Delta delta(gamma-CH2), reflects the strength of the H-bonded C-H-ax center dot center dot center dot Y-ax contact. (C) 2015 Elsevier Ltd. All rights reserved.
KW  - 2-Substituted adamantane derivatives
KW  - 2,2-Disubstituted adamantane derivatives
KW  - H-1 NMR
KW  - C-13 NMR
KW  - B3LYP/6-31+G(d,p) calculations
KW  - GIAO calculations
KW  - Substituent chemical shifts
Y1  - 2015
U6  - https://doi.org/10.1016/j.tet.2015.01.044
SN  - 0040-4020
VL  - 71
IS  - 16
SP  - 2463
EP  - 2481
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Koetz, Joachim
A1  - Jagielski, Nicole
A1  - Kosmella, Sabine
A1  - Friedrich, Alwin
A1  - Kleinpeter, Erich
T1  - CdS nanocubes formed in phosphatidylcholin-based template phases
N2  - The paper is focused on the characterization and use of phosphatidylcholine (PC)-based inverse microemulsions as a template phase for the CdS nanoparticle formation. The optically clear, isotropic phase in the oil corner was identified as a "classicalö water-in-oil microemulsion by means of NMR-diffusion measurements. Because of the very small dimensions of the water droplets, the isotropic phase shows a Newtonian-like flow behavior, and adequate amounts of bulk water cannot be detected by DSC. It is demonstrated that this w/o microemulsion can be used successfully as a nanoreactor for the formation of CdS nanoparticles with diameters of 4-5 nm. During the following process of solvent evaporation the individual small CdS nanoparticles aggregate to significant larger cubic nanoparticles, with an edge length of 2-40 nm, arranged in well-defined mosaic-like superstructures. In presence of SDS the nanocubes were stable up to 800 °C. It has to be stated here that polyelectrolytes prevent the formation of such well-ordered superstructures.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/09277757
U6  - https://doi.org/10.1016/j.colsurfa.2006.01.013
SN  - 0927-7757
VL  - 288
SP  - 43
EP  - 1-3
ER  - 
TY  - JOUR
A1  - Koetz, Joachim
A1  - Günther, Claudia
A1  - Kosmella, Sabine
A1  - Kleinpeter, Erich
A1  - Wolf, Gunter
T1  - Polyelectrolyte induced structural changes in the isotropic phase of the system sulfobetaine/pentanol/toluene/ water
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Koch, Andreas
A1  - Thomas, Steffen
A1  - Kleinpeter, Erich
T1  - Ab-initio study, semi-empirical calculation and NMR spectroscopy of keto-enol tautomerism of triazolopyrimidines
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Koch, Andreas
A1  - Starke, Ines
A1  - Kleinpeter, Erich
T1  - Conformational study of Dibenzo crown ethers and their complexation with Li+ and Na+
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Koch, Andreas
A1  - Mikhova, Bozhana
A1  - Kleinpeter, Erich
T1  - Ab initio MP2/GIAO/NBO study of the delta-syn-axial effect in C-13 NMR spectroscopy
N2  - The C-13 chemical shifts of 20 rigid bicyclic compounds have been calculated with ab initio HF and MP2 methods. The calculations showed very good reproducibility of the experimental values. The molecular orbital interactions in the rigid, nearly planar delta-syn-axial fragments in the isomeric groups of norbornane derivatives 1.x-4.x were studied in detail and were employed to explain the deshielding delta-syn-axial effect in C-13 NMR spectroscopy. (C) 2004 Elsevier B.V. All rights reserved
Y1  - 2004
SN  - 0022-2860
ER  - 
TY  - JOUR
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Study of the tautomerism by experimentally and theoretically estimated 13C and 15N chemical shifts
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Restricted rotation about particial C, N Double Bond
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Ab-initio study and semiempirical calculations of keto-enol tautomerism of triazolopyrimidines
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Klinka, Karel D.
A1  - Imrich, Jan
A1  - Danihel, I.
