Iron(III)-Catalyzed and Air-Mediated Tandem Reaction of Aldehydes, Alkynes and Amines: An Efficient Approach to Substituted Quinolines

An economic method for the construction of quinolines by the FeCl3-catalyzed three-component coupling/hydroarylation/dehydrogenation of aldehydes, alkynes, and amines was reported. Iron was used as catalyst for this reactions due to its low price, non-toxicity, and environmentally friendly characters. It was observed that during the synthesis of propargylamines by the FeCl3-catalyzed three-component coupling of aldehydes, alkynes, and amines, when aniline was used to replace the secondary amine, 2, 4- diphenyl-substituted quinoline, the propargylamine product was formed in 56% yield with 70% conversion after 48 hours under argon. Phenylacetylene and aniline were used as model substrates for exploring the aldehyde substrate scope. It was concluded that when the aromatic aldehyde carried an electron-donating group or an electron withdrawing group, the reactions proceeded to produce the corresponding quinolines.