Catalytic Reduction of Quinolines to Tetrahydroquinolines: A Comprehensive Review

Tetrahydroquinolines (THQs) are an important class of nitrogen‐containing heterocycles found in numerous biologically active molecules. Among the various synthetic approaches, the catalytic reduction of readily available quinolines represents the most straightforward and economically efficient route to access these valuable scaffolds. Driven by the utilization of diverse reducing agents, a wide array of excellent catalytic strategies has been developed. This review systematically summarizes the recent advances in this field over the past 5 years, covering methodologies such as hydrogenation, transfer hydrogenation, and electrocatalytic reduction. We anticipate that this comprehensive summary will provide valuable insights and guidance for the future development of more sustainable and greener catalytic systems.