Di(9-anthryl)carbene Revisited. Product Analysis and Spectroscopic Studies
作者:Ken-ichi Yoshida、Eiji Iiba、Yoshinori Nozaki、Katsuyuki Hirai、Yasutake Takahashi、Hideo Tomioka、Cheng-Tung Lin、Peter P. Gaspar
DOI:10.1246/bcsj.77.1509
日期:2004.8
Irradiation (λ > 300 nm) of di(9-anthryl)diazomethane (1) in degassed benzene gave the trimer (3) of dianthrylcarbene (2) as the main product along with a small amount of a tetramer (4). The structures of those oligomers were characterized as caged compounds produced as a result of three- and four-fold coupling at the 10 and 10′ positions of 2. Photolysis of 1 in the presence of oxygen with short wavelength UV light resulted in the formation of di(9-anthryl) ketone (5) and anthraquinone (6), while similar irradiation with a longer wavelength light gave 5 and 9-anthryl 9-anthracenecarboxylate (9), which was found to give 6 upon irradiation with a short wavelength light in the presence of oxygen. On the other hand, the photolysis of 4 gave 3 as the main product, while 3 was almost completely photostable under similar conditions. However, irradiation of both 3 and 4 in the presence of oxygen gave 6. In order to elucidate the reactions observed, we carried out spectroscopic studies (matrix EPR and UV/vis spectroscopies as well as laser flash photolysis) with 1, 3, and 4. These studies revealed that 3 generated a trimer diradical (10) formed as a result of C–C bond cleavage upon irradiation and that 10 reformed 3 almost exclusively, while similar photolysis of 1 and 4 generated the same two transient species, 10 and a dimer diradical. It is proposed that triplet carbene 2 equilibrates with the dimer diradical 2-2 and that the main decay pathway of this mixture is to generate the trimer diradical 10 while dimer diradical 2-2 undergoes coupling to produce the tetramer 4. The structure of the triplet carbene in equilibrium with diradicals is also discussed.
在脱气苯中对二(9-蒽基)二氮杂环丁烷(1)进行辐照(λ > 300 纳米),得到的主要产物是二(9-蒽基)二三碳烯(2)的三聚体(3)以及少量的四聚体(4)。这些低聚物的结构被定性为在 2 的 10 和 10′ 位置进行三倍和四倍偶联后产生的笼状化合物。在氧气存在的情况下,用短波长紫外光对 1 进行光解,可生成二(9-蒽基)酮(5)和蒽醌(6),而用较长波长的光照射可生成 5 和 9-蒽基 9-蒽羧酸酯(9),在氧气存在的情况下,用短波长光照射可生成 6。另一方面,光解 4 的主要产物是 3,而 3 在类似条件下几乎完全光稳定。不过,在有氧气存在的情况下照射 3 和 4 会产生 6。为了阐明所观察到的反应,我们对 1、3 和 4 进行了光谱研究(矩阵 EPR 和 UV/vis 光谱以及激光闪烁光解)。这些研究表明,3 在辐照时会产生一个由于 C-C 键裂解而形成的三聚二叉物(10),而且 10 几乎只对 3 进行重整,而 1 和 4 的类似光解也会产生同样的两个瞬态物种,即 10 和一个二聚二叉物。据推测,三重碳烯 2 与二聚二叉体 2-2 发生了平衡,这种混合物的主要衰变途径是生成三聚二叉体 10,而二聚二叉体 2-2 则通过耦合生成四聚体 4。此外,还讨论了与二拉呋喃平衡的三重碳烯的结构。