Abstract
Stable carbocations do not react with non-activated benzenes. The electrophiles, which can react with benzene, are reactive carbenium ions (> C+-X), substituted with a genuine electron-withdrawing group (-X), wherein the substituent X represents carbenium, oxonium, ammonium, O-protonated hydroxylamino, O-protonated N, N-dihydorxylamino, and trifluoromethyl. Experimental evidences, including spectroscopic ones, demonstrated the involvments of these cationic species as discrete reaction intermediates. In this context, a dicationic or tricationic species may participate in various cationic reactions such as the Gatterman-Koch, Pomeranz-Fritsch, Skraup, Bischler-Napieralski and other conventional reactions. Reinvestigations of these reactions should have important implications for the chemistry of Friedel-Crafts and related reactions.