A1  - Bohm, Stanislav
A1  - Kristian, Pavol
A1  - Harnul'akova, S.
A1  - Pihlaja, Kalevi
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Configuration and E/Z interconversion mechanism of O(S)-allyl-S(O)-methyl-N-(acridin-9-yl)iminothiocarbonate
N2  - The configuration and dynamic behavior of O-allyl-S-methyl-N-(acridin-9-yl)iminothiocarbonate (1) and its S- allyl-O-methyl regioisomer (2) were studied using quantum chemical calculations and by applying a novel graphical method to scatter maps obtained from MD simulations for evaluation of an NOE-weighted internuclear distance (r(NOE)). Energy calculations indicated that the Z configuration was predominant for each compound and, further, this was supported both by the calculated chemical shifts and the rNOE. Both N-inversion- and rotation-type transition-state structures were also calculated for the E/Z isomerization process, the results indicating that the preferred interconversion mechanism for 1 is N-inversion, but contrastingly, interconversion via rotation is equally as probable as N-inversion for 2. This supports the notion that one or the other or both pathways can be active and each system needs to be assessed on a case- by-case basis. Copyright (c) 2005 John Wiley & Sons, Ltd
Y1  - 2005
SN  - 0749-1581
ER  - 
TY  - JOUR
A1  - Klinka, Karel D.
A1  - Balentova, Eva
A1  - Bernát, Juraj
A1  - Imrich, Ján
A1  - Vavrusová, Martina
A1  - Pihlaja, Kalevi
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
T1  - Structural revision of products resulting from the reaction of methylhydrazine with acridin-9-yl isothiocyanate due to unexpected acridinyl migration And further reactions
N2  - The reaction of methyl acridin-9-ylthiosemicarbazide under basic conditions with methyl bromoacetate resulted in a 1,3-thiazolin-4-one structure as provided by X-ray crystallography. The structure forced a re-evaluation of the reactant methyl acridin-9-ylthiosemicarbazide, originally thought to be 2-methyl 4-acridin-9-ylthiosemicarbazide based on synthetic expectations, but which when examined by X-ray crystallography was found to be in fact the isomeric 2- methyl 1-acridin-9-ylthiosemicarbazide resulting from rearrangement via a spiro form which it is in equilibrium with in solution. The product resulting from reaction with methyl iodide was also studied and the previously reported semicarbazide produced by reaction with MNO was re-examined. In both cases, the 1,2 isomer rather than the 2,4 isomer was found to be present based on the sign of the 3JCH3,N11 coupling. Full characterization of the compounds was rendered by 1H, 13C, and 15N solution-state NMR, and in the solid state, by both 13C and 15N NMR.
Y1  - 2006
UR  - http://arkat-usa.org/home.aspx?VIEW=BROWSE&MENU=ARKIVOC
SN  - 1551-7004
ER  - 
TY  - JOUR
A1  - Klinka, Karel D.
A1  - Balentova, Eva
A1  - Bernát, Juraj
A1  - Imrich, Jan
A1  - Vavrusova, Martina
A1  - Kleinpeter, Erich
A1  - Pihlaja, Kalevi
A1  - Koch, Andreas
T1  - Tautomerism, regioisomerism, and cyclization reactions of acridinyl thiosemicarbazides
N2  - The regioselectivities of methyl- and phenylhydrazine with acridin-9-yl isothiocyanate (thus yielding thiosemicarbazides with acridine substituted on the urea-type side) were examined. Methythydrazine regioselectivity was high with the alpha-nitrogen atom overwhelmingly more nucleophilic than the beta-nitrogen atom; phenylhydrazine regioselectivity was poor but varied with the solvent and only in the case of ethanol was nucleophilic predominance of the alpha-nitrogen atom pronounced. Of note, whilst both phenyl thiosemicarbazides were present in solution only as spiro forms, the methyl product was present as an equilibrium mixture of open-chain and spiro thiosemicarbazides. Reactions on the NH2 blocked analogue of methyl acridin-9-ylthiosemicarbazide (1-isopropylidene-2- methylthiosemicarbazide) were also examined. Interestingly, present in the starting material itself was a structural motif of novelty wherein a triazolethione represented the major species of an equilibrium between cyclic and open-chain forms
Y1  - 2006
UR  - http://www3.interscience.wiley.com/journal/121521817/toc
U6  - https://doi.org/10.1002/jhet.5570430317
SN  - 0022-152X
ER  - 
TY  - JOUR
A1  - Klika, Karel D.
