Indium‐Catalyzed Formal N‐Arylation and N‐Alkylation of Pyrroles with Amines

Abstract Under indium Lewis acid catalysis, a nitrogen atom of N ‐unsubstituted pyrroles was replaced with a nitrogen atom of primary amines, thereby producing N ‐aryl‐ and N ‐alkylpyrroles. This system formally introducing such carbon frameworks to the pyrrole nitrogen atom shows unique selectivity: only the H−N(pyrrolyl) unit undergoes the N‐arylation and N‐alkylation even in the coexistence of a similar H−N(indolyl) part; and an aryl–halogen bond remains intact. These are clearly different from the typical method depending on the C−N(pyrrolyl) bond‐forming reaction with organic halides as substrates. From a viewpoint of pyrrole N‐protection–deprotection chemistry, worth noting is that a methyl group on the pyrrole nitrogen atom can be removed, albeit in a formal way. magnified image