Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
Photochem Photobiol Sci. 2022 Nov;21(11):1907-1914. doi: 10.1007/s43630-022-00267-3. Epub 2022 Jul 22.
A photochemical precursor to the 5-endo-10,11-dihydroazepine nitrenium ion (1) was synthesized and used to characterize the intermediate by laser flash photolysis and stable product analysis. In addition, DFT calculations were carried out on the nitrenium ion. These results were compared with earlier studies on the diphenylnitrenium ion in order to ascertain the effect of the 2 carbon bridge on the reactions and properties of 1. It is shown that the geometric constraints provided by the bridging group (a) destabilize the triplet state of 1 relative to the singlet state (b) substantially increase the lifetime of 1 relative to PhN by inhibiting the unimolecular cyclization pathway possible in the latter and (c) modestly increases the barrier for nucleophilic addition to the ring carbons.
合成了 5-endo-10,11-二氢氮杂环庚烷氮鎓离子（1）的光化学前体，并通过激光闪光光解和稳定产物分析来表征中间体。此外，还对氮鎓离子进行了 DFT 计算。将这些结果与以前关于二苯氮鎓离子的研究进行了比较，以确定 2 个碳桥对 1 的反应和性质的影响。结果表明，桥连基团（a）提供的几何约束会使 1 的三重态相对于单重态（b）显著不稳定，会大大延长 1 的寿命相对于 PhN，因为它抑制了后者中可能的单分子环化途径，并且（c）适度增加了亲核加成到环碳原子的障碍。
