Recent Synthetic Strategies for the Functionalization of Indole and Azaindole Scaffolds

Indole and azaindole are among the most predominant heterocyclic molecules due to their presence in various natural products, vitamins, amino acids, alkaloids, hormones, neurotransmitters, and natural pigments. They also serve as fundamental starting materials for synthesizing a wide range of complex organic molecules. Additionally, these compounds are of significant importance in medicinal chemistry due to their diverse biological activities and applications. Therefore, developing sustainable functionalization strategies for indole and azaindole are essential. This review explores recent synthetic methods for functionalizing indole and azaindole, including C−H activation, cross-coupling reactions, metal catalysis, organocatalysis, photocatalysis, and electrocatalysis, with a focus on recent advancements from 2019 to 2023.