- Enantioselective synthesis of cyclic enol ethers and all-carbon quaternary stereogenic centers through catalytic asymmetric ring-closing metathesis
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The first examples of catalytic asymmetric ring-closing metathesis (ARCM) reactions of enol ethers are reported. To identify the most effective catalysts, various chiral Mo- and Ru-based catalysts were screened. Although chiral Ru catalysts (those that do
- Lee, Ai-Lan,Malcolmson, Steven J.,Puglisi, Alessandra,Schrock, Richard R.,Hoveyda, Amir H.
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- Direct asymmetric aldol reactions in aqueous media catalyzed by a β-cyclodextrin-proline conjugate with a urea linker
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Covalently attaching proline to β-CD through a urea linkage resulted in the synthesis of a water-soluble chiral organocatalyst 1 in high yield. Catalytic asymmetric aldol condensations between aldehydes and acetone were carried out under water-containing
- Liu, Kegang,Zhang, Guoqi
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- Enantioselective synthesis of cyclic allylboronates by Mo-catalyzed asymmetric ring-closing metathesis (ARCM). A one-pot protocol for net catalytic enantioselective cross metathesis
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Mo-catalyzed asymmetric ring-closing metathesis (ARCM) reactions are used to synthesize cyclic allylboronates of high optical purity (89% ee to >98% ee). A one-pot procedure involving formation of allylboronates, Mo-catalyzed ARCM and functionalization of
- Jernelius, Jesper A.,Schrock, Richard R.,Hoveyda, Amir H.
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- Synthesis of Enantiomerically Pure β-Hydroxy Ketones via β-Keto Weinreb Amides by a Condensation/Asymmetric-Hydrogenation/Acylation Sequence
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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.
- Diehl, Julian,Brückner, Reinhard
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p. 278 - 286
(2017/01/24)
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- Improved conditions for the proline-catalyzed aldol reaction of acetone with aliphatic aldehydes
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The proline-catalyzed asymmetric aldol reaction between aliphatic aldehydes and acetone has, to date, remained underdeveloped. Challenges in controlling this reaction include avoiding undesired side reactions such as aldol condensation and self-aldolization. In recent years we have developed optimized conditions, which enable high yields and good to excellent enantioselectivities, and which are presented in this communication. Georg Thieme Verlag Stuttgart New York.
- Martínez, Alberto,Zumbansen, Kristina,D?hring, Arno,Van Gemmeren, Manuel,List, Benjamin
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supporting information
p. 932 - 934
(2014/05/06)
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- Preparation of the Enantiomerically Enriched Isomers of the Odorous Cyclic Ethers Clarycet, Florol, and Rhubafuran by Enzymatic Catalysis
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All the enantiomerically enriched stereoisomers of Clarycet (1), Florol (2), and Rhubafuran (3) were prepared by biocatalysis routes. Their absolute configurations were established, and their olfactory properties were fully evaluated.
- Abate, Agnese,Brenna, Elisabetta,Fronza, Giovanni,Fuganti, Claudio,Gatti, Francesco G.,Serra, Stefano,Zardoni, Enrica
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p. 765 - 780
(2007/10/03)
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- High-pressure-promoted asymmetric aldol reactions of ketones with aldehydes catalyzed by L-proline
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High-pressure conditions were applied to direct asymmetric aldol reactions between ketones and aldehydes with L-proline as a commercially available chiral amino acid catalyst.
- Sekiguchi, Yusuke,Sasaoka, Aika,Shimomoto, Ai,Fujioka, Shingo,Kotsuki, Hiyoshizo
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p. 1655 - 1658
(2007/10/03)
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- Enantioselective synthesis of medium-ring heterocycles, tertiary ethers, and tertiary alcohols by Mo-catalyzed ring-closing metathesis
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The Mo-catalyzed asymmetric ring-closing metathesis (ARCM) of various achiral trienes leads to the formation of medium-ring unsaturated heterocycles in high yield and with excellent enantioselectivity. Reactions may be carried out on gram scale and in the
- Kiely, Andrew F.,Jernelius, Jesper A.,Schrock, Richard R.,Hoveyda, Amir H.
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p. 2868 - 2869
(2007/10/03)
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- Direct asymmetric aldol reactions of acetone using bimetallic zinc catalysts
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(Equation presented) The enantioselective aldol reaction using a novel binuclear zinc catalyst of acetone with several aldehydes gave products in good yields (62-89%) with a high level of enantioselectivity (ee = 76-92%).
- Trost, Barry M.,Silcoff, Elliad R.,Ito, Hisanaka
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p. 2497 - 2500
(2007/10/03)
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- Proline-catalyzed asymmetric aldol reactions between ketones and alpha-unsubstituted aldehydes.
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[reaction: see text] With this communication we extend the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors. This important aldehyde class gives the corresponding aldols in 22-77% yield and up to 95% ee when the reactions are performed in pure acetone or in ketone/chloroform mixtures. On the basis of these results we have developed a concise new synthesis of (S)-ipsenol.
- List,Pojarliev,Castello
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p. 573 - 575
(2007/10/03)
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