Recent Progress in Palladium-Catalyzed Quinoline Formation: Synthetic Applications and Mechanistic Insights

Quinolines are key heterocyclic motifs with broad utility in pharmaceuticals, agrochemicals, and materials science. The development of efficient and sustainable synthetic routes to access structurally diverse quinolines remains an important goal in organic chemistry. This review focuses on the recent advances in palladium-catalyzed strategies for quinoline synthesis, emphasizing oxidative and tandem annulation methods. Reactions are categorized by substitution patterns on the quinoline scaffold—namely 2-aryl, 4-substituted, 2,3-, 2,4- and 3,4-disubstituted, 2,3,4-trisubstituted, and annulated derivatives—to facilitate mechanistic comparisons and highlight structural scope. Together, the reviewed strategies showcase the range of mechanistic possibilities available for constructing quinoline scaffolds via palladium catalysis. Overall, these Pd-catalyzed approaches offer powerful and versatile tools for the synthesis of complex quinoline frameworks, providing valuable alternatives to classical heterocycle forming reactions.