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- Title
Synthesis of Enantiomerically Pure β-Hydroxy Ketones via β-Keto Weinreb Amides by a Condensation/Asymmetric-Hydrogenation/Acylation Sequence.
- Authors
Diehl, Julian; Brückner, Reinhard
- Abstract
An established route to enantiomerically pure β-hydroxy ketones proceeds through the asymmetric hydrogenation of β-keto esters, an ester/amide exchange, and the use of the resulting β-hydroxy amide for the acylation of an organometallic compound. We shortened this route by showing that β-keto Weinreb amides are hydrogenated with up to 99 % ee in the presence of [Me2NH2]+{[RuCl(S)-BINAP]2(μ-Cl)3}-(0.5 mol-%) at room temp./5 bar. These Weinreb amides were prepared by seemingly obvious yet unprecedented condensations of lithiated N-methoxy-N-methylacetamide with carboxylic chlorides (51-87 % yield). The resulting β-hydroxy Weinreb amides were used for the acylation of organolithium and Grignard reagents. They thus gave enantiomerically pure β-hydroxy ketones (28 examples). A selection of these compounds gave anti-1,3-diols after another C=O bond hydrogenation, or syn-1,3-diols by a Narasaka-Prasad reduction.
- Subjects
ENANTIOMERIC purity; HYDROXY acids; AMIDES; HYDROGENATION; ACYLATION; CONDENSATION reactions
- Publication
European Journal of Organic Chemistry, 2017, Vol 2017, Issue 2, p278
- ISSN
1434-193X
- Publication type
Article
- DOI
10.1002/ejoc.201601202