@article{KleinpeterHeydenreichShainyan2021,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Shainyan, Bagrat A.},
  title     = {At the experimental limit of the NMR conformational analysis},
  series = {Organic letters},
  volume    = {23},
  journal   = {Organic letters},
  number    = {2},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1523-7060},
  doi       = {10.1021/acs.orglett.0c03878},
  pages     = {405 -- 409},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{ShainyanBelyakovSigolaevetal.2017,
  author    = {Shainyan, Bagrat A. and Belyakov, Alexander V. and Sigolaev, Yurii F. and Khramov, Alexander N. and Kleinpeter, Erich},
  title     = {Molecular Structure and Conformational Analysis of 1-Phenyl-1-X-1-Silacyclohexanes (X = F, Cl) by Electron Diffraction, Low-Temperature NMR, and Quantum Chemical Calculations},
  series = {The journal of organic chemistry},
  volume    = {82},
  journal   = {The journal of organic chemistry},
  number    = {1},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0022-3263},
  doi       = {10.1021/acs.joc.6b02538},
  pages     = {461 -- 470},
  year      = {2017},
  abstract  = {The molecular structure and conformational preferences of 1-phenyl-1-X-1-silacyclohexanes C5H10Si(Ph,X) (X = F (3), Cl (4)) were studied by gas-phase electron diffraction, low-temperature NMR spectroscopy, and high-level quantum chemical calculations. In the gas phase only three (3) and two (4) stable conformers differing in the axial or equatorial location of the phenyl group and the angle of rotation about the Si-C-ph bond (axi and axo denote the Ph group lying in or out of the X-Si-C-ph plane) contribute to the equilibrium. In 3 the ratio Ph-eq:Ph-axo:Ph-axi is 40(12):55(24):5 and 64:20:16 by experiment and theory, respectively. In 4 the ratio Ph-eq:Ph-axo is 79(15):21(15) and 71:29 by experiment and theory (M06-2X calculations), respectively. The gas-phase electron diffraction parameters are in good agreement with those obtained from theory at the M06-2X/aug-ccPVTZ and MP2/aug-cc-pVTZ levels. Unlike the case for M06-2X, MP2 calculations indicate that 3-Ph-eq conformer lies 0.5 kcal/mol higher than the 3-Ph-axo, conformer. As follows from QTAIM analysis, the phenyl group is more stable when it is located in the axial position but produces destabilization of the silacyclohexane ring: By low temperature NMR spectroscopy the six-membered ring interconversion could be frozen, at 103 K and the present conformational equilibria of 3 and 4 could be determined. The ratio of the conformers is 3-Ph-eq:3-Ph-ax = (75-77):(23-25) and 4-Ph-eq:4-Ph-ax = 82:18.},
  language  = {en}
}
@article{KirpichenkoShainyanKleinpeteretal.2018,
  author    = {Kirpichenko, Svetlana and Shainyan, Bagrat A. and Kleinpeter, Erich and Shlykov, Sergey A. and Tran Dinh Phien, and Albanov, Alexander},
  title     = {Synthesis of 3-fluoro-3-methyl-3-silatetrahydropyran and its conformational preferences in gas and solution by GED, NMR and theoretical calculations},
  series = {Tetrahedron},
  volume    = {74},
  journal   = {Tetrahedron},
  number    = {15},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2018.02.055},
  pages     = {1859 -- 1867},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@article{ShainyanSuslovaTranDinhPhienetal.2018,
  author    = {Shainyan, Bagrat A. and Suslova, Elena N. and Tran Dinh Phien, and Shlykov, Sergey A. and Kleinpeter, Erich},
  title     = {Synthesis, conformational preferences in gas and solution, and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations},
  series = {Tetrahedron},
  volume    = {74},
  journal   = {Tetrahedron},
  number    = {32},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2018.06.023},
  pages     = {4299 -- 4307},
  year      = {2018},
  abstract  = {1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature C-13 NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph-ax conformer (1-Ph-eq:1-Ph-ax ratio of 20:80\%, Delta G degrees (317 K) = -0.87 kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C-ipso and C(1,5) carbon signals in C-13 NMR spectra at 103 K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2 = 1:1:3), which is still liquid at 100 K, the 1-Ph-eq conformer was found to be the preferred one [(1-Ph-eq: 1-Ph-ax = 77\%: 23\%, K = 77/23 = 2.8; -Delta G degrees = -RT In K (at 103 K) = 0.44 +/- 0.1 kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X = H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph-ax conformer in the gas phase and of the Ph-eq conformer in solution is confirmed.},
  language  = {en}
}
@article{ShainyanSuslovaTranDinhPhienetal.2019,
