Divergent Synthesis of Pentacyclic Isoindolinones Enabled by Sequential Insertion of Two Different Isocyanides and Acid Promoted Cyclization of Ketenimines.

A palladium-catalyzed multicomponent reaction involving o -bromobenzaldehydes and two different isocyanides was developed to assemble series of isoindolinones with spiroindolenine or azepinoindole skeletons. This sequential insertion reaction features mild conditions, a wide substrate scope, and high efficiency. Preliminary mechanistic study indicated that the difference in steric hindrance between isocyanide components is crucial when regulating the reaction sequence, whereas the ligand also played an important role during the whole process.