Synthesis of Quinolinium Salts from N ‐Substituted Anilines, Aldehydes, Alkynes, and Acids: Theoretical Understanding of the Mechanism and Regioselectivity

Secondary anilines were first utilized in the four‐component coupling of aniline, aldehyde, alkyne, and acid to synthesize a variety of N ‐substituted quinolinium salts. This method was carried out under mild reaction conditions and exhibited excellent chemo‐ and regioselectivities. DFT calculation was performed to analyze the cyclization step, where the interaction/distortion model provided better insight into the singular selectivity of terminal/internal alkynes in reaction.