  author    = {Shainyan, Bagrat A. and Suslova, Elena N. and Tran Dinh Phien, and Shlykov, Sergey A. and Heydenreich, Matthias and Kleinpeter, Erich},
  title     = {1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational preferences in gas and solution by GED, NMR and theoretical calculations},
  series = {Tetrahedron},
  volume    = {75},
  journal   = {Tetrahedron},
  number    = {46},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2019.130677},
  pages     = {9},
  year      = {2019},
  abstract  = {1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature C-13 and Si-29 NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeSaxPheq conformer in gas phase (1-Ph-eq :1-Ph-ax = 55:45, Delta G degrees = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph-eq:1-Ph-ax = 65:35, Delta G degrees = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory. (C) 2019 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{ShainyanKirpichenkoKleinpeter2017,
  author    = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich},
  title     = {Conformational Preferences of the Phenyl Group in 1-Phenyl-1-X-1-silacyclo-hexanes (X = MeO, HO) and 3-Phenyl-3-X-3-silatetrahydropyrans (X = HO, H) by Low Temperature C-13 NMR Spectroscopy and Theoretical Calculations},
  series = {The journal of organic chemistry},
  volume    = {82},
  journal   = {The journal of organic chemistry},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0022-3263},
  doi       = {10.1021/acs.joc.7b02505},
  pages     = {13414 -- 13422},
  year      = {2017},
  abstract  = {New Si-phenyl-substituted silacyclohexanes and 3-silatetrahydropyrans have been synthesized and studied with respect to the conformational equilibria of the heterosix-membered ring by low temperature C-13 NMR spectroscopy and quantum chemical calculations. For 1-methoxy-1-phenylsilacyclohexane 1 and 3-phenyl-3-silatetrahydropyran 4 the conformational equilibria could be frozen and assigned. The Ph-ax reversible arrow Ph-eq equilibrium constants at 103 K are 2.21 for 1 and 4.59 for 4. In complete agreement with former studies of similar silicon compounds, molecules 1 and 4 prefer to adopt the Pheq conformation. The conformational equilibria of 1-hydroxy-1-phenylsilacydohexane 2 and 3-hydroxy-3-phenyl-3-silatetrahydropyran 3 could not be frozen at 100 K and proved to be heavily one-sided (if not anancomeric). Obviously, there is a general trend of predominance of Phax conformer in the gas phase and of Pheq in solution. For the isolated molecules of silanols 2 and 3, calculations allowed to explain the axial predominance of the phenyl group by a larger polarization of the Si-Ph than of the Si-O bond in the Phax conformer and additional destabilization of 3-Ph-eq conformer by repulsion of unidirectional dipoles of the endocyclic oxygen lone pair and of the highly polar axial Si-O bond.},
  language  = {en}
}
@article{ShainyanKirpichenkoKleinpeteretal.2015,
  author    = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich and Shlykov, Sergey A. and Osadchiy, Dmitriy Yu.},
  title     = {Molecular structure and conformational analysis of 3-methyl-3-phenyl-3-silatetrahydropyran. Gas-phase electron diffraction, low temperature NMR and quantum chemical calculations},
  series = {Tetrahedron},
  volume    = {71},
  journal   = {Tetrahedron},
  number    = {23},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2015.03.117},
  pages     = {3810 -- 3818},
  year      = {2015},
  abstract  = {The molecular structure and conformational behavior of 3-methyl-3-phenyl-3-silatetrahydropyran 1 was studied by gas-phase electron diffraction (GED-MS), low temperature C-13 NMR spectroscopy (LT NMR) and theoretical calculations. The 1-Ph-eq and 1-Ph-ax conformers were located on the potential energy surface. Rotation about the Si-C-ph bond revealed the phenyl ring orthogonal to the averaged plane of the silatetrahydropyran ring for 1-Ph-eq and a twisted orientation for 1-Ph-ax. Theoretical calculations and GED analysis indicate the predominance of 1-Ph-ax in the gas phase with the ratio of conformers (GED) 1-Ph-eq:1-Ph-ax=38:62 (Delta G degrees(307)=-0.29 kcal/mol). In solution, LT NMR spectroscopy gives almost the opposite ratio Ph-eq:1-Ph-ax=68:32 (Delta G degrees(103)=0.16 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of compound 1 in the gas phase and in solution. (C) 2015 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{ShainyanKirpichenkoKleinpeter2015,
  author    = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Kleinpeter, Erich},
  title     = {Stereochemistry of 3-isopropoxy-3-methyl-1,3-oxasilinane-the first 3-silatetrahydropyran with an exo-cyclic RO-Si bond},