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - DFT computational studies of hydrogen bonding-based diastereomeric complexes : limitations and applications to enantiodifferentiation
N2  - Molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory have been performed on diastereomeric complexes formed between chiral carboxylate anions and chiral urea receptors, a combination previously demonstrated to enable enantiodifferentiation by electrochemical sensing. The calculations correctly predicted the stability order of the enantiomers in acetonitrile solution when the distinction between the enantiomers was above the declared threshold reliability value of 1 kcal mol;1 for computations at this level of theory. Thus, the calculations can not only be applied to predict the likely success of undertakings using the analytical method, it can also, provided ;E is sufficient, potentially be used to determine the absolute configuration of chiral analytes with at least the racemate in hand. The previously successful enantiodifferentiations of various amino acids and alcohols using chiral ion mobility spectroscopy (CIMS) with (S)-2-butanol as the chiral selector were also evaluated by DFT calculations. The calculations again correctly predicted the stability order of the enantiomers when the calculated ;E was above the threshold value though cases not providing a value for ;E above the threshold value was problematic for this system. Attempts to address this shortcoming included an expanded conformational evaluation, a broader analytical approach, and an extended basis set.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/01661280
U6  - https://doi.org/10.1016/j.theochem.2009.08.003
SN  - 0166-1280
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Werner, Peter
A1  - Linker, Torsten
T1  - Synthesis and NMR spectroscopic conformational analysis of benzoic acid esters of mono- and 1,4-dihydroxycyclohexane, 4-hydroxycyclohexanone and the -ene analogue - The more polar the molecule the more stable the axial conformer
JF  - Tetrahedron
N2  - para-Substituted benzoic acid esters of cyclohexanol, 1,4-dihydroxycyclohexane, 4-hydroxy-cyclohexanone and of the corresponding exo-methylene derivative were synthesized and the conformational equilibria of the cyclohexane skeleton studied by low temperature H-1 and C-13 NMR spectroscopy. The geometry optimized structures of the axial/equatorial chair conformers were computed at the DFT level of theory. Only one preferred conformation of the ester group was obtained for both the axial and the equatorial conformer, respectively. The content of the axial conformer increases with growing polarity of the 6-membered ring moiety; hereby, in addition, the effect of sp(2) hybridization/polarity of C(4)= O/C(4)= CH2 on the present conformational equilibria is critically evaluated. Another dynamic process could be studied, for the first time in this kind of compounds. (C) 2017 Elsevier Ltd. All rights reserved.
KW  - Conformational analysis
KW  - A-values of COOAr on cyclohexane
KW  - Benzoic acid esters
KW  - Dynamic NMR
KW  - DFT calculations
Y1  - 2017
U6  - https://doi.org/10.1016/j.tet.2017.04.029
SN  - 0040-4020
VL  - 73
SP  - 3801
EP  - 3809
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Werner, Peter
A1  - Koch, Andreas
T1  - Push-pull allenes-conjugation, (anti)aromaticity and quantification of the push-pull character
JF  - Tetrahedron
N2  - Structures, H-1/C-13 chemical shifts, and pi electron distribution/conjugation of an experimentally available and theoretically completed set of push-pull allenes Acc(2)C=C=CDon(2) (Acc=F, CHO, CF3, C  N; Don=t-Bu, OMe, OEt, SMe, SEt, NCH2R) have been computed at the OFT level of theory. Both orthogonal linear and orthogonal bent structures have been obtained. In the latter case the push-pull character could be quantified by the quotient method. The C-13 chemical shift of the central allene carbon atom C-2 and chemical shift differences Delta delta(C-1, C-2) and Delta delta(C-2, C-3) of allene carbon atoms proved to be a quantitative alternative. TSNMRS of ring-closed push-pull allenes have been computed in addition and were employed to identify polar, carbene-like and carbone-like canonical structures of these molecules.
