Synthesis of Fused Isoquinolinone and Iminoisoindolinone Derivatives via a Copper-Catalyzed Regioselective Switching Process

Copper‐catalyzed base switching procedures for the synthesis of various fused isoquinolinone derivatives and iminoisoindolinone derivatives from the same starting materials have been developed. In these reaction sequences it is found that benzyl cyanide acts as a nucleophile in the presence of strong bases while it acts as a cyanide donor in the presence of weak bases. A wide substrate scope, good functional group tolerance, and handy reaction conditions are the important features of these protocols. Futhermore, using these protocols a wide variety of imidazolone‐fused isoquinolinone derivatives, pyrimidinone‐fused isoquinolinone derivatives, a diazapinone‐fused isoquinolinone derivative and iminoisoindolinone derivatives were accessed in excellent to moderate yields.