Palladium/Norbornene Cooperative-Catalyzed Cascade Decarboxylative Cyclization of 4‑Iodoisoquinolin-1(2H)‑ones with o‑Bromobenzoic Acids: Access to Diverse Fused Phenanthridinones and Hepta[1,2‑c]isoquinolinones

A novel three-component Pd/norbornene cooperative catalysis cascade decarboxylative [2+2+2]/[2+2+3]­cyclization of 4-iodoisoquinolin-1­(2H)-ones and o-bromobenzoic acids or 8-bromo-1-naphthoic acid has been developed. The method affords a range of fused phenanthridinones and hepta­[1,2-c]­isoquinolinones and displays unique regioselectivity and broad substrate scope. Palladium/norbornene (Pd/NBE)-catalyzed C–H activation and subsequent decarboxylative coupling reactions were involved, and NBE acts as a building block for the construction of rigid nonplanar molecular architectures.