KW  - Push-pull allenes
KW  - Push-pull character
KW  - C-13 NMR spectroscopy
KW  - Quotient method
KW  - TSNMRS
KW  - ICSS
KW  - Aromaticity
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2013.01.027
SN  - 0040-4020
VL  - 69
IS  - 11
SP  - 2436
EP  - 2445
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Thomas, Steffen
A1  - Uhlig, G.
A1  - Rudorf, Wolf-Dieter
T1  - Study of the distribution of pi-Electrons in Push-Pull Alkenes by 1H an 13C NMR spectroscopy
Y1  - 1993
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Thomas, Steffen
A1  - Fischer, G.
T1  - 13C and 15N NMR study of 1,2,4-Triazolo[1,5-a]pyrimidines with one tautomerism-introducing substituent
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Szatmári, István
A1  - Lázár, László
A1  - Koch, Andreas
A1  - Heydenreich, Matthias
A1  - Fulop, Ferenc
T1  - Visualization and quantification of anisotropic effects on the 1H NMR spectra of 1,3-oxazino[4,3- alpha]isoquinolines - indirect estimates of steric compression
N2  - The anisotropic effects of the phenyl, alpha- and beta-naphthyl moieties in four series of 1,3-oxazino[4,3- a]isoquinolines on the H-1 chemical shifts of the isoquinoline protons were calculated by employing the Nucleus Independent Chemical Shift (NICS) concept and Visualized as anisotropic cones by a through-space NMR shielding grid. The signs and extents of these spatial effects on the H-1 chemical shifts of the isoquinoline protons were compared with the experimental H-1 NMR spectra. The differences between the experimental delta (H-1)/ppm values and the calculated anisotropic effects of the aromatic moieties are discussed in terms of the steric compression that occurs in the Compounds studied.
Y1  - 2009
U6  - https://doi.org/10.1016/j.tet.2009.07.038
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Ströhl, D.
A1  - Peinze, S.
A1  - Brandt, W.
A1  - Schmidt, R.
A1  - Neubert, K.
T1  - The solution conformation of cyclic ß-casomorphine-5 analogues
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Ströhl, D.
A1  - Peinze, S.
T1  - Solution conformation of tripeptides by NMR spectroscopy and force field calculations
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stojanovic, Milovan
A1  - Markovic, Rade
A1  - Baranac-Stojanovic, Marija
T1  - Synthesis of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions
N2  - Syntheses of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined and discussed. The formation of (5,6)-membered systems was feasible with all nucleophiles tried (O, S and N), while the closing of the five-membered ring was restricted to O- and S-nucleophiles. The closure of a four-membered ring failed. Instead, the bicyclic (5,6)-membered acetal derivative and the tricyclic system with an eight-membered central ring were obtained from the substrates containing O and S nucleophilic moieties, respectively. The reaction outcome and stereochemistry are rationalized using quantum chemical calculations at B3LYP/6-31G(d) level. The exclusive cis-stereoselectivity in the formation of (5,6)- and (5,5)-membered systems results from thermodynamic control, whereas the formation of the eight-membered ring was kinetically controlled.
Y1  - 2012
SN  - 1477-0520
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stohß, S.
A1  - Schroth, W.
T1  - Stereochemistry and complexational behaviour of dibenzo-crown ethers
Y1  - 1992
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Starke, Ines
A1  - Ströhl, D.
A1  - Holdt, Hans-Jürgen
T1  - NMR spectroscopic study of the solution structure and complexational behaviour of bis-benzocrown ethers
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Starke, Ines
A1  - Ströhl, D.
