Sodium Tetraarylborates as Effective Nucleophiles in Rhodium/Diene-Catalyzed 1,4-Addition to β,β-Disubstituted α,β-Unsaturated Ketones: Catalytic Asymmetric Construction of Quaternary Carbon Stereocenters

Shintani, Ryo; Tsutsumi, Yoshitaka; Nagaosa, Makoto; Nishimura, Takahiro; Hayashi, Tamio

doi:10.1021/ja905432x

Cited by 170 publications

(77 citation statements)

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“…From mechanistic aspects, it is clear that the reaction proceeds through the formation of an rhodium/aryl species, and the enone is activated by the Lewis acidity of the aluminum reagent. [6,12] In summary, we have shown that aryl alanes are excellent nucleophiles for the rhodium-catalyzed conjugate addition reaction. Whilst elevated temperatures are usually required with boron nucleophiles, only 1.2 to 1.5 equivalents of alane afforded the same transformation overnight at 5 8C.…”

Section: L3mentioning

confidence: 96%

“…[5] Only recently have a few articles appeared that report the rhodium-catalyzed formation of quaternary centers on enones, [6] of which one [6b] presents a single example with poor yield. In the more general studies, [6a,c] several parameters in the original protocol [7] needed to be changed: [7] boronic acids were replaced by tetraarylborates [6a] and boroxines, [6c] and chiral diene ligands were used because commercially available binap did not give any conversion.…”

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confidence: 99%

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Rhodium‐Catalyzed Asymmetric 1,4‐Addition of Aryl Alanes to Trisubstituted Enones: Binap as an Effective Ligand in the Formation of Quaternary Stereocenters

et al. 2010

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Section: L3mentioning

confidence: 96%

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confidence: 99%

Rhodium‐Catalyzed Asymmetric 1,4‐Addition of Aryl Alanes to Trisubstituted Enones: Binap as an Effective Ligand in the Formation of Quaternary Stereocenters

et al. 2010

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“…Quaternary stereocenters can be constructed at the b-position of carbonyl groups by catalytic asymmetric conjugate addition of carbon-based nucleophiles to b,b-disubstituted a,b-unsaturated carbonyl compounds [61][62][63][64]. We previously developed a catalytic enantioselective conjugate addition of cyanide to b-monosubstituted a,b-unsaturated N-acylpyrroles and ketones using gadolinium catalysts derived from ligands 5 and 7 [65][66][67][68][69][70][71].…”

Section: Catalytic Enantioselective Conjugate Addition Of Cyanide To mentioning

confidence: 99%

Multimetallic Multifunctional Catalysts for Asymmetric Reactions

Shibasaki

Kanai

Matsunaga

et al. 2011

Bifunctional Molecular Catalysis

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The utility of several types of multimetallic asymmetric catalysts is reviewed. The appropriate design of multidentate chiral ligands provides homobimetallic, heterobimetallic, and polymetallic catalysts upon complexation with metal cations. Cooperative work of multiple catalytically active sites in the asymmetric multimetallic catalysts allows for enhanced catalytic activity and stereoselectivity over monometallic catalysts. Facile systematic tuning of the asymmetric multimetallic catalysts by manipulation of multidentate ligand structure and combination of metal cations enables the generation of diverse set of catalysts having distinct three-dimensional and catalytic properties, boosting the optimization process to identify the best catalyst for a specific reaction of interest.

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“…Sogar quartäre Zentren lassen sich mit gutem ee-Wert, wenn auch deutlich geringerer Ausbeute aufbauen (Eintrag 11). [18] Von besonderem Interesse ist die Koordinationsweise dieser neuen Ligandenklasse. [16] Tabelle 1: Eignung der Olefin-Oxazolin-Liganden 1-18 für die 1,4-Addition von Phenylboronsäure an Cyclohexenon.…”

Section: Björn T Hahn Friederike Tewes Roland Fröhlich Und Frank Gunclassified

Olefin‐Oxazoline (OlefOx) – modulare, leicht zu variierende Liganden für die asymmetrische Katalyse

et al. 2010

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In memoriam Keith FagnouDer Oxazolinring ist ein allgegenwärtiges und privilegiertes Strukturmotiv chiraler Liganden.[1] Die Starrheit des Fünf-rings, seine einfache Synthese und die Verfügbarkeit unterschiedlich substituierter Derivate sind äußerst attraktiv. Am bekanntesten sind wohl die Bisoxazolin-(BOX) [2] und Phosphan-Oxazolin-Liganden (PHOX), [3] aber viele andere heterozweizähnige Oxazolinliganden wie Phosphinite, [4] Phosphite, [5] Pyridine, [6] Phosphoramidate, [7] Phenole, [8] Alkohole, [9] Sulfoxide, [10] Sulfonamide, [11] Thioether [12] und N-heterocyclische Carbene [13] wurden ebenfalls erfolgreich in der asymmetrischen Katalyse eingesetzt. Trotz der strukturellen Diversität dieser Systeme fällt auf, dass nur h 1 -Donoren mit dem Oxazolinfragment kombiniert wurden. Angesichts des jüngsten Erfolgs chiraler Olefinliganden in der asymmetrischen Katalyse [14] schien uns eine Kombination von h 2 -bindenden Alkenen mit Oxazolinen vielversprechend, weil sie neue Koordinationsgeometrien und Möglichkeiten eröffnen sollte. Wir stellen hier die Synthese modularer und einfach variierbarer Olefin-Oxazolin-Liganden (OlefOx) und ihre erfolgreiche Anwendung in der asymmetrischen Katalyse vor.Zunächst wurden mehrere Olefin-Oxazoline mit unterschiedlichen sterischen und elektronischen Eigenschaften synthetisiert (Schema 1).In allen Fällen wurden Olefin und Oxazolin ortho-ständig über einen Benzolring (innerer Ring) verbrückt. Als illustratives Beispiel sei die dreistufige Synthese von Ligand 5 diskutiert (Schema 2 und 3). Ausgehend von kommerziell Schema 1. Die im Rahmen dieser Studie hergestellten Olefin-OxazolinLiganden.Schema 2. Synthese des Olefin-Oxazolin-Liganden 5.[16] Reagentien und Bedingungen: a) (S)-Phenylalaninol, CH 2 Cl 2 , RT, 16 h; danach NBromsuccinimid (NBS), RT, 30 min, 75 %; b) tBuLi, LiNCy 2 (Cy = Cyclohexyl), ClPO(OEt) 2 , THF, À78 8C bis RT, 16 h, 47 %; c) KOtBu, Toluol, 3,4-Dimethoxybenzaldehyd, RT, 15 h, 74 %.

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Sodium Tetraarylborates as Effective Nucleophiles in Rhodium/Diene-Catalyzed 1,4-Addition to β,β-Disubstituted α,β-Unsaturated Ketones: Catalytic Asymmetric Construction of Quaternary Carbon Stereocenters

Cited by 170 publications

References 50 publications

Rhodium‐Catalyzed Asymmetric 1,4‐Addition of Aryl Alanes to Trisubstituted Enones: Binap as an Effective Ligand in the Formation of Quaternary Stereocenters

Rhodium‐Catalyzed Asymmetric 1,4‐Addition of Aryl Alanes to Trisubstituted Enones: Binap as an Effective Ligand in the Formation of Quaternary Stereocenters

Multimetallic Multifunctional Catalysts for Asymmetric Reactions

Olefin‐Oxazoline (OlefOx) – modulare, leicht zu variierende Liganden für die asymmetrische Katalyse

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