A convenient and efficient synthesis of substituted quinolines via a simple one-pot reaction of an aniline, an aromatic aldehyde, and an enolizable aliphatic aldehyde in the presence of the iridium catalyst [IrCl 2H(cod)]2 under oxygen as an oxidant was developed. The reaction proceeds with Mannich-type imine formation followed by nucleophilic addition to give β-amino aldehydes. Dehydrative cyclization takes place to give dihydroquinoline, which is then dehydrogenated by aerobic oxidation to give 2-aryl-3-alkylquinolines. Dialkylquinolines were obtained by the reaction with anilines and aliphatic aldehydes in good yields.
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