Intramolecular cyclization reaction - Palladium(0)-catalyzed cyclization is more effective than tin hydride mediated reaction

Intramolecular CH arylation of pyrone, pyridone, uracil, imidazole, and benzimidazole derivatives are carried out in the presence of a Pd catalyst to form potentially bioactive fused heterocyclic compounds, whereas the n-Bu3SnH-mediated aryl radical cyclization of the precursors 3 afforded mainly halogen-reduced uncyclized products.