Enantioselective synthesis of tetrahydroisoquinolines via catalytic intramolecular asymmetric reductive amination

A highly efficient intramolecular asymmetric reductive amination transformation catalyzed by an iridium complex of Bu-t-ax-Josiphos has been realized via a one-pot N-Boc deprotection/cyclization/asymmetric hydrogenation sequence. This convenient and practical method provides chiral tetrahydroisoquinolines, which are of great importance and common in natural products and biologically active molecules, in moderate to high yields (78-96%) and good to excellent enantioselectivities (80-99% ee).