Conformational analysis of cis-3, 5-dioxa-bicyclo[5.4.0]undecane and its 4-substituted derivatives by DNMR, molecular modeling, and GIAO/DFT methods.
Temperature-dependent (1)H and (13)C-NMR spectra of the title compounds are presented. Coalescence effects are discussed and assigned to dynamic process--the interconversion of bicyclic system. The free energies of activation covered the range 39-52 kJ/mol. The dioxepane ring adopts twist-chair (TC) conformation. GIAO/DFT calculation of isotropic shieldings for the set of low-energy conformations showed that only one conformer is present at 298 K in solution that matched well with experimental data.
Migda
Wojciech
W
Department of Organic Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.
Stankiewicz
Anna
A
Szneler
Edward
E
Ulman
Lucyna
L
Rys
Barbara
B
D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000592:standards; D008958:Models, Molecular; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D011522:Protons; D012015:Reference Standards; D013696:Temperature
D019086:Bridged Bicyclo Compounds, Heterocyclic; D002247:Carbon Isotopes; D011522:Protons