TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Kirpichenko, Svetlana V.
A1  - Kleinpeter, Erich
T1  - Stereochemistry of 3-isopropoxy-3-methyl-1,3-oxasilinane-the first 3-silatetrahydropyran with an exo-cyclic RO-Si bond
JF  - Tetrahedron
N2  - 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.
KW  - 1,3-Oxasilinanes
KW  - Conformational equilibrium
KW  - Barrier to ring inversion
KW  - Solvent effects
KW  - Assignment of stereochemistry
Y1  - 2015
U6  - https://doi.org/10.1016/j.tet.2015.07.047
SN  - 0040-4020
VL  - 71
IS  - 38
SP  - 6720
EP  - 6726
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
T1  - Silacyclohexanes and silaheterocyclohexanes-why are they so different from other heterocyclohexanes?
JF  - Tetrahedron
N2  - Stereochemical studies on silaheterocyclohexanes is a 'hot topic' as evidenced by the growing number of publications. During last 10 years a substantial number of substituted silacyclohexanes and heterocyclohexanes containing sulfur, oxygen or nitrogen as the second (or third) heteroatom have been synthesized and studied by variable temperature dynamic NMR spectroscopy, gas-phase electron diffraction, variable temperature IR, Raman, microwave spectroscopy with respect to thermodynamic (frozen conformational equilibria) and kinetic (barrier to ring inversion) information. As the stereochemistry of cyclohexane and its N-, O-, P-, S-hetero analogues is one of keystones of modern theoretical and synthetic organic and heterocyclic chemistry, the stereochemistry of silacyclohexane and its hetero analogs is an important element of theoretical and synthetic organosilicon chemistry. The various classes of saturated six-membered rings were critically compared and studied in detail with respect to differences in their stereochemistry and dynamic behavior.
KW  - Silacyclohexanes
KW  - Silaheterocyclohexanes
KW  - Conformational equilibrium
KW  - Barrier to ring inversion
KW  - Steric effects
KW  - Electrostatic effects
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2013.04.126
SN  - 0040-4020
VL  - 69
IS  - 29
SP  - 5927
EP  - 5936
PB  - Elsevier
CY  - Oxford
ER  -