Iodine/Palladium Approaches to the Synthesis of Polyheterocyclic Compounds

A simple, straightforward strategy for the synthesis of polyheterocyclic compounds (PHCs) is reported, which involves iterative cycles of palladium-catalyzed Sonogashira coupling, followed by iodocyclization using I-2 or ICl. A variety of heterocyclic units, including benzofurans, benzothiophenes, indoles, and isocomarins, can be efficiently incorporated under mild reaction conditions. In addition, variations of this strategy afford a variety of linked and fused PHCs.