Kinetische Differenzierung von β‐Ketoestern durch Ruthenium(II)‐Binap‐katalysierte asymmetrische Hydrierung

Krämer, Rainer; Brückner, Reinhard

doi:10.1002/ange.200700021

Cited by 11 publications

(11 citation statements)

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“…On the basis that b-keto amides are more electron rich [10] 1,3-dicarbonyls than b-keto esters, they can preferably be anchored by ruthenium catalysts even in the presence of a large excess of the coordinating THF. [11] However, Cerveny and co-workers reported that methyl acetoacetate can still Abstract: A series of 3-oxoglutaric acid derivatives have been hydrogenated in different solvents in the presence of [RuClA C H T U N G T R E N N U N G (benzene)(S)-SunPhos]Cl (SunPhos = (2,2,2',2'-tetramethyl- [4,4'bibenzo[d]A C H T U N G T R E N N U N G [1,3]dioxole]-5,5'-diyl)bis(diphenylphosphine)).…”

Section: Resultsmentioning

confidence: 99%

Ruthenium‐Catalyzed Asymmetric Hydrogenation of 3‐Oxoglutaric Acid Derivatives: A Study of Unconventional Solvent and Substituent Effects

Tao

et al. 2012

Chemistry A European J

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A series of 3-oxoglutaric acid derivatives have been hydrogenated in different solvents in the presence of [RuCl(benzene)(S)-SunPhos]Cl (SunPhos = (2,2,2',2'-tetramethyl-[4,4'-bibenzo[d][1,3]dioxole]-5,5'-diyl)bis(diphenylphosphine)). Unlike simple β-keto acid derivatives, these advanced analogues can be readily hydrogenated in uncommon solvents such as THF, CH(2)Cl(2), acetone, and dioxane with high enantioselectivities. Two possible catalytic cycles have been proposed to explain the different reactivities of these 1,3,5-tricarbonyl substrates in the tested solvents. The C-2 and C-4 substituents had notable but irregular influence on the reactivity and enantioselectivity of the reactions. More pronounced solvent effects were observed: the ee values increased from around 20% in EtOH or THF to 90% in acetone. Inversion of the product configuration was observed when the solvent was changed from EtOH to THF or acetone, and a mixed solvent system can lead to better enantioselectivity than a single solvent.

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Section: Resultsmentioning

confidence: 99%

Ruthenium‐Catalyzed Asymmetric Hydrogenation of 3‐Oxoglutaric Acid Derivatives: A Study of Unconventional Solvent and Substituent Effects

Tao

et al. 2012

Chemistry A European J

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“…Our range of substrates consisted of β‐ketoamides 5 a – d (see Scheme ) and three of the previously studied β‐ketoesters 7 a – d 6 (see Table 1). The β‐ketoalkanoyl moieties of these compounds were not uniform.…”

Section: Resultsmentioning

confidence: 99%

“…In our standard set‐up for AH (Table 1), methanol solutions (4.0 mL) of 0.5 mmol amounts of β‐ketoamides 5 a – d were hydrogenated in the presence of 2.5 μmol (0.5 mol %) “[{RuCl 2 (binap)} 2 ]⋅NEt 3 ”,5, 14 that is, under the conditions already employed for the AHs of β‐ketoesters 7 a – d 6. After 24 h, workup by flash chromatography on silica gel15 provided the corresponding ( S )‐hydroxyamides 6 a – d in very good yields (94–98 %).…”

Section: Resultsmentioning

confidence: 99%

“…Pairs of β‐ketoesters 1 (Het 1 =OR′) and 2 (Het 1 =OR′′) can be hydrogenated asymmetrically with considerable differences in the reaction rate using Noyori's method2, 3 and “[{RuCl 2 (binap)} 2 ]⋅NEt 3 ”4, 5 as a catalyst (Scheme ): As we found,6 β‐ketoesters 1 with a relatively electron‐rich substituent Het 1 =OR′ are hydrogenated completely on time scales, on which β‐ketoesters 2 with a more electron‐deficient substituent Het 2 =OR′′ remain essentially untouched. Appropriate pairs of substrates contained, amongst others, Het 1 =O‐ t Bu/Het 2 =O‐CH 2 ‐CF 3 or Het 1 =O‐CH 2 ‐CF 3 /Het 2 =O‐CH(CF 3 ) 2 .…”

