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 ¹³C NMR spectra of the 2,7-diisopropyl derivative (ΔG^⧧ = 6.5 kcal mol^-1). The barrier is lower than that measured for a trans thianthrene dioxide derivative (ΔG^⧧ = 9.35 kcal mol^-1). These results agree well with ab initio theoretical predictions.