A1  - Holdt, Hans-Jürgen
T1  - NMR spectroscopic study of the solution structure and complexational behaviour of bis-benzocrown ethers
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stamboliyska, Bistra A.
T1  - Hyperpolarizability of donor-acceptor azines subject to push-pull character and steric hindrance
N2  - The push-pull character of two series of donor-acceptor azines has been quantified by C-13, N-15 chemical shift differences of the partial C(1)=N(1) and N(2)=C(2) double bonds in the central linking C(1)=N(1)-N(2)=C(2) unit and by the quotient of the occupations of the bonding pi and anti-bonding pi* orbitals of these bonds. Excellent correlation of the latter push-pull parameter with the corresponding bond lengths d(C=N) strongly recommend both the occupation quotients pi*/pi and the corresponding bond lengths as reasonable sensors for quantifying the push, pull character along the C=N-N=C linking unit, for the donor-acceptor quality of the two series of azines and for the molecular hyperpolarizability beta(0) of these compounds. Within this context, reasonable conclusions concerning the interplay of steric hindrance in the chromophore, push-pull character and hyperpolarizability of the azines and their application as NLO materials will be drawn.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2009.09.026
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stamboliyska, Bistra A.
T1  - Quantification of the Push-Pull Character of Donor-Acceptor Triazenes
N2  - The Push-pull character of two series of donor-acceptor triazenes has been quantified by C-13 and N-15 chemical shift differences of the partial N(1)=N(2) and N(3)=C(4) double bonds in the central linking C=N-N=N-C unit and by the quotient of the occupations of both the bonding pi and antibonding orbitals pi* of these partial double bonds. Excellent correlations of the two estimates, to quantify the push-pull effect, with the bond lengths strongly recommend the occupation quotients pi*/pi, the N-15 chemical shift differences Delta delta[N(l),N(2)], and the corresponding bond lengths as reasonable sensors for quantifying charge alternation along the C=N-N=N-C linking unit, for the donor- acceptor quality of the triazenes 1 and 2 and for the molecular hyperpolarizability beta(0) of these compounds. Within this context, certain Substances can be strongly recommended for NLO application.
Y1  - 2008
UR  - http://pubs.acs.org/doi/full/10.1021/jo8013758
U6  - https://doi.org/10.1021/Jo8013758
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Shainyan, Bagrat A.
A1  - Suslova, Elena N.
T1  - Conformational analysis of N-phenyl- and N-trifyl-4,4-dimethyl-4-silathiane 1-sulfimides
Y1  - 2011
SN  - 0894-3230
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Shainyan, Bagrat A.
A1  - Suslova, Elena N.
T1  - Conformational analysis of 4,4-dimethyl-4-silathiane and its S-oxides
Y1  - 2011
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Shainyan, Bagrat A.
A1  - Kirpichenko, Svetlana V.
A1  - Shlykov, Sergei A.
T1  - Structure and Conformational Properties of 1,3,3-Trimethyl-1,3-Azasilinane : Gas Electron Diffraction, Dynamic NMR, and Theoretical Study.
Y1  - 2012
SN  - 1089-5639
ER  - 
TY  - GEN
A1  - Kleinpeter, Erich
A1  - Shainyan, Bagrat A.
