Reluctant Azoalkanes: The Photochemical Behavior of Acyclic, Bridgehead-Centered Azoalkanes on 185- and 350-nm Irradiation

Article abstract of DOI:10.1021/ja00357a028

Azo-1-adamantane (1a), azobicyclo<2.2.2>octanes (1b and 1c), and azo-1-norbornane (1d) isomerize to cis-azoalkanes but are reluctant to lose nitrogen directly upon long-wavelength irradiation.Use of 185-nm light is shown to enhance deazatization quantum yields considerably, though photoisomerization remains an important reaction.In the case of 1a especially, thermolysis of the cis isomer is the dominant decomposition mechanism at long and probably at short wavelength; however, the cis isomer of 1d is thermally stable.It follows that the second excited singlet state is responsible for deazatization of 1d.The products of photolyisis in pentane have been identified, and the amount of bridgehead radical hydrogen abstraction relative to recombination is found to increase under short-wavelength irradiation.