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.