2690-19-9Relevant articles and documents
On the Mechanism of the Benzophenone-Sensitized Photolysis of 2,3-Diazabicyclohept-2-ene in the Laser Jet: Evidence for Intermolecular Triplet Diradical Reactions
Adam, Waldemar,Finzel, Ralf,Walther, Barbara
, p. 2137 - 2142 (2007/10/02)
The benzophenone-sensitized laser jet photolysis of 2,3-diazabicyclohept-2-ene (1) affords, besides the previously reported cyclopentene and housane (2), also cyclopentane, cyclopentadiene, and the dimers bicyclopent-2-en-1-yl (7), 3-cyclopentylcyclopent-1-ene (8), and 1,1'-bicyclopentyl (9).As a model reaction, the pyrolysis of dimer 8 at 600 deg C/ 20 Torr leads to the other dimers 7 and 9 together with cyclopentadiene, cyclopentene, and traces of cyclopentane.Control experiments showed that H abstraction by the cyclopentane-1,3-diyl diradical (3) from cyclohexene (as model substrate for cyclopentene) and addition to housane (2) with formation of diradical 6 are unlikely pathways.Instead, the product data available can be best explained in terms of an intermolecular disproportionation of two diradicals 3 to give the cyclopent-2-en-1-yl (4) and cyclopentyl (5) radical pair, which is subsequently converted to the observed products by in-cage and out-of-cage coupling and H transfer reactions.Such intermolecular diradical chemistry becomes feasible due to the high steady-state concentrations (ca. micromolar) generated in the laser jet.Two-photon processes take place, but are of subordinate importance. - Key Words: Laser jet/ Azoalkane/ Diradical/ Radical coupling
