M. Abe, W. Adam*, Thomas Heidenfelder
Feb 17, 2000
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0
Influential Citations
56
Citations
Journal
Journal of the American Chemical Society
Abstract
The direct and benzophenone-sensitized photodenitrogenation of the diethoxy-substituted diazene 3 in nonprotic solvents, e.g. n-hexane, benzene, and acetonitrile, afforded exclusively the housane 4 through the intermediary 2,2-diethoxy-1,3-diphenylcyclopentane-1,3-diyl diradical 2b. Alternatively, in the presence of methanol, the formation of the adduct 6 competed through trapping of the allylic cation 5. The intervention of the intermediates was corroborated by laser-flash photolysis experiments of the diazene 3. The diradical intermediate was characterized by its strong transient absorption at 545 nm, which decayed with a first-order lifetime in the microsecond range. The diradical lifetimes increased in the order n-hexane (0.52 μs), benzene (0.88 μs), acetonitrile (1.01 μs), and chloroform (3.73 μs). The singlet ground state of the 2,2-diethoxy-substituted 1,3-diradical 2b is suggested by the absence of EPR signals at low temperature, the lack of quenching by molecular oxygen, and the calculated (UB3LY...