Epoxidation of substituted norbornenes. Stereochemical aspects and accompanying intramolecular transformations

Kas’yan, L. I.

doi:10.1070/rc1998v067n04abeh000355

Cited by 13 publications

(7 citation statements)

References 191 publications

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“…14 Nevertheless, in the examples reported here, the substrates have no polar substituents but still solvent effects are observed. We anticipate, that in all cases examined, a hydrogen bonding is formed 16 between the incoming dioxirane and the suitable bridge protons leading to an improved regio-and diastereoselectivity. Thus, in the limonene series, a hydrogen bonding between the proton of the C-4 position and the dioxirane could be developed in the transition state (Figure ), leading to favored syn-addition (towards C-4 proton).…”

Section: Methodsmentioning

confidence: 89%

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Substrate-Induced Diastereoselectivity in the Dimethyldioxirane Epoxidation of Simple Alkenes and Dienes

Asouti¹,

Hadjiarapoglou²

2001

Synlett

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Various alkenes and dienes, such as (R)-or (S)-limonene 2, 2-carene 6, 3-carene 8, (R)-a-pinene 10, (S)-a-pinene 12, and endo-dicyclopentadiene 14 were transformed into the corresponding mono-and bis-epoxides by epoxidation with dimethyldioxirane (as an acetone solution). The selectivity observed in these epoxidations is explained by the assumption of hydrogen bonding between bridge protons and the dioxirane.Dimethyldioxirane (DMD, in situ or isolated as solution) has been established 1 as a widely-used oxidant, due to the convenience of its isolation 2 from cheap, commercially available starting materials, its efficiency, and its performance under strictly neutral conditions. Its reaction mode includes epoxidation 3 of alkenes, oxygen insertion 4 into s-bonds, and heteroatom oxidation. 5 Alkene epoxidation has found numerous applications 6 in the total syntheses of natural products. However, there are only few impressive results of regio-and diastereoselective epoxidations with DMD, i.e. the regioselective epoxidation 7 of a disubstituted double bond over a trisubstituted enol ether moiety, and the exclusive epoxidation 8 at the endocyclic double bonds of pentafulvenes.We thought that this powerful oxidant might be more regio-and diastereoselective than initially assumed. A more systematic investigation of simple strained alkenes could lead to interesting observations concerning transition states of the epoxidation mechanism. Herein, we report the DMD epoxidations of simple bicyclic alkenes and dienes yielding often regio-and diastereoselectively the corresponding mono-and bis-epoxides.Epoxidation of (R)-(+)-limonene R-2 with dimethyldioxirane at -5°C yields a 65:35 mixture of mono-epoxides R-3, R-4 (66% yield at 90% conversion) and bis-epoxide R-5 (34% yield at 90% conversion) (Scheme 1). The mixture of epoxides R-3, R-4 was separated from R-5 by column chromatography; addition of another equivalent of dimethyldioxirane led to the isolation of bis-epoxide R-5. The corresponding 8,9-epoxide was not detected in the crude reaction mixture, a fact that indicates the electrophilic character of dimethyldioxirane and its preference for the more electron-rich double bond of the molecule. Although the diastereoselectivity was poor [ratio R-3/R-4 = 1:8], it is better than many other oxidation protocols involving oxidants such as mCPBA 9 or PhIO, 10 H 2 O 2 11 and various Fe-porphyrins. The diastereoselectivity was influenced by the co-solvent used in the epoxidation (Table 1). When acetonitrile or methanol, were used as co-solvents (entries 4, 6) the conversion was quantitative but the diastereoselectivity was low, while in the case of methanol the formation of bis-epoxide was negligible (1 %). In contrast, when dichloromethane was used (entries 1, 3), the conversion was smaller, the diastereoselectivity better, and bis-epoxide R-5 was formed in larger amounts. The best diastereoselectivity was observed in the case of petroleum ether (entry 5), where also the lowest conversion was obtained. Scheme 1It seems that the dias...

