A facile and metal-free method for the preparation of free base meso-aminodiarylporphyrins from readily available meso-bromodiarylporphyrins is described. Simple treatment of meso-bromoporphyrins with sodium azide and sodium ascorbate in DMF affords the corresponding meso-aminoporphyrins in very good yields. This method involves the aromatic nucleophilic substitution (SAr) of a bromo group with an azido group and the subsequent in situ reduction of the introduced azido group by sodium ascorbate. This amination reaction can be scaled up to gram scale without any decrease of the product yield. The amination reaction of free base meso-dibromoporphyrin affords a monoaminated product selectively, whereas that of the Ni(II) complex furnishes a diaminated product that is oxidized by air under ambient conditions but isolable as a trifluoroacetyl ester. Metal-insertion reactions of the obtained free base aminoporphyrins afford the corresponding metal complexes (Ni(II), Cu(II), Zn(II), and Pd(II)) all in good yields except the Pd(II) complex. Synthetic methods for the preparation of N-mono- or dialkylaminoporphyrins from the free base meso-aminoporphyrins have been also established.

Polyaniline, which is formed by the oxidative polymerization of aniline, is a widely explored conducting polymer with several stable oxidation states, and can be applied in advanced materials, including sensing...

Porphyrins and their metal complexes have been attracting significant attentions due to their characteristic chemical, or physicochemical properties derived from their 18π aromaticity.  Recently, nitrogen-based substituents (e.g., amino, amido, imido, imino, and azo groups) have been energetically introduced on the porphyrin periphery because of their strong influence of the p-electron system of the porphyrin.  Among them, meso-aminoporphyrins are the simplest nitrogen-substituted porphyrins.  Because of a wide variety of reactivities of the amino groups, meso-aminoporphyrins have been utilized as useful precursors for other nitrogen-substituted porphyrins.  Despite their synthetic usefulness, there have been only a few practical methods for the preparation of meso-aminoporphyrins.  In this presentation, we present a facile and efficient synthetic method for meso-aminoporphyrins from meso-bromoporphyrins.1  This method involves the aromatic nucleophilic substitution (SNAr) of a bromo group with azide2 and the following in-situ reduction of the introduced azide group by sodium ascorbate.  A simple treatment of 10 equiv. of sodium azide and sodium ascorbate with meso-bromodiarylporphyrins affords the corresponding meso-aminoporphyrins almost quantitatively.  This reaction is easily scalable up to a gram scale without the decrease of the product yield.  We also performed the oxidative oligomerization of meso-aminoporphyrins to afford the polyaniline-like π-conjugated oligomers.3  We will also report the synthesis, structural characterization, and redox behavior of the obtained oligomers.   References (1) K. Yamashita, K. Kataoka, S. Takeuchi, M. S. Asano, K. Sugiura, in preparation. (2) K. Yamashita, K. Kataoka, M. S. Asano, K. Sugiura, Org. Lett. 2012, 14, 190–193. (3) K. Yamashita, S. Takeuchi, M. S. Asano, K. Sugiura, in preparation.   Figure 1

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