Generation of radical ions of pyrazolines and construction of an electron transfer system.

近年来研究了由环偶氮烷烃通过光诱导电子转移（PET）生成的自由基阳离子，并通过重排和溶剂添加生成了一些特征化合物。当生成的自由基阳离子由于其几何约束和稳定性而具有重排的可能性时，反应机制变得复杂，因为这些物种似乎参与了脱氮。在我们之前使用1-吡唑啉和9,10-二氰蒽（DCA）作为电子接受敏化剂的研究中，发现PET反应会引起芳基迁移，涉及自由基阳离子中间体。尽管人们对含氮自由基阳离子的行为非常感兴趣，但PET反应的含氮产物尚未得到，产物均为氮消除化合物。在这个项目中，我们报告了第一个使用环偶氮烷烃进行PET反应的例子，其中从具有外环双键的3-烷基基-1-吡唑啉的自由基阳离子中获得氮保留产物，并且通过激光闪光光解（LFP）技术成功检测了氮保留自由基阳离子。

Radical cations generated from cyclic azoalkanes by photoinduced electron transfer (PET) have recently been investigated and produced a few characteristic compounds by rearrangements and solvent additions. The reaction mechanisms become complex when the generated radical cations have the possibility of rearranging due to their geometric constraints and stabilities, as these species appear to be involved in denitrogenation. In our previous studies using the 1-pyrazolines and 9,10-dicyanoanthracene (DCA) as an electron accepting sensitizer, the PET reaction was found to cause aryl migration involving the radical cation intermediates. In spite of the fact that the behavior of the nitrogen-retained radical cations are of considerable interest, nitrogen-retained products by the PET reaction have not been obtained, and the products are nitrogen-eliminated compounds. In this project, we report the first example of the use of cyclic azoalkanes for the PET reaction in which nitrogen-retained products are obtained from the radical cation species of 3-alkylidene-1-pyrazolines having an exocyclic double bond, and that the successful detection of the nitrogen-retained radical cations was accomplished by a laser flash photolysis (LFP) technique.