Visible‐Light‐Promoted Chelating N ‐Heterocyclic Carbene Palladium Catalysis for Amide Bond Formation From Aldehydes and Secondary Amines

ABSTRACT Photoinduced transition metal catalysis has emerged as a powerful tool in synthetic chemistry. Among various catalytic systems, N ‐heterocyclic carbene (NHC) metal complexes are particularly attractive due to their tunable electronic properties and ability to stabilize charge‐transfer states. Herein, we report the first application of visible‐light‐promoted, chelating NHC‐palladium complexes as efficient photocatalysts for the oxidant‐free synthesis of tertiary amides via the direct coupling of aromatic aldehydes with secondary amines. The novel pyrimidine/pyridine hydroxylalkyl di‐functionalized NHC‐Pd catalysts exhibit high activity under mild conditions. Under the optimized reaction conditions, employing 1.0 mol% catalyst loading in 1,4‐dioxane under irradiation with 10W blue LEDs (λ = 455 nm) at room temperature in air, the desired amide products were obtained in good to excellent yields (up to 92%) within 12 h. Control experiments unequivocally demonstrated that both the catalyst and light irradiation are indispensable for the reaction to proceed. Mechanistic studies suggest a reaction pathway involving a photoinduced metal‐to‐ligand charge transfer (MLCT) process, with molecular oxygen playing a crucial role. This atom‐economical method demonstrates broad functional group compatibility across a range of electronically diverse aldehydes and structurally varied secondary amines, offering a practical and sustainable alternative to conventional amide coupling strategies. This work not only provides an efficient and oxidant‐free route to valuable tertiary amides but also reveals new opportunities for chelating NHC‐metal complexes in photochemical transformations.