Transition-Metal-Catalyzed C–H/N–H Annulation Reactions between Imidazoles and Alkynes for the Synthesis of Fluorescent Benzimidazo[2,1‑a]Isoquinolines

This review summarizes recent advances in C–H/N–H annulation reactions between imidazoles and alkynes for the synthesis of imidazo­[2,1-a]­isoquinolines via transition-metal catalysis, including rhodium, ruthenium, cobalt, palladium, and nickel systems. These synthetic strategies enable the construction of highly conjugated fused heteropolycyclic aromatic frameworks. By providing an overview of the reported methodologies and discussing key regio- and stereochemical aspects, this article offers a concise guide to the synthesis and functionalization of these complex molecular architectures, with the aim of stimulating future studies toward applications in electronic and optoelectronic devices, which remain largely underexplored.