Silver‐Catalyzed Carbocyclization of Azide‐Tethered Alkynes: Expeditious Synthesis of Polysubstituted Quinolines

Abstract

A silver-catalyzed carbocyclization of azide-tethered alkynes has been developed for the synthesis of polysubstituted quinolines in good to high yields. Mechanistic studies indicate that this reaction is initiated by a silver-catalyzed 6-endo-dig azide-yne cyclization, followed by a formal RÀX (X=Cl, Br, or I) insertion with external halide through a ylide intermediate. The salient features of this reaction include readily available materials, inexpensive silver-catalyst, mild reaction conditions, good functional group tolerance, and ease in further transformations.

2-Azidobenzaldehyde-Based [4+2] Annulation for the Synthesis of Quinoline Derivatives

“…Metal-catalyzed 6- endo -dig azide–yne cyclization of azide-tethered alkynes 112 has been developed for the synthesis of multi-substituted 4-alkoxy quinolines 113 – 117 ( Scheme 23 ) [ 142 , 143 , 144 ]. For example, Xu and coworkers synthesized 115 and 116 via the AgSbF 6 -catalyzed cyclization of azide-tethered alkynes.…”

Metal-Promoted Heterocyclization: A Heterosynthetic Approach to Face a Pandemic Crisis

“…An innovative and elegant pathway to achieve polysubstituted quinolines 29 was proposed by Xu et al, whereby an Ag(I) catalyst promotes 6-endo-dig cyclization of 2 azide alkyne derivatives 27 followed by an R-X 28 insertion into the imino carbene gen erated in the catalytic cycle (Scheme 18) [57]. Readily available materials, the cheap silver catalyst, and mild reaction conditions make this procedure appealing for organic chemists.…”

Rhodium-catalyzed coupling-cyclization ofo-alkynyl/propargyl arylazides oro-azidoaryl acetylenic ketones with arylisocyanides: synthesis of 6H-indolo[2,3-b]quinolines, dibenzonaphthyridones and dihydrodibenzo[b,g] [1,8]-naphthyridines

“…In this text, transition-metal-catalyzed reactions of organic azides with isocyanides have emerged as powerful tools for the construction of N-containing compounds employing carbodiimides generated by the coupling reaction of organic azides with isocyanides as a key intermediate. 10 In addition, o -alkynyl/propargyl arylazides 11,12 and o -azidoaryl acetylenic ketones 13 have been recognized as versatile building blocks in organic synthesis. In stark contrast, reports on the transition-metal-catalyzed coupling-cyclization reaction of o -alkynyl/propargyl arylazides or o -azidoaryl acetylenic ketones with isocyanides are considerably rare.…”