On laser photolysis of azoalkane 1 at elevated temperature, besides the expected denitrogenation into the tricyclane 2 via 1,3-diradical 2, the diazoalkane Z_ is directly observed, denitrogenating into vinylcyclopentene 2. The bicyclo[2.2.llheptane-2,6-diyl diradical 2, in principle accessible via denitrogena-Lion of the azoalkane 1 ', would be expected to generate a variety of products (Eq. I), of which n /hv N=N -N2 If -3% \ n/hv (7) N2 -N2 = (Eq. I) the tricyclane 2, cr-pinene (3) and the vinylcyclopentene 5 are likely ones. For example, analogous to the 5,6-benzobicyclo[2.2.2loct-5-ene-2,7-diyl diradical 2, ring closure of 2 would afford i, while migration of the C,-C7 bond to either radical site would lead to a-pinene (4). Alternatively, the 1,3-diradical 2 could suffer fragmentation into the carbene f3, which on 1,2shift of hydrogen would produce the vinylcyclopentene 2. However, such a process is more likely to be observed in 185-nm photolyses.3 Since 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) cycloaddition to cc-pinene (4) gave the urazole precursor to the azoalkane 1, the latter was prepared and its denitrogenation investigated in order to explore the chemical transformations of the 1,3-diradical 2.4'5
The results of the thermal and photochemical denitrogenations are collected in Table .