Enantioselective 1,3‐Dipolar Cycloaddition of Nitrones with Ethyl Vinyl Ether: The Difference between Brønsted and Lewis Acid Catalysis

Jiao, Peng; Nakashima, Daisuke; Yamamoto, Hisashi

doi:10.1002/ange.200705314

Cited by 70 publications

(42 citation statements)

References 55 publications

(14 reference statements)

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“…2b, left side. The intermolecular H-bonding interaction of the N(1)–H with THF in the crystal is involved, indicating that N(1)–H can intermolecularly activate the Lewis basic substrate24, nitrone 2 (refs 34, 44, 45), in the present catalysis. The coordination patterns of the acetate anions in I also have a characteristic role in constructing a specific chiral environment; one of the acetates coordinates to the Ni-centre in the equatorial-equatorial mode, in which the acetate anion is symmetrically bridging [C(19)–O(1): 1.265(2) Å, C(19)–O(2): 1.266(2) Å].…”

Section: Resultsmentioning

confidence: 89%

“…(ii) Catalytic asymmetric [3+2] cycloaddition using transient enolate has yet to be developed, despite the long history of enolate studies253839. Only a few IED cycloadditions with electron-rich alkenes (such as enol ethers and silyl ethers), not enolate, have been reported with asymmetric catalysts25262728293031323334. The [3+2] cycloaddition, which is controlled by the lowest unoccupied molecular orbital of the dipole and the highest occupied molecular orbital of the 1,3-dipolarophile, can be also categorized as ‘type III' according to Sustmann's classification40.…”

Section: Resultsmentioning

confidence: 99%

“…1c). This report provides insights into the elusive mechanistic basis for inverse-electron-demand (IED) [3+2] cycloaddition25262728293031323334 of α-ketoesters with ( E )-nitrones (Fig. 1d).…”

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Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

et al. 2017

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Chiral metal catalysts have been widely applied to asymmetric transformations. However, the electronic structure of the catalyst and how it contributes to the activation of the substrate is seldom investigated. Here, we report an empirical approach for providing insights into the catalytic activation process in the distorted Ni(II)-catalysed asymmetric [3+2] cycloaddition of α-ketoesters. We quantitatively characterize the bonding nature of the catalyst by means of electron density distribution analysis, showing that the distortion around the Ni(II) centre makes the dz2 orbital partially ‘naked', wherein the labile acetate ligand is coordinated with electrostatic interaction. The electron-deficient dz2 orbital and the acetate act together to deprotonate the α-ketoester, generating the (Λ)-Ni(II)–enolate. The solid and solution state analyses, together with theoretical calculations, strongly link the electronic structure of the centrochiral octahedral Ni(II) complex and its catalytic activity, depicting a cooperative mechanism of enolate binding and outer sphere hydrogen-bonding activation.

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Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

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Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

et al. 2017

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“…[246] Es wurde über die Synthese einer chiralen, pseudo-C 2 -symmetrischen, von Binol abgeleiteten N-Triflylphosphoramid-Brønsted-Säure [247,248] und ihrer Metallkomplexe [249] sowie einer chiralen N-Triflylthiophosphoramid-Brønsted-Säure [250] und ihre Verwendung in enantioselektiven Umsetzungen berichtet. Kürzlich wurde ein stärker saures und gänzlich C 2 -symmetrisches Bis(sulfonylimino)-Analogon beschrieben, [251] das eine hoch effiziente enantioselektive Mukaiyama-Aldolreaktion vermittelte.…”

Section: Kohlenstoff-sauerstoff-verknüpfungenunclassified

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

2010

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Der steigende Bedarf an neuen selektiven und umweltverträglichen Methoden in der organischen Synthese treibt die Entwicklung effizienterer Reaktionssysteme an. In diesem Zusammenhang hat man sich häufig auf Übergangsmetalle, Liganden und Additive konzentriert; dem Gegenion des Metallkations wurde weniger Aufmerksamkeit geschenkt. Kürzlich wurden Metallsalze mit einem oder mehreren Triflimidat‐Gegenion(en) (Tf2N−) beschrieben. Triflimidate bilden eine einzigartige Katalysatorklasse mit außergewöhnlicher σ‐ und π‐Lewis‐Acidität, die durch die starke Delokalisierung der Ladung im Triflimidation sowie seine sterische Hinderung begründet wird. Daher wird praktisch kein nucleophiles Verhalten und eine hohe positive Ladungsdichte am Metallkation beobachtet, die seine Lewis‐Acidität verstärkt. Folglich sind Metalltriflimidate häufig effizienter als entsprechende ‐halogenide oder ‐triflate. Dieser Aufsatz beschreibt Methoden zur Herstellung von Metalltriflimidaten und deren Einsatz als Katalysatoren.

