Hydrogen-Bonding Asymmetric Metal Catalysis with α-Amino Acids: A Simple and Tunable Approach to High Enantioinduction

While asymmetric transition-metal catalysis has become a powerful method for constructing chiral products, a challenge in this field is the identification of the correct ligand for high selectivity. We report here a simple approach to chiral catalyst formation: coupling of an available pool of Brønsted acids, namely, amino acid derivatives, with tunable ligands on copper catalysts. This system can be used to generate many different chiral environments simply by changing the amino acid or ligand employed and provides a scaffold for rapid screening and identification of the correct combination for high enantioselectivity. The latter is illustrated in the copper-catalyzed alkynylation of imines in up to 99% ee.