Intramolecular Thioether Migration in the Rhodium-Catalyzed Ene-Cycloisomerization of Alkenylidenecyclopropanes by a Metal-Mediated β-Sulfide Elimination.

Reported is the first example of a rhodium-mediated β-sulfide elimination, which represents a new mode of reactivity for late-transition-metal chemistry. This serendipitous discovery facilitates an ene-cycloisomerization of allylic-sulfide-containing alkenylidenecyclopropanes (ACPs) to afford five-membered carbo- and heterocyclic rings with concomitant intramolecular thioether migration. Interestingly, similar selectivity is obtained with both E- and Z-allylic sulfides and the reaction is also feasible with an allylic selenide. Mechanistic studies are consistent with an inner-sphere transfer of the sulfide, which is remarkable given the propensity for sulfides to poison transition-metal catalysts. Finally, this type of atom-economical rearrangement is envisioned to prompt the development of related processes given the utility of sulfides in target-directed synthesis.