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Section: Methodsmentioning

confidence: 89%

“…When excess of endo-dicyclopentadiene 14 was employed, then a mixture (49:51) of epoxides 15, 16 were produced. With excess of dimethyldioxirane, bis-epoxide 17 was quantitatively produced.…”

Section: Methodsmentioning

confidence: 99%

Substrate-Induced Diastereoselectivity in the Dimethyldioxirane Epoxidation of Simple Alkenes and Dienes

Asouti¹,

Hadjiarapoglou²

2001

Synlett

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“…4) with the purpose of checking the best match between theoretical and experimental data. Even though that the exo ‐stereoselectivity of epoxidation in norbornene derivatives is preferential in most cases, the endo isomer 4a was verified. The calculated chemical shifts of the structures 2a , 2b , 3a , 3b , 4a and 4b can be found in the Supporting information (Table S1).…”

Section: Resultsmentioning

confidence: 99%

Structural elucidation of dioxa‐cage compounds from tetrahydroisobenzofuran‐1(3H)‐one: analysis of NMR data and GIAO chemical shifts calculations

Resende

Alvarenga

2016

Magnetic Reson in Chemistry

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The polycyclic compounds, especially the dioxa-cages, have attracted considerable attention in recent years. In our work, a series of 9β-substituted 3-oxo-4,11-dioxatetracyclo[5.2.1.1 .0 ]undecane compounds were unexpectedly isolated during bromination, chlorination and epoxidation reactions of the 3-hydroxy-3a,4,7,7a-tetrahydro-4,7-methanoisobenzofuran-1(3H)-one. After careful analysis of the NMR data, the chemical shifts of the isolated and the expected products were predicted by theoretical calculations using density functional theory and gauge including atomic orbitals. The best correlation between calculated and experimental data was evaluated by comparing mean absolute errors and applying DP4 probability methodology. Results from both approaches indicated a correct structural elucidation. Copyright © 2016 John Wiley & Sons, Ltd.

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“…The IR spectra are not substantially informative for structural confirmation of compounds (18)(19)(20)(21)(22)(23)(24)(25)(26) as both characteristic absorption bands (860-850 cm -1 , ν C-O, 3040-3020 cm -1 , ν C-H of the epoxynorbornane fragment) occupy the same regions as the benzenering bonds vibrations. However, the signals of the H 2 and H 3 protons of the epoxide cycle, in the 2.9-3.1 ppm region of the 1 H NMR spectra, are characteristic of epoxy compounds [23,24,29,30].…”

Section: Epoxidation Of Ureasmentioning

confidence: 99%

“…However, the signals of the H 2 and H 3 protons of the epoxide cycle, in the 2.9-3.1 ppm region of the 1 H NMR spectra, are characteristic of epoxy compounds [23,24,29,30]. Additional, important proof for the epoxide structure was the shift to high field (0.84-0.66 ppm) of the signal of one of the protons (H 7a ) at the bridge carbon atom, a phenomenon caused by the influence of the magnetic field of the threemembered ring.…”

Section: Epoxidation Of Ureasmentioning

confidence: 99%

Azabrendanes V. Synthesis and reactions of stereoisomeric exo- and endo-5-aminomethylbicyclo[2.2.1]hept-2-ene-based ureas

Kas’yan

Kas’yan²,

Tarabara

et al. 2008

Open Chemistry

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Epoxidation of substituted norbornenes. Stereochemical aspects and accompanying intramolecular transformations

Cited by 13 publications

References 191 publications

Substrate-Induced Diastereoselectivity in the Dimethyldioxirane Epoxidation of Simple Alkenes and Dienes

Substrate-Induced Diastereoselectivity in the Dimethyldioxirane Epoxidation of Simple Alkenes and Dienes

Structural elucidation of dioxa‐cage compounds from tetrahydroisobenzofuran‐1(3H)‐one: analysis of NMR data and GIAO chemical shifts calculations

Azabrendanes V. Synthesis and reactions of stereoisomeric exo- and endo-5-aminomethylbicyclo[2.2.1]hept-2-ene-based ureas

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