Solvent-Free Mechanosynthesis of Polysubstituted 1,2-Dihydroquinolines from Anilines and Alkyne Esters

A novel one-pot reaction of anilines with acetylenedicarboxylate diesters in the presence of boron trifluoride, iodine, and trifluoroacetic acid or methylsulfonic acid has been developed under solvent-free ball-milling conditions, affording a variety of polysubstituted 1,2-dihydroquinolines bearing multiple ester groups in moderate to excellent yields. The present protocol features mild reaction conditions, short reaction time, and feasibility of large-scale synthesis, providing a facile and practical alternative to 1,2-dihydroquinoline synthesis. Intriguingly, the generated 1,2-dihydroquinolines can be further transformed into quinoline derivatives.