  series = {Tetrahedron},
  volume    = {71},
  journal   = {Tetrahedron},
  number    = {38},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2015.07.047},
  pages     = {6720 -- 6726},
  year      = {2015},
  abstract  = {Molecular structure and conformational behavior of 3-isopropoxy-3-methyl-3-oxasilinane is studied by low temperature C-13 NMR spectroscopy and theoretical calculations (DFT, MP2). Two conformers, 1-ROax and 1-ROeq, were found experimentally and located on the potential energy surface. LT C-13 NMR spectroscopy gives almost equal population of the two conformers at 98 K with Delta G(98K)degrees=0.02 kcal/mol in favor of 1-ROax and Delta G(98K)(\#)=4.5 kcal/mol. The corresponding DFT calculated values (Delta G(98K)degrees=0.03 kcal/mol, Delta G(98K)(\#)=5.1 kcal/mol) are in excellent agreement with the experiment. Detailed DFT and MP2 calculations of the solvent effect on the conformational equilibrium were performed and highlighted the leveling out of the two conformers when transferred from gas to solution. (C) 2015 Published by Elsevier Ltd.},
  language  = {en}
}
@article{ShainyanKirpichenkoChipaninaetal.2015,
  author    = {Shainyan, Bagrat A. and Kirpichenko, Svetlana V. and Chipanina, Nina N. and Oznobikhina, Larisa P. and Kleinpeter, Erich and Shlykov, Sergey A. and Osadchiy, Dmitriy Yu.},
  title     = {Synthesis and Conformational Analysis of 3-Methyl-3-silatetrahydropyran by GED, FTIR, NMR, and Theoretical Calculations: Comparative Analysis of 1-Hetero-3-methyl-3-silacyclohexanes},
  series = {The journal of organic chemistry},
  volume    = {80},
  journal   = {The journal of organic chemistry},
  number    = {24},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0022-3263},
  doi       = {10.1021/acs.joc.5b02355},
  pages     = {12492 -- 12500},
  year      = {2015},
  abstract  = {3-Methyl-3-silatetrahydropyran 1 was synthesized and its molecular structure and conformational behavior was studied by gas-phase electron diffraction (GED), FTIR, low temperature H-1 and C-13 NMR spectroscopy, and by theoretical calculations (DFT, MP2). Two conformers; 1-ax and 1-eq; were located on the potential energy Surface. In the gas phase; a slight predominance of the axial conformer was determined, with the ratio 1-ax:1-eq = 54(9):46(9) (from GED) or 53:47 or 61;39 (from IR). In solution, LT NMR spectroscopy at 103 K gives the ratio 1-ax:1-eq = 35:65 (-Delta G(103)degrees = 0.13 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the corresponding solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of 3-methyl-3-silatettahydropyran in the gas phase and in solution. Comparative analysis of the effect of heteroatom in 1-hetero-3-methyl-3-silacyclohexanes on the structure, stereoelectronic interactions, and relative energies of the conformers is done.},
  language  = {en}
}
@article{ShainyanKleinpeter2014,
  author    = {Shainyan, Bagrat A. and Kleinpeter, Erich},
  title     = {Conformational flexibility of 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline and its monoheterocyclic analogs},
  series = {Russian journal of general chemistry},
  volume    = {84},
  journal   = {Russian journal of general chemistry},
  number    = {7},
  publisher = {Pleiades Publ.},
  address   = {New York},
  issn      = {1070-3632},
  doi       = {10.1134/S1070363214070135},
  pages     = {1325 -- 1329},
  year      = {2014},
  abstract  = {Conformational behavior of the first cyclic organosilicon vinylsulfide, 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline as well as its monoheterocyclic analogs, 3,4-dihydro-2H-pyran, 3,4-dihydro-2H-thiopyran, and 1,1-dimethyl-1,2,3,4-tetrahydrosiline is studied in comparison with the carbocyclic analog, cyclohexene, using the methods of low-temperature NMR spectroscopy and theoretical calculations at the DFT and MP2 levels of theory. The barrier to the ring inversion with respect to that in cycloxene is increased in 3,4-dihydro-2H-pyran and 1,1-dimethyl-1,2,3,4-tetrahydrosiline, but, in contrast to the suggestions made in the literature, is decreased in 3,4-dihydro-2H-thiopyran. In 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline the barrier is intermediate between those in the corresponding monoheterocycles, 1,1-dimethyl-1,2,3,4-tetrahydrosiline and 3,4-dihydro-2H-thiopyran. The observed variations are rationalized from the viewpoint of the interaction of the pi-electrons of the C=C double bond with the orbitals of heteroatoms in the ring. The structure of the transition state for the ring inversion is discussed.},
  language  = {en}
}