Ionic Liquid and Sc(OTf)₃ as a Sustainable Combo for Photochemical One‐Pot Aza‐Diels‐Alder Reaction to Access 2,4‐Diarylquinolines

A sustainable photochemical methodology has been developed to synthesize biologically active 2,4‐diarylquinolines by aza‐Diels‐Alder reaction (Povarov reaction) using [BMIM][BF 4 ] and Sc(OTf) 3 under organic solvent‐free conditions. This photo‐catalyst‐free multicomponent approach demonstrates the reaction in a recyclable medium, high functional group tolerance, a broad substrate scope, and applicability to synthesize bioactive quinolines starting directly from aldehyde, amine and alkyne. The reaction of imines with alkynes was additionally explored under thermal and photochemical conditions to investigate the influence of photochemical conditions. Deuterium labelling experiments revealed that the reaction proceeds through an initial imine formation, which subsequently undergoes a concerted [4 + 2] cycloaddition with the alkyne. The [BMIM][BF 4 ] and Sc(OTf) 3 combo was successfully recovered and reused for four reaction cycles without significant loss in reactivity.