Enantioselective Direct Synthesis of Free Cyclic Amines via Intramolecular Reductive Amination

Chiral cyclic amines can be prepared via intramolecular reductive amination of N-Boc-protected amino ketones in a one-pot process. With the complex of iridium and f-spiroPhos as the catalyst, a range of N-Boc-protected amino ketones are smoothly transformed into chiral cyclic free amines in high yields and excellent enantioselectivities (up to 97% ee). Moreover, this method can also be successfully applied to the synthesis of a κ-opioid receptor selective antagonist, (S)-1.