Divergent Synthesis of Atropisomeric Diarylamines Enabled by Bromine‐Masked Indolines

Abstract

Herein, we report the use of a bromine atom as a masking group for the synthesis atropisomeric diarylamines via organocatalytic N‐arylation of 7‐bromoindolines. The bromine atom acts as a bulky group to temporarily stabilize the configuration by steric hindrance. Upon unmasking, less sterically hindered diarylamines are obtained, with configurational stability potentially maintained through intramolecular hydrogen bonding. Moreover, the gram‐scale reaction and post‐modifications of the axially chiral diarylamines demonstrated the utility of this protocol. Thermal racemization experiments combined with X‐ray crystallography revealed the respective contributions of steric repulsion and intramolecular hydrogen bonding in stabilizing the configurations. This approach not only provides a useful method for the atroposelective construction of conical diarylamines, but also paves the way for a better understanding of stable axial chirality and its role in shaping chemical reactivity and biological activity.