Synthesis of condensed tetra- and polycyclic nitrogen heterocycles with a five-membered azacyclic core induced by ionic palladium catalysts

•The use of various ionic palladium catalysts in intra- and intermolecular cyclizations.•Synthesis of tetra- and polycyclic nitrogen heterocycles with a five-membered core.•The use of ligands allowing the synthesis of chiral products.•Focus on reaction conditions determining catalyst performance.•Mechanistic considerations providing insight into product formation. This review focuses on recent results with respect to the use of varied ionic palladium preparations in the synthesis of tetra- and polycyclic heterocycles bearing a five-membered azacyclic core. Results have been selected with focus on studies of the last six years (2018–2023) with a handful of exceptions. A general characteristic of all methods treated here is that the nitrogen-containing five-membered ring is formed via ring closing of appropriate starting materials. Selected examples discussed will reveal that numerous condensed ring systems can be successfully accessed. Major features are wide product ranges, high product yields, and stereoselectivities often achieved under mild reaction conditions.