Section: Introductionmentioning

confidence: 95%

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Asymmetric Hydrogenations One by One: Differentiation of up to Three β‐Ketocarboxylic Acid Derivatives Based on Ruthenium(II)–Binap Catalysis

Krämer

Brückner

2007

Chemistry A European J

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Noyori-type reductions of pairs of beta-ketoamides and beta-ketoesters with elemental hydrogen (4 bar) proceeded substrate by substrate. When Et(2)NH(2) (+)[{RuCl(S)-binap}(2)](mu-Cl)(3)(-) was employed as a catalyst in a methanol or ethanol solution, the substrates were reduced at room temperature in the order beta-ketopyrrolidide > or = beta-ketopiperidide > or = beta-keto(N,N-diethylamide) > beta-keto(alkyl esters) > beta-keto(oligofluoroalkyl esters). This is the first time that beta-ketoamides have been reduced asymmetrically (91 to >98 % ee) under such mild conditions. Monitoring the concentrations of these beta-ketocarboxyl acid derivatives and their respective hydrogenation products over the course of time showed that the most electron-rich substrate is captured by the catalyst preferentially and exothermically; whether this occurs reversibly or irreversibly remains to be determined. The hydrogenation product is subsequently formed. The last transformation includes the rate-determining step. The combination of these events explains why starting from appropriate mixtures of substrates a "first-choice substrate" reacted from early on while the "second-choice substrate" stayed virtually untouched over an extended period of time and reacted no earlier than after the "first-choice substrate" had disappeared. From then onward, however, the "second-choice substrate" also reacted relatively rapidly.

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“…[23] This opened the door for the anticipated asymmetric hydrogenation. [24] By using 1 mol-% of (R)-[{RuCl(tol-BINAP)} 2 (μ-Cl) 3 The installation of the long spacer of mycoside B was preceded by a four-step synthesis of building block 20, as depicted in Scheme 3. Despite the potential of the alkyne zipper reaction to afford α,ω-bifunctionalized aliphatic chains of different lengths, its application to natural product synthesis has been very infrequent since its introduction by Brown and Yamashita in 1975.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of the Phenolic Glycolipid Mycoside B and the Glycosylated p‐Hydroxybenzoic Acid Methyl Ester HBAD‐I, Virulence Markers of Mycobacterium tuberculosis

Barroso¹,

Geerdink²,

Horst³

et al. 2013

Eur J Org Chem

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The phenolic glycolipid mycoside B, present in Mycobacterium bovis and hypervirulent strains of Mycobacterium tuberculosis, has been synthesized for the first time. Multiple methyl groups were introduced by the extensive use of catalytic asymmetric 1,4‐addition reactions, asymmetric hydrogenation of a β‐keto ester afforded the basis for the central 1,3‐diol moiety, and introduction of the 2‐O‐methyl‐α‐L‐rhamnoside unit was achieved by stereoselective glycosylation with p‐iodophenol and subsequent Sonogashira coupling, providing a basis for the generation of analogues. In addition, the related monosaccharide HBAD‐I, present in the same species, has been efficiently synthesized for the first time by selective methylation of the hydroxy group at C‐2 of a rhamnoside.

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Kinetische Differenzierung von β‐Ketoestern durch Ruthenium(II)‐Binap‐katalysierte asymmetrische Hydrierung

Cited by 11 publications

References 64 publications

Ruthenium‐Catalyzed Asymmetric Hydrogenation of 3‐Oxoglutaric Acid Derivatives: A Study of Unconventional Solvent and Substituent Effects

Ruthenium‐Catalyzed Asymmetric Hydrogenation of 3‐Oxoglutaric Acid Derivatives: A Study of Unconventional Solvent and Substituent Effects

Asymmetric Hydrogenations One by One: Differentiation of up to Three β‐Ketocarboxylic Acid Derivatives Based on Ruthenium(II)–Binap Catalysis

Total Synthesis of the Phenolic Glycolipid Mycoside B and the Glycosylated p‐Hydroxybenzoic Acid Methyl Ester HBAD‐I, Virulence Markers of Mycobacterium tuberculosis

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