Diastereo- and Regioselective Synthesis of Diquinanes and Related Systems from Tricyclo[3.3.0.02,4]octanes by Chemical Electron Transfer (CET)

Adam, Waldemar; Heidenfelder, Thomas; Şahin, Coşkun

doi:10.1055/s-1995-4072

Cited by 34 publications

(34 citation statements)

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“…the wide-spread diquinanes (Scheme 8). 37 In particular the CET methodology with trisarylaminium salts constitutes an effective method for this purpose. On one hand, back electron transfer to the cyclopentane-1,3-diyl radical cations is minimized and, on the other hand, this reaction may be run on a preparative scale.…”

Section: Synthetic Potentialmentioning

confidence: 99%

“…On one hand, back electron transfer to the cyclopentane-1,3-diyl radical cations is minimized and, on the other hand, this reaction may be run on a preparative scale. 37 Moreover, when the methylene bridge of the housane is spiro-substituted, this oxidative rearrangement allows the preparation of polycyclic structures through stereocontrolled ring expansion. For instance, the triquinane-related olefin 23 in Scheme 9 was obtained in excellent yield upon oxidation of the spiro-substituted tricyclooctane 22 with catalytic amounts of TBA• + , in which the quarternary center is perfectly diastereo-and regioselectively introduced.…”

Section: Synthetic Potentialmentioning

confidence: 99%

“…Surely, this novel synthetic methodology provides an efficent and convenient access to unusual cyclopentanoid derivatives. 37…”

Section: Synthetic Potentialmentioning

confidence: 99%

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Regio- and diastereoselective rearrangement of cyclopentane-1,3-diyl radical cations generated by electron transfer

Adam¹,

Heidenfelder²

1999

Chem. Soc. Rev.

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Cyclopentane-1,3-diyl radical cations are readily available from azoalkanes or bicyclo[2.2.0]pentanes (housanes) by electron transfer. These short-lived intermediates may stabilize by numerous chemical processes, predominantly by 1,2-migration to form the corresponding cyclopentene derivatives after back electron transfer. This review focuses on the regio-and diastereoselectivities in the rearrangement of the strained cyclopentane-1,3-diyl radical cations and explores the mechanism of this novel 1,2-migration. This highly selective transformation offers attractive opportunities for the convenient and efficient synthesis of complex polycyclic structures.

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Section: Synthetic Potentialmentioning

confidence: 99%

Section: Synthetic Potentialmentioning

confidence: 99%

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Regio- and diastereoselective rearrangement of cyclopentane-1,3-diyl radical cations generated by electron transfer

Adam¹,

Heidenfelder²

1999

Chem. Soc. Rev.

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“…Pyrazoles 3c – f were synthesized in the reaction of tetrazines 1 (Ar = Ph or 3,5-dimethoxyphenyl) with 2,2-dialkoxy-5,5-dimethyl-Δ 3 -1,3,4-oxadiazolines 2 [29], which are the precursor of the dialkoxycarbene (Scheme 3). Azoalkanes AZc–f (λ max ≈ 360 nm with ε ≈ 100) were obtained by a cycloaddition reaction with cyclopentadienes, and followed by a hydrogenation reaction [30–31]. The synthesis of AZg (Ar = 3,5-dimethoxyphenyl, Ar’ = H) was performed from the corresponding 1,3-diketone 4 (Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

Fujiwara²,

Abe

2013

Beilstein J. Org. Chem.

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Summary Background: Localized singlet diradicals are in general quite short-lived intermediates in processes involving homolytic bond-cleavage and formation reactions. In the past decade, long-lived singlet diradicals have been reported in cyclic systems such as cyclobutane-1,3-diyls and cyclopentane-1,3-diyls. Experimental investigation of the chemistry of singlet diradicals has become possible. The present study explores the substituents and the effect of their substitution pattern at the C(1)–C(3) positions on the lifetime of singlet octahydropentalene-1,3-diyls to understand the role of the substituents on the reactivity of the localized singlet diradicals. Results: A series of singlet 2,2-dialkoxy-1,3-diaryloctahydropentalene-1,3-diyls DR were generated in the photochemical denitrogenation of the corresponding azoalkanes AZ. The ring-closed products CP, i.e., 3,3-dialkoxy-2,4-diphenyltricyclo[3.3.0.02,4]octanes, were quantitatively obtained in the denitrogenation reaction. The first-order decay process (k = 1/τ) was observed for the fate of the singlet diradicals DR (λmax ≈ 580–590 nm). The activation parameters, ΔH ‡ and ΔS ‡, for the ring-closing reaction (σ-bond formation process) were determined by the temperature-dependent change of the lifetime. The energy barrier was found to be largely dependent upon the substituents Ar and Ar’. The singlet diradical DRf (Ar = 3,5-dimethoxyphenyl, OCH2Ar’ = OCH2(3,5-dimethoxyphenyl)) was the longest-lived, τ293 = 5394 ± 59 ns, among the diradicals studied here. The lifetime of the parent diradical DR (Ar = Ph, OCH2Ar’ = OCH3) was 299 ± 2 ns at 293 K. Conclusion: The lifetimes of the singlet 1,3-diyls are found to be largely dependent on the substituent pattern of Ar and Ar’ at the C(1)–C(3) positions. Both the enthalpy and entropy effect were found to play crucial roles in increasing the lifetime.

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“…Synthesis and Photolysis of the Azoalkanes 1c and 1d: The saturated azoalkanes 1c and 1d , which are Me‐ and Ph‐substituted on the bridgehead positions were prepared as described in the literature 9,13. Their photolysis afforded under all conditions exclusively the known housanes anti ‐ 2c , d 14 …”

Section: Methodsmentioning

confidence: 99%

Preferred Formation of anti‐Housane (Retention) in the Sensitized Photodenitrogenation of Cyclopentane‐Annellated DBH‐Type Azoalkanes through Long‐Range Steric Effects in the Cyclization of the Triplet Cyclopentane‐1,3‐diyl Diradicals

Adam¹,

Diedering²,

Martí³

2003

Eur J Org Chem

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Keywords: DBH / Azoalkanes / Photolysis / Triplet diradical / Long-range steric effects / DiastereoselectivityThe photolysis of the cyclopentene-and cyclopentane-annellated DBH-type azoalkanes 1a and 1b affords under singlet conditions (high-temperature direct photolysis) predominantly the inverted housanes syn-2 in similar amounts for both derivatives 2a and 2b. Under triplet conditions (low-temperature direct or benzophenone-sensitized photolysis), the photolysis leads to the retained housane anti-2 as the major diastereomer, but with a substantial difference in the syn/ anti-housane ratio for 2a (38:62) and for 2b (6:94). This significant difference in the anti stereoselectivity of the triplet

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Diastereo- and Regioselective Synthesis of Diquinanes and Related Systems from Tricyclo[3.3.0.02,4]octanes by Chemical Electron Transfer (CET)

Cited by 34 publications

References 0 publications

Regio- and diastereoselective rearrangement of cyclopentane-1,3-diyl radical cations generated by electron transfer

Regio- and diastereoselective rearrangement of cyclopentane-1,3-diyl radical cations generated by electron transfer

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

Preferred Formation of anti‐Housane (Retention) in the Sensitized Photodenitrogenation of Cyclopentane‐Annellated DBH‐Type Azoalkanes through Long‐Range Steric Effects in the Cyclization of the Triplet Cyclopentane‐1,3‐diyl Diradicals

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