Ring inversion dynamics of derivatives of thianthrene di- and tetraoxide

The ring inversion barrier for thianthrene tetraoxide was determined by making use of the variable temperature C-13 NMR spectra of the 2,7-diisopropyl derivative ( Delta G(double dagger) = 6.5 kcal mol(-1)). The barrier is lower than that measured for a trans thianthrene dioxide derivative ( Delta G(double dagger) = 9.35 kcal mol(-1)). These results agree well with ab initio theoretical predictions.