Symmetry Breaking in Asymmetric Catalysis:  Racemic Catalysis to Autocatalysis

Mikami, Kōichi; Yamanaka, Masahiro

doi:10.1021/cr000260z

Cited by 209 publications

(56 citation statements)

References 226 publications

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“…[76][77][78][79][80][81][82][83][84] Gemische aus chiralen und achiralen Liganden können bekanntlich mit Übergangsmetallen Heterokomplexe bilden und so günstige oder nachteilige Wirkungen auf die asymmetrische Katalyse haben. [89][90][91][92] Ausgehend von Untersuchungen an Gemischen verschiedener chiraler einzähniger Liganden wurde aber ein neues Prinzip in die asymmetrische Katalyse eingeführt. [93][94][95][96][97][98] [92-95, 97, 99-101] Durch Selbstorganisation unter Gleichgewichtsbedingungen entstehen homochirale und heterochirale Komplexe, wobei die heterochiralen Komplexe mit zwei nicht identischen chiralen Liganden aktiver oder selektiver (oder beides) sein können als die gewöhnlich entstehenden homochiralen Katalysatoren.…”

Section: Phosphoramidite: Struktur Synthese Und Eigenschaftenunclassified

“…Das Konzept der asymmetrischen Katalyse mit flexiblen Biphenyl-Liganden ist wohlbekannt [90,91,125,126] und wurde auch erfolgreich auf die Phosphoramidit-Liganden L16 mit einem achiralen, flexiblen Biphenol als Diol und einer chiralen Aminogruppe angewendet (Abbildung 5). [127,128] Später wurden Biphenol-Liganden mit verschiedenen Substituenten in 2-und 4-Stellung beschrieben.…”

Section: Neue Entwicklungenunclassified

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Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

2010

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Die asymmetrische Katalyse mit Übergangsmetallkomplexen ist die Grundlage unzähliger stereoselektiver Umwandlungen und hat damit das Bild der modernen Synthesechemie gewandelt. Der Schlüssel zum Erfolg war die Entwicklung chiraler Liganden zur Kontrolle der Regio‐, Diastereo‐ und Enantioselektivität. Dabei haben sich Phosphoramidite als eine äußerst vielseitige und leicht zugängliche Klasse von chiralen Liganden erwiesen. Ihre modulare Struktur ermöglicht die Herstellung von Ligandenbibliotheken und erleichtert die Feinabstimmung für eine bestimmte katalytische Reaktion. Phosphoramidite bewirken oft außerordentlich hohe Stereoselektivitäten, und ihre einzähnige Natur ist in der kombinatorischen Katalyse, die gemischte Liganden verwendet, unverzichtbar. In diesem Aufsatz werden neue Entwicklungen in der asymmetrischen Katalyse mit Phosphoramiditen diskutiert, wobei der Schwerpunkt auf der Bildung von Kohlenstoff‐ Kohlenstoff‐ und Kohlenstoff‐Heteroatom‐Bindungen liegt.

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Section: Phosphoramidite: Struktur Synthese Und Eigenschaftenunclassified

Section: Neue Entwicklungenunclassified

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

2010

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“…Since the diastereomeric catalyst (S a ,S,S)-1a was less active (entry 2), (R a ,S,S)-1a constitutes a matched pair and (S a ,S,S)-1a would be a mismatched pair for oxidative coupling of 2-naphthol. The tropos-type 72) complexes (S,S)-7 and 8, with free rotation of either phenyl-phenyl or phenyl-naphthyl units, were also prepared, though their reaction rates were decreased compared to (R a ,S,S)-1a (entries 7,8). In the case of the complexes (S,S)-7 and 8, the equilibrium between matched and mismatched conformations diminished the reaction rate.…”

