Examples of internally alkylated azuliporphyrins were prepared by MacDonald-type “3 + 1” condensations. 2-Methyl- and 2-ethylazulene reacted with an acetoxymethylpyrrole in the presence of an acid catalyst to give azulitripyrranes. Following cleavage of the terminal protective groups, condensation with a diformylpyrrole in the presence of hydrochloric acid and oxidation with ferric chloride afforded 21-alkylazuliporphyrins. An azulene dialdehyde similarly reacted with an N-methyltripyrrane to generate a 23-methylazuliporphyrin. The products could only be isolated in protonated form and the free-base internally alkylated azuliporphyrins proved to be unstable. Nevertheless, the dications are highly diatropic and the internal alkyl group resonances were shifted upfield to beyond -3 ppm. Reaction of a 23-methylazuliporphyrin with palladium(II) acetate primarily afforded a palladium(II) complex with loss of the internal methyl substituent. However, two palladium(II) benzocarbaporphyrins were also identified that were formed by sequential oxidative ring contraction and methyl group migration. Internally alkylated azuliporphyrins provide new insights into the reactivity of the system and the results show that the introduction of alkyl substituents within porphyrinoid cavities greatly modifies the properties of these structures.

中文翻译：

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内部烷基化氮杂卟啉的合成

内部烷基化的氮杂卟啉的例子是通过 MacDonald 型“3 + 1”缩合制备的。2-甲基-和2-乙基薁与乙酰氧基甲基吡咯在酸催化剂存在下反应生成azulitripyrranes。在末端保护基团断裂后，在盐酸存在下与二甲酰基吡咯缩合并用氯化铁氧化得到21-烷基氮杂卟啉。薁二醛与ñ-甲基三吡喃生成 23-甲基唑卟啉。产物只能以质子化形式分离，并且游离碱内部烷基化的氮卟啉被证明是不稳定的。然而，双阳离子是高度变质的，并且内部烷基共振被移到高场超过-3 ppm。23-甲基azuliporphyrin 与乙酸钯(II) 的反应主要提供了钯(II) 配合物，其中失去了内部甲基取代基。然而，还发现了两种钯 (II) 苯并碳卟啉，它们是由连续的氧化环收缩和甲基迁移形成的。