  Since the hypervalent twist followed by reductive elimination is a general
reaction pattern for hypervalent iodine reagents, mechanistic studies about the
hypervalent twist step provide significant guidance for experiments. Our
previous work showed there are two types of hypervalent twist models, i.e.
apical twist and equatorial twist. We applied both hypervalent twist models to
explain the isomerization mechanism of two important electrophilic
trifluoromethylating reagents, Togni I and Togni II. To the best of our
knowledge, there are less detailed studies about the different twist modes
between both reagents, which are important to predict the right reaction
mechanism and especially, understand well the differences of reactivity and
stability. Here, we successfully identified Togni II's isomerization pathway
via equatorial twist, and suggested different hypervalent twist models should
be considered to predict the right mechanisms of reactions with hypervalent
iodine reagents.
