Contemporary carbocation chemistry: Applications in organic synthesis

Organic chemists have developed a vast array of synthetic methodologies based on carbocationic intermediates. A series of carbocationic reactions have been described by Yoshida's group in which the 'cation pool' strategy is used. This is accomplished through the use of irreversible, oxidative reactions under non-nucleophilic conditions. The carbocations then react with nucleophiles in a second step. This method is analogous to the preparation of carbanionic reagents such as Grignard or organolithium species, generally as a concentrated solution, and this is followed by electrophilic trapping of the carbanion. Using the cation pool method, oxidative C-H bond dissociation provides a good route to diarylmethyl carbocations. The Yoshida group has also developed a combined electrochemical-chemical oxidation route mediated by alkoxysulfonium ions. An innovative method for generating carbocations has been described by Li and coworkers in which 1,3-dicarbonyl groups are used as leaving groups.