Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations
作者:Götz Bucher、Gernot Heitmann、Rainer Herges
DOI:10.3762/bjoc.9.191
日期:——
Coarctate reactions are defined as reactions that include atoms at which two bonds are made and two bonds are broken simultaneously. In the pursuit of the discovery of new coarctate reactions we investigate the fragmentation reactions of cyclic ketals. Three ketals with different ring sizes derived from indan-2-one were decomposed by photolysis and pyrolysis. Particularly clean is the photolysis of
Coarctate 反应被定义为包括两个键形成和两个键同时断裂的原子的反应。为了发现新的缩氨酸反应,我们研究了环状缩酮的裂解反应。来自indan-2-one的三个不同环大小的缩酮通过光解和热解被分解。特别干净的是 indan-2-one ketal 1 的光解,它产生邻醌二甲烷、二氧化碳和乙烯。该机制形式上对应于光化学允许的缩氨酸裂解。五环缩酮的热解产生多种产物。这与辐射时观察到的缩氨酸裂解在热化学上被禁止的事实是一致的,尽管这个排除原则不适用于螯合反应。相比之下,七环缩酮 3 的裂解在热化学上是允许的,而在光化学上是禁止的。在热解 3 时,分离出几种产物,这可以通过缩氨酸裂解来解释。然而,反应不太干净,逐步机制可能会相互竞争。