Cyclobutene photochemistry. Adiabatic photochemical ring opening of alkylcyclobutenes
作者:William J. Leigh、J. Alberto Postigo、K.C. Zheng
DOI:10.1139/v96-105
日期:1996.6.1
The photochemistry of the cis and trans isomers of a series of dimethylbicyclo(n.2.O)alk-(n+2)-enes (n = 2-5) (bicyclic cyclobutene derivatives in which the C=C bond is shared by the two rings) in pentane solution is described. Irradiation of these compounds using monochromatic 193- or 214-nm light sources results in ring opening to yield the corresponding 1,2-bis(l-ethylidene)cycloalkanes (C,-C,)
一系列二甲基双环 (n.2.O)alk-(n+2)-enes (n = 2-5)(双环环丁烯衍生物,其中 C=C 键被共享)的顺式和反式异构体的光化学描述了戊烷溶液中的两个环)。使用单色 193 或 214 nm 光源照射这些化合物会导致开环,以高化学和量子产率产生相应的 1,2-双(1-亚乙基)环烷烃 (C,-C,)。在所有情况下,反应都以高 (70-90%) 程度的反旋立体选择性进行。还测定了异构 E,E-和 E,Z-1,2-双(1-亚乙基)环烷烃的直接顺、反光异构化的量子产率。环丁烯辐照的产物分布与波长有关,但是对于 214 nm 激发,从环丁烯开环获得的异构二烯分布与根据异构二烯的顺式、反式光异构化的量子产率计算的分布非常一致,前提是该过程涉及纯粹的旋转开环以产生单个二烯处于最低激发单线态的异构体。结果与轨道对称控制的开环绝热机制一致。