CONFORMATIONAL PREFERENCES AND RESTRICTED RING INVERSION IN THIANTHRENIUM YLIDES

Abstract Thianthrene reacts with dialkyl diazomalonates to form, depending upon stoichiometry, both mono-and diylides. The monoylide exists perferentially in the pseudo-equatorial geometry but undergoes ring inversion at room temperature. The trans-diylide, unlike trans-thianthrene disulfoxide, does not undergo rapid ring inversion at room temperature. VT NMR indicates a barrier of 19 kcal/mole.