Cationic Gold(I)-Catalyzed Cascade Bicyclizations for Divergent Synthesis of (Spiro)polyheterocycles

We herein report an expeditious synthetic strategy to access diverse
(spiro)­polyheterocycles from easily available starting materials in
two operational steps including an Ugi four-component reaction and
a cationic gold­(I)-catalyzed cascade bicyclization. Divergent synthesis
of these structurally complex pyrido­[2,1-a]­isoindol-4­(6H)-ones and spiroisoquinoline-pyrrole-3,5′-diones
via a cascade nucleophilic cyclization/intramolecular 1,3-migration/1,5-enyne
cycloisomerization process and a tandem hydroamination/Michael addition
sequence, respectively, was controlled by substituents, where the
electronic effect on the migrating groups and steric effect of the
secondary amide moieties play crucial roles.