Asymmetric Bromolactonization Catalyzed by a C₃‐Symmetric Chiral Trisimidazoline

A productive alliance: In an enantioselective organocatalytic bromolactonization of 5‐substituted hex‐5‐enoic acids (see scheme), it appears that the formation of an ion pair through interaction of the trisimidazoline catalyst 1 with the substrate both creates a chiral environment and promotes the cyclization by activating the carboxylic acid. DBDMH=1,3‐dibromo‐5,5‐dimethylhydantoin.