T1  - Very low-temperature dynamic Si-29 NMR study of the conformational equilibrium of (1,1-phenyl-1,1-silacyclohex-1-yl)disiloxane
T2  - Magnetic resonance in chemistry
Y1  - 2019
U6  - https://doi.org/10.1002/mrc.4870
SN  - 0749-1581
SN  - 1097-458X
VL  - 57
IS  - 6
SP  - 317
EP  - 319
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Seidl, Peter Rudolf
T1  - The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis
N2  - Carbon-13 NMR is widely used in the determination of the stereochemistry of organic compounds. Changes in chemical shifts caused by interactions of groups that are close in space normally result in shielding of the carbon and deshielding of the hydrogen nuclei that are involved. This is not always the case, however, and further work on the origin of these effects would be desirable. Early applications of theoretical methods to the study of NMR shielding parameters were not particularly successful, but in recent years, the calculation of NMR shielding parameters by theoretical methods has developed into a useful and popular tool for structural studies by NMR. A promising approach to the problem of distinguishing and evaluating stereochemical influences on carbon and hydrogen chemical shifts is provided by natural chemical shielding (NCS) analysis. This method allows a partitioning of theoretical NMR shieldings into magnetic contributions from bonds and lone pairs of the molecule using the natural bond orbital (NBO) method. In order to investigate the origins of steric effects, we employed the NCS analysis to axial/equatorial-Me-cyclohexane, norbornane and exo/endo-Me-norbornane, in addition to n-pentane in the anti, gauche and g(P) g(M) conformations. Our results indicate that distortions in molecular structure due to steric effects can result in bond stretching or compression or in angular distortions. Changes in bond lengths result in the predictable shielding or deshielding of the nuclei that are involved. Where the molecular framework may be distorted to alleviate strain, chemical shifts appear to reflect changes in angles. Copyright (C) 2004 John Wiley Sons, Ltd
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Seidl, Peter Rudolf
T1  - The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis
Y1  - 2005
SN  - 0894-3230
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Schulenburg, Anja
A1  - Zug, Ines
A1  - Hartmann, Horst
T1  - The interplay of thio(seleno)amide/vinylogous thio(seleno)amide "Resonance" and the anisotropic effect of thiocarbonyl and selenocarbonyl functional groups
N2  - [GRAPHICS] Amino-substituted thio(seleno)acrylamides 1-4 were synthesized and their H-1 and C-13 NMR spectra assigned. Both the NMR data and the results of theoretical calculations at the ab initio level of theory were employed to elucidate the adopted structures of the compounds in terms of E/Z isomerism and s-cis/s-trans configuration. In the case of the asymmetrically N(Me)Ph-substituted compounds, ab initio GIAO-calculated ring current effects of the N-phenyl group were applied to successfully determine the preferred conformer bias. The restricted rotations about the two C-N partial double bonds were studied by DNMR and the barriers to rotation (Delta G(c)(double dagger)) determined at the coalescence temperatures, and these were discussed with respect to the structural differences between the compounds. The barriers to rotation were also calculated at the ab initio level of theory where the best results (R-2 = 0.8746) were obtained only with inclusion of the solvent at the SCIPCMHF/6-31G* level of theory. The calculations also provided means of assessing structural influences which were not available due to inaccessible rotation barriers. By means of natural bond orbital (NBO) analysis of 1-4, the occupation numbers of nitrogen lone pairs and bonding/antibonding pi/pi* orbitals were shown to quantitatively describe thio(seleno)amide/vinylogous thio(seleno)amide "resonance". Finally, the thio(seleno)carbonyl anisotropic effect was quantitatively calculated by the GIRO method and visualized by isochemical shielding surfaces (ICSS). Only marginal differences between the two anisotropic effects were calculated and are therefore of questionable utility for previous and future applications with respect to stereochemical assignments
Y1  - 2005
SN  - 0022-3263
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Schulenburg, Anja
T1  - Quantification of the push-pull effect in tolanes and a revaluation of the factors affecting the C-13 chemical shifts of the carbon atoms of the C=C triple bond
N2  - Variously substituted tolanes were employed to show that the push-pull effect is also active in C equivalent to C triple bonds by the successful correlation of the occupation quotient pi*/pi of the pi orbital in resonance with the substituted phenyl moieties of tolanes versus the bond length of the C equivalent to C triple bond. In addition, the influences of the ortho phenyl ring substituents on the C-13 chemical shifts of the triple bond carbon atoms, which were estimated by Rubin et al.(4) to be "inapplicable for describing triple bond polarization", were re-evaluated, leading to the conclusion that, while anisotropic effects of ortho substituents are negligible, the steric ortho-substituent effects do in fact dominate the deviations obtained. A detailed theoretical NBO/NCS study has been employed to illuminate the facts of this case
Y1  - 2006
UR  - http://pubs.acs.org/journal/joceah
U6  - https://doi.org/10.1021/Jo060199j
SN  - 0022-3263
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Schulenburg, A.
