The Observation of Two Different Base-catalyzed Processes Occurring in Directly Observable Carbonium Ion Rearrangements

Chiu, N. W. K.; Sorensen, T. S.

doi:10.1139/v73-416

Cited by 4 publications

(2 citation statements)

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“…The formation of cyclopentenyl cations from pentadienyl cations were well documented . Compound 3 involved the establishment of intermediaries γ‐lactones 5 via a cyclopentenyl zwitterion, and one of these, 5c could be isolated (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Novel π_2s+π_2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Dillenschneider

Dufossé²,

Fouillaud³

et al. 2015

Journal of Heterocyclic Chem

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A new, easy and rapid synthesis of γ-dilactones is cis-fused with a cyclopentenic ring via cyclization of 7-chlorotriethylenic-malonic acids. The key step implicates an intramolecular cyclization to a cyclopentenyl cation, according to an electrocyclic π 2s + π 2a conrotatory process. This cyclopentenyl cation led to unstable γ-lactones intermediates that are rearrange to more stable isomers. δ-lactones (6Z and 6E-(3-chlorobut-2-en-2-yl)-5-methyl-3,6-dihydro-2H-pyran-2-one) were obtained as secondary products. Mechanistic pathways were considered. The structures of the newly synthesized compounds were established by elemental and spectral data.

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Section: Resultsmentioning

confidence: 99%

Novel π_2s+π_2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Dillenschneider

Dufossé²,

Fouillaud³

et al. 2015

Journal of Heterocyclic Chem

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“…1,2,3,4,5-pentamethylcyclopentenyl cation eventually forms a translcis ratio of 3.9, starting from either relatively pure isomer. The usual equilibration mechanism would involve deprotonation-reprotonation at C-9 and the rate for such reactions becomes faster the weaker the acid solvent (stronger bases present) (12).…”

Section: Stereochemistry Of Cyclized Ions I V (Question 2 -mentioning

confidence: 99%

Arylallyl cations and their stereospecific cyclization to bicyclic trienylic cations

Dytnerski¹,

Ranganayakulu²,

Singh³

et al. 1982

Can. J. Chem.

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A series of arylallyl alcohols, where aryl = 2,6-dimethylphenyl, mesityl, duryl, orpentamethylphenyl, was prepared. On addition to strong acid, these generate arylallyl cations. In some cases these allyl cations are observable and were characterized as in situ solution species by nmr spectroscopy. In other cases, an immediate cyclization takes place, leading stereospecifically to a series of bicyclic trienyl cations, which were also thoroughly characterized. The stereochemistry of this cyclization reaction, which was initially expected to follow the "rules" for electrocyclic ring closures, was probed in some detail. It is tentatively concluded that the stereochemistry in the products is not that expected from a conrotatory ring closure. Two diarylmethyl cations were also prepared. However, these did not cyclize. Chem. 60,2993Chem. 60, (1982. On aprkpark une serie d'alcools arylallyliques ou le groupe aryl = dimethyl-2,6 phenyle, mesityle, duryle ou pentam6thylph6nyle. Ces alcools en presence d'acides forts produisent des cations arylallyles. Dans certains cas on observe ces cations allyles et on les caractkrise in situ en solution par la spectroscopie de rmn. Dans d'autres cas il se produit immkdiatement une cyclisation, qui conduit de f a~o n ster6osptcifique B des series de cations trienyles bicycliques que l'on a entiirement caract6risCs. On a etabli de f a~o n detaillee la sterkochimie de cette reaction de cyclisation, qui pensait-on devait suivre les rkgles de fermeture electrocyclique de cycles. On conclut que la steriochimie des produits n'est pas celle attendue d'une fermeture conrotatoire de cycle. On a egalement prepare deux cations diarylmtthyles. Toutefois ces cations ne se cyclisent pas.[Traduit par le journal] Introduction secondly, in the event that ring closure does occur, The pentadienyl + , cyclopentenyl (1 + , 11) cation what is the stereochemical outcome? The possible ring closure was first observed nearly 20 years ago reactions are summarized below, the numbers in (I), subsequently classified as an "electrocyclic" brackets referring to the above questions: closure by Woodward and Hoffmann (2) and then, using methyl-substituted derivatives of I of fixed geometry, shown (3) to follow the predicted conrotatory mode.

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ChemInform Abstract: THE OBSERVATION OF TWO DIFFERENT BASE‐CATALYZED PROCESSES OCCURRING IN DIRECTLY OBSERVABLE CARBONIUM ION REARRANGEMENTS

Chiu¹,

Sorensen²

1973

Chemischer Informationsdienst

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The Observation of Two Different Base-catalyzed Processes Occurring in Directly Observable Carbonium Ion Rearrangements

Cited by 4 publications

References 3 publications

Novel π_2s+π_2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Novel π_2s+π_2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Arylallyl cations and their stereospecific cyclization to bicyclic trienylic cations

ChemInform Abstract: THE OBSERVATION OF TWO DIFFERENT BASE‐CATALYZED PROCESSES OCCURRING IN DIRECTLY OBSERVABLE CARBONIUM ION REARRANGEMENTS

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The Observation of Two Different Base-catalyzed Processes Occurring in Directly Observable Carbonium Ion Rearrangements

Cited by 4 publications

References 3 publications

Novel π2s+π2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Novel π2s+π2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Arylallyl cations and their stereospecific cyclization to bicyclic trienylic cations

ChemInform Abstract: THE OBSERVATION OF TWO DIFFERENT BASE‐CATALYZED PROCESSES OCCURRING IN DIRECTLY OBSERVABLE CARBONIUM ION REARRANGEMENTS

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Novel π_2s+π_2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene

Novel π_2s+π_2a Electrocyclization of Triethylenic‐Malonic Acids Exemplified for a One‐Pot Synthesis of New γ‐Dilactones cis‐Fused with a Cyclopentene