Mechanistic insights for the multicomponent synthesis of quinolines toward different catalysts

Since the 19th century, quinolines have been widely studied, presenting vast applications in medicine,
functional materials, and ligands in catalysis1. Recently, the A3 (Aldehyde-Amine-Alkyne) multicomponent
coupling appears as a straightforward strategy to access quinoline scaffold trough metal catalysis. The
suggested mechanism involves a propargylamine intermediate after akyne insertion to an iminium
intermediate2. Curiously, the assumption of a cycloaddition pathway through a well know Povarov-like
mechanism is less commom in literature3. In this study, we investigate the mechanism for A3 reaction involving
Cu(OTf)2, FeCl3, YCl3 and Montmorillonite K-10 catalysts using isotopic and kinect studies. DFT data support
the experimental results for Povarov-type mechanism preferences for FeCl3 and K-10 catalysts.