Asymmetric Hydrogenation of α-Amino Esters into Optically Active β-Amino Alcohols through Dynamic Kinetic Resolution Catalyzed by Ruthenabicyclic Complexes
Hiroki Ishikawa, Taiga Yurino, Ryo Komatsu, Mingyuan Gao, Noriyoshi Arai, Taichiro Touge, Kazuhiko Matsumura, Takeshi Ohkuma
Abstract
Racemic α-substituted α-amino esters were hydrogenated into enantioenriched β-amino alcohols through dynamic kinetic resolution with chiral ruthenabicyclic complexes. The reaction was carried out with a substrate/catalyst molar ratio of 200–1000 under 15 atm of H 2 at 25 °C to afford a variety of β-substituted β-aminoethanols in up to 96% ee (24 examples). The mechanistic studies including deuteration experiments suggested that the reaction proceeds with 1,2-hydride migration of the α-amino acetalate intermediate into the α-hydroxy imine followed by the continuous reduction of the imino compound, affording the amino alcohol product.