Copper-Catalyzed Ring Expansion of Cyclopropyl Ketones/Formation of N-acyliminium/Hetero-[4 + 2]-Cycloaddition: A Route to Substituted Pentacyclic Isoindolin-1-one.

A Cu-catalyzed three-component cascade cyclization among 2-formylbenzonitrile, cyclopropyl ketones, and diaryliodonium salts for the construction of fused isoindolin-1-one compounds is achieved. Pentacyclic isoindolinone derivatives could be obtained in moderate to good yields. The proposed mechanism involved a ring expansion of cyclopropyl ketones/formation of N-acyliminium/hetero-[4 + 2]-cycloaddition process.