Asymmetric Hydrogenation of α-Amino Esters into Optically Active β-Amino Alcohols through Dynamic Kinetic Resolution Catalyzed by Ruthenabicyclic Complexes

Org Lett. 2023 Apr 7;25(13):2355-2360. doi: 10.1021/acs.orglett.3c00740. Epub 2023 Mar 24.

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 H2 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.