Indole-based atropisomers are a very important class of axially chiral
compounds. However, the atroposelective synthesis of axially chiral
2-arylindole remains largely unexplored. In this study, we report the
successful synthesis of atropisomeric 2-arylindoles using direct
amination of indoles with p-quinonediimines in the presence of chiral
phosphoric acid as a catalyst. Quinonediimine acts as an aminating
reagent through formal polarity inversion of imine. The malonate group
on the 2-aryl of 2-indoles was found to be essential for high
enantioselectivity of the products. This could be due to the additional
interaction between the ester group and the catalyst, as well as the
intramolecular hydrogen bonding. Our findings provide a new strategy for
the asymmetric construction of 2-arylindole atropisomers.