Enantioselective and Diastereoselective Construction of Chiral Amino Alcohols by Iridium-f-Amphox-Catalyzed Asymmetric Hydrogenation via Dynamic Kinetic Resolution
The iridium-f-amphox-catalyzed asymmetric hydrogenation of racemic α-amino β-unfunctionalized ketones proceeds via a DKR (dynamic kinetic resolution) process for the construction of various chiral N,N-disubstituted α-amino β-unfunctionalized alcohols in quantitative yields with excellent enantioselectivities and diastereoselectivities (all products >99% ee and >99:1 dr, TON up to 100 000). Importantly, this catalytic asymmetric hydrogenation with a DKR process provided a highly efficient and powerful synthetic strategy for the preparation of key chiral intermediates of the preclinical antitumor agent (S,S)-R116010.
Organocatalytic asymmetric synthesis of functionalized 4 H -chromenes via a one-pot Domino Michael-Hemiacetalization and dehydration sequence
A one-pot thiourea-catalyzed enantioselective synthesis of polyfunctionalized 4H-chromenes via a domino Michael-hemiacetalization reaction and subsequent dehydration is reported. Starting from 2-nitrovinylphenols and -keto esters, the new protocol affords the 4H-chromenes bearing a variety of functional groups with good to excellent yields (76-95%) and enantioselectivities ranging from 30-99%ee. Both enantiomers are available at will depending on the ephedrine or pseudoephedrine-based thiourea catalyst used. Georg Thieme Verlag Stuttgart - New York.
Enders, Dieter,Urbanietz, Gregor,Raabe, Gerhard
experimental part
p. 1905 - 1911
(2011/07/31)
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