Conjugated macrocycles related to the porphyrins. Part 18: Synthesis and spectroscopic characterization of electron-rich benzi- and oxybenziporphyrins: influence of steric and electronic factors on porphyrinoid aromaticity
作者:Daniel T Richter、Timothy D Lash
DOI:10.1016/s0040-4020(01)00256-3
日期:2001.4
Although 4,6-dihydroxyisophthalaldehydes failed to condense with tripyrranes to produce porphyrinoid products, the related dimethoxydialdehydes reacted with tripyrrane 9 to give, following oxidation with aqueous ferric chloride solution, nonaromatic dimethoxybenziporphyrins 20 in excellent yields. In the presence of TFA, dications were generated that showed weakly diatropic properties by proton NMR
尽管4,6-二羟基间苯二甲醛不能与三吡喃冷凝以产生卟啉类产物,但是相关的二甲氧基二醛与三吡喃9反应,在用氯化铁水溶液氧化后,以优异的产率得到了非芳族二甲氧基苯并卟啉20。在存在TFA的情况下,生成的质子通过质子NMR光谱显示出弱的变渗性。该观察结果归因于甲氧基单元促进电荷离域的能力。用50当量治疗20。的三溴化硼裂解了一种甲基醚,生成了相关的甲氧基氧基苯并卟啉24。这些卟啉类化合物由于在这些结构中存在18个π电子离域路径而显示出较强的反磁环电流。经TFA处理后,所得指示剂显示出明显降低的环电流,尽管与不存在甲氧基取代基时相比,它们的变径特性得以保留的程度要大得多。对于20和24,当不存在相邻的烷基取代基时,甲氧基在电荷离域上更有效,这导致增加的亲核性。用HBr在回流的乙酸中处理20a,裂解两个甲基醚,得到高度不溶的羟氧基苯并卟啉17。尽管无法评估游离碱的光谱性质,但该化合物可溶于TFA-氯