H‐Bond Donor‐Directed Switch of Diastereoselectivity in the Enantioselective Intramolecular Aza‐Henry Reaction of Ketimines

We report an H‐bond donor controlled diastereoselective switchable intramolecular aza ‐ Henry reaction of ketimines derived from α‐ketoesters and 2‐(2‐nitroethyl)anilines, allowing facile access to chiral tetrahydroquinolines bearing an aza‐quaternary carbon stereocenter, which are privileged scaffold for medicinal researches. While newly developed cinchona alkaloid derived phosphoramide‐bearing quaternary ammonium salt C2 selectively give cis ‐adducts in up to 20 : 1 dr and 99 % ee, the corresponding urea‐bearing analogue C8 preferentially give trans ‐adducts in up to 20 : 1 dr and 99 % ee.