T1  - Quantification of the push-pull effect in substituted alkenes
N2  - The quotient of the occupation numbers of pi bonding and pi* antibonding orbitals of the central C=C partial double bond, pi*(C=C)/pi(C=C), proved to be a useful parameter to quantify the push-pull effect completely for the first time in substituted alkenes by examination of a comprehensive set of compounds. (c) 2005 Elsevier Ltd. All rights reserved
Y1  - 2005
SN  - 0040-4039
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Schainyan, Bagrat A.
A1  - Kirpichenko, Svetlane V.
T1  - Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane : low temperature dynamic NMR and computational study
N2  - 1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the PhaxMeeq and PheqMeax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined.
Y1  - 2012
SN  - 1551-7004
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Rolla, Nadja
A1  - Koch, Andreas
A1  - Taddei, Fernando
T1  - Hyperconjugation and the increasing bulk of OCOCX3 substituents in trans-1,4-disubstituted cyclohexanes destabilize the diequatorial conformer
N2  - The trans diesters of 1,4-cyclohexanediol with a number of acetic acid analogues, CX3COOH, of varying steric hindrance and polarity (CX3 = Me, Et, iso-Pr, tert-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, CBr3) were synthesized, and the axial, axial/equatorial, equatorial conformational equilibria were studied by low-temperature H-1 NMR spectroscopy in CD2Cl2. The structures and relative energies of the axial, axial and equatorial, equatorial conformers were calculated at both the MP2/6-311G* and the MP2/6-311+G* levels of theory, and it was only by including diffuse functions that a good correlation of Delta G degrees(calcd) vs Delta G(exptl) could be obtained. Both the structures and the energy differences of the axial, axial and equatorial, equatorial conformers are discussed with respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions sigma(C-C)/sigma(C-H)->sigma*(C-O), together with a steric effect which also destabilizes the equatorial, equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference of the axial, axial conformers with respect to their equatorial, equatorial analogues was greater than expected from the conformational energies of the corresponding substituents in the monosubstituted cyclohexyl esters. The reason for this very interesting and unexpected result is also discussed
Y1  - 2006
UR  - http://pubs.acs.org/journal/joceah
U6  - https://doi.org/10.1021/Jo0600858
SN  - 4393-4399
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Pihlaja, Kalevi
A1  - Sinkkonen, Jari
A1  - Stájer, Gezá
A1  - Koch, Andreas
T1  - 1-Oxo-1,3-dithiolanesùsynthesis and stereochemistry
N2  - 1-Oxo-1,3-dithiolane (4) and its cis- andtrans-2-methyl (5,6), -4-methyl (7,8) and -5-methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3-dithiolanes (1-3) with NaIO4 in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with 1H and 13C NMR spectroscopy and molecular modelling. The sulfoxides 4-6 and 8-10 attain two S(1) type envelopes (sometimes slightly distorted) the S=Oax envelope greatly dominating. Cis-4-methyl-1-oxo-1,3-dithiolane is a special case exhibiting both two closely related S=Oax (30 and 27%) as well as S=Oeq (21 and 22%) forms [S(1) and C(4) envelopes, respectively]. The relative energies of these conformations, the values of 1H-1H coupling constants and 1H and 13C chemical shifts were estimated by computational methods and they support well the conclusions based on the experimental data.
Y1  - 2011
SN  - 0749-1581
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Pihlaja, Kalevi
T1  - Functions containing a thiocarbonyl group and at least one halogen, also at least one chalcogen and no halogen
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Neuvonen, Kari
A1  - Neuvonen, Helmi
A1  - Koch, Andreas
T1  - Taft equation in the light of NBO computations : Introduction of a novel polar computational substituent constant scale for alkyl groups
Y1  - 2012
SN  - 2210-271X
ER  -