Acid‐Mediated Condensation of 2‐Aminoaryl Cyclopropyl Ketones with Aldehydes for the Synthesis of 2,3‐Dihydrofuro[3,2‐c]quinolines

A method for the synthesis of 2,3‐dihydrofuro[3,2‐c]quinolines via TfOH or TMSOTf mediated condensation of 2‐aminoaryl cyclopropyl ketones with aldehydes has been developed. The reaction proceeds under transition metal or halogen free conditions, giving access to the target molecules in 27‐90% isolated yields. Mechanistic study indicates that the reaction sequence involves imine formation, intramolecular Mannich condensation, Cloke‐Wilson rearrangement, and auto‐oxidation.