Ring-opening reactions of MCPs with sulfonamides promoted by metal triflate Lewis acids.

The reaction of aromatic MCPs with sulfonamides catalyzed by Lewis acids affords the corresponding ring-opened homoallylic sulfonamides in good yields and the reaction of aliphatic MCPs with sulfonamides gives the corresponding pyrrolidine derivatives under the same conditions. Through deuterium-labeling experiments, we found that the reaction process is involved with the rearrangement of a cyclopropylcarbinyl cation and a nonclassic carbonium ion.