This review summarises recent applications of pyridinium salts in radical-mediated difunctionalization of alkenes. We hope this review will provide a comprehensive overview of this topic and promote the wider development and application of pyridinium salts.

A Cu-catalyzed cascade annulation of enynals with alkenyl or alkynyl α-bromocarbonyls for the synthesis of various cyclohexenone-fused polycyclic compounds is described.

An unprecedented Pd-catalyzed trans-addition of boronic acids to ynamides has been reported, giving α,β-disubstituted enamides in high yields with excellent regio- and stereoselectivity. A possible mechanism involving the palladium carbene intermediate has been proposed to account for the unusual trans-addition.