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“…Although several organocatalytic asymmetric nitrone [3+2] cycloadditions have been documented, [5] the enantioselective intramolecular version remains a challenge. Herein, we disclose an organocatalytic one-pot asymmetric synthesis of bicyclic isoxazolidines through a domino process involving a Michael addition/ in situ condensation/intramolecular nitrone [3+2] cycloaddition sequence.…”

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confidence: 99%

Highly Stereoselective One‐Pot Synthesis of Bicyclic Isoxazolidines with Five Stereogenic Centers by an Organocatalytic Process

et al. 2009

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Dedicated to Professor Pierre Vogel on the occasion of his 65th birthday Intramolecular nitrone/alkene cycloadditions have received a great deal of attention as a useful methodology for the formation of the intriguing frameworks found in natural products and biologically interesting compounds.[1] The key feature of this approach is the suitable elaboration of the primary cycloadducts, which has proven to be a practical strategy for making different heterocyclic systems.[2] Owing to the labile nature of the NÀO bond under mild reducing conditions, the isoxazolidines provide easy access to a variety of 1,3-difunctional amino alcohols.[3] Particularly, if the intramolecular cycloaddition of nitrone is linked to olefin moiety by a tether of appropriate length, the regio-and diastereoselectivities can be dramatically improved. Most importantly, the introduction of a stereogenic center at the a position of the nitrone can result in asymmetric induction, leading to the generation of new stereocenters having defined configurations.[4] However, multistep synthetic routes were required to synthesize molecules bearing stereocenters at the a position of the nitrone and the olefin moiety from optical sources, such as amino acids and sugars. Although several organocatalytic asymmetric nitrone [3+2] cycloadditions have been documented, [5] the enantioselective intramolecular version remains a challenge. Herein, we disclose an organocatalytic one-pot asymmetric synthesis of bicyclic isoxazolidines through a domino process involving a Michael addition/ in situ condensation/intramolecular nitrone [3+2] cycloaddition sequence.In 2003, our group first described the a-aminoxylation of aldehydes with excellent enantioselectivity. [6a,b] Recently, we also reported highly stereoselective syntheses of tetrahydro-1,2-oxazines by tandem a-aminoxylation and aza-Michael addition.[6] Surprisingly, when we changed the electron-withdrawing group in an aldehyde from a nitro or a malonate group to an ester group, an unexpected bicyclic isoxazolidine product was obtained in 11 % yield with high regioselectivity, endo/exo selectivity, and diastereoselectivity (Scheme 1), by an intramolecular nitrone [3+2] cycloaddition. This finding led us to investigate whether enantiopure bicyclicisoxazolidine products could be obtained if we introduced a stereogenic center at the a position of the aldehyde by asymmetric organocatalysis, which would then undergo subsequent in situ condensation and intramolecular nitrone [3+2] cycloaddition.Recently, asymmetric organocatalytic domino reactions have provided efficient ways to construct complex molecules, and have become a powerful tool in organic chemistry. [7] Among the organocatalytic reactions explored, extensive efforts have been devoted to the Michael addition of aldehydes to nitroolefins. [8] We rationalized that by introducing a stereocenter at the a position of the aldehyde through an asymmetric Michael addition and then subsequent in situ condensation and intramolecular cycloaddition, a novel approach to ...

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Enantioselective 1,3‐Dipolar Cycloaddition of Nitrones with Ethyl Vinyl Ether: The Difference between Brønsted and Lewis Acid Catalysis

Cited by 70 publications

References 55 publications

Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

Highly Stereoselective One‐Pot Synthesis of Bicyclic Isoxazolidines with Five Stereogenic Centers by an Organocatalytic Process

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