The first step of the net dehydrogenation is the installation of the "onium" leaving group, and given that this occurs at an aromatic C-H bond we used DKIE analysis to probe this step. A mixture of toluene 1m and deuterated toluene 1m-d8 was subjected to the first step of the standard conditions for each strategy (Scheme 5). Thianthrenation of toluene via activation by Tf2O in acetonitrile yielded a DKIE of 1.6 (Scheme 5a). This result is consistent with Wang's DKIE of 1.4 obtained for the same system albeit conducted in DCM, but stands in contrast to the DKIE of 2.7 obtained by Ritter when TTO is activated by a combination of TFAA and TfOH. Ritter has suggested that the stability of TT +• as a persistent radical and, therefore, the fast and reversible formation and cleavage of the C-S bond relative to slow deprotonation of the Wheland intermediate is the cause of the primary DKIE of 2.7. However, the substantially lower DKIE obtained by us and Wang, 1.6 and Scheme 4. Synthetic applications of net dehydrogenation of arenes into arynes.