Department of Molecular Chemistry and Biochemistry, Faculty of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
J Org Chem. 2011 Aug 5;76(15):6108-15. doi: 10.1021/jo2007994. Epub 2011 Jul 1.
Coupled oxidation of [tetraarylporphyrinato]iron(III) chloride carrying substituents in the ortho or para positions was performed by allowing the iron porphyrin to react with dioxygen, ascorbic acid, and pyridine to give biladienone as the major product and bilindione as a minor one. Efforts to find reaction conditions and workup procedures to obtain bilindione improved the yields of triarylbilindiones ranging between 2% and 19%. Electron-withdrawing substituents in the para position on the aryl groups increased the selectivity of bilindione relative to biladienone: the isolated yields of bilindione and biladienone were 2% and 85% (OMe), 6% and 44% (COOMe), and 7% and 28% (CN), respectively. Electronic effects of substituents affected both isolation procedures and the spectroscopic properties of bilindiones. Tri(4-methoxyphenyl)bilindione showed a red-shifted electronic absorption compared to unsubstituted and 4-methoxycarbonyl substituted analogues. This was ascribed to the destabilization of the HOMO-1 level by the methoxy groups.
对位或邻位取代的[四芳基卟啉基]铁（III）氯化物的偶联氧化是通过使铁卟啉与氧气、抗坏血酸和吡啶反应来进行的，主要产物为双烯酮，次要产物为双并二酮。为了找到获得双并二酮的反应条件和后处理程序，我们努力提高了三芳基双并二酮的产率，范围在 2%到 19%之间。芳基对位的吸电子取代基增加了双并二酮相对于双烯酮的选择性：分离得到的双并二酮和双烯酮的产率分别为 2%和 85%（OMe）、6%和 44%（COOMe）、7%和 28%（CN）。取代基的电子效应既影响了双并二酮的分离程序，也影响了它们的光谱性质。与未取代和 4-甲氧基羰基取代的类似物相比，三（4-甲氧基苯基）双并二酮的电子吸收发生了红移。这归因于甲氧基的存在使 HOMO-1 能级失稳。
