Photoredox-Catalyzed Radical Cascade Cyclization of <i>N</i> -Cyanamide Alkenes with <i>N</i> -Aminopyridinium Salts: Modular Synthesis of Polycyclic Quinazolinones

A photoredox-catalyzed strategy enables the dual N-centered radical cascade cyclization of <i>N</i>-cyanamide olefins with <i>N</i>-sulfon/benzoylaminopyridinium salts, efficiently constructing 48 amide-decorated 2,3-fused polycyclic quinazolinones in yields of up to 86%. This metal- and base-free protocol exhibits mild reaction conditions. Moreover, they are compatible with a variety of functional groups and can accommodate a range of substrate structures. Notably, the method's practical utility is highlighted by successful gram-scale implementation and facile downstream derivatization.