Palladium Catalysts: Synthesis of Five-MemberedN-Heterocycles Fused with Other Heterocycles

In recent decades, a large number of reports related to the synthesis of N, O, and S containing heterocycles have appeared owing to a wide variety of their biological activity. The metal catalyzed synthesis of heterocycles is becoming an important and highly rewarding protocol in organic synthesis. Palladium-mediated cyclization reactions have been recognized as some of the simplest and useful tools for regio- as well as stereoselective syntheses of carbo- and heterocyclic compounds. This review focuses on the use of palladium as a catalyst for the synthesis of nitrogen containing five-membered heterocylces fused with other heterocycles. It describes the formation of different types of heterocyclic rings.