Section: Preparation Of Dinuclear Vanadium(iv) Complexesmentioning

confidence: 99%

Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation Mechanism

Takizawa

2009

CHEMICAL & PHARMACEUTICAL BULLETIN

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Catalytic asymmetric reactions are among the most powerful synthetic methods to obtain optically active compounds.1,2) Recent challenges focus on the development of asymmetric catalysts for carbon-carbon bond-forming reactions with high activity and broad substrate generality, which lead to practical, efficient, and environmentally benign chemical syntheses. Dual activation systems for substrates such as nucleophiles and electrophiles lead to enhanced reaction rates and more specific control of the transition structure with respect to the catalyst's asymmetric environment. Dual activation catalyses can be classified into three categories ( Fig. 1): Type 1) dual activation using two different kinds of catalysts [3][4][5][6][7][8][9][10][11][12] ; Type 2) conjugated-type dual activation with a functional group such as a phosphate which has both acidic and basic sites in one functionality [13][14][15] ; and Type 3) dual activation by two catalytic sites in a single catalyst. For efficient dual activation of the substrates, a balance between these two functionalities in the catalyst is required. For example, in an acid-base type catalyst the selfquenching reaction of acidic and basic moieties on the catalyst can lead to its inactivation.We postulated that a chiral complex possessing two identical metal centers in a single molecule, which could activate two substrates simultaneously in a homolytic coupling reaction of 2-naphthol molecules, would enhance the reaction rate with high enantioselectivity. To achieve the new dual activation catalysis in an oxidative coupling reaction, we designed the catalyst (R a ,S,S)-1 42) bearing two active sites attached to a binaphthyl skeleton, taking advantage of the activation entropy (Fig. 2). Activation entropy strongly con- Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation MechanismShinobu TAKIZAWA This review describes our recent efforts in the development of chiral dinuclear vanadium complexes which work as dual activation catalysts for oxidative coupling of 2-naphthols. A chiral dinuclear vanadium(IV) complex (R a ,S,S)-1a possessing (S)-tert-leucine moieties at the 3,3 -positions of the (R)-binaphthyl skeleton was developed, and found to promote oxidative coupling of 2-naphthol to afford (S)-1,1 -bi-2-naphthol (BINOL) with 91% ee. To verify the dual activation mechanism, mononuclear vanadium(IV) complex (S)-10 was also prepared. Kinetic analysis revealed that the reaction rate of oxidative coupling of 2-naphthol promoted by (R a ,S,S)-1a is 48.3 times faster than that of (S)-10. In the coupling reaction, the two vanadium metals in the chiral complex activate two molecules of 2-naphthol simultaneously achieving a high reaction rate with high enantiocontrol. Since the dinuclear vanadium(IV) complex was found to be readily oxidized to afford a corresponding vanadium(V) species during preparation in air, a new synthetic procedure using VOCl 3 and a convenient one-pot procedure using VOSO 4 under O 2 have been applie...

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“…The concept of chiral amplification, an example of a nonlinear effect, which previously was largely ignored, now makes consideration of nonlinear effects important for all asymmetric reactions (143,144). Since the example of Scheme 16 is indeed an amino alcohol, the question of whether this enantiomerically pure product can serve as its own catalyst, i.e., the concept of autocatalysis, arises (145,146). Furthermore, combining autocatalysis with chiral amplification raises the question of whether a small amount of product of low ee can catalyze its own formation with high ee.…”

Section: Asymmetric Coc Bond Formationmentioning

confidence: 99%

Asymmetric Catalysis: An Enabling Science

Trost

2004

ChemInform

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Chirality of organic molecules plays an enormous role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form is one of the most difficult challenges. The advances being made stem from the convergence of a broader understanding of theory and how structure begets function, the developments in the interface between organic and inorganic chemistry and, most notably, the organic chemistry of the transition metals, and the continuing advancements in the tools to help define structure, especially in solution. General themes for designing catalysts to effect asymmetric induction are helping to make this strategy more useful, in general, with the resultant effect of a marked enhancement of synthetic efficiency.

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Symmetry Breaking in Asymmetric Catalysis: Racemic Catalysis to Autocatalysis

Cited by 209 publications

References 226 publications

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation Mechanism

Asymmetric Catalysis: An Enabling Science

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