Inversion of Enantioselectivity during the Platinum-Catalyzed Hydrogenation of an Activated Ketone

Two competing reaction pathways, which lead to opposite enantiomers, occur in the hydrogenation of 1 over chirally modified platinum, as revealed by catalytic and NMR spectroscopic experiments: the fast reduction of the ketoform 1 a (minor species) and the slow hydrogenolysis of the hydrate 3 (major species).