@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{ShainyanMoskalikHeydenreichetal.2014, author = {Shainyan, Bagrat A. and Moskalik, Mikhail Yu and Heydenreich, Matthias and Kleinpeter, Erich}, title = {Conformational equilibrium and dynamic behavior of bis-N-triflyl substituted 3,8-diazabicyclo[3.2.1]octane}, series = {Magnetic resonance in chemistry}, volume = {52}, journal = {Magnetic resonance in chemistry}, number = {8}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0749-1581}, doi = {10.1002/mrc.4086}, pages = {448 -- 452}, year = {2014}, abstract = {Restricted rotation about the N-S partial double bonds in a bis-N-triflyl substituted 3,8-diazabicyclo[3.2.1]octane derivative 1 has been frozen at low temperature (Delta G* = 11.6 kcal mol(-1)), and the existence of all four rotamers about the two N-S bonds, 3-in, 8-in, 3-in, 8-out, 3-out, 8-in, and 3-out, 8-out, respectively, proved experimentally by NMR spectroscopy and theoretically by DFT and MP2 calculations. Copyright (C) 2014 John Wiley \& Sons, Ltd.}, language = {en} }