Asymmetric hydrogenation of β-amino ketones with the bimetallic complex RuPHOX-Ru as the chiral catalyst

Abstract

Asymmetric hydrogenations of a series of β-amino ketones were carried out with a bimetallic complex (RuPHOX-Ru) as the chiral catalyst. Almost all the reactions (performed in a mixed solvent system of toluene and H2O in the presence of KOH) gave quantitative conversions into their respective products with up to 99.9% ee. The RuPHOX-Ru catalyst is stable to both moisture and air. The procedure has the benefits of being inexpensive, environmentally friendly and highly efficient. Under a relatively low catalyst loading (TON = 2000), key intermediates of fluoxetine, tomoxetine and nisoxetine could be obtained in quantitative yield and in up to 99.9% ee. This methodology represents a promising alternative to the synthesis of the aforementioned drugs and their analogues.