title: 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.
abstract: 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.
authors.affiliation: Department of Organic Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Migda
authors.forename: Anna
authors.initials: A
authors.lastname: Stankiewicz
authors.forename: Edward
authors.initials: E
authors.lastname: Szneler
authors.forename: Lucyna
authors.initials: L
authors.lastname: Ulman
authors.forename: Barbara
authors.initials: B
authors.lastname: Rys
mesh_terms: 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
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D002247:Carbon Isotopes; D011522:Protons