Selective Synthesis of 2- and 7-Substituted Indole Derivatives via Chelation-Assisted Metallocarbenoid C–H Bond Functionalization

Abstract

Functionally substituted indole derivatives are important intermediates for the synthesis of new potential drug candidates exhibiting strong bioactivities. Over the past few years, significant progress has been made in the direct C–H functionalization of the indole ring through the usage of metal-catalyzed intermolecular cross-coupling with diazo compounds. Directing group strategy provides a unique possibility for selective insertion of carbenes catalytically generated from diazo compounds into challenging indole C2–H and C7–H bonds. This short review summarizes recent advances in carbenoid functionalization of indole derivatives under chelation-controlled metal catalysis.1 Introduction2 Indole C2 Alkylation with α-Diazotized Meldrum’s Acid3 Indole C2 Alkylation with Diazomalonate Derivatives and Related Compounds4 Indole C7 Alkylation with Diazomalonates and Related Compounds5 Tandem Indole C2–H Alkylation/Cyclization6 Indoline C7 Alkylation with Diazomalonates and Related Compounds7 Tandem Indoline C7–H Alkylation/Cyclization8 Conclusion