Recent advances in catalytic approaches for the synthesis of 3-substituted indoles: mechanisms and strategies

This review provides a comprehensive overview of recent advances in the synthesis of 3-substituted indoles, highlighting various catalytic methodologies employed to improve the reaction efficiency, selectivity, and sustainability. This article discusses base-catalyzed methods, amino acid catalysts, Brønsted acid catalysts, and Lewis acids and their unique roles in enhancing the synthesis of these valuable compounds. Additionally, the application of ionic liquids, surfactants, and heteropolyacid-based catalysts was explored for their green chemistry benefits, demonstrating reduced environmental impact and improved reaction outcomes. Electrochemical approaches using simple electrodes and phase-transfer catalysts are also examined as eco-friendly and efficient alternatives. This review underscores the broad versatility and applicability of these catalytic systems in synthesizing 3-substituted indoles, which are important intermediates in pharmaceuticals, material sciences, and natural product synthesis while emphasizing the need for continued innovation toward more sustainable and efficient synthesis methods.