Photoisomerization pathways of 8,16-methno[2.2]metacyclopane-1,9-diene. A model case for adiabatic electrocyclic ring closure in the excited singlet state
作者:Jakob Wirz、Gabriele Persy、Erika Rommel、Ichiro Murata、Kazuhiro Naksuji
DOI:10.1002/hlca.19840670137
日期:1984.2.1
Below − 30°C the reaction path consists of a three quantum process (two di-π-methane rearrangements and photochemical 1,7-H shift) involving two thermally stable, but light-sensitive isomers 8,11b-methanocyclodeca[cde]naphthalene (2b) and 9H -cyclohepta[def]-phenanthrene (3b). At room temperature the rearrangement 2b4a proceeds with a single excitation step bypassing the ground state intermediate 3b
标题化合物1b理想地满足了在最低激发态(1 1b *)发生绝热光异构化的理论要求,实际上,观察到的主要一次光反应是向其荧光价异构体10b,10c-甲基顺式的转化-10b 10c-二氢py(1 1a *)。已对形成先前观察到的光产物8b,9a-dihydro-9 H-环丙烷[ e ] re(4a)的机理进行了详细分析(方案)。低于−30°C,反应路径包括三个量子过程(两个二-π-甲烷重排和光化学1,7-H转变),涉及两个热稳定但光敏异构体8,11b-甲基环十萘[萘] (2b)和9 H-环庚[def]-菲(3b)。在室温下,重排2b4a绕过基态中间体3b进行单个激发步骤。最后,在长时间照射(4a)时,亚甲基损失以产生pyr。化合物2b完成了亚甲基与pyr的CC键的所有可能的加合物的系列。