Bioactive four-membered heterocyclic compounds: the anti --> syn interconversion in dithietane-1,3-dioxide.

The anti-dithietane-1,3-dioxide --> syn-dithietane-1,3-dioxide isomerization reaction has been theoretically studied on the frame of MO theory both in the gas phase and in solution. In the gas phase the anti (II(a)) <--> syn (II(s)) equilibrium is slightly displaced to the anti isomer formation. The syn concentration ([Syn]) is ca. 36% in the gas phase, whereas in low polarity solvent, such as carbon tetrachloride, [Syn] is ca. 63%. In medium-high polarity solvents like acetonitrile and dimethyl-sulfoxide the [ anti]/[ syn ] ratio is ca. 0.37.