Recent Advances in Intramolecular C─N Bond Formation for Pyrrolidine Synthesis

Pyrrolidines constitute a privileged class of nitrogen heterocycles that are ubiquitous in pharmaceuticals, bioactive molecules, and functional materials, thereby continuing to stimulate the development of efficient and versatile synthetic strategies. Among these, intramolecular C─N bond formation represents one of the most fundamental and broadly applicable approaches for the construction of pyrrolidine frameworks. Despite its central importance, a systematic overview focusing specifically on this ring‐closing paradigm has been lacking. This review summarizes key advances reported between 2013 and 2025 in the synthesis of pyrrolidines via intramolecular C─N bond formation, focusing specifically on examples featuring a polar ring‐closure step N: → C(+/δ + ). The discussion is organized according to the ring‐formation mechanism, encompassing transition‐metal‐catalyzed and metal‐free cyclization of alkenyl and alkynyl amines, tandem annulation processes, intramolecular nucleophilic additions to carbonyl compounds, nucleophilic substitution reactions, and regioselective C(sp 3 )‐H activation of aliphatic amines, including Hofmann‐Löffler‐Freytag‐type transformations. By highlighting mechanistic features, substrate scope, and synthetic utility, this review aims to provide a comprehensive and practical reference for the design of new pyrrolidine syntheses based on intramolecular C─N bond formation.