Chemistry of Ammonium Betaines: Application to Ion-Pair Catalysis for Selective Organic Transformations

Uraguchi, Daisuke; Ooi, Takashi

doi:10.5059/yukigoseikyokaishi.76.1144

“…In contrast, using Cs 2 CO 3 and C5 equipped with a neutral axially chiral residue bearing an aromatic OH group, stereoselectivity was considerably higher. However, nearly complete diastereoselectivity was only attained with control catalyst C6 containing an achiral zwitterionic imidazolium/aryloxide moiety [26] . In agreement with the observation that the configuration of the axially chiral binaphthol unit has a minor effect on stereocontrol, enantioselectivity was high with C6 .…”

Section: Methodssupporting

confidence: 82%

Enantiodivergent [4+2] Cycloaddition of Dienolates by Polyfunctional Lewis Acid/Zwitterion Catalysis

Miškov-Pajić

¹

,

Willig

²

,

Wanner

³

et al. 2020

Angewandte Chemie

8

0

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Diels-Alder reactions have become established as one of the most effective ways to prepare stereochemically complex six-membered rings. Different catalysis concepts have been reported, including dienophile activation by Lewis acids or H-bond donors and diene activation by bases. Herein we report a new concept, in which an acidic prodiene is acidified by a Lewis acid to facilitate deprotonation by an imidazoliumaryloxide entity within a polyfunctional catalyst. A metal dienolate is thus formed, while an imidazolium-ArOH moiety probably forms hydrogen bonds with the dienophile. The catalyst type, readily prepared in few steps in high overall yield, was applied to 3-hydroxy-2-pyrone and 3-hydroxy-2-pyridone as well as cyclopentenone prodienes. Maleimide, maleic anhydride, and nitroolefin dienophiles were employed. Kinetic, spectroscopic, and control experiments support a cooperative mode of action. High enantioselectivity was observed even with unprecedented TONs of up to 3680. Scheme 1. Comparison of previous Diels-Alder approaches with that presented.

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“…However, nearly complete diastereoselectivity was only attained with control catalyst C6 containing an achiral zwitterionic imidazolium/aryloxide moiety. [26] In agreement with the observation that the configuration of the axially chiral binaphthol unit has a minor effect on stereocontrol, enantioselectivity was high with C6. Nevertheless, these results demonstrate that the presence of the zwitterionic moiety (achiral or chiral) is necessary to attain high control.…”

supporting

confidence: 87%

Enantiodivergent [4+2] Cycloaddition of Dienolates by Polyfunctional Lewis Acid/Zwitterion Catalysis

Miškov-Pajić

¹

,

Willig

²

,

Wanner

³

et al. 2020

View full text Add to dashboard Cite

Diels-Alder reactions have become established as one of the most effective ways to prepare stereochemically complex six-membered rings. Different catalysis concepts have been reported, including dienophile activation by Lewis acids or H-bond donors and diene activation by bases. Herein we report a new concept, in which an acidic prodiene is acidified by a Lewis acid to facilitate deprotonation by an imidazoliumaryloxide entity within a polyfunctional catalyst. A metal dienolate is thus formed, while an imidazolium-ArOH moiety probably forms hydrogen bonds with the dienophile. The catalyst type, readily prepared in few steps in high overall yield, was applied to 3-hydroxy-2-pyrone and 3-hydroxy-2-pyridone as well as cyclopentenone prodienes. Maleimide, maleic anhydride, and nitroolefin dienophiles were employed. Kinetic, spectroscopic, and control experiments support a cooperative mode of action. High enantioselectivity was observed even with unprecedented TONs of up to 3680.

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“…To validate the mechanism, DFT computational calculations were conducted at the M062x/6-311++G(d,p)//M062x/6-31G(d) level of theory. 13 On the basis of these experimental and DFT computational results and previously reported findings for PTCs, 14,15 a plausible catalytic cycle mechanism for the asymmetric (3 + 3) cycloaddition reaction is proposed: the reaction under the catalyst reaction mechanism (Scheme 3). In PTC condition, the hydroxyl group in catalyst Ie acts as a bridge role in the deprotonation/protonation process.…”

mentioning

confidence: 86%

Highly Enantioselective Synthesis of [1,2,4]Triazino[5,4-a]isoquinoline Derivatives via (3 + 3) Cycloaddition Reactions of Diazo Compounds and Isoquinolinium Methylides

Wu

¹

,

Yan

²

,

Li

³

et al. 2022

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An array of chiral [1,2,4]triazino [5,4-a]isoquinoline derivatives were obtained in excellent yields (up to 98%) and with excellent enantioselectivities (up to 99% ee) via a new highly asymmetric (3 + 3) cycloaddition reaction of diazo compounds and isoquinolinium methylides, with a bifunctional chiral phasetransfer catalyst (PTC). Density functional theory calculations show that PTC has a bridge role in the deprotonation/protonation process. The obtained products were transformed into densely functionalized polycyclic heterocompounds with multiple stereocenters.

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Chemistry of Ammonium Betaines: Application to Ion-Pair Catalysis for Selective Organic Transformations

Cited by 9 publications

References 87 publications

Enantiodivergent [4+2] Cycloaddition of Dienolates by Polyfunctional Lewis Acid/Zwitterion Catalysis

Enantiodivergent [4+2] Cycloaddition of Dienolates by Polyfunctional Lewis Acid/Zwitterion Catalysis

Enantiodivergent [4+2] Cycloaddition of Dienolates by Polyfunctional Lewis Acid/Zwitterion Catalysis

Highly Enantioselective Synthesis of [1,2,4]Triazino[5,4-a]isoquinoline Derivatives via (3 + 3) Cycloaddition Reactions of Diazo Compounds and Isoquinolinium Methylides

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