Metal-Free Synthesis of 2-Substituted Quinolines via High Chemoselective Domino Condensation/Aza-Prins Cyclization/Retro-Aldol between 2-Alkenylanilines with β-Ketoesters.

A highly chemoselective domino condensation/aza-Prins cyclization/retro-aldol between 2-alkenylanilines with β-dicarbonyl compounds under metal-free conditions was accomplished, giving a large category of valuable 2-substituted quinolines in good yields with excellent functional group toleration. This newly established process, adopting β-ketoesters as masked C1 synthons via C-C cleavage, could even be simplified into a three-component [3 + 2 + 1] domino version consisting of exceedingly low-priced commercial starting materials. The synthetic application of products was exemplified by several intriguing chemical operations.