Recent advances in synthesis of tricyclic pyrrole/pyrrolidine-containing scaffolds

Tricyclic compounds containing pyrrole or pyrrolidine scaffolds represent a privileged class of structures in pharmaceutical chemistry, owing to their prevalence in natural products and drug molecules. This review systematically summarizes the synthetic methodologies developed over the past five years for the construction of these complex frameworks, with a focus on transition-metal catalysis and organocatalysis. In transition-metal catalysis, significant advances have been made using palladium, rhodium, copper, and other metals, enabling a wide range of transformations such as C-H activation/annulation, [2 + 2 + 1] annulation, and stereodivergent cooperative catalysis. These strategies have facilitated the efficient construction of diverse tricyclic skeletons with high regio-, diastereo-, and enantioselectivity, as well as broad functional group tolerance. Organocatalytic approaches, including the use of chiral phosphoric acids, DMAP, and related catalysts, have emerged as powerful complements, offering metal-free alternatives with excellent stereocontrol and operational simplicity, particularly in cascade and cycloaddition reactions. The review provides an in-depth analysis from perspectives including reaction design, catalytic mechanisms, stereocontrol, and synthetic applications. It aims to serve as an up-to-date reference for researchers in related fields, fostering the further application of these privileged scaffolds in drug discovery and natural product synthesis.