Rhodium(III)-Catalyzed C–H Activation in Indole: A Comprehensive Report (2017–2022)

Abstract In the realm of synthetic organic chemistry, the catalysis of directed C–H activation by transition metals is an outstanding and efficient method for the synthesis of natural products, organic materials, and fundamental organic building blocks. Notably, this strategy has experienced remarkable advances in recent years, particularly in its application to various substrate classes, including the essential indole scaffold. Indole is a highly sought-after target in organic chemistry. The significance of indole extends beyond its use in total synthesis and drug discovery. It also serves as an important tool in the development of pharmaceutical agents, agrochemicals, and materials. By targeting indole, synthetic chemists can access a wide range of bioactive compounds, which opens new avenues for drug development and chemical biology research. The synthesis of structurally varied indoles has been greatly aided by the development of a comprehensive toolkit made possible by the use of C–H activation as a versatile functionalization platform. This review highlights the latest breakthroughs in rhodium-catalyzed C–H activation at the C2, C4, and C7 positions of the indole scaffold. These developments represent significant progress in the field and hold promising potential for further advances in the synthesis of indole-based compounds. 1 Introduction 2 The Development of Rhodium-Catalyzed C–H Activation 3 General Mechanistic Introduction to Rh(III)-Catalyzed C–H Activation 4 Direct C–H Functionalization of Indoles 4.1 C2 Activation of Indoles 4.2 C4 Activation of Indoles 4.3 Dual C–H Activation Strategy 4.4 C7 Activation of Indoles 5 Conclusion