Ring Inversion Dynamics of Derivatives of Thianthrene Di- and Tetraoxide<sup>§</sup>

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