[6+6]Photocycloadditions in Face-to-Face Benzo/Pyridazino Substrates – En Route to Azapagodanes
作者:Thomas Mathew、Joern Tonne、Gottfried Sedelmeier、Clemens Grund、Manfred Keller、Dieter Hunkler、Lothar Knothe、Horst Prinzbach
DOI:10.1002/ejoc.200601075
日期:2007.5
In two specifically constructed rigid, proximate, “face-to-face” benzo/pyridazino systems (shortest π,π distances ca. 3 A) photoequilibration with the photo[6+6]cycloadducts has been established by 254-nm irradiation (ratios ca. 2:1). The failure to observe such “benzene/heteroarene” photodimers for differently substituted benzo/pyridazino analogues is related to unfavorable UV absorption characteristics
在两个专门构建的刚性、近似、“面对面”苯并/哒嗪系统(最短 π,π 距离约 3 A)中,通过 254 nm 辐射建立了光 [6+6] 环加合物的光平衡(比率约 2:1)。未能观察到不同取代的苯并/哒嗪基类似物的此类“苯/杂芳烃”光二聚体与相应光异构体对的不利紫外吸收特性有关,如由它们的受体/供体取代基决定的。高度应变的光[6+6]环加合物具有足够的热持久性,可以添加标准的亲二烯体,从而为获得新型氮杂帕戈丹型笼分子提供了可能。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)