Recent Progress in Gold‐Catalyzed Reactions of Alkynes for the Construction of Indole Frameworks

Abstract

Indole heterocycles hold an important position in chemical landscape because of their prominence in natural products and pharmaceuticals. Consequently, development of new and efficient strategies to access indole scaffold are of continuous interest. For the past few years, gold‐catalyzed activation of alkyne has emerged as a powerful strategy for constructing the heterocyclic skeleton. The present review highlights recent advances (2018–2023) toward synthesis of indole skeletons via gold‐catalyzed annulations of alkynes. A variety of alkynes, such as, ynamides, azido alkynes, ortho‐alkynyl anilines, propargylic alcohols, ortho‐alkynyl phenylimines, and miscellaneous alkynes are employed affording various indole architectures under gold catalysis. Moreover, mechanisms are included in most of the cases for better understanding of the reaction pathway.

Copper–Catalyzed Construction of the Indole Core: Recent Advancements

“…[46][47][48] However, during last few years, the use transition-metal as catalyst for obtaining this skeleton has achieved a milestone. [49][50][51][52] In this regard, copper has gained attention as an alternative to precious metals due to its low toxicity, high catalytic activity and cost-effectiveness. In the present review, we highlight recent advances (2019-2023) in copper-catalyzed annulations for the construction of indole motifs.…”

“…Various other organocatalytic and metal‐free approaches have also been adopted accordingly [46–48] . However, during last few years, the use transition‐metal as catalyst for obtaining this skeleton has achieved a milestone [49–52] . In this regard, copper has gained attention as an alternative to precious metals due to its low toxicity, high catalytic activity and cost–effectiveness.…”

Modular synthetic strategies for dipyrrolopyrazines

“…Our group later published a 4-step approach via a sequence of Sonogashira and Buchwald–Hartwig couplings, followed by gold( i )-catalysed 21–29 cyclisation affording N -phenyl-substituted dipyrrolopyrazines in an overall yield of up to 51% (Scheme 1). 30 Additional functionalisation was achieved by bromination of the pyrrolo-CH.…”

Gold-Catalyzed “Back-to-Front” Synthesis of 4-Silyloxyindoles

“…On the other hand, gold-catalysis has emerged as a versatile tool for constructing diverse carbon- and heterocyclic frameworks, 7 particularly through the annulation of suitable functionalized alkynes to synthesize various indole skeletons. 8 However, while benzannulation of indolyl alkynols represents a well-established route to carbazole synthesis, 9 the analogous benzannulation of alkyne-tethered pyrroles remains underdeve-loped. 10 To date, only particular examples of Au-catalyzed synthesis of indoles from pyrroles have been reported.…”