to high stereoselectivity being observed for 13e and 13g, respectively. Use of cyclic alkene side chains led to the formation of tri- and tetracyclic products with high degrees of stereoselectivity in most cases. Some of the polycyclic ring systems that were prepared constitute the core skeleton of a number of complex alkaloids. The substrate 29 underwent an unexpected [2+2] photocycloaddition to yield
许多 N-链烯基取代的马来酰亚胺衍生物的紫外线照射导致以极好的产率形成复杂的全氢氮杂茚。整个过程可以被认为是一个正式的分子内 [5+2] 环加成。通过合适的烯醇与各种马来酰亚胺的Mitsunobu偶联制备底物。烯基侧链的甲基取代以良好的产率得到环加合物 13a-g,分别对 13e 和 13g 观察到中等至高的立体选择性。在大多数情况下,环状烯烃侧链的使用导致形成具有高度立体选择性的三环和四环产物。一些已制备的多环系统构成了许多复杂生物碱的核心骨架。
Reaction Control in Synthetic Organic Photochemistry: Switching between [5+2] and [2+2] Modes of Cycloaddition
作者:Claudio Roscini、Kara L. Cubbage、Malcolm Berry、Andrew J. Orr-Ewing、Kevin I. Booker-Milburn
DOI:10.1002/anie.200904059
日期:2009.11.2
Split personality: Reaction conditions that enable powerful control over the mode of photocycloaddition in maleimides have been developed. Direct irradiation favors the [5+2] mode whereas sensitized irradiation allows a complete switch to the [2+2] mode (see scheme; TBS=tert‐butyldimethylsilyl).