Richter Daniel T, Lash Timothy D
Department of Chemistry, Illinois State University, Normal, IL 61790-4160, USA.
J Org Chem. 2004 Dec 10;69(25):8842-50. doi: 10.1021/jo040239o.
Sapphyrins are an important group of expanded porphyrins that show valuable anion binding characteristics. In this study, a "4 + 1" route to sapphyrin systems has been developed. Reaction of dialdehydes with a known tetrapyrrole intermediate 11b incorporating a bipyrrolic subunit afforded a wide range of sapphyrin-type products. The best conditions for these reactions involved carrying out the condensation of the dialdehydes with the tetrapyrrole in TFA-dichloromethane, followed by oxidation with dilute aqueous solutions of ferric chloride. A pyrrole dialdehyde reacted under these conditions to give sapphyrin in 50% yield, while furan and thiophene dialdehydes afforded the corresponding oxa- and thiasapphyrins in 66-90% yield. Pyrrole dialdehydes with fused phenanthrene or acenaphthylene rings also reacted with 11b to give the related phenanthro- and acenaphthosapphyrins in excellent yields. As was the case for acenaphthoporphyrins, the acenaphthosapphyrin gave longer wavelength absorptions than the corresponding phenanthrene fused structure, although the differences were not as marked as those seen in the porphyrin series. Reaction of 11b with 1,3-diformylindene gave a benzocarbasapphyrin in 38% yield, while a triformyl cyclopentadiene reacted with the tetrapyrrole to give a carbasapphyrin aldehyde in 7-12% yield. The free base carbasapphyrins were unstable but the monoprotonated hydrochloride salts could easily be isolated and characterized. Carbasapphyrins retain a strong diatropic ring current due to the presence of 22pi electron delocalization pathways. In the presence of trifluoroacetic acid, C-protonated dications are generated. Condensation of 1,3-azulenedicarbaldehyde with 11b gave an azulisapphyrin dihydrochloride salt in 35% yield, and this also showed a strong diatropic ring current. Addition of base gave the unstable free base form, while pyrrolidine formed an unstable adduct that showed an intense Soret band at 480 nm. These results demonstrate that many of the themes observed for modified porphyrins and carbaporphyrins also apply to the sapphyrin series, although in some cases reduced stability hampers these investigations.
蓝宝石啉是一类重要的扩展卟啉，具有宝贵的阴离子结合特性。在本研究中，已开发出一种合成蓝宝石啉体系的“4 + 1”路线。二醛与含有联吡咯亚基的已知四吡咯中间体11b反应，得到了多种蓝宝石啉型产物。这些反应的最佳条件是在三氟乙酸 - 二氯甲烷中使二醛与四吡咯进行缩合反应，然后用氯化铁稀水溶液氧化。吡咯二醛在这些条件下反应，以50%的产率得到蓝宝石啉，而呋喃和噻吩二醛则以66 - 90%的产率得到相应的氧杂和硫杂蓝宝石啉。带有稠合菲或苊烯环的吡咯二醛也与11b反应，以优异的产率得到相关的菲并和苊并蓝宝石啉。与苊并卟啉的情况一样，苊并蓝宝石啉的吸收波长比相应的菲稠合结构更长，尽管差异不如在卟啉系列中那么明显。11b与1,3 - 二亚甲酰基茚反应，以38%的产率得到苯并碳杂蓝宝石啉，而三亚甲酰基环戊二烯与四吡咯反应，以7 - 12%的产率得到碳杂蓝宝石啉醛。游离碱碳杂蓝宝石啉不稳定，但单质子化的盐酸盐很容易分离和表征。由于存在22π电子离域途径，碳杂蓝宝石啉保留了很强的抗磁环电流。在三氟乙酸存在下，会生成C - 质子化的双阳离子。1,3 - 薁二甲醛与11b缩合，以35%的产率得到薁蓝宝石啉二盐酸盐，它也显示出很强的抗磁环电流。加入碱会得到不稳定的游离碱形式，而吡咯烷形成一种不稳定的加合物，在480 nm处显示出强烈的Soret带。这些结果表明，在修饰卟啉和碳杂卟啉中观察到的许多规律也适用于蓝宝石啉系列，尽管在某些情况下稳定性降低阻碍了这些研究。
