Halogen Bond Catalyzed Bromocarbocyclization

A halogen bond catalyzed bromo‐carbocyclization of N‐cinnamyl sulfonamides and O‐cinnamyl phenyl ethers has been developed. N‐methyl 4‐iodopyridinium triflate is used as the halogen‐bonding organocatalyst and the reaction is highly chemoselective. This report represents the first proof‐of‐concept for halogen‐bonding organocatalyst‐promoted electrophilic halogenation. Mechanistic study suggests the autocatalytic nature of this reaction. All hail the halo: A halogen bond catalyzed bromo‐carbocyclization of N‐cinnamyl sulfonamides and O‐cinnamyl phenyl ethers is described. N‐methyl 4‐iodopyridinium triflate is used as the halogen‐bonding organocatalyst. The reaction features good yield, high chemoselectivity, mild reaction conditions, broad substrate scope, and the catalyst is air and moisture stable.