In this review, we summarise the recent applications of pyridinium salts in radical-mediated difunctionalization of alkenes. Pyridinium salts are a privileged class of compounds that show great utility in natural...

Construction of challenging and important allcarbon quaternary centers has received growing attention. Herein, with oxalates as activating groups for tertiary alcohols, we report photoredox-catalyzed gem-difluoroallylation to construct all-carbon quaternary centers enabled by efficient tertiary radical addition to α-trifluoromethyl alkenes. This transformation shows good functional group tolerance for both α-trifluoromethyl alkenes and oxalates. Moreover, this strategy is also successfully applied to the synthesis of monofluoralkenes from the corresponding electronrich gem-difluoroalkenes and cesium tertiary alkyl oxalates under modified conditions.

The direct monofluoroalkenylation of C(sp3)–H bonds is of great importance and quite challenging. Current methods have been restricted to the monofluoroalkenylation of activated C(sp3)–H bonds. Here, we reported the photocatalyzed C(sp3)–H monofluoroalkenylation of inactivated C(sp3)–H bonds with gem-difluoroalkenes via 1,5-hydrogen atom transfer. This process shows good functional group tolerance, such as halides (F, Cl), nitrile, sulfone, ester, and pyridine, and good γ-selectivity. Moreover, this method succeeds in the photocatalyzed gem-difluoroallylation of inactivated C(sp3)–H with α-trifluoromethyl alkenes.