Proline-derived aminotriazole ligands: Preparation and use in the ruthenium-catalyzed asymmetric transfer hydrogenation

The preparation of 2-triazolyl- and 2-triazolylmethylpyrrolidines from L-proline and L-trans-4-hydroxyproline is described, along with their evaluation as chiral ligands in ruthenium-catalyzed asymmetric transfer hydrogenation. Modular evolution of the ligands by introduction of remote substituents is also presented, showing a surprisingly important effect on the performance of the ligands.