Regioselective Asymmetric Formal (3+2) Cycloadditions of Nitrone Ylides from Isatins and Enals

Chen, Yurong; Zhan, Gu; Du, Wei; Chen, Ying‐Chun

doi:10.1002/adsc.201600805

Cited by 19 publications

(6 citation statements)

References 43 publications

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“…On the other hand, Du, Chen et al exploited stable and readily available N -benzyl nitrones of isatins 919 as precursors of the corresponding ylides in catalytic asymmetric γ,α-regioselective [3 + 2] cycloadditions to enals 920 ( Scheme 232 , eq 2). 621 The reactions proceeded smoothly under the assistance of TMS-protected diphenyl prolinol A4 and a catalytic amount of trimethylamine, giving rise, after reduction with NaBH 4 , to N -hydroxy-pyrrolidinyl derivatives 921 in moderate to good yields and considerable enantioselectivity. The detection in the reaction of a Michael adduct intermediate from N -benzyl nitrone ylide (R 1 = Me, R 3 = Ph) and cinnamaldehyde confirmed the supposed stepwise mechanism for this cycloadditive process.…”

Section: Vinylogous Amides and Lactamsmentioning

confidence: 99%

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

et al. 2020

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The principle of vinylogy states that the electronic effects of a functional group in a molecule are possibly transmitted to a distal position through interposed conjugated multiple bonds. As an emblematic case, the nucleophilic character of a π-extended enolate-type chain system may be relayed from the legitimate α-site to the vinylogous γ, ε, ..., ω remote carbon sites along the chain, provided that suitable HOMO-raising strategies are adopted to transform the unsaturated pronucleophilic precursors into the reactive polyenolate species. On the other hand, when “unnatural” carbonyl ipso -sites are activated as nucleophiles (umpolung), vinylogation extends the nucleophilic character to “unnatural” β, δ, ... remote sites. Merging the principle of vinylogy with activation modalities and concepts such as iminium ion/enamine organocatalysis, NHC-organocatalysis, cooperative organo/metal catalysis, bifunctional organocatalysis, dicyanoalkylidene activation, and organocascade reactions represents an impressive step forward for all vinylogous transformations. This review article celebrates this evolutionary progress, by collecting, comparing, and critically describing the achievements made over the nine year period 2010–2018, in the generation of vinylogous enolate-type donor substrates and their use in chemical synthesis.

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Section: Vinylogous Amides and Lactamsmentioning

confidence: 99%

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

et al. 2020

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“…16 The asymmetric formal (3+2) cycloaddition of isatin-derived nitrone ylides and enals was also accomplished (Scheme 10). 17 As mentioned in Section 2, an N-benzyl group is necessary to reach the acidity able to start the reaction. In fact nitrones with simple N-alkyl or N-allyl groups were unreactive.…”

Section: Short Review Syn Thesismentioning

confidence: 99%

Enantioselective Vinylogous Reactions of 3-Alkylidene Oxindoles

Dalpozzo

Mancuso

2018

Synthesis

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Oxindoles represent an important class of bioactive compounds and synthetic derivatives found in many natural products. Most of these compounds are chiral molecules and the challenge of their asymmetric synthesis has fascinated many research groups. In particular, the creation of chiral centers out of the oxindole ring by vinylogous addition to 3-alkylidene-substituted oxindoles (3-alkylidene-1,3-dihydro-2H-indol-2-ones) has emerged in recent years. This review aims to give an overview of this topic.1 Introduction2 Aldol and Mannich Reactions3 Addition to Unsaturated Carbonyl Compounds4 Addition to Nitroalkenes5 Miscellaneous6 Conclusion

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“…The effect of hydrogen bonds, and the factors that influenced the stereochemistry were explored to get useful information on organocatalytic reactions of nitrone ylides and the potential role of thiourea in iminium catalysis. Both in our preliminary communication [17] and a previous similar study with isatin-derived nitrones, [18] triethylamine was used to deprotonate the nitrone 7 and generate the nitrone ylide assuming a mechanism involving the anion derived from 7. Under this hypothesis the role of thiourea 3 was limited to activate the carbonyl group in the first step and/or the nitrone moiety in the second one.…”

mentioning

confidence: 99%

A Case Study of Thiourea‐Assisted Iminium Formation by Hydroxyl Anion Binding: Kinetic, Spectroscopic and Computational Evidences

et al. 2017

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The experimental and computational study of the mechanism of the iminium-organocatalyzed formation of Nhydroxypyrrolidines from nitrones, as a case study, revealed a hitherto unknown mode of action for the Schreiner's thiourea used as co-catalyst. The experimental data suggest that thiourea promotes the formation of the iminium ion through hydroxyl anion recognition forming a stable ion pair. Such an ion pair facilitates enolization of the nitrone through a H-bond network thus promoting the reaction with iminium ion. The computational model supports the mechanism and the catalytic cycle. This mechanistic rationale is supported by the lack of reactivity of preformed iminium ion with the nitrone in the absence of thioureahydroxyl complex and the observed reactivity when a complex thiourea-tetrabutylammonium hydroxide is added.

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Regioselective Asymmetric Formal (3+2) Cycloadditions of Nitrone Ylides from Isatins and Enals

Cited by 19 publications

References 43 publications

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

New Developments of the Principle of Vinylogy as Applied to π-Extended Enolate-Type Donor Systems

Enantioselective Vinylogous Reactions of 3-Alkylidene Oxindoles

A Case Study of Thiourea‐Assisted Iminium Formation by Hydroxyl Anion Binding: Kinetic, Spectroscopic and Computational Evidences

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