A SYSTEMATIC STUDY OF BENZYL CATION INITIATED CYCLIZATION REACTIONS

A systematic investigation of benzyl cation initiated cyclization reactions to form six-membered carbocycles is presented. The generation of benzyl cations from benzylic bromides, ethers, and alcohols followed by intramolecular capture provided good yields of cyclized products by use of several different cyclization terminators (e.g., phenyl, alkene, beta-keto ester). A study on the effect of changing the electronic nature of substituents para to the benzyl cation showed that even electron-withdrawing substituents such as quaternary ammonium afford high yields of cyclization products. The formation of five- and seven-membered carbocycles was briefly investigated and found to be less general than the formation of the corresponding six-membered carbocycles.