Photochemical and ESR spectral evidence for a stereoselective rearrangement of radical cations derived from azoalkanes and bicyclopentanes

Adam, Waldemar; Walter, Heimo; Chen, Guo Fei; Williams, Ffrançon

doi:10.1021/ja00034a037

Cited by 47 publications

(41 citation statements)

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“…Attempts to generate the EPR spectrum of the 1-methylcyclopentene radical cation in NaZSM5 gave a very poor result, as if adsorption was quite limited. Reported EPR spectra of the radical cation in Freon matrixes 40 and our own experimental results in perfluoromethylcyclohexane 41 show that the hyperfine couplings are quite matrix dependent. Therefore direct comparison of these spectra to the spectrum in HZSM5 is problematic.…”

Section: Resultsmentioning

confidence: 67%

Hydrogen Atom Addition to Hydrocarbon Guests in Radiolyzed Zeolites

et al. 1999

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The formation of H adducts during radiolysis of zeolites containing olefinic and aromatic hydrocarbon guests was demonstrated to occur by H atom transfer from the zeolite to the adsorbed molecules. The H adducts and other paramagnetic radiolysis products (radical cations and H-loss radicals) were detected by EPR spectroscopy. The mechanism of H adduct formation was confirmed by, inter alia, H/D isotopic labeling and comparison of results in HZSM5 and H−Mordenite to results in their Na+-exchanged counterparts. The effects of charge transfer among radiolysis products and zeolite−adsorbate interactions on the relative yields of trapped species is discussed. It is proposed that molecules smaller that a critical size adsorb inhomogeneously in ZSM5, forming aggregates in which ion−molecule reactions occur. Interpretation of the experimental results was aided by quantum chemical calculations of the molecular properties of the intermediates and their reaction energetics. This included evaluation of electron-transfer exothermicities, activation energies for H addition, and the relative acidities of the radical cations.

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Section: Resultsmentioning

confidence: 67%

Hydrogen Atom Addition to Hydrocarbon Guests in Radiolyzed Zeolites

et al. 1999

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“…and γ ‐irradiated at 77 K for a typical radiation dose of 0.2 Mrad (1 Mrad=10 kGy=1×10 4 J kg −1 ). Additional details of sample preparation and reasons for the recommended concentration range are given elsewhere 10d, 32, 33…”

Section: Methodsmentioning

confidence: 99%

Ionized Bicyclo[2.2.2]oct-2-ene: A Twisted Olefinic Radical Cation Showing Vibronic Coupling

et al. 2002

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“…Besides EPR spectroscopy under matrix-isolation conditions 23,24 and pulse-radiolysis 25,26 studies, also chemical trapping 7,27 proved helpful in detecting and characterizing the transient radical cations derived from azoalkanes and housanes. Thereby valuable mechanistic insight has been gained into the chemical behavior of these short-lived reactive intermediates.…”

Section: Evidence For Transient Radical Cationsmentioning

confidence: 99%

“…For example, the cyclopentane-1,3-diyl radical cation 1• + derived from the corresponding housane by g radiolysis at 80-90 K was shown to possess a puckered conformation. 23 For the spectral characterization of the phenyl-substituted radical cations 3• + and 4• + , EPR was inconclusive because of unresolved hyperfine structure. However, time-resolved optical absorption spectroscopy allowed the detection and characterization of such transients, generated from the corresponding housanes or azoalkanes by pulse radiolysis.…”

Section: Evidence For Transient Radical Cationsmentioning

confidence: 99%

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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Photochemical and ESR spectral evidence for a stereoselective rearrangement of radical cations derived from azoalkanes and bicyclopentanes

Abstract: spectrum (Cl, NH3) m/z 439.2267 [(M + NH4+), caled for C22H35N2-OsS 439.2223].

Cited by 47 publications

References 0 publications

Hydrogen Atom Addition to Hydrocarbon Guests in Radiolyzed Zeolites

Hydrogen Atom Addition to Hydrocarbon Guests in Radiolyzed Zeolites

Ionized Bicyclo[2.2.2]oct-2-ene: A Twisted Olefinic Radical Cation Showing Vibronic Coupling

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

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