PhI(OAc)2 induced intramolecular oxidative bromocyclization of homoallylic sulfonamides with KBr as the bromine source

(Diacetoxyiodo)benzene (PhI(OAc)2) was found to be a powerful reagent to induce the intramolecular oxidative bromocyclization of homoallylic sulfonamides utilizing KBr as the bromine source. The reaction affords 2-substituted-4-bromo-pyrrolidines in moderate to excellent yields under a mild metal-free condition, and offers good manipulability by avoiding the use of highly toxic and caustic bromine (Br2).