Convergent Synthesis of 2-Aryl-Substituted Quinolines by Gold-Catalyzed Cascade Reaction

Abstract

Key words quinoline; gold catalysis; tandem reaction; heterocyclic compound; cyclization A quinoline skeleton is often observed in biologically important natural products, for example; quinoline alkaloid quinine exhibits medicinally vital antimalarial activity.

Gold catalysis in quinoline synthesis

“…In 2016, Tokuyama and co-workers reported a gold-catalyzed cascade reaction of anilines bearing acetal groups 56 with terminal aryl alkynes 57 , furnishing 2-arylquinolines 58 in 38–66% yields (Scheme 19). 49 A proposed mechanism for this cascade reaction involved intermolecular addition of gold acetylide 57-A to oxonium ion 56-A in the formation of amino alkyne intermediate 56-B, followed by 6- endo-dig cyclization through attack of nitrogen to the gold-activated alkyne moiety. A final aromatization via removal of the protecting group delivered the quinoline products 58 .…”

Advancements in Gold‐Catalyzed Cascade Reactions to Access Carbocycles and Heterocycles: An Overview

“…i PrOH in toluene at 110 °C for 7–11 h (Scheme 43). [82] The reaction followed sequential steps of [4+2]‐cycloaddition of aryl alkyne, the addition of gold acetylide to an oxonium ion for giving amino alkyne intermediate, and 6‐endo‐dig cyclization of amino alkyne intermediate where nitrogen attacked to the gold activated alkyne moiety.…”

Synthesis of Propargylic Ethers by Gold-Mediated Reaction of Terminal Alkynes with Acetals

“…Recently, we developed a modular synthesis of substituted pyrroles from aminoacetals and alkynes via gold-mediated tandem catalysis [21][22][23][24] (Chart 1). The cascade reaction is initiated by the formation of gold acetylide 4 from alkyne 2, which adds to the oxonium ion 5 to form 6.…”