Visible‐Light‐Mediated Free Radical Synthesis

This chapter concentrates on the photocatalytic generation of radical intermediates that have already been encountered in the past and generated through other pathways. It particularly emphasizes how photocatalysis can really improve the reaction conditions and outcomes. Different oxygenated moieties can be introduced by photocatalysis in place of an initial C—H bond. The development of visible-light photoredox catalysis for radical synthesis has demonstrated high efficiency, selectivity, versatility, and functional group tolerance in various transformations, becoming of great interest in cascade processes intramolecular radical steps. One of the most developed cascade sequence is tandem intermolecular radical addition/homolytic aromatic substitution, which first comprises radical addition onto activated double bond followed by cyclization onto arene and rearomatization by subsequent oxidation of the radical adduct. Radical multicomponent processes have emerged as a convenient and flexible strategy to elaborate complex molecular building blocks. Among them, visible-light photoredox catalysis proved to be efficient for promoting radical/cationic multicomponent reactions (MCRS).