@article{KleinpeterHeydenreichKochetal.2012,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Koch, Andreas and Linker, Torsten},
  title     = {Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer},
  series = {Tetrahedron},
  volume    = {68},
  journal   = {Tetrahedron},
  number    = {10},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2012.01.022},
  pages     = {2363 -- 2373},
  year      = {2012},
  abstract  = {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.},
  language  = {en}
}
@article{LazarevaAlbanovShainyanetal.2012,
  author    = {Lazareva, Nataliya F. and Albanov, Alexander I. and Shainyan, Bagrat A. and Kleinpeter, Erich},
  title     = {Synthesis and conformational properties of substituted 1,4,2-oxazasilinanes low temperature NMR study and quantum chemical calculations},
  series = {Tetrahedron},
  volume    = {68},
  journal   = {Tetrahedron},
  number    = {4},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2011.11.077},
  pages     = {1097 -- 1104},
  year      = {2012},
  abstract  = {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.},
  language  = {en}
}
@article{ShainyanKleinpeter2012,
  author    = {Shainyan, Bagrat A. and Kleinpeter, Erich},
  title     = {Conformational preferences of Si-Ph,H and Si-Ph,Me silacyclohexanes and 1,3-thiasilacyclohexanes. Additivity of conformational energies in 1,1-disubstituted heterocyclohexanes},
  series = {Tetrahedron},
  volume    = {68},
  journal   = {Tetrahedron},
  number    = {1},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2011.10.082},
  pages     = {114 -- 125},
  year      = {2012},
  abstract  = {The conformational equilibria of 1-phenyl-1-silacyclohexane 1, 3-phenyl-1,3-thiasilacyclohexane 2, 1-methyl-1-phenyl-1-silacyclohexane 3, and 3-methyl-3-phenyl-1,3-thiasilacyclohexane 4 have been studied for the first time by low temperature C-13 NMR spectroscopy at 103 K. Predominance of the equatorial conformer of compound 1 (Ph-eq/Ph-ax=78\%:22\%) is much less than in its carbon analog, phenylcyclohexane (nearly 100\% of Ph-eq). And in contrast to 1-methyl-1-phenylcyclohexane, the conformers with the equatorial Ph group are predominant for compounds 3 and 4: at 103 K, Ph-eq/Ph-ax ratios are 63\%:37\% (3) and 68\%:32\% (4). As the Si-C bonds are elongated with respect to C-C bonds, the barriers to ring inversion are only between 5.2-6.0 (ax -> eq) and 5.4-6.0 (eq -> ax) kcal mol(-1). Parallel calculations at the DFT and MP2 level of theory (as well as the G2 calculations for compound 1) show qualitative agreement with the experiment. The additivity/nonadditivity of conformational energies of substituents on cyclohexane and silacyclohexane derivatives is analyzed. The geminally disubstituted cyclohexanes containing a phenyl group show large deviations from additivity, whereas in 1-methyl-1-phenyl-1-silacyclohexane and 3-methyl-3-phenyl-1,3-thiasilacyclohexane the effects of the methyl and phenyl groups are almost additive. The reasons for the different conformational preferences in carbocyclic and heterocyclic compounds are analyzed using the homodesmotic reactions approach.},
  language  = {en}
}
@article{ShainyanKirpichenkoKleinpeter2012,
  author    = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich},
  title     = {Synthesis and conformational analysis of 1,3-azasilinanes},
  series = {Tetrahedron},
  volume    = {68},
  journal   = {Tetrahedron},
  number    = {36},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2012.05.106},
  pages     = {7494 -- 7501},
  year      = {2012},
  abstract  = {1-Isopropyl-3-methyl-3-phenyl-1,3-azasilinane 1 and 1-isopropyl-3,3-dimethyl-1,3-azasilinane 2 were synthesized and a detailed analysis of their NMR spectra, conformational equilibria and ring inversion processes is presented. Low temperature H-1/C-13 NMR spectroscopy, iteration of the H-1 NMR spectra and quantum chemical calculations showed slight predominance of the PheqMeax over the PhaxMeeq conformer of 1 at low temperature. The barrier for the chair to chair interconversion of both compounds was measured to be 8.25 kcal/mol.},
  language  = {en}
}
@article{CsuetoertoekiSzatmariKochetal.2012,
  author    = {Cs{\"u}t{\"o}rt{\"o}ki, Renata and Szatmari, Istvan and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc},
  title     = {Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2-c] quinazolin-13-ones},
  series = {Tetrahedron},
  volume    = {68},
  journal   = {Tetrahedron},
  number    = {24},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2012.04.026},
  pages     = {4600 -- 4608},
  year      = {2012},
  abstract  = {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.},
  language  = {en}
}
@article{CsuetoertoekiSzatmariHeydenreichetal.2012,
  author    = {Csuetoertoeki, Renata and Szatmari, Istvan and Heydenreich, Matthias and Koch, Andreas and Starke, Ines and Fueloep, Ferenc and Kleinpeter, Erich},
  title     = {Novel piperidine-fused benzoxazino- and quinazolinonaphthoxazines-synthesis and conformational study},
  series = {TETRAHEDRON},
  volume    = {68},
  journal   = {TETRAHEDRON},
  number    = {31},
  publisher = {PERGAMON-ELSEVIER SCIENCE LTD},
  address   = {OXFORD},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2012.05.048},
  pages     = {6284 -- 6288},
  year      = {2012},
  abstract  = {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.},
  language  = {en}
}