title: 1-Oxo-1,3-dithiolanes--synthesis and stereochemistry.
abstract: 1-Oxo-1,3-dithiolane (4) and its cis- and trans-2-methyl (5,6), -4-methyl (7,8) and -5-methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3-dithiolanes (1-3) with NaIO(4) in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with (1)H and (13)C NMR spectroscopy and molecular modelling. The sulfoxides 4-6 and 8-10 attain two S(1) type envelopes (sometimes slightly distorted) the S=O(ax) envelope greatly dominating. Cis-4-methyl-1-oxo-1,3-dithiolane is a special case exhibiting both two closely related S=O(ax) (30 and 27%) as well as S=O(eq) (21 and 22%) forms [S(1) and C(4) envelopes, respectively]. The relative energies of these conformations, the values of (1)H-(1)H coupling constants and (1)H and (13)C chemical shifts were estimated by computational methods and they support well the conclusions based on the experimental data.
authors.affiliation: Department of Chemistry, University of Turku, Vatselankatu 2, FI-20014, Turku, Finland. kpihlaja@utu.fi
authors.forename: Kalevi
authors.initials: K
authors.lastname: Pihlaja
authors.forename: Jari
authors.initials: J
authors.lastname: Sinkkonen
authors.forename: Gezá
authors.initials: G
authors.lastname: Stájer
authors.forename: Andreas
authors.initials: A
authors.lastname: Koch
authors.forename: Erich
authors.initials: E
authors.lastname: Kleinpeter
mesh_terms: D006571:Heterocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D006571:Heterocyclic Compounds; C012948:1,3-dithiolane