Recent advance in carbocation-catalyzed reactions

摘要

Carbocations such as tropylium and trityl cation, can be stable enough to be isolated and used without inert conditions. They can act as Lewis acids to lower the LUMO of electrophile, thus promoting reactions with nucleophiles. Additionally, the interaction between carbocations and alcohols can form Bronsted acids with enhanced acidity. Furthermore, electrophoto activation of TAC^(+)(trisaminocyclopropenium ion)delivers the excited radical dication TAC·^(2+*), which is a strong oxidant and capable of oxidizing a range of challenging substrates. Moreover,^(n)Pr-DMQA^(+) is disclosed as a versatile photoredox catalyst as its excited state can be quenched through both oxidation and reduction. This review summarizes recent advance in carbocation-catalyzed reactions. These developed methods provide an environmentally friendly pathway for the synthesis of valuable compounds and will inspire chemists to discover more interesting transformations promoted by carbocations.