Thermal Behavior of Free-Base and Core-Modified Bicyclo[2.2.2]octadiene-Fused Porphyrins
Thermal Behavior of Free-Base and Core-Modified Bicyclo[2.2.2]octadiene-Fused Porphyrins
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DOI：
10.1002/ejoc.200700711
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发表时间：
2008
影响因子：
2.8
通讯作者：
H. Uno;Y. Shimizu;Hiroki Uoyama;Yousuke Tanaka;T. Okujima;N. Ono
中科院分区：
文献类型：
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作者：
H. Uno;Y. Shimizu;Hiroki Uoyama;Yousuke Tanaka;T. Okujima;N. Ono
详细研究了四重双环[2.2.2]辛二烯稠合卟啉的多步热裂解，得到四苯并卟啉。在第一次从卟啉衍生物中挤出乙烯分子后，相对的双环[2.2.2]辛烷部分优先进行第二次逆Diels-桤木反应，得到对-二苯并卟啉衍生物而不是邻-二苯并卟啉衍生物。这两种苯并卟啉衍生物以相似的速率分解得到三苯并卟啉衍生物。热重分析不能区分这些碎片的温度区域。相反，第三和第四破碎明显发生阶梯。存在一个三苯并卟啉衍生物优先存在的温度区域。在21，23-二硫杂卟啉衍生物的情况下，在片段化过程中主要形成具有在核修饰的卟啉发色团的吡咯部分处稠合的苯并部分的opp-21，23-二硫杂二苯并卟啉。在21-硫代卟啉衍生物的情况下，乙烯分子从与噻吩部分相邻的双环[2.2.2]辛烷部分选择性地挤出，得到21-硫代苯并[q]卟啉，然后得到21-硫代苯并[g，q]卟啉衍生物。在这些情况下，最后的乙烯挤出也非常缓慢地发生。（© Wiley-VCH Verlag GmbH & Co. KGaA，69451魏因海姆，德国，2008）
Multistep thermal fragmentation of quadruply bicyclo[2.2.2]octadiene-fused porphyrins giving tetrabenzoporphyrins was examined in detail. After the first extrusion of an ethylene molecule from the porphyrin derivative, the opposite bicyclo[2.2.2]octadiene moiety preferentially underwent the second retro-Diels–Alder reaction to give an opp-dibenzoporphyrin derivative rather than an adj-dibenzoporphyrin derivative. These two benzoporphyrin derivatives then decomposed to give a tribenzoporphyrin derivative in similar rates. The temperature regions of these fragmentations could not be distinguished by thermogravimetric analysis. In contrast, the third and the fourth fragmentations obviously occurred stepwise. There was a temperature region where the tribenzoporphyrin derivative preferentially existed. In the case of the 21,23-dithiaporphyrin derivative, opp-21,23-dithiadibenzoporphyrin, possessing benzo moieties fused at the pyrrole parts of the core-modified porphyrin chromophore was predominantly formed during the fragmentation. In the case of the 21-thiaporphyrin derivative, an ethylene molecule was extruded selectively from the bicyclo[2.2.2]octadiene moiety adjacent to the thiophene part to give 21-thiabenzo[q]porphyrin and then 21-thiabenzo[g,q]porphyrin derivatives. In these cases, the last ethylene extrusion also occurred very slowly. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)