title: Conformational mobility of thianthrene-5-oxide.
abstract: [reaction: see text] Data on the apparent dipole moment of thianthrene-5-oxide (1) and (1)H NMR spectra in different solvents support the conformational mobility of 1, which flaps between two limit boat conformations with the sulfinyl group in pseudoequatorial and pseudoaxial positions, respectively. The conformational equilibrium of 1 occurs too fast for the (1)H NMR (500 MHz) time-scale even at -130 degrees C, and the equilibrium constant has not been determined. The apparent dipole moments of 1 in n-hexane and 1,4-dioxane and the (1)H NMR spectra of 1 and the model compounds cis- and trans-thianthrene-5,10-dioxides (2) and thianthrene (5) in different solvents and at various temperatures confirm that the relative position of the conformational equilibrium of 1 is solvent-dependent, and more polar solvents favor the conformation with the sulfoxide group in the pseudoaxial position (1(')(ax)). Variable-temperature (1)H NMR spectra have established the interconversion barrier of trans-2 and confirmed that the conformational equilibrium of cis-2 is strongly displaced toward the conformation with both sulfinyl groups in the pseudoequatorial position. The (1)H NMR data support the transannular interaction of the functional groups in 1 and trans-2.
authors.affiliation: Departamento de Química Orgánica, Universidad de Valencia, Spain.
authors.forename: María Elena
authors.initials: ME
authors.lastname: González-Núñez
authors.forename: Rossella
authors.initials: R
authors.lastname: Mello
authors.forename: Jorge
authors.initials: J
authors.lastname: Royo
authors.forename: Gregorio
authors.initials: G
authors.lastname: Asensio
authors.forename: Isidro
authors.initials: I
authors.lastname: Monzó
authors.forename: Francisco
authors.initials: F
authors.lastname: Tomás
authors.forename: Jesús García
authors.initials: JG
authors.lastname: López
authors.forename: Fernando López
authors.initials: FL
authors.lastname: Ortiz