Asymmetric Synthesis of Acyclic Amines Through Zr‐ and Hf‐Catalyzed Enantioselective Alkylzinc Reagents to Imines

Readily available chiral amino acid‐based ligands are used in metal‐catalyzed additions of alkylzinc reagents to various aromatic and aliphatic imines; the desired amine products are formed efficiently and in high levels of optical purity. In cases where the more Lewis acidic Zr salts afford lower efficiency, Hf‐based catalysts deliver significantly higher yields with similar enantioselectivities. Critical structural features of the N‐activating groups as well as the optimal chiral ligands are discussed. A mechanistic working model is presented to rationalize the existing data and to serve as a predictive tool.