Syntheses of chiral hybrid O,N-donor ligands for the investigation of lanthanide complex reactivities in direct aldol condensations

Młynarski, Jacek; Jankowska, Joanna; Rakiel, Bartosz

doi:10.1016/j.tetasy.2005.02.023

Cited by 20 publications

(7 citation statements)

References 31 publications

(18 reference statements)

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“…Catalyst development for the direct asymmetric aldol‐Tishchenko reaction : Our discovery that ytterbium‐triflate complexes with chiral diols16 and aminoesters18a effectively catalyzed the aldol‐Tishchenko reaction between diethyl ketone and aromatic aldehydes prompted us to test the catalytic activity of a range of chiral ligands for this process. Based on our previous observations, we expected that ligands containing both a hydroxy group and an amino function should be useful and active for the reaction.…”

Section: Resultsmentioning

confidence: 99%

Chiral Ytterbium Complex‐Catalyzed Direct Asymmetric Aldol‐Tishchenko Reaction: Synthesis of anti‐1,3‐Diols

Młynarski

Rakiel

Stodulski

et al. 2006

Chemistry A European J

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The asymmetric aldol-Tishchenko reaction of aromatic aldehydes with aliphatic and aromatic ketones has been developed as an efficient strategy for the synthesis of anti-1,3-diols in good yield with high diastereocontrol and good levels of enantioselectivity. This domino-type reaction is catalyzed by a chiral ytterbium complex that promotes both the aldol reaction through enolization of the carbonyl compound and the Evans-Tishchenko reduction of the aldol intermediate. The stereochemistry of the resulting diols is also investigated and finally proved by using CD techniques.

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Section: Resultsmentioning

confidence: 99%

Chiral Ytterbium Complex‐Catalyzed Direct Asymmetric Aldol‐Tishchenko Reaction: Synthesis of anti‐1,3‐Diols

Młynarski

Rakiel

Stodulski

et al. 2006

Chemistry A European J

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“…Previously, we reported our initial attempt at the asymmetric aldol–Tishchenko reaction with a glycine‐based chiral ligand complexed with Yb salts, by which the direct asymmetric aldol reaction of 3‐pentanone was efficiently accomplished 12. In our preliminary experiments, we could not achieve satisfactory enantioselectivity (20 % ee , Scheme ).…”

Section: Resultsmentioning

confidence: 93%

“…In this light, it is surprising that, despite the increasing acceptance of chiral lanthanide complexes as direct aldol reaction catalysts,10 the application of modified amino acids as chiral ligands is limited mainly to zinc complexes 11. One example of a chiral lanthanide complex application is the direct, asymmetric, aldol–Tishchenko reaction promoted by chiral Yb complexes 12…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Yb Complexes with Amino‐Acid‐Armed Ligands for Direct Asymmetric Tandem Aldol Reduction Reactions

2008

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A synthetic route to a series of C 2 -symmetric chiral ligands armed with selectively protected amino acids have been developed with the aim to study the potential of the corresponding Yb(III) complexes for enantioselective direct aldol reactions. These ligands, which contain chiral bis(ester) or bis(amide) moieties, were readily prepared in enantiomerically pure form by the reaction of (S,S)-hydrobenzoin or (S,S)-diphenylethylenediamine with various chiral amino acids. In this article, the asymmetric aldol-reduction reaction leading to 1,3-diols (known as the aldol-Tishchenko reaction) has been performed with an elaborated family of ligands. This unique tandem reaction was catalysed by chiral [a] 5553 Yb complexes that promote both the aldol reaction of unactivated carbonyl compounds and the Evans-Tishchenko reduction of the aldol intermediates. 1,3-anti-Diols with three stereogenic centers have been isolated as a result of the condensation of aliphatic ketones with aromatic aldehydes with up to 64 % ee. Additional detailed investigations of the nature of the binding of both class of ligands have also been carried out with high-resolution 1 H-, 13 C-, and 14 N-NMR techniques.(5554 Scheme 2. Asymmetric aldol-Tishchenko reaction promoted by the ligand 1-Yb complex.

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“…Binding of the amine to the hydroxy group through a hydrogen bond (type‐ 18 structure) was supposed to be essential for catalytic activity 34. We presumed that the amino group fixed to the molecule would exhibit catalytic activity as well, and that such a defined architecture would form a more efficient catalyst 35. To realize this concept and make use of the general principle of the two‐center ligand, we reported the synthesis of a catalyst composed of ytterbium triflate and a bis(aminoester)‐type ligand 21 .…”

Section: Condensation Of Aldehydes To Ketones and Ketone Aldolsmentioning

confidence: 99%

Direct Asymmetric Aldol‐Tishchenko Reaction

Młynarski

2006

Eur J Org Chem

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The asymmetric direct aldol reaction of nonpreactivated substrates constitutes one of the most powerful tools in current synthetic chemistry. In the last few years, chiral metal complexes have been found to catalyze the direct aldol addition of unmodified ketones to aldehydes with both high efficiency and selectivity. However, many problems have to be overcome in this still young field of chemistry. The most challenging aspect of this chemistry is the substrate limitation of known catalysts. In this field, the asymmetric aldol‐Tishchenko reaction can be regarded as a parallel methodology that expands the scope of possible applications. In the aldol‐Tishchenko reaction, two aldehyde molecules undergo addition to form an aldol adduct, which is subsequently reduced by a third aldehyde to yield 1,3‐diol monoesters through a [3,3]‐bond reorganization. With the use of aldehydes and ketones in the aldol‐Tishchenko reaction, diols with three adjacent stereogenic centers can be created in one single operation. Thus, the reaction can be regarded as an extremely atom efficient method for the construction of enantiomerically enriched products that can serve as fundamental building blocks in synthesis. Moreover, the aldol‐Tishchenko condensation is nowadays the most efficient methodology available for the direct catalytic asymmetric aldol reaction of methylene ketones. This article provides a synopsis of this field and highlights some of the challenges that still remain.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Syntheses of chiral hybrid O,N-donor ligands for the investigation of lanthanide complex reactivities in direct aldol condensations

Cited by 20 publications

References 31 publications

Chiral Ytterbium Complex‐Catalyzed Direct Asymmetric Aldol‐Tishchenko Reaction: Synthesis of anti‐1,3‐Diols

Chiral Ytterbium Complex‐Catalyzed Direct Asymmetric Aldol‐Tishchenko Reaction: Synthesis of anti‐1,3‐Diols

Synthesis of Yb Complexes with Amino‐Acid‐Armed Ligands for Direct Asymmetric Tandem Aldol Reduction Reactions

Direct Asymmetric Aldol‐Tishchenko Reaction

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