Protected propargylic acetals. Nicholas–Prins cyclization leading to functionalized 2-alkynyl-tetrahydropyrans. Intramolecular trapping by allenes

Olier, Clarisse; Gastaldi, Stéphane; Gil, G.; Bertrand, M.

doi:10.1016/j.tetlet.2007.09.021

Cited by 23 publications

(15 citation statements)

References 26 publications

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“…It is important to keep in mind that the Co-complex 23b is the common starting compound for both target structures 12 and 13, because the formation of both isopropenyl and F-isopropyl moieties has been observed during the Nicholas cyclization depending on the nature of starting materials and acids. − Therefore, with two starting Co-complexes for the Nicholas cyclization in hand we were ready to synthesize target 10-memered enediynes.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The replacement of the Lewis acid with HBF 4 ·OEt 2 led to the yield increase of Co-complex of F-isopropyl enediyne 26 up to 30%, while the yield of the compound 27 decreased to 3%. This result correlate with the reported earlier for the Nicholas cyclization through dialkyl-substituted double bond . However, this conditions also afforded macrocyclic byproducts with hydrated Co-free triple bond 29 , 30 (Scheme ).…”

Section: Results and Discussionmentioning

confidence: 99%

“…This result correlate with the reported earlier for the Nicholas cyclization through dialkyl-substituted double bond. 96 However, this conditions also afforded macrocyclic byproducts with hydrated Co-free triple bond 29, 30 (Scheme 6). 101 Notably, that the similar hydration of a triple bond has been observed previously under HBF 4 -promoted substitution of a triazene function in alkynylaryltriazenes with a fluorine.…”

Section: T H Imentioning

confidence: 99%

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Relative Reactivity of Benzothiophene-Fused Enediynes in the Bergman Cyclization

et al. 2018

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To find promising analogues of naturally occurring enediyne antibiotics with a sufficient reactivity in the Bergman cyclization and moderately stable under isolation and storage, a scale of relative enediynes reactivity was created on the basis of calculated free activation energies for the Bergman cyclization within 12 known and new benozothiophene, benzene, and cinnoline annulated 9- and 10-membered enediynes. To verify the predicted reactivity/stability balance, three new carbocyclic enediynes fused to a benzothiophene core bearing 3,4,5-trimethoxybenzene, fluoroisopropyl, and isopropenyl substituents were synthesized using the Nicholas-type macrocyclization. It was confirmed that annulation of a 3,4,5-trimethoxybenzene moiety to a 10-membered enediyne macrocycle imparts high reactivity to an enediyne while also conferring instability under ambient temperature. Fluoroisopropyl-substituted 10-membered enediyne from the opposite end of the scale was found to be stable while moderately reactive in the Bergman cyclization. Along with the experimentally confirmed moderate reactivity (DSC kinetic studies), (fluoroisopropyl)enediyne showed a significant DNA damaging activity in plasmid cleavage assays comparable with the known anticancer drug Zeocin.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Section: T H Imentioning

confidence: 99%

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Relative Reactivity of Benzothiophene-Fused Enediynes in the Bergman Cyclization

et al. 2018

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“…The transformation is initiated by a 1,6-hydride transfer from the 6-O-benzyl group to C-3 of cation 4 (R 1 = Bn, R 2 = Ph) [34,35], which generates an oxocarbenium ion 8. The latter might evolve by two different routes: i) hydrolysis and loss of benzaldehyde to give 6-hydroxy derivative 9, which by protonation would generate a pyranosidic Nicholasoxocarbenium ion 10 [36] whose cyclization will lead to 1,6-anhydro derivative 6; ii) a Prins-type cyclization [37][38][39] leading to bicyclic Nicholas-oxocarbenium ion 11, and thence hemiketal 12, whose ring opening will lead to oxepane hydroxy-ketone 7. We have also shown that some of these transformations are reversible, e.g., oxepane 7 evolved to 1,6-anhydro derivative 6 upon treatment with BF 3 ·OEt 2 (CH 2 Cl 2 , -20 °C, 8 h), thus implying reversibility in the steps 7 → 12 → 11 → 8, the latter step being a retro-Prins fragmentation [40].…”

Section: -O-benzyl and 6-o-allyl Derivativesmentioning

confidence: 99%

Ferrier–Nicholas pyranosidic cations: application to diversity-oriented synthesis

López

Lobo

Miranda

et al. 2014

Pure and Applied Chemistry

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Pyranosidic allylic (Ferrier) cations that share dicobalt hexacarbonyl propargyl (Nicholas) stabilization at C-1, can be easily generated by treatment of hexacarbonyldicobalt alkynyl glycals with BF 3 ·OEt 2 , and display a remarkable reactivity leading to a variety of products. The substituent at O-6 in these glycals plays a pivotal role in directing the outcome of the transformations. Accordingly, 6-O-benzyl or 6-O-allyl groups cause a series of transformations resulting in the stereoselective formation of oxepanes through a process that involves an initial hydride transfer step from the allyl or benzyl substituent to the Ferrier-Nicholas cation. On the contrary, 6-OH derivatives undergo an overall ring contraction to branched tetrahydrofuran derivatives. 6-O-Silyl derivatives, in the presence of heteroaryl nucleophiles, were transformed into C-3 branched bis-C-Cglycosides, containing two of such molecules.

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“…Unfortunately, there were no Prins or aza-Prins reactions of simple ynals in the literature. The closest precedence was a cobalt-mediated reaction, where the cobalt complex serves to mask the alkyne to produce protected 2-alkynyl tetrahydropyrans . We were encouraged, however, by iron-promoted aza-Prins reactions of enals for the synthesis of 2-vinyl piperidines .…”

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confidence: 99%

Nickel-Catalyzed Domino Cross-Electrophile Coupling Dicarbofunctionalization Reaction To Afford Vinylcyclopropanes

et al. 2021

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We have established a nickel-catalyzed domino reaction that harnesses sulfonamide, alkyl chloride, and alkyne functionalities in a multistep sequence to afford vinylcyclopropanes bearing tetrasubstituted olefins. The starting materials are prepared by iron-promoted aza-Prins reactions of ynals. This method provides rapid synthetic access to valuable building blocks with applications in medicinal chemistry. Experimental and computational results support the initiation of the catalytic cycle by oxidative addition of the propargylic sulfonamide, and a key ambiphilic allenylnickel intermediate leads to a bifurcated reaction pathway that generates olefin isomers.

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Protected propargylic acetals. Nicholas–Prins cyclization leading to functionalized 2-alkynyl-tetrahydropyrans. Intramolecular trapping by allenes

Cited by 23 publications

References 26 publications

Relative Reactivity of Benzothiophene-Fused Enediynes in the Bergman Cyclization

Relative Reactivity of Benzothiophene-Fused Enediynes in the Bergman Cyclization

Ferrier–Nicholas pyranosidic cations: application to diversity-oriented synthesis

Nickel-Catalyzed Domino Cross-Electrophile Coupling Dicarbofunctionalization Reaction To Afford Vinylcyclopropanes

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