One-pot solvent-free synthesis of quinolines by C–H activation/C–C Bond formation catalyzed by recyclable iron(III) triflate

A novel application of highly stable Fe(OTf)₃ as an efficient catalyst for carbon–carbon bond formation via the activation of a terminal alkyne C–H bond under solvent-free conditions is described. Notably, this protocol of green synthesis, which produced quinolines from the reaction of amines, aldehydes and terminal aryl alkynes, shows attractive characteristics including concise one-pot conditions, high atom economy, very limited energy consumption, and the sequential catalytic process requires only a catalytic (5 mol%) amount of Fe(OTf)₃ with short reaction periods (3 h). Meanwhile, the catalyst was easily recovered from the reaction system and reused smoothly with only a little loss of activity.