Activation of Electrophilic Sites by Adjacent Cationic Groups

This chapter describes our studies of electrophilic systems having adjacent, stable cationic centers. We have shown in a wide variety of systems that stable cationic centers (i.e., ammonium, pyridinium, and phosphonium groups) can enhance the reactivities of some electrophiles. This enhanced reactivity is evident by reactions with weak nucleophiles, but may also involve unusual rearrangements or regiochemistry in the conversions. Using this chemistry, reactive dicationic systems can be generated and studied.