Formation of Axially Chiral N-Aryl Indoles and Stereoselective Functionalization

Significance

Using planar chiral arene chromium complexes, the stereoselective synthesis of axially chiral N-aryl indoles by a nucleophilic substitution reaction was achieved. Stereoselective Cr(CO)₃ migration to the arene ring of the indole occurred by refluxing 4 in toluene to give a single diastereo­mer. The migration proceeds in an intramolecular fashion and the 1,3-dioxolane group (R³) is crucial for this reaction. Further chemo- and stereoselective transformation to control the chirality at the side chain is possible utilizing the planar chiral indole fragment. The stereochemical integrity of Cr-free N-aryl indoles 3 or 4 is stable to heating.