Reaction of hexafluorothioacetone dimer with ketene dimethylacetal and dimethyl thioacetal

It was demonstrated that the fluoride anion catalyzed reaction of 2,2,4,4-terakis(trifluoromethyl)dithienane-1,3 (1, cyclic dimer of hexafluorothioacetone) with ketene dimethylacetal (2, 1,1-dimethoxy ethylene) leads to the formation of 2,2-bis(trifluoromethyl)-3,3-bis(methoxy)thietane (3), rather than expected 2,2-bis(trifluoromethyl)-4,4-bis(methoxy)thietane isomer (4). Compound 3 is a kinetic product and upon storage at ambient temperature undergoes quantitative isomerization into 4. The isomerization proceeds through the formation of free hexafluorothioacetone, which was trapped as cycloadduct with quadricyclane. It was also demonstrated that the ethylene 2 is able to react with dimer 1 in the absence of the catalyst. The reaction results in unusual ring opening process producing (2,2-dimethoxyvinyl)(1,1,1,3,3,3-hexafluoro-2-(1,1,1,3,3,3-hexafluoropropan-2-yl)thio)propan-2-yl)sulfane (11).