Copper(II)-Catalyzed Enantioselective Addition of Aryl Amines to Isatin-Derived <i>N</i>-Boc-Ketimines for the Synthesis of Acyclic <i>N</i>,<i>N</i>′-Ketals

Here, we demonstrated a copper(II)-catalyzed enantioselective addition of aryl amines to isatin-derived <i>N</i>-Boc-ketimines using chiral O-N-N tridentate ligands derived from BINOL and proline. Generally, the chiral acyclic <i>N</i>,<i>N</i>'-ketals were obtained in high yields (up to 98%) and excellent ee values (up to 98%). Various aryl amines could be tolerated and a gram-scale reaction was also possible. Further, an X-ray diffraction experiment confirmed that the configuration of isatin-derived <i>N</i>-Boc ketimine should be (<i>Z</i>). Confirmation of the configuration of the ketimine would make it easier to understand the rationale for stereofacial selective activation of the electrophile with either organo- or Lewis acid-based catalysts.