Regioselective rearrangement of bridgehead-methyl-substituted radical cations derived from bicyclo[2. 1. 0]pentanes and 2,3-diazabicyclo[2. 2. 1]hept-2-enes through photoinduced electron transfer and radiolytic oxidation. Product distribution and matrix ESR studies

Journal Article · Tue Mar 22 23:00:00 EST 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00085a043· OSTI ID:7267359

Adam, W; Sahin, C; Sendelbach, J; Walter, H ^[1]; Chen, G F; Williams, F ^[2]

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1. Univ. of Wuerzburg (Germany)
2. Univ. of Tennessee, Knoxville, TN (United States)

Cyclopentane-1,3-diyl radical cations were generated from the 1-methyl- and 1,4-dimethyl substituted bicyclo-[2.1.0]pentanes 1b,c through photoinduced electron transfer (PET) and radiolytic oxidation. The unsymmetrical bridgehead-substituted bicyclopentane 1b rearranged spontaneously and exclusively to the 3-methylcyclopentene 3b under PET conditions. ESR studies showed similarly that 3b[sup [sm bullet]+] was the only final oxidation product of 1b; the initial radical cation 1b[sup [sm bullet]+] was not detected because it rearranges rapidly and stereoselectively by a 1,2-hydrogen shift to 3b[sup [sm bullet]+], even at 80 K, and no trace of the more stable 1-methylcyclopentene radical cation 3a[sup [sm bullet]+] was observed. This contra-thermodynamic regioselectivity is rationalized in terms of essential localization of positive charge at the tertiary center as the reaction proceeds in the 1,3-diyl radical cation 1b[sup [sm bullet]+]. The symmetrical dimethyl derivative 1c rearranged much more reluctantly than 1b despite its lower oxidation potential, and this is attributed to the greater persistence of radical cation 1c[sup [sm bullet]+] through its reluctance to undergo a 1,2-H shift. The oxidation of these azoalkanes generates highly reactive transients, presumably diazenyl radical cations, which readily denitrogenate and undergo 1,2-H shifts in either a consecutive or concerted manner to form olefin radical cations. 25 refs., 6 figs., 2 tabs.

• DOE Contract Number: FG05-88ER13852
• OSTI ID: 7267359
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 116:6; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
ALKANES
ALKENES
CATIONS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHROMATOGRAPHY
CYCLOALKANES
CYCLOALKENES
DATA
DECOMPOSITION
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
EXPERIMENTAL DATA
GAS CHROMATOGRAPHY
HYDROCARBONS
INFORMATION
IONS
MAGNETIC RESONANCE
MASS SPECTROSCOPY
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDATION
PHOTOCHEMICAL REACTIONS
RADIATION EFFECTS
RADICALS
RADIOLYSIS
RESONANCE
SEPARATION PROCESSES
SPECTROSCOPY