Discussion Addendum for: Indium‐Catalyzed Heteroaryl–Heteroaryl Bond Formation through Nucleophilic Aromatic Substitution: Preparation of 2‐Methyl‐3‐(thien‐2‐yl)‐1H‐indole

Abstract

One of the most frequently utilized strategies for constructing bonds on heteroaryl scaffolds is transition metal catalysis, where diverse types of bonds can now be constructed on heteroaryl rings. Another option for functionalizing heteroaryl rings is the nucleophilic aromatic substitution reaction. The C–C bond cleavage is observed during the indium‐catalyzed three‐component alkylation of pyrroles or indoles with alkynes or carbonyl compounds and nucleophiles. The electron‐rich compound that is next focused on is an amine, thereby allowing the synthesis of a broad range of heteroarylamines. This chapter describes Nitrogen–Heteroaryl Bond‐Forming reaction followed by Carbon–Heteroaryl Bond‐Forming Annulation. The chemistry of the indium–heteroarene π‐complex can be further applied to a distinct type of reaction: indium‐catalyzed formal N‐arylation and N‐alkylation of pyrroles. This transformation involves a unique nitrogen–nitrogen exchange strategy, or in other words, a pyrrole‐ring opening–closing strategy.