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.