Substrate‐ and Catalyst‐Controlled C−H Bond Activation/Annulation for Construction of Pyrido[2,3,4‐de]quinazolinones and Indolo[1,2‐c]quinazolinones

Abstract A substrate and catalyst‐controlled synthetic strategy was employed to construct two distinct types of fused polycyclic heterocycles, namely pyrido[2,3,4‐ de ]quinazolinones and indolo[1,2‐ c ]quinazolinones. The most notable advantage of this method is its ability to rapidly generate two different polycyclic scaffolds via a simple C−H activation and subsequent cyclization cascade pathway. Specifically, sulfoxonium ylides played a crucial role in both transformations, serving as a two‐carbon synthon and a one‐carbon synthon, to independently construct the two fused polycyclic scaffolds through [4+2] and [4+1] annulation pathways, respectively.