Copper-catalyzed alkylation reactions of indole: An overview

The development of effective techniques to produce functionalized indoles has garnered a lot of interest in synthetic organic chemistry. One of the most efficient processes for creating C–C bonds between indoles and electron-deficient substrates is the alkylation reaction. Since the advent of chiral transition metal-catalyzed alkylation reactions, Cu-catalyzed processes have gained attention for their ability to yield alkylated products. In this review, an overview of Cu-catalyzed alkylation reaction of indoles with various substrates, such as nitroalkenes, β,γ-unsaturated α-ketoesters, alkylidene malonates, N-sulfonyl aldimines, diazo compounds, alcohols, and other alkylating agents are discussed, covering the literature up to 2021.

Graphical abstract

Indoles belong to a significant class of heterocycle due to its wide range of biological properties. As a result, indoles and its derivatives are of great interest to researchers. Transition metal-based Friedel–Crafts alkylation reaction for synthesizing alkylated indoles has gained more attention because they can afford the Friedel–Crafts adducts with high efficiency and selectivity. Among the various transition metals used, Cu has acquired considerable acceptance since it is less hazardous, inexpensive, eco-friendly, and has a huge spectrum of substrate scope. Cu-catalyzed alkylation reaction of indoles are highlighted in this review.