Krishnamoorthy G, Schieffer Stefan, Pescatore John, Ulsh Richard, Liu Robert S H, Liu Jin
Department of Chemistry, University of Hawaii, Honolulu, HI 96822-2275, USA.
Photochem Photobiol Sci. 2004 Nov-Dec;3(11-12):1047-51. doi: 10.1039/b412128g. Epub 2004 Oct 26.
The photoreactions of 1,4-diphenyl-1,3-butadienes (DPB) fused with a bicyclo[2.2.1]heptano ring under direct irradiation were examined in solution at room temperature and in organic glass at liquid nitrogen temperature. Photocyclization yielding a phenylnaphthalene compound was shown to be preceded by facile E,E to E,Z photoisomerization. The reverse E,Z to E,E isomerization took place with equal ease in low temperature organic glass and in solution at room temperature. The pattern of reaction at low temperature is consistent with the involvement of the Hula-twist mechanism. However, complexity in conformational population, suggested by ab initio calculated data, made the experimental evidence less clear-cut than in previously reported examples of HT.
在室温下的溶液中和液氮温度下的有机玻璃中，研究了与双环[2.2.1]庚烷环稠合的1,4 - 二苯基 - 1,3 - 丁二烯（DPB）在直接照射下的光反应。结果表明，在光环化生成苯基萘化合物之前，容易发生E,E到E,Z的光异构化。在低温有机玻璃和室温溶液中，E,Z到E,E的反向异构化以相同的难易程度发生。低温下的反应模式与胡拉扭转（Hula - twist）机理相符。然而，从头算计算数据表明构象群体存在复杂性，这使得实验证据不如先前报道的胡拉扭转（HT）例子那样明确。
