Practical Asymmetric Hydrogenation of 3-Quinuclidinone Catalyzed by the XylSkewphos/PICA−Ruthenium(II) Complex

Abstract

Asymmetric hydrogenation of 3-quinuclidinone with RuBr 2 [( S, S )-xylskewphos](pica) in a base containing ethanol affords ( R )-3-quinuclidinol in 88−90% ee (XylSkewphos = 2,4-bis(di-3,5-xylylphosphino)pentane, PICA = α-picolylamine). The optical purity of the product is readily increased to >99% by recrystallization. The hydrogenation of a 4.3-kg scale with a substrate-to-catalyst molar ratio of 100 000 under 15 atm of H 2 at 30−45 °C completes in 4 h. Use of methanol or 2-propanol as a solvent decreases the catalyst efficiency. RuCl 2 (skewphos)(pica), and RuCl 2 (tolbinap)(pica) which have similar structures, are less effective for this reaction.