Copper(II)-Catalyzed\nEnantioselective Addition of\nAryl Amines to Isatin-Derived <i>N</i>‑Boc-Ketimines\nfor the Synthesis of Acyclic <i>N</i>,<i>N</i>′‑Ketals

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