Ligand Tuned Reactivity of Iron Catalysts Toward Green Synthesis of 1,4‐Dihydropyridine, 4‐Hydropyran, and Aminopyrazole Derivatives in Aqueous Medium

ABSTRACT Ligands are the important part of a metal‐catalyzed process. New ligand designing for metal‐catalyzed organic transformations is the focused area of current research. Ligand enabled iron‐catalyzed reactions provide sustainable alternatives to the costly metal‐based methodologies. Furthermore, the one‐pot multicomponent strategies displayed significant attention for the scientific community to access valuable scaffolds. Herein, we have demonstrated new ligand tuned iron‐catalyzed one‐pot multicomponent reactions for the synthesis of diverse heterocyclic scaffolds. New and very simple “nitrogen–oxygen” (“N─O”) type chelating ligands were prepared and applied successfully for the iron‐catalyzed multicomponent cascade reactions enabling the synthesis of diverse heterocyclic scaffolds, including 1,4‐dihydropyridines, 4H‐pyrans, and aminopyrazoles. Prepared ligands as well as all products were well characterized. Mechanistic studies using UV–visible spectroscopy support the in situ formation of the ligand metal complex. The one pot, three component reactions employ readily available aromatic aldehydes and proceed under mild aqueous conditions through sequential carbon carbon bond forming steps, affording the desired heterocycles in good yields with satisfactory selectivity. The methodology also demonstrates good scalability and broad functional group tolerance, recyclable up to five times, underscoring its practical applicability along with green chemistry metrices.