Synthesis of Five- and Six-Membered Heterocycles Through Palladium- Catalyzed Reactions

Over the last years, palladium-catalyzed coupling reactions have been extensively studied and the names of Heck, Stille, Suzuki and Sonogashira are well known for their contribution to this chemistry. Extension of the coupling reactions allowing introduction of heteroatoms have followed and the Buchwald-Hartwig reaction is now a concept for this chemistry. Another achievement in this field is the possibility offered by the methodology to acceed to heterocyclic compounds either through a direct construction of the heterocyclic ring or by a two-step procedure (coupling followed by an heteroannulation). We are in the following paper going to review these ways of preparing heteroaromatic compounds either as single ring system or condensed to other aromatic rings.