Functionalization of fused N ‐heterocyclic frameworks using organometallic reagents: Reactivity, selectivity, and biological application

Abstract

Benzo‐fused N ‐heterocycles, such as quinoline, isoquinoline, phthalazine, quinoxaline, cinnoline, and quinazoline derivatives, are pivotal scaffolds in pharmaceuticals, medicinal chemistry, agrochemicals, and materials science. Over the past three decades, organometallic reagent‐mediated strategies have transformed the highly regioselective functionalization of arenes and heteroarenes, enabling efficient carbon–carbon, carbon–heteroatom, and carbon–halogen bond formation under sustainable conditions. Transition metal‐catalyzed cross‐coupling, CH activation, photochemical, electrochemical, flow reaction, and 2,2,6,6‐tetramethylpiperidine (TMP)–bases‐involved directed metalation strategies offer versatile access to structurally diverse benzo‐fused bicyclic N ‐heteroaromatics and their related scaffolds. This review highlights recent advances in the functionalization of benzo‐fused pyridine scaffolds using a variety of organometallic reagents (Li, Mg, Zn, B, Al, etc.) between 2010 and 2025, emphasizing reaction scope, tolerance of sensitive functional groups, regioselectivity, enantioselectivity, and sustainable approaches for the development of biologically relevant N ‐heterobicyclic compounds. Furthermore, the review paper describes the biological, pharmaceutical, medicinal, and other relevant applications of benzo‐fused N ‐heterocyclic compounds.